. .. 2 4 APR 1978
ARCHIEF
ARL/Aero. Note 359UNCLASSIFIE6
ab
v. Scheepsbouwkunde
Technische Hogeschgn!
Meer° Note 359
DEPARTMENT OF DEFENCE
AUSTRALIAN DEFENCE SCIENTIFIC
SERVICE
AERONAUTICAL RESEARCH LABORATORIES
MELBOURNE VICTORIAAerodynamics Note 359
FURTHER STUDIES ON A SHIP MODEL
FITTED WITH VORTEX GENERATORS TO
IMPROVE THE VELOCITY DISTRIBUTION
OF THE FLOW INTO THE PROPELLER.
by
N. MATHESON
UNCLASSIFIED
AUSTRALIAN DEFENCE SCIENTIFI,C SERVICE
AERONAUTICAL RESEARCH LABORATORIES
AERODYNAMICS NOTE 359
FURTHER STUDIES ON A SHIP MODEL
FITTED WITH VORTEX GENERATORS TO
IMPROVE THE VELOCITY DISTRIBUTION
OF THE FLOW INTO THE PROPELLER.
by
N. MATHESON
SUMMARY
A set of vortex generators, designedfrorn model tests in a wind tunnel andfitted to a 13,0001 (13,000 ton) ship, produced a significant reduction in stern vibration which had been originally caused by the propeller operating in a strongly non-uniform wake. It was estimated that these generators would require an increase in delivered power of
16%. A further series of wind tunnel tests were undertaken on a reflex model to
develop a generator system which would require less power yet still improve the
velocity distribution of the fluid over the propeller face sufficiently to eliminate
vibration. The results of these tests are given in this report. It is recommended that the vortex generators already fitted to the ships be replaced with a new set which has a delivered power penalty of 12%.
CONTENTS
NOMENCLATURE. 3-4
I. INTRODUCTION.
MODIFIED VORTEX GENERATOR SYSTEMS FITTED TO
LYSAGHT ENTERPRISE AND ENDEAVOUR. 5-7
2.1 Angle of incidence of vortex generators. 6
2.2 Size of vortex generators. 6
2.3 Number of vortex generators. 6
2.4 Towing tank tests of a model fitted with vortex generators. 6
2.5 Vortex generators fitted to the Lysaght Enterprise. 6
2.6 Vortex generators fitted to the Lysaght Endeavour. 7
WIND TUNNEL TESTS OF MODIFIED VORTEX
GENERATORSDESIGNED FOR A LOW POWER PENALTY. 7-13
3.1 Model details and experimental equipment. 7
12 Model experiments and results. 7
3.2-1
Axial velocity distribution in the wake for the six vortex
generator system hl = 10.7mm (0.42in) h2 = 113 = 13.2mm
(0.52in), a = 18°. 8
3.2-2 Axial velocity distributions in the wake for the four vortex
generator systems fitted
to the
L,ysaght Enterprise andEndeavour. 9
3.2-3
Axial velocity distributions in the wake for four vortex
generators similar to those fitted to the Lysaght Endeavour, but
reduced in size and incidence. 10
3.2-4
Axial velocity distributions in the wake for four vortex
generators located at new positions on the hull. 10
3.2-5
Axial velocity distributions in the wake for two vortex
generator systems. 11
12-6 Resistance of model fitted with vortex generators. 12
EXTRAPOLATION OF MODEL RESULTS TO THE FULL SIZE
SHIP. 14-18
4.1 Dimensional scaling of the vortex generators. 14
4.2 Power required for the ship fitted with vortex generators. 14
VORTEX GENERATOR SYSTEM RECOMMENDED FOR
THESHIPS. 19 CONCLUSIONS. 19 ACKNOWLEDGEMENTS. 19 REFERENCES. 20 APPENDICES. 21-37 FIGURES. DISTRIBUTION.
DATA CONTROL SHEET.
3
Thickness of vortex generator D/ (1/2 p U2S) = Resistance coefficient
Resistance
FN U/ N/F1..pp= Froude number
Acceleration due to gravity Height of vortex generator
Lpp Length between perpendiculars (ship or 'model)
Length of vortex generator
PD Power delivered to propeller
PE Effective power
Radius of propeller
RN ULppl V = Reynolds number
Radius from centre of propeller shaft, in the propeller plane, at which velocities were measured
Surface area
Thrust deduction fraction Freestream velocity
Axial velocity component in the propeller plane Wake fraction
a
Angle of incidence of the vortex generator to the local surface streamlineSCD, 6PD, SP E = Increment inCD, PD,PE respectively, caused by fitting vortex generators
no
Quasi-propulsive coefficientHull efficiency
Open water propeller efficiency
riR Relative rotative efficiency
0 Angular position in the propeller plane at which axial velocities were
measured. (Origin at top dead centre and measured as positive in a clockwise direction when viewed from aft)
Kinematic viscosity
Subscripts
1,2,3 Denotes vortex generator identity
The Lysaght Enterprise and Endeavour are sister ships built recently by the Newcastle State Dockyard, New South Wales, Australia, for the Australian Department of Transport. Initially these ships suffered from severe vibration at the stern which prevented operation at the design
speed of 18 knot. Tests on the Lysaght Enterprise indicated that the
vibration occurred predominantly at the propeller blade frequency of 9.3Hz (560 c. p.m.) with local accelerations of upto 2.g. It was concluded that the vibration arose principallyfrom the propeller working in a
non-uniform axial velocity field. This wake non-non-uniformity produces cyclic
variations in flowincidence at the propeller blades which can lead to intermittentcavitation and the propagation of strong pressure pulses into the water near the propeller. Pressure pulses of this type produce a discrete vibration input to the hull in addition to cyclic variations in thrust and torque.
In parallel with other attempts to find a solution to the vibrationproblem the Aeronautical
Research Laboratories were asked to examine the flow about the stern using a reflex model in the
wind tunnel, and to devise a system of vortex generators which would create a more uniform
velocity distribution into the propeller in the expectation that this would reduce the vibration intensity. Wind tunnel tests were carried out using a 1/48 scale reflex model (2.7m (9ft) Lpp) and a system of six vortex generators were developed which substantially improved the velocity in the wake of the model'. It was recommended that these generators be geometrically scaled and fitted to the ship. The size and position of the generators, to both ship and model scale, are given in Fig.
I.
Resistance tests were carried out in the wind-tunnel from which it wasestimated that fitting the vortex generators to the ship would require an increase in effective power of 26% in full load, and 20% in ballast, in order to maintain a speed of 18 knot.' These power increases were calculated assuming that the increase in resistance coefficient caused by fitting the generatorsis independent of both Froude number and Reynolds number. The increase in delivered power was not estimated
because relevant propulsion factors could not be found from thewind tunnel tests. However, at
that stage, a similar increase in delivered power was expected. Although the predicted power increases were within the allowable limit of approximately 1,500kW (2,000hp) at 18 knot, it was later realised that the increase in fuel consumption would be unacceptable. In the meantime tests were carried out in an English towing tank on a somewhat larger model fitted with geometrically similar vortex generators to determine changes in delivered power2'3. From these tests it was estimated that increases in effective and delivered power of 28% and 37% respectively would be needed to attain 18 knot in the full load condition; increases in power of this order were not acceptable. The higher percentage increase in delivered power resulted mainly from a reduced hull efficiency caused by a reduction in the wake fraction. However, the tank tests confirmed the
improvements in axial velocity in the wake found from the windtunnel tests. In general, slightly
smaller velocities were found from the towing tank tests, probablydue to the presence of a wave
crest at the stern.
As no other proposals had given comparable improvements in velocity it was decided to modify the vortex generators in an attempt to reduce the power penalty to an acceptable level while still maintaining a suitable wake.
This report gives details of the vortex generators fitted to the Lysaght
Enterprise andEndeavour, together with the results from an additional series of wind tunnel tests with modified vortex generators designed for lower power penalties.
2.
MODIFIED VORTEX GENERATOR SYSTEMS
FITTEDTO LYSAGHT
ENTERPRISE AND ENDEAVOUR.
When the original recommendation was made that six vortex generators, as shown in Fig. I,
be fitted to the Lysaght Enterprise, it was known that their design wasconservative. It was said
that the ship had adequate excess power to cope with the likely power penalty, and emphasis was placed on achieving the highest axial velocity of the flow into the propeller in order to maximize the probability that the vibration problem would be eliminated.
Later, when the power penalty was more closely examined and further data became available
from tank tests, it was clear that a less conservative approach had to beadopted. The three main
aspects of the design with greatest potential for reducing the power penalty while still maintaining a satisfactory velocity distribution of the flow into the propeller are:
The angle of incidence of the vortex generators. The size of the vortex generators.
The number of vortex generators.
2.1 Angle of incidence of vortex generators.
An angle of incidence of 25° was originally recommended to take account of the change in angle of attack as the ship rolls in heavy seas. The wind tunnel results showed that the effectiveness
of the vortex generators varied little over an angle of attack ranging from 15° to 40°. Thus, by choosing an angle of incidence of 25° there was a margin of 10° before the effectiveness of the generators dropped significantly at low angles, and a somewhat larger margin before stalling caused a loss of effectiveness at the higher angles.
Since it is unlikely that the ship would be operated at full speed in rough seas it was considered that these large margins were unduly conservative, and that the angle of incidence could be reduced to 18°. Such a modification was estimated to reduce the effective power penalty from 26% to 20% at 18 knot. However, a power increase of this magnitude was still not acceptable.
2.2 Size of vortex generators.
Since decreasing the incidence of the generators did not reduce the power penalty sufficiently
it was also necessary to reduce their size. Although previous results' showed that smaller
generators were less effective in improving the flow into the propeller it was considered that some loss of effectiveness could be tolerated in order to reduce the power penalty.
Owing to scale effects the boundary layer on the 'smooth' ship (RN = 1.1 x 109 at 18 knot) is relatively thinner than on the model (RN = 1.2 x 10') tested in the wind tunnel. However, this is mostly offset by hull roughness and fouling which increases the boundary layer thickness on the ship the longer it remains in service. These effects were conservatively allowed for in the original vortex generator design by simply geometrically scaling the generators from the model to the ship. A less conservative extrapolation would reduce the power penalty but would also lower the margins for fouling, and other effects such as propeller action and the stern wave.
After considering the trade-off between reduced performance and lower power penalty with smaller generators it was decided that the vortex generators on the ship could be reduced in size from h, = 0.61m(24in), h2 = h3 = 0.76m(30in) to h, = 0.51m(20in), h2 = h3=0.63m(25in). This was expected to produce a slightly lower, but acceptable axial velocity distribution of the flow into the propeller with a reduction in the effective power penalty from 20% to 13%.
2.3 Number of vortex generators.,
The power penalty could be further reduced by removing one pair of vortex generators.
Examination of existing data and flow pattern photographs indicated that the two leading
generators (No. 3 pair) were the least effective in bringing high energy fluid into the propeller disc. However, it was felt that their removal might cause the vortices from the other generators to alter
their position and produce a significant reduction in the axial velocity of the flow into the
propeller. Reducing the drag penalty by removing one pair of vortex generators was therefore not recommended.
2.4 Towing tank tests of a model fitted with vortex generators.
The modified vortex generator system for the ship h, = 0.51m(20in), h2 = h3=0.63m(25in), a = 18° was tested at model scale in a towing tank4'5 to determine the velocity distribution of the flow into the propeller and delivered power. The axial velocity distribution over the propeller disc found from the towing tank tests is plotted in Fig. 2 with the previous results for the larger generators at a = 25° from both towing tank and wind tunnel tests. As expected, only small changes in the velocity distribution of the flow into the propeller disc occurred compared with the
original generators. At 18 knot the effective and delivered power penalty for the ship was reduced to 13% (as estimated from interpolation of wind tunnel results) and 23% respectively. Although these power increases were significantly lower than the increases of 28% and 37% respectively,
estimated for the original vortex generators, a 23% increase in delivered power was again
considered too large.
2.5 Vortex generators fitted to the Lysaght Enterprise.
A further modification to the vortex generators was considered necessary to reduce the 23%
before the first ship, the Lysaght Enterprise, was scheduled for dry docking. Following a further appraisal of the evidence available it was decided to delete the forward pair of vortex generators,
(No. 3 pair - Fig. 1), and to fit four generators at an angle of incidence of 18° with height h,=
0.51m(20in), h2 = 0.63m(25in). The position and size of the vortex generators fitted to the Lysaght Enterprise are given in Fig. 3. It was estimated that there would be an acceptable increase in delivered power of approximately 16% (1,120k W (1,500hp)).
Trials with the Lysaght Enterprise fitted with vortex generators were carried out in both full load and ballast draught conditions in deep water off the coast of New South Wales during August 1974. The trials were considered successful as the stern vibration, previously severe above 16 knot, had virtually disappeared. Although the power absorbed by the vortex generators could not be accurately determined it appeared to be satisfactory.
2.6 Vortex generators fitted to the Lysaght Endeavour.
The Lysaght Endeavour was drydocked soon after trials of the Lysaght Enterprise fitted with vortex generators. In view of the successful trials with the Lysaght Enterprise it was expected that some reduction in axial velocity in the wake could be tolerated without vibration problems occurring. Similar generators to those on the Enterprise were therefore fitted to the Endeavour, but at a reduced angle of incidence of 16° instead of 18°. This reduction in incidence was expected to lower the power penalty to about 15%. These vortex generators were also successful as no vibration problems were encountered with the Lysaght Endeavour during trials.
3. WIND TUNNEL TESTS OF MODIFIED VORTEX GENERATORS DESIGNED FOR A
LOW POWER PENALTY.
Soon after the trials with Lysaght Enterprise, additional wind tunnel studies were requested aimed at refining the vortex generators to further reduce the power penalty while still producinga
velocity distribution of the flow into the propeller which would still prevent vibration. In view of the success with the vortex generators during sea trials it was considered that a somewhat less uniform axial velocity distribution of the flow into the propeller could be accepted. Details of the
wind tunnel tests, and the results, are given in the following sections for a model fitted with a
number of the more effective vortex generator systems tested.
3.1 Model details and experimental equipment.
All additional wind tunnel tests were carried out with the 1/48 scale mirror-image model used for the previous tests The principal ship particulars from which the model was scaled are given in Table 1. Section lines, bow and stern contours, and the stern arrangement are shown in Figs 4, 5, 6
and 7. The model was fitted with a propeller arch fairing which had been fitted to the ship soon
after its initial trials.
The current series of wind tunnel tests were carried out in a similar manner to those previously reported'. The same equipment was used in both cases. Local axial flow velocities in the propeller plane were measured using pitot probes connected to a multitube manometer. These pitot tubes were mounted on an arm which could be rotated about the centre of the propeller shaft to enable velocities to be determined at selected angular positions for any radii from the hub up to r/ R =
1.23. The resistance of the model both with and without vortex generators was measured using
an external mechanical drag balance.
Surface flow patterns were made visible using french chalk mixed with kerosene painted on to the model surface.
3.2 Model experiments and results.
The axial velocity distribution over the propeller disc, resistance of the model, and the surface flow pattern were used to assess the performance of each set of vortex generators. The majority of the axial velocities were measured on the starboard side of the propeller disc. Some measurements were always taken on the port side of the disc to check for symmetry. More detailed results were
taken on the port side if significant asymmetry was found. All flow patterns and velocities were
taken at a Reynolds number of 1.2 x 10, while the resistance of the model was measuredover a
range of Reynolds number from approximately 8 x 106 to 1.2 x 10. All the present tests were made
Table 1 Principal ship particulars.
with the model in full load draught. A list of the more effective vortex generators is given in Table 2. Resistance coefficients and axial velocity distributions over the propeller disc are given later in the report for these generators.
The model was initially re-tested both without vortex generators and with the originally-proposed six vortex generator system shown in Fig. 1, in order to check for repeatability of results. The axial velocities and resistance coefficients from both tests are tabulated in Appendix 1. There was no significant difference between either the velocity distributions through the propeller disc or the resistance characteristics, both with or without the vortex generators, as compared with the original results. Therefore, the results from further tests with different vortex generators are directly comparable with those from the previous tests.
3.2-1 Axial velocity distribution in the wake for the six vortex generator system
hi = 10.7mm (0.42in), hi= h; = 13.2mm (0.52in), a = 18°
The six vortex generator system tested in the towing tank 4'5 was correspondingly scaled to hi = 10.7mm (0.42in), h2 = h3 = 13.2mm (0.52in), a = 18°, and tested in the wind tunnel. This provided comparitive data which enabled the delivered power to be estimated for other generator systems tested in the wind tunnel, (see section 52) even though propulsive factors, other than wake
8
Condition Load Ballast
Length between perpendiculars Breath-moulded
Type of bow Shell plating
Mean draught - moulded
Trim at rest .
Equivalent mean draught - moulded at level trim
Displacement - moulded
Wetted surface coefficient Length displacement ratio Block coefficient
Maximum section coefficient Prismatic coefficient
Longitudinal centre of buoyancy from amidships
Half angle of entrance of waterline Length of entrance
Length of parallel middle body Length of run
Bilge radius Rise of floor
Half flat of bottom of amidships
131.96m (432.67ft) 22.57m (74.00ft) Raked Flush welded 7.32m (24.00ft) Level
-13,433t (13,170 ton) 6.178 5.601 0.600 0.956 0.628 4.94m (16.20ft) aft 110 72.58m (237.97ft) 59.38m (194.70ft) 3.66m (12.00ft) 0.15m (0.50ft) 0.15m (0.50ft) 131.96m (432.67ft) 22.57m (74.00ft) Raked Flush welded 5.02m (16.46ft) 1.9Im (6.25ft) by stern 5.12m (16.78ft) 8,476t (8,310 ton) 6.580 6.530 0.541 0.933 0.580 6.92m (22.69ft) aft 8° 72.58m (237.97ft) -59.38m (194.70ft) 3.66m (12.00ft) 0.15m (0.50ft) 0.15m (0.50ft)Machinery: Single screw geared diese , two eight cylinder turbo charged MAN R8V52/ 55 geared to propeller shaft. Maximum continuous rating (a) Total brake power of 11,940kW (16,000hp) (b) Mean delivered power of 8,950 (12,000hp) (corresponds to mean between clean and fully fouled condition).
Propeller: 4.88m(16ft) diameter, 4 blades R.H., controllable pitch, 140 r.p.m. The speed of the vessel is varied by changing propeller pitch.
(a) Six vortex generators in the positions shown on Fig. I.
hi = 12.7mm (0.50in), h2 = h3 = 15.9mm (0.63in), a = 25° hi = 10.7mm (0.42in), h2 = h3 = 13.2mm (0.52in), a = 18°
(b) Four vortex generators in the positions shown on Fig. 3.
hi = 10.7mm (0.42in), h2 =- 13.2mm (0.52in), a= 18° (Enterprise)
hi = 10.7min (0.42in), h2 = 13.2mm (0.52in), a = 16° (Endeavour)
hi = 10.7mm(0.42in), h2 = 13.2mm (0.52in), a = 13° hi = 8.4mm (0.33in), h2 = 10.7mm (0.42in), a = 16°
(c) Four vortex generators in the positions shown on Fig. 14.
hi = 7.9mm (0.3 tin), h2 = 10.7rnm (0.42in), a = 17°, 200, 24°. hi = 6.4mm (0.25in), h2 = 7.9mm (0.31in), a = 17°, 200, 24°.
(d) Two vortex generators in the positions shown on Fig. 19.
(e) Two vortex generators - No. 2. generators only of the system shown in Fig. 3.
1. h2 = 13.2mm (0.52in), a = 18°.
fraction, are not available. The axial velocity components of the fluid passing through the
propeller disc from both tests are plotted in Fig. 8 and tabulated in Appendix 2. There was little difference between the two sets of results considering that different models and equipment were used, that free surface effects were present in the towing tank, and that the tests were made at different Reynolds numbers of approximately 8.0 x 106 in the towing tank (corresponding to FN 0.258) and 1.2 x 107 in the wind tunnel.
3.2-2 Axial velocity distributions in the wake for the four vortex generator systems fitted to the Lysaght Enterprise and Endeavour.
The axial velocity distributions through the propeller disc of the model fitted with vortex generators hi = 10.7mm (0.42in), h2 = 13.2mm (0.52in) corresponding to those on the Lysaght Enterprise and Endeavour were measured in the wind tunnel. The axial velocity distributions are plotted in Fig. 9 and tabulated in Appendix 3. Velocities in the region 90°<0<270° are not included in the figure because they remained approximately constant. Results for the model
without vortex generators and with the original six vortex generator system (hi= 12.7mm (0.50in), h2 =- h3 = 15.9mm (0.63in), a = 25°) are also plotted in Fig. 9.
9
1. h = 13.2mm (0.52in), a = 14°, 20°.
2. h = 10.7min (0.42in), a = 17°, 20°.
For both sets of generators the axial velocities at r/ R = 1.23 were well below those for the
larger system, especially for 30°<0 <30°. In this region the velocities for the generators at 18°
incidence were up to 50% above those for the generators at 16°. In the regions 35°<0<90° and
2700<0<3400 both sets of vortex generators produced axial velocities below those for the bare hull. At r/ R = 0.96 the velocities with the generators at 18° and 16° incidence were similar to one another although they were well below those for the six vortex generator system except at 0 =0°
where they were almost the same. Over the inner radii, r/ R = 0.68 and 0.41, all the velocity
distributions were similar.. A significant aspect of the results is that the four and six vortex
generator systems produced approximately the same velocity at
the top dead centre of the
propeller disc. Thus, the low velocity region at 0= 0° thought to be a major cause of the vibration, was still eliminated with only four vortex generators.
A significant asymmetry in the velocity distribution over the propeller disc occurred when the vortex generators were set at 16° compared with the results when they were set at 18°. This asymmetry was quite pronounced at r/ R = 0.68 and to a lesser extent at r/ R = 1.23. If the incidence of the generators on the port side (low velocity region) was increased by 10, to 170, and that on the
starboard side decreased by 1°, to 15°, then the low velocities which previouslyoccurred on the
port side appeared on the starboard side as shown in Fig. 10.
More symmetrical velocity distributions could not be obtained with additional small changes in the angle of incidence of the vortex generators. It seems that with these generators an angle ofincidence of about 16° is rathercritical in creating a symmetrical axial velocity distribution into the propeller, probablybecause
one (or more) of the vortices 'burst', that is, brokedown upstream of the propeller disc6'7.
The surface flow pattern over the stern of the model with the generators set at 16° is shown in Fig. 11. The asymmetry which appeared in the wake velocities is visible in the flow pattern forward of the upper section of the propeller disc, and supports the idea that one of the vortices on the port
side had broken down. On the starboard side the flow pattern is similar to thatformed with six
vortex generators in the first series of tests' and shown in Fig. 12 for comparison.
3.2-3 Axial velocity distributions in the wake for four vortex generators similar to those
fitted to the Lysaght Endeavour, but reduced in size and incidence.
The axial velocity distribution through the propeller disc of the model fitted with vortex
generators similar to those on the Lysaght Endeavour, but reduced inincidence from .16° to 13°,
are tabulated in Appendix 3, and plotted in Fig. 13.
At r/ R = 0.96, 0.68 and 0.41 the axial velocities over the top half of the propeller disc were generally lower than those for the generators at 16°, but there was some improvement compared with the results for the bare hull. However at r/ R = 1.23 the velocities were even lower than those without generators. There was also an asymmetry in the velocity distribution of the flowwhich was more pronounced than when the generators were set at 16°. This asymmetry in the velocity distribution was again found to be reversible with small changes in generator incidence, and is also
probably caused by the vortices bursting.
Owing to the flow asymmetry and the low values of velocity near the top of the propellerdisc
these vortex generators were considered unsatisfactory. Consequently, the
incidence wasincreased to the original value of 16° but the size of the generators was reduced to
111 =8.4mm (0.33in), h2 = 10.7mm (0.4iin). Results with these generators are plotted in Fig. 13 and tabulated in Appendix 3. Compared with the bare hull there was a large improvement in the velocity over the inner region of the propeller, but the improvements over the outer region, where the majority of the load is taken, were not considered sufficient to eliminate,vibration. In this case
the velocity distribution was far more symmetrical than for the previous generators. From these
results it seems preferable to use smaller generators at relatively high angles of incidence rather
than large generators at low angles of incidence.
3.2-4 Axial velocity distributions in the wake for four vortex generators located at new positions on the hull.
Since the generator system discussed in section 3.2-3 did not produce satisfactory velocity
distributions additional tests were made with similar generators relocated onthe hull. The new
positions were established specifically from tests with only four vortex generators,whereas the
previous four generator systems formed part of a six generator configuration. The most suitable
location found for the generators is shown in Fig.
14. The dimensions given correspond toto the local surface streamlines. All generators had the triangular shape shown in Fig. 1. The axial velocity distribution through the propeller disc of the model fitted with the new vortex generator system is plotted in Fig. 15 and tabulated in Appendix 4. Velocity distributions are also plotted in Fig. 15 (and tabulated in Appendix 4) for the same generators set at angles of incidence of 24° and 17°. The results for a = 20° and 24° were very similar except in the region 340°<0 <20° for r/ R = 1.23, where the axial velocities with a = 24° were 20%to 30% greater than those for a = 20°. When the generators were set at 17° the axial velocity ratios were much lower than those for a = 20°, especially in the region r/R = 1.23 and 0.96 when 340°<0<20°. The axial velocities
for the model without vortex generators and with vortex generators hi =
10.7mm (0.42in), h2 = I3.2mm (0.52in), a = 16°, (Endeavour) at the previous location are also plotted in Fig. 15.The new generators reduced the velocity ratios over the inner radii of the propeller compared with the results for generators fitted to the Lysaght Endeavour at model scale, but still maintained large increases in axial velocity through the important outer region of the propeller disc. They also eliminated the asymmetry in the velocity distribution which had been prominent at r / R = 0.68. The generators were not set at angles smaller than 17° because it was considered that the velocity distribution produced at these low angles of incidence would not be sufficiently uniform to prevent vibration.
In an attempt to further reduce the power penalty the generators were reduced in size to hi = 6.4mm (0.25in), h2 = 7.9rnm (0.31in) and re-tested in the same location at the same angles of incidence of 17°, 20° and 24°. The resulting axial velocity ratios over the propeller plane are plotted in Fig. 16, and tabulated in Appendix 4. Again, for comparison, the axial velocities for the model without vortex generators and with generators hi = 10.7mm (0.42in), h2 =13.2mm (0.52in) at a = 16°, are included in Fig. 16. There is little difference between the velocity distributions over the inner radii of the propeller disc for these generators and the larger ones at corresponding angles of incidence. At the top of the propeller disc near the blade tip the velocity ratios were very similar for both generator systems at an incidence of 24°, but at a = 17° and 20° the velocities with the smaller generators were significantly lower than those with the larger generators. Further out, at r/ R = 1.23 the wake velocities with the smaller generators were lower than those with the larger ones and were very similar to the results for the bare hull. Again, there was no asymmetry in the
axial velocity distributions for the smaller generators compared with the generators hi =
10.7mm (0.42in), h2 = 13.2mm (0.52in) at a = 16°. This can also be seen from the surface flow pattern shown in Fig. 17 for the generators hi = 6.4mm (0.25in), h2 = 7.9mm (0.3Iin) at a = 20°
compared with the flow pattern shown in Fig. 11 for the generators fitted to the Lysaght
Endeavour to model scale. The improvements in the surface flow pattern produced by fitting vortex generators can be seen from a comparison of Figs. 11, 12, and 17 with the flow pattern for the bare hull' shown in Fig. 18.
3.2-5 Axial velocity distributions in the wake for two vortex generator systems. Tests were made with two vortex generators (one port and one starboard) in an attempt to reduce the power penalty even further while still improving the axial velocity distribution into the propeller sufficiently to eliminate the vibration problems. Following the same procedure used with the previous generator systems a number of tests were made to find the most suitable location. The position chosen is shown on Fig. 19. The dimensions given correspond to generators with height h = 13.2mm (0.52in) at an angle of incidence of 20° to the local surface streamline. Three different sizes of generator were tested corresponding to heights h = 13.2mm (0.52in), h = 10.7mm (0.42in), h = 8.4mm (0.33in).
The axial velocity distributions of the flow in the propeller plane of the model are plotted in Fig. 20 for generators h = 13.2mm (0.52in) at angles of incidence of 14° and 20°. Similar results are
plotted in Figs. 21 and 22 for the other two generator sizes h = 10.7mm (0.42in) and h =
8.4mm (0.33in) respectively, at angles of incidence of 17° and 20°. The results are also tabulated in Appendix 5. For comparison, the axial velocities for the model without vortex generators and with those fitted to the Lysaght Endeavour, to model scale, are also plotted in Figs. 20,21 and 22. The surface flow pattern with the two vortex generator system h = I0.7mm (0.42in) at a = 17° is shown in Fig. 23.
Each of the two vortex generator systems improved the axial velocities into the propeller as compared with the model without generators. However, it was considered that none of the velocity distributions would produce an adequate reduction in ship vibration. Both larger generators and increased angles of incidence were tried but low axial wake velocities still occurred over the top of the propeller disc in the region 340°<0 <200. One of these systems might have been suitable if the vibration had not been so severe.
Removing one pair of the existing vortex generators on the ship is one of the simplest configuration changes that could be made without drydocldng. An additional set of velocity measurements was therefore made for the model fitted with only the No. 2 generators of the system fitted to the Lysaght Enterprise shown in Fig. 3. The results are plotted in Fig. 24 and tabulated in
Appendix 5. The axial velocities were, in general, slightly lower than those for the previous two vortex generator systems, and it is not expected that these generators would reduce vibration to an acceptable level.
3.2-6 Resistance of model fitted with vortex generators.
The resistance of the model both with and without vortex generators was measured using a mechanical drag balance. The majority of the results were taken over a Reynolds number range of 8.0 x 106 to 1.2 x 10. Corrections were applied for the interference effects of the shroud around the mounting sting, blockage (both solid and wake), compressibility, and the pressure gradient in the tunnel. The resistance coefficients for the model fitted with each of the vortex generator systems listed in Table 2 are plotted in Fig. 25 and tabulated in Appendix 6. Resistance coefficients are also plotted in Fig. 25 for the model without generators and with the initially proposed six vortex generator system shown in Fig. 1.
The increase in resistance coefficient for the model fitted with each vortex generator system at a Reynolds number 107 is given in Table 3. The increases ranged from less than 1% for the two vortex generator system with h = 8.4mm (0.33in) at a = 17° to 26% for the large six vortex generator system.
None of the systems produced an overall reduction in model resistance as discussed in Ref. 8. However, it is of interest that the small two vortex generator systems at low incidence produced significant increases in the velocity of the fluid through some parts of the propeller disc with only small increases in resistance.
Table 3 Increase in resistance coefficient for the model fitted with vortex generators.
(a) Six vortex generator systems in the positions shown on Fig. 1.
12 SCD hi = 10.7mm (0.42in) hi = 13.2mm (0.52in) h3 = 13.2mm (0.52in) hi = 12.7mm (0.50in) h2 = 15.9mm (0.63in) h3 = 15.9mm (0.63in) 18° 25° 0.00040 0.00090
Four Vortex generator systems in the positions shown on Fig. 14.
Two vortex generator systems in the positions shown on Fig. 19.
Two vortex generator systems formed by removing the No. 1 pair of generators in Fig. 3.
13 SCD
a
hi = 10.7mm (0.42in) hi = 8.4mm (0.33in) h2 = 13.2mm (0.52in) h2 = 10.7mm (0.42in) 18° 0.00027 -(Enterprise) 16° 0.00022 0.00012 (Endeavour) 13° 0.00010a
6CD hi = 7.9mm (0.31in) hi = 6.4mrn (0.25in) h2 = 10.7mm (0.42in) h2 = 7.9mm (0.31in) 17° 0.00007 0.00004 200 0.00012 0.00008 24° 0.00020 0.00013a
(5CDh = 8.4mm (0.33in) h = 10.7mm (0.42in) h= 13.2mrn (0.52in)
14° 0.00002 17° 0.00001 0.00007 20° 0.00004 0.00010 0.00014
a
OCD h = 13.2trirn (0.52in) , 18° 0.000144. EXTRAPOLATION OF MODEL RESULTS TO THE FULL SIZE SHIP.
The experimental results from tests of the model must now be applied to the full size ship; in particular the physical size of the generators to be fitted to the ship must be determined and an estimate made of the increased power required to propel the ship at its design speed.
4.1 Dimensional scaling of the vortex generators.
Since physical constraints limit the test Reynolds number of the model to about 1/90 of that for the full scale ship the flow over the model will differ from that over the ship. Furthermore, both structural roughness and fouling of the hull will cause other changes to the flow about the ship compared with that over the smooth model tested in the wind tunnel. These factors must be allowed for in determining the size of the vortex generators for the ship.
As the boundary layer on the 'smooth' ship is relatively thinner than that on the model, simple geometric scaling of the size of the vortex generators will result in oversize units being fitted to the ship. These generators would then induce relatively stronger vortices on the ship than those on the model. It would therefore appear to be more logical to scale the generators according to the relative thickness of the two boundary layers. This can be done by using flat plate boundary layer theory. Although this theory neglects the three dimensional nature of the hull it should still give a good estimate of the relative thickness between the two layers. For the 'smooth' ship steaming at 18 knot it was estimated that the relative thickness of the boundary layer would be only about 40% of that on the model.
In order to allow for structural and paint roughness, and hull fouling, it was assumed that the skin friction coefficient would be increased by 0.00049 (the commonly accepted value for typical surface roughness) and that 30% more effective power would be required to overcome hull fouling. Taken together, these effects would increase the relative thickness of the boundary layer on the ship from 40% of that on the model to about 80%.
There are other factors not represented in the model tests which will effect the flow about the ship. Propeller action will have a favourable influence by reducing the pressure over the stern. On the other hand, the stern wave will most likely have a detrimental effect by increasing the adverse
pressure gradient over the stern. Estimates of these two effects show that the propellereffect
should be dominant. In addition to these effects, the motion of the ship, such as rolling, will create an unsteady asymmetrical flow over the hull which combines with the stern wave and scale effects to alter the effective angle of incidence of the vortex generators. Although the majority of the
vortex generator systems tested are not sensitive in small changes of incidence some allowance
should be made for these unknown changes in flow direction.
Taking all of the above factors into account, it is recommended that the size of the generators
on the ship should be made 90% of their geometrically scaled size. Therefore,for example, the
10.7mm (0.42in) generators on the model would become 0.46m (18in) high on the-ship. The alteration in relative spacing between the generators caused by scaling in this way was not expected to be significant in view of the relatively small changes involved.
4.2 Power required for the ship fitted with vortex generators.
The increased power which must be delivered to the propeller to achieve the design speed of the ship fitted with vortex generators is of major concern. Unfortunately, this power increase cannot be directly calculated from the increase in resistance coefficient measured from model tests since the various propulsion factors cannot be readily determined from tunnel tests. However, the increase in delivered power was estimated using values of delivered and effective power predicted from towing tank tests and by making the following assumptions:
The wavemaking resistance will not be altered by the generators since they are too far beneath the surface to influence the stern wave, and they are too far aft to influence the bow wave system which contains the majority of the wavemaking energy.
The increases in resistance coefficient (given in Table 3) determined from wind tunnel tests remain constant, independent of Reynolds number and are directly applicable to the ship with vortex generators. (The increases in effective power for the ship calculated using the resistance coefficients are given in Table 4).
heights are applicable to the model).
(a) Six vortex generator systems in the positions shown on Fig. 1.
(b) Four vortex generator systems in the positions shown on Fig. 3.
(c) Four vortex generator systems in the positions shown on Fig. 14.
15
a
OPE hi = 10.7rnm (0.42in) h2 = 13.2mm (0.52in) h3 = 13.2mm (0.52in) hi = 12.7mm (0.50in) h2 = 15.9mm (0.63in) h3 = 15.9mm (0.63in) 18° 25° 540kW (730hp) 1,220kW(1,640hp) SPEa
hi = 10.7mm(0.42in)hi = 8.4mm(0.33in)
h2 = 13.2mm (0.52in) h2 = 10.7mm (0.42in) 18° 310 kW (490hp) (Enterprise) 16o 300kW (400hp) 160kW (220hp) (Endeavour) 13° 130kW(180hp) SPEa
h = 7.9mm (0.31in)
hi = 6.4mm (0.25in) h2 = 10.7mm (0.42in) h2 = 7.9mm (0.31in) 17o 100kW (130hp) 50kW( 70hp) 20° 160kW (220hp) 110kW(150hp) 24° 270kW (360hp) 180kW (240hp)(d) Two vortex generator systems in the positions shown on Fig. 19.
(e) Two vortex generator systems formed by removing the No. 1 pair of generators in Fig. 3.
The relative rotative efficiency, nR, and open water propeller efficiency no, are unaltered
with the generators fitted to the hull.
The thrust deduction fraction, t, remains constant.
The wake fraction, w, is independent of both Reynolds and Froude number.
Assumption three means that the quasi-propulsive coefficient given by equation (1), is
71D = PElPD nR . no (1)
directly proportional to hull efficiency nH, and assumption four means that the hull efficiency,
given by equation (2), is dependent only on the wake fraction w. Assumption five allows the
7711-(l ( t) / (1 w) (2)
wake fractions found from model tests in the wind tunnel to be directly applied to the ship. The delivered power for the ship with vortex generators was then calculated from equation
(3).
PD =
V. G.
](1-*V.G.)1
(1-W)1[PD + (PEKG.- PE) PI)/ PE (3)-'
Values of the delivered and effective power, Pb=6,950kW (9,310hp) and PE= 4,650kW (6,240hp) predicted from towing tank tests3'4 were used in equation (3) to estimate the delivered power for the ship with vortex generators. It would have been more accurate to use power data from actual ship trials, but these were not available. The delivered power predicted using equation (3) for the
two sets of generators, hl = 12.7mm (0.50in), h2 = h3 = 15.9mm (0.63in), a = 25° and h =
10.7mm (0.42in), h2 =h3 = 13.2mm (0.52in), a= 18°, (model scale), which had also been tested in the towing tank3'4, are listed in Table 5, with the values predicted from the tank tests. In both cases the power predicted using wind tunnel data was greater than the power estimated from tank tests. This difference is mainly caused by neglecting the propulsion factors, except wake fraction, when
16 OPE
a
h -= 8.4mm (0.33in) h = 10.7mm (0.42in) h = 13.2mm (0.52in)140 30kW ( 40hp) 170 15kW (20hp) 100kW (130hp) 20° 50kW (70hp) 130kW (180hp) 190kW (25011p)
a
OPE h = 13.2mm (0.52in) 180 190kW (250hp)estimating delivered power from the wind tunnel tests. To allow for these effects the increment in delivered power for the ship with each set of vortex generators, found from equation 3, was multiplied by 0:83. This correction factor was the mean ratio of the increase in delivered power from the towing tank results and from equation 3, for the two sets of generators tested in the tank.
The increase in delivered power for each vortex generator system calculated using this procedure is given in Table 6, expressed as a percentage of the delivered power 6,950kW (9,310hp) for the ship without generators. As expected, there is a significant reduction in power when either the size, incidence, or number of generators is reduced. The vortex generators actually fitted to the Lysaght Enterprise and Endeavour were geometrically scaled from the generators on the model. However, since it is now recommended that the modified generators for the ship be reduced to 0.90 of their geometrically scaled size, the power penalty for the ship will also be smaller. This reduction in power cannot be determined accurately, but it is estimated to be of the order of 1%, depending on the size of the generators. While it should be remembered that the increases in delivered power in Table 6 are only approximate, the relative increases should be sufficiently accurate to enable an alternative vortex generator system to be chosen for the ship.
Table 6 Estimated increase in PD for the ship fitted with vortex generators. (Note: generator heights are applicable to the model).
(a) Six vortex generator systems in the positions shown on Fig. I.
17 Generator PD Wind Tunnel (equation 3) Towing Tank
,
hl = 12.7mm (0.50in) h2 = h3 = 15.9mm (0.63in), a =25° h1 = 10.7mm (0.42in) h2 = h3 ---= 13.2mtn (0.52in), a = 18° 10,070kW (13,500hp) 8,900kW (11,930hp) 9,530kW (12,770hp) 8,6-00kW (11,510hp) . ' SPDa
hi = 10.7rnm (0.42in) h1 = 12.7mm (0.50in) h2 = 13.2mm (0.52in) h2 = 15.9mm (0.63in) h3 = 13.2mm (0,52in) h3 = 15.9mm (0.63in) 18° 231/2% 25° 371/2%(b) Four vortex generator systems in the positions shown on Fig. 3.
Four vortex generator systems in the positions shown on Fig. 14.
Two vortex generator systems in the positions shown on Fig. 19.
Two vortex generator systems formed by removing the No. 1 pair of generators in Fig. 3.
18 SPD hi = 10.7mm (0.42in) h1 = 8.4mm (0.33in) h2 = 13.2mm (0.52in) h2 = 10.7mm (0.42in) 18° 171/2% . (Enterprise) 16° 16% 11% (Endeavour) 13° 71/2% aPD ,
a
hi = 7.9mm (0.31in) hi = 6.4mm (0.25in) h2 = 10.7mm (0.42in) h2 = 7.9mm (0.31in) 17° 10% 8% - 20° 14% 91/2% 24° 17% 121/2%a
apph = 8.4mm (0.33in) h = 10.7mm (0.42in) h= 13.2mm (0.52in)
14° 7% 170 6% 9/2% 20° 8% 11% 12% a SPD h = 13.2mm (0.52in) 18° 101/2% .
The decision as to which vortex generator system shouldbe fitted to the ships in the light of model tests is made difficult by the fact that it is not known by how much the axial velocity of the
flow into the propeller must be improved to eliminate vibration problems. As a result, there is a
strong tendency to err on the conservative side and choose a set of generators which give big improvements in the flow; improvements which may be greater than necessary to eliminate
vibration problems and which incur an unnecessarily large drag, power and fuel penalty.
Fortunately, a solution to this problem may be near at hand in thecomplex prediction technique
recently developed by the S.S.P.A. and Det Norske Veritaslu. This technique gives reasonable
estimates of the magnitude of the pressure fluctuations on thehull (and hence vibration) when a
propeller is operating in a fluid with a specified velocity distribution.
Based on the wind tunnel tests reported here, and without the benefit of the prediction
technique just mentioned, it is recommended that the four vortex generator system hi =
6.4mm (0.25in), h2 = 7.9mm (0.31in), a= 24° (model scale) is the most suitable. Both the size and location of these generators for the full scale ship are given in Fig. 26. The size was determined as 0.90 of the geometrically scaled size as recommended in section 4.1. The increase in delivered power for the Lysaght Endeavour fitted with these generators, allowing for the relative reduction
in size, was estimated to be reduced from 16% to 111/2%.
The two vortex generator systems were not considered suitable because they did not produce a sufficiently uniform velocity distribution, whereas the six vortex generator systems were eliminated because they absorbed too much power.
It is also recommended that the velocity distribution for the vortex generator system h, = 6.4mm (0.25in), h2= 7.9mm (0.31in) at a= 24° (model scale) be used in the S.S. P.A. Det Norske
Veritas pressure fluctuation prediction technique to determinethe likelihood of significant stern
vibration with these generators. If it is considered that there is an excessive safety margin then
another set, with a smaller power penalty such as hi = 7.9mm (0.3Iin), h2= 10.7mrn (0.42in) at a= 17° might be suitable. The converse is also true. If the program indicates that vibration might' be troublesome then it would not be worthwhile changing the vortex generators. The accuracy of the Det Norske Veritas prediction technique should also be tested by comparing the estimated
vibration characteristics for the Lysaght Endeavour, calculated using the velocity distributions
from the wind tunnel tests, with the trial results.
6. CONCLUSIONS.
From tests on a reflex model in a wind tunnel, a number of sets of vortex generators have been
developed which produce various improvements in the axial velocity of flow into the propeller,
combined with a range of power increments. It is considered that the generator system shown in
Fig. 26 is the most suitable alternative to those already fitted to the ships. These generators are expected to produce satisfactory vibration characteristics and will require an increase in delivered horsepower of approximately 12% compared with 16% for the existing generators on the Lysaght Endeavour, and 171/2% for the Lysaght Enterprise. Before fittingthe generators to the ship the
axial velocity distribution of the flow through the propeller, foundfrom model tests, should be
used in the S.S.P.A. Det. Norske Veritas prediction technique to check that vibration will be
acceptable.
ACKNOWLEDGEMENTS
The author wishes to thank those people who assisted with the project; in particular, Mr. R.
Campbell and Staff from the Australian Department of Transport
(Shipbuilding Division),Professor P.T. Fink from the University of New South Wales,
(Member of the AustralianShipbuilding Board), and Miss D.A. Lemaire from the Aeronautical Research Laboratories, for
their very helpful suggestions and comments during the project.
Matheson, N.
Lambourne, N.C.
. Hall, M.G.
Clements, R. E.
Johnsson, C.A. and Sontvedt, T.
REFERENCES
"Wind Tunnel Studies of a Ship Model using Vortex
Generators to Improve Wake Velocities". Department of
Supply, Australian Defence Scientific Service, Aeronautical Research Laboratories, Aerodynamics Note 347, April 1974.
"Supplementary Report on Flow Visualization and Wake
Survey Experiments Model Hull STA 1886 Model Propeller STA 663". Unpublished report for the Shipbuilding Division of the Australian Department of Transport; Vickers Limited Ship Model Experiment Tanks, Report RM STA 1886/7, 1974.
Supplementary Report on Resistance and Propulsion
Experiments Model Hull STA 1886 Model Propeller STA 663". Unpublished report for the Shipbuilding Division of the Australian Department of Transport; Vickers Limited Ship Model Experiment Tanks, Report RM STA 1886/4, 1974.
Supplementary Report on Resistance
and Propulsion
Experiments Model Hull STA 1886 Model Propeller STA 663". Unpublished report for the Shipbuilding Division of the Australian Department of Transport; Vickers Limited Ship Model Experiment Tanks, Report RM STA 1886/6, 1974.
Supplementary Report on Flow Visualization and Wake
Survey Experiments Model'Hull STA 1886 Model Propeller STA 663". Unpublished report for the Shipbuilding Division of the Australian Department of Transport; Vickers Limited Ship Model Experiment Tanks, Report RM STA 1886/8, 1974. "The Breakdown of Certain Types of Vortex". A.R.C., CP.
915, 1967.
"Vortex Breakdown". Annual Review of Fluid Mechanics, Vol. 4, 1972. Annual Reviews Inc., Palo Alto, California. "The Control of Flow Separation at the Stern of a Ship Model using Vortex Generators". Trans. R.I.N.A., Vol. 107, 1965. "Principles of Naval Architecture". Edited by J.P. Comstock, The Society of Naval Architects and Marine Engineers, New York, 1967.
"Propeller Excitation and Response of 230,000 TDW Tankers: Full Scale/ Model Experiments and Theoretical Calculations". Det Norske Veritas Publication No. 79, November 1972.
1.1 Axial velocity component ratios in the propeller plane of the model for the original'
and present tests, both without vortex generators and with the six vortex generator system hi = 12.7mm (0.50in), h2 h3 = 15.9mm (0.63in), a =25°, shown in Fig. 1.
1.1.1. Without vortex generators
21 0 (°) u/ U
r/R = 1.23
r/R = 0.96
r/R = 0.68
r/ R = 0.41 Original Results Current Results Original Results Current Results Original Results Current Results Original Results Current Results 0 0.17 0.15 0.12 0.13 0.12 0.12 0.11 0.10 10 0.28 0.27 0.23 0.21 0.19 0.19 0.14. 0.14 20 0.41 0.42 0.40 0.39 0.33 0.34 0.21 0.23 30 0.55 0.56 0.57 0.56 0.52 0.50 0.34033
50 0.75 0.77 0.79 0.80 0.79 0.78 0.61 0.60 70 0.88 0.90 0.90 0.90 0.90 0.90 0.84 0.82 90 0.93 0.94 0.93 0.94 0.93 0.94 0.91 0.90 110 0.94 0.95 0.94 0.94 0.93 0.94 0.92 0.93 130 0.95 0.95 0.94 0.94 0.94 0.94 0.93 0.93 150 0.96 0.95 0.95 0.94 0:93 0.94 0.92 0.94 170 0.95 0.95 0.94, 0.95 0.92 0.90 0.74 0.80 180 0.95 0.95 0.93 0.95 0.88 0.88 0.72 0.77 190 0.95 0.95 0.91 0.82 330 0.52 0.55 0.49 0.31 350 0.25 0.19 0.17 0.13APPENDIX 1 (Cont'd)
1.1.2 Six Vortex Generator System h1= 12.7mm (0.50in), h2 = h3 = 15.9mm (0.63in), a =
25°
22
u/ U
r/R = 1.23
r/ R = 0.96r/R = 0.68
r/ R = 0.410
(°) Original
Current Original Current Original Current Original Current
Results Results Results Results Results Results Results Results0 0.58 0.60 0.57 0.60 0.58 0.61 0.67 0.63 5 0.74
-
0.71-
0.69-
0.73 -10 0.82 0.81 0.86 0.87 0.83 0.83 0.82 0.80 20 0.78 0.74 0.88 0.86 0.88 0.87 0.89 0.88 30 0.73 0.70 0.87 0.85 0.88 0.88 0.90 0.91 50 0.77 0.77 0.90 0.89 0.90 0.91 0.91 0.91 70 0.87 0.88 0.92 0.92 0.92 0.92 0.91 0.92 90 0.92 0.93 0.92 0.93 0.92 0.92 0.91 0.92 110 0.93 0.94 0.93 0.94 0.92 0.93 0.92 0.92 130 0.94-
0.93-
0.92-
0.92 -150 0.95 0.95 0.94 0.95 0.93 0.94 0.92 0.92 170 - 0.95 0.95 0.93 0.94 0.93 0.93 0.80 0.79 180 0.95 0.95 0.94 0.94 0.90 0.93 0.71 0.70 190 0.95 0.95 0.94 0.94 0.92 0.93 0.74 0.77 250 0.94 0.94 0.92 , 0.93 0.92 0.92 0.89 0.90 290 0.89--
0.92-
0.91 0.86 . -330 0.76 0.74 0.86 0.85 0.88 0.89 0.86 0.90 350 0.83 0.82 0.86 0.86 0.82 0.84 0.81 0.811.2 Resistance coefficients for the original' and current tests of the model without vortex
generators and with six vortex generators hi = 12.7mm (0.50in), h2 = h3 = 15.9mm (0.63in), a = 25°.
23
Without Vortex Generators
Vortex Generators h, --= 12.7mm (0 :50in), h2 = hi = 15.9mm (0.63in), a = 25°
Original Current Original Current
Results Results Results Results
RNx10-6 Cpx103 RNx10-6 Cpx103 RNx10-6 C0x103 RNx 1 0-6 Cpx 103 7.33 3.64 8.13 3.60 7.89 4.55 8.34 4.52 8.04 3.58 9.00 3.57 8.60 4.49 9.06 4.46 8.95 3.56 9.82 3.52 9.66 4.43 9.89 4.40 9.55 3.52 10.52 3.48 10.26 4.40 10.81 4.37 10.40 3.48 11.82 3.45 11.05 4.35 11.94 4.30 11.64 3.45 12.34 4.28 8.54 3.56 8.08 4.55 9.26 3.54 8.93 4.45 9.95 3.51 9.75 4.42 11.00 3.47 10.48 4.37 12.10 3.43 11.42 4.32 12.64 4.26 ,
APPENDIX 2
Axial velocity component ratios in the propeller plane of the model fitted with six vortex generators hi = 10.7mm (0.42in), h2 = h3 = 13.2mm (0.52in), at a.= 18°.
24 0 (°) u/ U
r/R
r/ R r/ R. r/ R = 1.23 = 0.96 0.68 = 0.41 0 0.62 0.62 0.64 0.65 10 0.53 0.76 0.86 0.84' 20 0.63 0.74 0.85 0.88 30 0.67 0.75 0.86 0.88 50 0.75 0.81 0.89 0.88 70 0.87 0.91 0.92 0.89 90 0.93 0.92 0.92 0.91 130 0.95 0.93 0.93 0.92 170 0.95 0.94 0.91 0.77 180 0.95 0.94 0.92 0.73 270 0.94 0.93 0.92 0.92 310 0.76 0.80 0.87 0.87 330 0.68 0.74 0.86 0.85 350 0.54 0.75 0.84 0.833.1 Axial velocity component ratios in the propeller plane of the model fitted with four vortex generators /11 = 10.7mm (0.42in), h2 = 13.2mm (0.52in) at a= 18° and 16°.
25 0 (°) u/ U
r/R = 1.23
r/ R = 0.96 r / R = 0.68 r/R = 0.41a=
a=
a=
a=
a=
a=
a=
a =
18° 16° 18° 16° 18° 16° 18° 16° 1 0 0.44 0.29 0.55 0.54 0.60 0.60 0.62 0.60 10 0.48 0.35 0.75 0.70 0.87 0.86 0.84 0.85 20 0.50 0.45 0.73 0.71 0.86 0.87 0.91 0.91 30 0.59 0.64 0.71 0.74 0.87 0.87 0.91 0.92 50 0.59 0.62 0.64 0.64 0.89 0.75 0.90 0.92 70 0.69 0.70 0.71 0.71 0.88 0.89 0.91 0.92 90 0.93 0.93 0.92 0.93 0.92 0.92 0.92 0.92 110 0.95 0.94 0.94 0.94 0.93 0.93 0.93 0.93 130 0.95 0.95 0.94 0.94 0.93 0.92 0.93 0.93 150 0.95 0.95 0.95 0.94 0.93 0.93 0.92 0.92 170 0.95 0.95 0.95 0.94 0.90 0.89 0.63 0.64 180 0.95 0.95 0.95 0.95 0.92 0.90 0.60 0.59 290 0.70-
0.72-
0.88-
0.92 -310 0.68 0.68 0.66 0.65 0.83 0.70 0.91 0.91 330 0.41 0.35 0.60 0.61 0.84 0.62 0.90 0.90 340 0.37 0.34 0.68 0.67 0.86 0.68 0.89 0.90 350 0.44 ' 0.29 0.72 0.66 0.86 0.70 0.82 0.80APPENDIX 3 (Cont'd)
12
Axial velocity component ratios in the propeller plane of the model fitted with fourvortex generators hi = 10.7mm (0.42in), h2 = 13.2mm (0.52in), with the two port
generators set at a = 17° and the two starboard generators set at a = 15°.
26 0 (°) u/ U
r/R
= 1.23 r/ R=0.96
r/ R :).68 r/ R = 0.41 0 0.28 0.63 0.64 0.65 10 0.27 0.68 0.74 0.80 20 0.29 0.66 0.74 0.90 30 0.40 0.65 0.70 0.92 50 0.67 0.64 0.76 0.92 70 0.80 0.78 0.88 0.93 290 0.72 0.72 0.86 0.92 310 0.61 0.63 0.74 0.91 330 0.67 0.75 0.85 0.91 340 0.48 0.72 0.88 0.92 350 0.37 0.76 0.87 0.873.3 Axial velocity component ratios in the propeller plane of the model fitted with four vortex generators of various sizes and angles of incidence.
27 0 1°) u/ U
r/R = 1.23
r/R = 0.96
r/R =0.68
r/R = 0.41 hi =10.7mrn h1=8.4mm 111=10.7mm h1=8.4mm hi =10.7mm h1=8.4mm hi =10.7mm h1=8.4mm (0.42in) h2=13.2mm (0.33in) h2=10.7mm (0.42in) h2=13.2mm (0:33in) , h2=10.7mm (0.42in) h2=13.2mm (0.33in) h2=10.7mm (0.42in) h2=13.2mm (0.33in) h2=10.7mm(0.52in) (0.421n) (0.52in) (0.42in) (0.52in) (0.42in) (0.52in) (0.42in)
a= 13° a= 16° a= 13° a = 16° a= 13° a
=6°
a= 13° a=16° 0 0.09 0.11 0.18 0.30 0.44 0.53 0.54 0.57 10 0.15 0.16 0.40 0.47 0.68 0.76 0.69 0.75 20 0.26 0.36 0.60 0.58 0.82 0.79 0.90 0.84 30 0.55 0.55 0.71 0.66 - 0.87 0.82 0.93 0.90 50 0.73 0.60 0.74 0.64 0.86 0.85 0.93 0.92 70 0.79 0.78 0.79 0.82 Q.90 0.90 0.91 0.93 90 0.94 0.90 0.93 0.92 0.93 0.931. 0.92 0.93 290 0.80-
0.91 0.90-
0.90 -310 0.69 0.63 0.86 0.66 0.69 0.87 0.71 0.93 330 0.41 0.59 0.76 0.69 0.48 0.77 0.41 0.89 340 0.33 0.42 0.81 0.52 0.50 0.76 0.33 0.82 350 0.20 0.21 0.60 0.30 0.26 0.63 0.27 0.64APPENDIX 4
4.1 Axial velocity component ratios in the propeller plane of the model fitted with four-vortex generators hi = 7.9mm (0.3 tin), h2 = 10.7mm (0.42in), at a= 17°, 200 and 24°.
28 0 (0) u/ U
r/R = 1.23
r/ R = 0.96r/R = 0.68
r/R = 0.41a= a= a= a= a= a= a= a= a= a= a= a=
170 20° 24° 170 200 24° 17° 20° 24° 17° 20° 24° 0 0.21 0.36 0.49 0.34 0.48 0.50 0.38 0.44 0.47 0.39 0.45 0.49 10 0.32 0.56 0.66 0.53 0.72 0.72 0.50 0.63 0.62 0.44 0.58 0.61 20 0.45 0.59 0.62 0.74 0.76 0.78 0.74 0.80 0.82 0.62 0.77 0.80 30 0.56 0.62 0.63 0.71 0.76 0.78 0.84 0.88 0.86 0.77 0.88 0.88 50 0.72 0.67 0.65 0.83 0.86 0.87 0.90 0.90 0.91 0.91 0.91 0.93 70 0.82 0.85 0.80 0.92 0.93 0.93 0.92 0.92 0.93 0.93 0.93 0.92 90 0.91 0.90 0.91 0.93 0.93 0.93 0.93 0.93 0.93 0.93 0.92 0.93 310 0.73 0.70 0.66 0.85 0.85 0.84 0.88 0.89 0.90 0.90 0.90 0.91 330 0.67 0.66 0.64 0.71 0.72 0.76 0.84 0.86 0.87 0.82 0.87 0.88 340 0.56-
0.63 0.73-
0.76 0.77-
0.82 0.73-
0.79 350 0.38 0.53 0.67 0.61 0.72 0.76 0.58 0.65 0.68 0.55 0.61 0.644.2 Axial velocity component ratios in the propeller plane of the model fitted with four vortex generators hl = 6.4mm (0.25in), h2 = 7.9mm (0.31in), at a = 17°, 200 and 24°..
29 64 (0) u/ U
r/R = 1.23
r/R = 0 96
r/R = 0.68
r/R = 0.41a= a= a= a= a= a= a= a= a=
a= a=
a=
170 200 24° 170 20° 24° 17° 20° 24° 170 20° 24° 0 0.19 0.21 0.37 0.24 0.35 0.49 0.32 0.39 0.45 0.32 0.38 0.42 10 0.34 0.35 0.49 0.51 0.61 0.67 0.48 0.55 0.57 0.43 0.48 0.52 20 0.54 0.53 0.56 0.72 0.72 0.71 0.74 0.76 0.78 0.64 0.66 0.72 30 0.67 0.64 0.60 0.70 0.69 0.70 0.84 0.85 0.85 0.79 0.81 0.83 50 0.69 0.67 0.66 0.85 0.84 0.84 0.89 0.89 0.90 0.91 0.91 0.91 70 0.90 0.87 0.84 0.93 0.91 0.91 0.93 0.90 0.91 0.94 0.93 0.92 90 0.93 0.93 0.93 0.93 0.93 0.94 0.93 0.92 0.93 0.94 0.92 0.92 310 0.68-
0.65 0.82-
0.82 0.86 0.88 0.85-
0.89 330-
0.65 0.61-
0.67 0.67-
0.81 0.83-
0.77 0.81 340 0.51 0.52 0.56 0.62 0.70 0.69 0.65 0.72 0.76 0.51 0.67 0.70 350 0.36 0.34 0.47-
0.55 0.66-
0.51 0.57-
0.47 0.52APPENDIX 5
5.1 Axial velocity component ratios in the propeller plane of the model fitted with two
vortex generators h = 13.2mm (0.52in), at a= 14° and 200.
30 0 u/ U (0)
r/R = 1.23
r R = 0.96
r/R = 0.68
r/R = 0.41a =
a=
a="-a=
a=
a=
a=
a =
14° 20° 140 20° 140 20° 140 20° 0 0.13 0.25 0.18 0.30 0.24 0.33 0.27 0.37 10 0.26 0.47 0.34 0.51 0.35 0.52 0.33 0.50 20 0.58 0.79 0.70 0.83 0.66 0.79 0.55 0.76 30 0.78 0.69 0.86 0.85 0.82 0.87 0.73 0.87 50 0.63 0.56 0.79 0.73 0.91 0.91 0.91 0.91 70 0.79 0.69 0.89 0.83 0.89 0.92 0.91 0.91 90 0.93 0.94 0.93 0.93 0.92 0.92 0.91 0.92 310 0.63 0.56 0.77 0.72 0.90 0.90 0.89 0.90 330 0.76 0.78 0.83 0.87 0.78 0.84 0.71 0.83 340 0.54 0.77 0.63 0.78 0.61 0.74 0.55 0.72 350 0.26 - 0.41 0.34 0.45 0.37 0.47 0.37 0.485.2 Axial velocity component ratios in the propeller plane of the model fitted with two vortex generators h = 10.7mm (0.42in), at a= 17° and 200.
31 0 (0) u/ U
r R = 1.23
r R = 0.96
r R = 0.68
r/R = 0.41a=
a=
a=
a=
a=
a=
a=
a=
170 200 170 20° 170 20° 17° 20° 0 0.19 .0.24 0.27 0.29 0.29 0.32 0.31 0.33 10 0.35 0.50 0.40 0.50 0.39 0.48 0.37 0.46 20 0.68 0.74 0.75 0.80 0.69 0.75 0.60 0.70 30 0.70 0.65 0.84 0.83 0.83 0.86 0.77 0.83 50 0.57 0.54 0.78 0.76 0.91 0.91 0.91 0.91 70 0.82 0.80 0.91 0.92 0.92 0.92 0.93 0.93 90 0.93-
0.92-
0.92-
0.93 -290 0.83-
0.92-
0.92-
0.93 -310 0.57 0.56 0.73 0.72 0.89 0.89 0.87 0.88 330 0.71 0.71 0.82 0.82 0.77 0.79 0.70 0.73 340 0.63 0.68 0.-69 0.72 0.64 0.66 0.57 0.58 350 0.34 0.38 0.41 0.43 0.41 0.42 0.38 0.40APPENDIX 5 (Cont'd)
5.3 Axial velocity component ratios in the propeller plane of the model fitted with two
vortex generators h = 8.4mm (0.33in), at a= 17° and 20°.
32 0 (0) u/ U
r/R = 1.23
r/R =0.96
r/R =0.68
r/R = 0.41a=
a=
a=
a=
a=
a=-
a=
a=
17° 200 170 20° 17° 20° 170 20° 0 0.18 0.23 0.23 0.28 0.24 0.29 0.24 0.28 10 0.35 0.45 0.42 0.48 0.36 0.41 0.32 0.36 20 0.59 0.63 0.69 0.71 0.60 0.63 0.48 0.53 30 0.62 0.62 0.80 0.80 0.76 0.78 0.64 0.69 50 0.56 0.54 0.80 0.79 0.88 0.89 0.85 0.87 70 0.85 0.84 0.87 0.92 0.92 0.92 0.92 0.92 90 0.93 0.93 0.94 0.94 0.93 0.93 0.93 0.93 290-
0.83-
0.89 '-
0.91-
0.90 310 0.55 0.53 0.76 0.76 0.87 0.87 0.83 0.84 330 0.59 0.60 0.78 0.78 0.74 0.76 0.62 0.65 340 0.52 0.58 0.66 0.69 0.58 0.60 0.47 0.49 350 0.34 0.40 0.43 0.46 0.38 0.40 0.33 0.365.4 Axial velocity component ratios in the propeller plane of the model fitted with the two vortex generator system h = 13.2mm (0.52in), at a = 18°, formed by removing the first two generators from the four vortex generator system fitted to the Lysaght Enterprise.
33 0 (°) u/ U
r/R =
r/R =
r/R =
r/R =
1.23 0.96 0.68 0.41 0 0.15 0.25 0.32 0.38 10 0.29 0.43 0.45 0.47 20 0.67 0.83 0.81 0.76 30 0.74 0.83 0.88 0.87 50 0.62 0.63 0.90 0.93 70 0.75 0.80 0.90 0.91 90 0.95 0.94 0.93 0.91 270 0.95 0.94 0.92 0.92 290 0.74 0.79 0.91 0.92 310 0.62 0.61 0.88 0.91 330 0.74 0.84 0.87 0.85 340 0.60 0.77 0.75 0.74 350 0.32 0.43 0.48 0.53APPENDIX 6
6.1
Resistance coefficients for the model fitted with six vortex generators hi =
10.7mm (0.42in), h2 = h3 = 13.2mm (0.52in), at a = 18°.
6.2 Resistance coefficients for the model fitted with four vortex generators in the
positions shown in Fig. 3.
34 RN X 10 CD X 103 8.50 3.97 9.35 3:95 10.06 3.89 11.12 3.85 12.14 3.81
/11=10.7mm (0.42in), h2=13. 2mm (0.52in) h2=10.7mm (0.42in)hi =8.4mm (0.33in)
a = 13° (Endeavour)a = 15° (Enterprise)a = 18° a = 16° RNx 10 6 CDX 103 RArX 106 CDX103 RNX 10 6 CDX103 RNX 10 6 CDX103 8.34 3.67 8.52 3.80 8.46 3.85 8.35 3.71 9.34 3.64 9.48 3.75 9.34 3.81 9.16 3.64 10.10 3.59 10.03 3.70 10.10 3.75 9.90 3.61 10.86 3.54 10.89 3.67 11.00 170 10.83 3.59 12.11 3.52 12.23 3.60 12.23 3.68 11.96 3.52
positions shown in Fig. 14. 35 hi = 7.9mm (0.31in), h2 = 10.7mm (0.42in) a = 17° a = 20° a = 24° RNx10-6 Cbx103 Rivx10-6 Cpx163 RNx10-6 C x103 8.33 3.68 8.28 3.71 8.19 3.79 9.11 3.62 9.03 3.65 9.02 3.72 9.85 3.58 9.78 3.63 9.78 3.72 10.74 3.52 10.58 3.59 10.69 168 11.96 3.51 11.94 3.55 11.86 3.62 hi = 6.4mm (0.25in), h2 = 7.9mm (0.31in) _ a = 17° a = 20° a = 24° Rnix10-6 C0x103 RNx10-6 Cpx103 RNx10-6 Cbx103 8.09 3.63 8.13 3.68 8.10 3.74 8.85 3.58 9.04 3.62 8.90 3.69 9.58 3.56 9.61 3.60 9.66 3.65 10.58 3.52 10.60 3.57 10.74 3.63 11.58 3.48 11.70 3.52 11.78 3.57
6.4 Resistance coefficient for the model fitted with two vortex generators in the positions shown in Fig. 19. 36 h = 8.4mm (0.33in) a = 17° a = 20° RNx10-6 Cpx103 RNx10-6 ,Cox103 8.08 3.61 7.92 3.64 8.86 3.59 8.80 3.62 9.54 3.52 9.54 3.57 10.34 3.49 10.39 3.52 11.62 3.46 11.54 3.49 h = 10.7mm (0.42in) a = 17° a = 20° RNx10-6 Cox103 RNx10-6 C0x103 8.00 3.65 7.99 3.68 8.80 3.62 8.79 3.66 9.51 3.61 9.50 3.64 10.29 3.55 10.40 3.59 11.51 3.52 11.46 3.56 h = 13.2mm (0.52in) a = 17° a = 20° RNx10-6 Cpx103 RNx10-6 Cpx103 8.07 3.62 8.13 3.73 8.69 3.60 8.86 3.68 9.60 3.55 9.41 3.66 10.31 3.52 10.21
164
11.57 3.47 11.42 3.61four vortex generator system fitted to the Lysaght Enterprise shown in Fig. 3. 37 h = I3.2mm (0.52in), a = 18° RNx10-6 C0x103 8.36 3.73 9.19 3.70 9.97 3.64 10.79 3.60 12.03 3.54
92,7 mm (3,65 in) 4,45 m (14,60 ft) 39,6 mm (1,56 in) 190m (6,24 ft) 95
L.
121' 9 mm (4,80 in) I 5,86 m (19,20 ft)511
14ztel\IN(a) Vortex generator positions
69,1 mm (2,72 in) 3,32m
(1088 ft)
Position and size of the six vortex generator system for the model and ship, at an angle of incidence of 25° to the local surface streamlines on the model.
37,1 mm (1,46 in) 1,78 m
(5;84 ft)
Note:
1.;
Similar generators are fitted to opposite side of hull. (/)
= Girth measurement..
3.;
Underlined dimensions apply to the full scale ship.
4.
Generators fitted normal to hull surface at 2/3 of generator length aft of the forward tip.
Station No. 2 Station No. 1'/2 43 mm (1,7 in) 79 mm (3,1 in) 14,2 mm (0,56 in) 3,78 m (12,4 ft) 0,68 m (2,24 ft) 2,07 m (6,8 ft) (Along keel) (Along keel)
Kea tr.
Shape to surface curvature and attactrto hull
Forward edge of generator
Fig. 1. (cont.) (b) Vortex generator positions
. . -Generator No. h r 1 45,7 mm (1,80'in)1 ' 12,7 mm (050 in) 3,81 mm (0,150 in) 220 m (7 20 ft) ' ' 0 6,10 m (2.00 ft) ' 0 183 m (0L 60 ft)
.a.- ...
57,2 mm (2,25,in) 15,9 mm (0,63 in) " 4,45 mm (0,175, in) 2 2,74 m (9,00 ft) 0 763.m (2 50 ft) 0,214.m.(0,70 ft) 57,2 mm (2,25 in) 15,9 mm (0,63 in) 4,45 mm (0,175 in) 3 2,74 pi, (9,00 ft) 0,763 m (2,50 ft) ' 0 214 m (0,70 ft)1.0 0.8 0-6 u/L1 0.2 0-0
Axial velocity distributions of the flow in the propeller plane of the models tested in a wind tunnel and towing tank at full load draught with six vortex generators.
160 180 I I 1 I 1 I I I -I e .d11111111Pal awl:am o.. . .0"" I
/
/
/
/1
. ./
/
1
/
Bare hult Wind tunnel r/R = 1,23I
-/
12,7 mm(0.50 in), h2 = h3 = 15,9 mm (0.63 in), a = 25° h1 =/
h=
/
12, 7 mm,(0.50 in), h2 = h3 = 15,9 mm (0.63 in), a =25°_
1 ./
/
Towing tank r/R = 1,13 mm (0.42 in), h2 = h3 = 13,2 mm (0.52 in), a =18° -h1 = 10,7 -se e .'Note: Generator heights correspond to 2,7m
. (9 ft) .Lpp model 1 I I. I i 0 20 60' 40 80 100 120 140
10
0.804
0.200
1 I I 1 1 I 1..-
--/
/
/
/
./
/
/
/
I Wind Towing tunnel r/13 = 0,96 tank r/R = 0,93 Note: Generator 1 Bare hull h1 = 12,7 mm h1 = 12,7 mm hi = 10,7 mm to a 2,7 m (9 I a (0.50 in), h = h3 (0.50 in), h2 = h3= (0.42 in), h2 = h3 ft) Lpp model = 15,9 mm (0.63 15,9 mm (0.63 = 13,2 mm (0:52 a in), a= 25° in), a = 25° in), a = 18°/
/
/
/
/
-heights correspond a a/
/
/
I I 0 20 40 60 80 100 120 140 160 0 FIG 2 (Continued) 0.6 u/U1 - 0 0.8
0.6
u/U 0.4 0.200
20 ,40 FIG 2 (Continued) 0....
mi. ....----No em..m...''.. -7:41°.. ... .... --...---... n.'"....---/
/
/
1/
/
,/
/
/
/
/
Bare hull/
Wind tunnel r/R = 0,68 1 h= 12,7 mm (0.50 in), h= h = 15,9 mm (0.63 in), a = 25°/
1 2/
1 h1 = 1,2,7 mm (0.50 in), h2 = h = 15,9 mm (0.63 in), a = 25°/
Towing tank r/R = 0,73/
h1 =10,7 mm (0.42 in), h2 = h3 = 13,2 mm (0.52 in), a = 1 8°/
/
..-,
Note: Generator heights correspond to a 2,7 m (9 ft) Lpp model
. 1 I I I i I I i I I 1 , .... 100 120. 140 80 60
!["Un papiro aramaico da El Hibeh del Museo Archeologico di Firenze", Edda Bresciani, "Aegyptus", 39, 1959, fasc. 1-2 : [recenzja]](data:image/gif;base64,R0lGODlhAQABAIAAAP///wAAACH5BAEAAAAALAAAAAABAAEAAAICRAEAOw==)