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Washlnqton,D.C. 20007PROGRESS IN FRICTIONAL DRAG REDUCTION SUM1ER 1968 TO SUMNER 1969
by
Paul S. Granville
Drag-Reduction Monitor for Ordnance Systems Hydroballistics Advisory Committee (ORDHAC)
This document has been approved for public release and sale; its distribution is unlimited.
August 1969 Hydromechanics Laboratory Technical Note 143
Lab. v. Scheepsbouwkunde
Tcchniche Hogeschool
PROGRESS IN FRICTIONAL DRAG REDUCTION SUMMER 1968 TO SUMMER 1969
'by
Paul S. Granville
Drag-Reduction Monitor for Ordnance Systems Hydroballistics Advisory Committee (ORDHAC)
This document has been approved for public release and sale; its distribution is unlimited.
August 1969
Hydrouiechanics Laboratory Technical Note 143
LIST OF MEtERS OF SUBCOVUVIITTEE ON DRAG RUCTION
P. S. Granville, Naval Ship R & D Center, Carderock-Chairman and Drag Reduction Monitor
A. G. Fa1ula, Naval Undersea R & D Cent-er., Pasadena J. W. Hoyt, Naval Undersea R & D Center, Pasadena )4
R. H. Nadolink, Naval Underwater Weapons R & E Station Newport
PROGRESS IN FRICTIONAL DRAG REDUCTION
A most notable event in the field of drag reduction for the period of sumier
1968
to suinnier 196.9 was the Symposium on ViscousDrag Reduction held in Dallas September 21 and 25,
1968;
the pro-ceedings of which are published by Plenum Press, New York.The great variety of papers presented underscores the significant fact that there is no unanimity of opinion concerning various aspects of drag reduction, particularly the basic mechanism.
This should not be. surprising since turbulent flow in general has no adequate basic theory. Turbulent flow is essentially a macro-scale phenomenon whose complexity is still discernable on our scale while laminar flow is a micro-scale phenomenon whose complexity is not evident on our scale. Even though there is intensive activity in the molecular motions, laminar flow appears well ordered in our scale and can be treated on the basis of
continuum
mechanics;the principal assumption being that the shear. stress is a function of rate of strain.
The
contri-bution of continuum mechanics to turbulent flow for ordinary fluids is only that continuum mecianics, that is laminar flow, holds in the micro-scale. The result is the
coefficient of viscosity as a cor-relating parameter, Reynolds number, and the averaging Reynolds equations of motion for turbulent flow.
For predicting drag additional relations are required between the velocity profile and the wall shear stess, the so called simil-arity laws (or its equivalent, relations for the eddy viscosity). For polymer solutions exhibiting drag reduction there is the addition-al complication of viscoelasticity which is a micro-scaddition-ale phenomenon amenable to analysis by continuum mechanics. A. White
(P-63)
demon-strates that elasticeffects seem to be divorced from Toms drag-reducing effects.
A direct technique to distinguish the two is to study the flow past large
roughnesses (fully-developed roughness flow). Elastic effects produce drag reduction while Toms.effects produce
none. An interesting observation by A. White is that
solutions exhibiting elastic effects show no Toms effects at all in the drag reduction, that is there is no diameter effect and no onset
effect which are characteristic of the Toms effect. An additional observation is that the friction line of the soap solutions is close to the maximum friction line for the Toxns effect.
From the point of view of predicting drag the analysis of the Toms effect proceeds from the assumption that an additional parameter length, time or mass, is involved. Virk and Merrill
(P-58)
demon-strate that it is the length scale of the radius of gyration of the polymer molecule. Seyer and Metzner (P_149) assert it is a relaxation time obtained from normal-stress measurements (elastic effects).
Another attack on the mechanism is through the study of the structure of the wall turbulence since it is observed that the Toms
effect thickens the. laminar sublayer. Black (P-la) presents an analy-tical study of wall turbulence to explain the thickening of the laminar sublayer through increased stability by the action ofthe polymer molecules in either inhibiting vortex stretching (an elastic effect) or reducing the intensity of turbulence in the sublayer.
What is needed in terms of an adequate theory for the Toms effect is one that indicates the optimum configuration of molecular structure or one that leads to passive technique. It is still prohibitive to keep discharging large quantities of polymers for any sustained oper-ation in external use.
Hydrodynamic studies are now advancing from those for uniform concentrations to those involving non-uniform concentrations arising from injections of polymer solutions into existing boundary layers.
P-l8,
P_21, and P-62 are efforts in this direction. P-2 deals with analytical problems of stage 4 where the concentration profile coincideswith the velocity profile. Additional experimental data is needed for the preceeding stages which involve more complicated mass diffusions.
An interesting experiment was polymer ejection tests on a Briti5h ship, the coastal minesweeper HMS HIGEBURTON, which had widespread publicity through Time magazine (p_1). A frictional drag reduction of 22% on an average, 36% maximum, is reported. for a speed of 9 knots
even though the ejection system was considered not too good.
Another interesting aspect of drag reduction concerns cheating in boat races. The Olympic Committee had a representative from the University of Sol4thampton checking the water for drag reduction at last year's Olympic games ii Mexico City.
An infomative swiimary of the physcial and chemical properties of water-soluble polymers is given in P-15. Background material on the most-popular drag-reducing polymers is presented in convenient form.
More specific details for polyox are given in P-3 and P-54.
The Russian viewpoint on drag reduction is presented in P.4. The hypothesis is proposed that the polymer molecules immobilize part of the solvent to form rigid aggregates. Distinction is made between the effects on turbulence close to the wall and in jet flows.
It is maintained that the aggregates stabilize laminar vortices in the transitional sublayer so that the laminar sublayer is thickened and
the wall shear stress is decreased. The effect of the aggregates on the inertial vortices in jet flow is opposite: the intensity of the inertial vortices is incresed.
The reduction of turbulent skin friction by compliant surfaces seems to have reached an uncertain stage. Blick, the principal
promoter, still reports reductions up to 38% in 0-3. On the other hand Lissaman and Harris in P-1 report an indifferent 10% for similar
b) H. L. H. J. J. P. R. F. Dove ) S. Canham) Catchpole Long
To eject continuously a solution of polyox in salt water into the ships boundary layer and to measure the consequent reductions of thrust, shp (shaft horse power) etc.
An average reduction of shp amounted to about 12 per cent, at 9 Knots. The maximum value was
19
per cent. These results cor-respond to frictional reductions of 22 and36
percent respectively. Much better results could be achieved by modifications to tech-nique as revealed by the trial.An unrestricted, detailed report is in preparation.
ARIZONA STATE UNIVSITY, DEPARTMENT OF CHEMICAL ENGINEING, TEMPE, ARIZONA 85281
Large Disturbances in Pipe Flow of Dilute Polymer Solutions Neil S. Berman
A Laser Doppler Velocimeter is used to measure the fluctuations at points in a pipe downstream of a disturbance. The decay or amplification of the disturbance is measured as a function of
frequency and amplitude. Both pure water and several polymer solutions in concentrations of 5 to 20 ppm are used in the study.
Laminar flow measurements have been made on pure water and a 20 ppm Separan
AP-30
solution. A sleeve oscillation inside the pipe was used to create the disturbance. The laminar velocity profile was blunt and not parabolic for the polymer solution.Numbers refer to bibliography.
Admiralt,y Experiment Works
Admiralty Materials Laboratory
6
LABORATORY SUMMARY OF DRAG REDUCTION RESEARCH
1969
Title of Project
Principal Investigator Description of Project Results
Public at ions *
ADMIRALTY E)ERIMENT WORKS, }IASLAR, ENGLAND
a) Trials on HMS HIGHBIJRTON. Effect of the ejection of Polyox into the boundary layer.
Oscillations in the frequency range from 0.25 to, l.P Hz had ampli-tudes approximately one-third of those for pure water. Other measure-ments have been made at higher Reynolds numbers.
e) P.- 9
N. S. Berman and V. A. Santos, "Laminar Velocity Profiles in Devel-oping Flows Using a Laser Doppler Technique, A.I.Ch.E. Journal 15
323 (1969)
W. A. Hanson, D. F. Jankowski, and N. S. Berman, "An Investigation of Finite Disturbances in Hagan-Poeseuille Flow Using a Laser-Dop-pler Velocimeter." Paper presented at A.I.Ch.E. free forum, Los Angeles, December
1968.
N. S. Berman and J. Bac, "Laser Doppler Measurements of the Decay of a Finite Disturbance in Laminar Pipe Flow of a Dilute Polymer Solution." Paper presented at ACS Northwest regional
meeting, Salt Lake City, June
1969.
CALIFORNIA INSTITUE OF TECHNOLOGY, DIVISION OF ENGINEERING AND APPLI SCIENCE, PASADENA, CALIFORNIA
91109
a) Heat Transfer and Friction of Dilute Polymer Solutions
b). A. J. Acosta, R. H. Sabersky
Heat transfer and drag measurements have been made on small wires approximately .001 inch to .005 inch diameter in dilute solutions of "Poly-Ox." The maximum Reynolds number was about 50, so the flow regimes were always laminar The experiments were carried out in small towing tank and a small rotating test basin.
An apparatus for the simultaneous measurement of heat transfer and friction in smooth and rough tubes in turbulent flow has just been completed. It is modelled on Hoyt's apparatus but is considerably larger to accommodate existing electrically heated heat transfer tubes. Research with this apparatus will commence this summer.
Significant alteration of the normal drag coefficient and heat
transfer coefficient were found in laminar flow for the small wires. Under some conditions of wire size and polymer concentration both of these coefficients were found to become independent of Reynolds number. Under tbese conditions the heat transfer and drag were found to be correlated w'ith the parameter D2'I'/', D being the wire diameter, 't a calculated relaxation time, and' the solution viscosity. Visual observations of the flog around the cylinder and of the flow issuing from small jets convince one that these effects are truly fluid mechanical and are not due to superficial coating of polymer.
"Laminar Flow about Circular Crlinders," D. F. James and A. J. Acosta, in manuscript form for publication.
UNIVERSITY OF DELAWARE, DEPARTMENT OF CHEMICAL ENGINEERING, NEWARK, DELAWARE
19711
A. B. Metzner
1. Measurement of the viscoelastic properties of very dilute polymer solutions (near the threshold concentration at which drag
reduc-tions first begins.).
-2. Development of drag-reducing fluids which do not possess the
usual adverse decrease in efficacy with increasing scale of the. system.
1. Viscoelastic continuum properties have been calculated from
experimental measurements of the extensional and shear viscos-ities of the fluids used. The ratio of these two quantities, which is equal to three for Newtonian fluids, increases with increasing viscoelasticity of the fluid. The material used was a degraded polyacrylainide solution for which the threshold concentration at which drag-reduction begins in small pipes is about T5 p.p.m. Measurements of this above-mentioned viscosity ratio were made at concentrations of 25, 50, 100,
860,
1,000 and 3,000 p.p.m. The measured viscosity ratios found were 3.0 at the two lowest (non th'ag-reducing)'concentrations, and approx. 10,000 at 100 p.p.m. The relevance of these to the drag-reduc-tion problem is considered in the publicadrag-reduc-tion listed below.2. Work on more efficient fluids for large systems has only begun but a suite of potentially interesting compositions has been identified.
P - 149
GENERAL ELECTRIC COMPANY, RESEARCH AND DEVELOPMENT CENTER, SCHENECTADY, NEW YORK 12301
Basic Investigations
P. N. Shankar, W. B. Giles
Transition experiments and laser velocity profile measurements using a Doppler shift technique are being conducted in the 1
i/14
in. dia. facility.Delayed transition is observed with guar gum while earlier transition occurs with, polyethylene oxide, small pipes show transition but not turbulence. The accuracy of the laser is approximately ±1% and data is obtainable within 5 mils of the wall.
THE UNIVERSITY OF IOWA, INSTITUTE OF HYDRAULIC RESEARCH, IOWA CITY, IOWA
522140
Ship Hydroynamics Louis Landweber
Effect of Guar-Gum on turbulent flow in pipes and boundary layers for concentrations 50 wppxn
1. In pipe flow there is practically no influence on velocity-defect
law.
2.. With variation in concentration a family of parallel lines of
the logarithmic part of the inner law is obtained with the von-Kruin number remaining C = 2.50. Thus'the surface-drag reduction is due to the thickening Of the laminar sublayer.
3. Effect of Guar Gum on flat-plate boundary layer was predicted
by assuming that the inner-law variation is the same as for the pipe flow and that the outer law is unaffected by the pres--ence of the additive.. It was found that, for concentration of 50 ppm, the value of H is increased or decreased by the Guar Gum according as is greater or less than.
560.
At a ReynoldsCL
number of R.13' and the same concentration (50 ppm), the drag
coefficient was CD = 0.003, in comparison with the value CD = 0.0014.
without the additive.
e) P 28
UNIVERSITY COLLEGE LONDON, DEPARTMENT OF CHEMICAL ENGINEERING, LOID0N WCI, ENGLAND
1. a) Heat fransfer in dilute polymer solutions
Dr. D. A. White
A feasible study on the general effect of polymers in such systems.
Polymers do not have a beneficial effect or heat exchanger performance and research into this field has relevance to heat transfer problems in non-Newtonian Fluids rather than being of irmnediate practical importance.
P-
6,
P-66
2. a) Flow of dilute polymer solutions over flat plates
Dr. D. A. White
& d) Development of simple design method for predicting drag reduction on flat plates and hulls of Ships.
e)
P-6
3. a) Experimental investigations of veloc:ity profiles in pipe
flow of gel and polymer solutions Dr. D. A. White, J. A. Bond
Investigation of maximum drag asymptote exhibited by these solutions
14. Work is also under way on Couette Flow of dilute polymer solutions
including velocity profile measurements and development of low degradation rate pipe viscometer.
LTV RESEARCH CENTER, DALLAS, TEXAS 75222 Study of Drag-Reducing Additives C. S. Well, Jr.
Basic: study of turbulence structure, roughness effects, diffusion, normal stress effects, correlation of friction and flow properties, wail pressure fluctuations.
Applied: prediction of drag reduction in external flow, devel-opment of coatings.
1) Several additive solutions which are drag-reducing show eve-dence of normal stresses in a thrust-measuring apparatus.
2 Effects of roughness in turbulent shear flow of a drag
re-ducing fluid are consistent with the concept of a thickened sublayer.
3) Experiments show a systematic effect of pipe. diameter below a critical value which diminishes the degree of drag re-duction. This has been correlated with the drag reduction properties of various fluids.
) Wall pressure fluctuations are reduced at relatively high
frequencies and increased at low frequencies for relatively high concentrations of additives. The wide-band signal is changed very little.
e)
P-53, P-6o, p-6i,
-6
McMASTER LJNIVRSITY, DEPARTIVrENT OF MECHANICAL ENGINEERING, HAMILTON,
ONTARIO, CAI'TADA
1. a) Investigation of rnethods for the control of liquid boundary
layers. B. Latto
Measurement of the total and viscous drag on a flat plate in homogeneous and injected dilute polymer solution flows. Also, investigation of methods to control the transition
and separation of liquid boundary layers.
Drag and turbulence measurements in both homogeneous and injected flows have been made. Some conclusions to the effect of injection velocity and initial concentration have been presented.
Three papers have been submitted for publication on the effects of dilute polymer flows on external boundary layer phenomena.
P- 50, P=38
2. a,) Drag ar'id Drag Coefficients of Sphere Trains
in Tubes 0. F. Round
Measurement of pressure drop due to spheres of diffeient diameters in different diameter tubes. Drag coefficients are related to diameter ratio, fluid, spacing of train, sphere-sphere interaction. A later extension of the study will report the use of boundary lager additives to reduce drag.
3. a) The influence on hydrodynamic drag of high molecular
weight compounds in the turbulent bounary layer.
J. H. T. Wade
A rotating disk apparatus was used to meaSure drag reduction as a fnction of concentration (0 - 100 ppm) for three polyacrylamides and two guar gums. Some degi'ading tests were also carried out.
Drag reductiob.s on a circular disk were Obtained using torque measurements for a number of aqueous solutions
of high molecular weight compounds Degrading experiments allowed the extrapolation of the drag results tO zero
shear time. Polyacrylamides MRL-159 and MRL-295 offer about 35% drag reduction and 30 ppm when he necessary corrections have been applied.
P-5l
. a) Measurement of diffusivity in the fully
developed turbulent flow of a dilute polymer solution.
J. H. T. Wade,
A closed loop has been eSigned with a simple pipe flow test section to measure the diffusivity in iully developed turbulent flow. A saline solution injected on the center iThé with concentätion curves to be measured dotnstream will assist in xperimentally de-termining the diffusivity.
5. a) nvestigatio.n of the relaxation times of dilute
polymer solutions. J. H. T. Wade
A vibrating plate apparatus is designed to measure optically the wave attenuations and, hence, the relaxation time of dilute polymer solutions.
THE UNIVERSIT.Y OF MICHIGAN - COLLEGE OF ENGINEERING, DEPARTNT OF ENGINEERING MECiANICS, ANN ARBOR, MICHIGAN
Effect of Polymer Additives on Flow Stability W. P. Graebel
c) Experimental and theoretical studies on. (i) stability of Couette flow between counter rotating cylinders, and also (2) pipe flow. (3) Measurements of turbulence intenSities n the pipe flow of Polyox solutions usiri
a laser flowrneter.
d) (1) Experithental work shows a strong influence on sition to turbulence, and lesser one on laminar
tran-sition. Theoretical studies Still in progress. (2)
Theoretical work in progress. (3) Apparatus.
devel-oped and teSts in progress.
UNIVERSITY OF MINNESOTA, ST. ANTHONY FALLS ffYDRAULIC LABORATORY, MINNEAPOLIS, MINNESOTA 551ii14
1. a) Influence of Drag Reducing Polymer on Surface Pressure Fluctuation
J. M. Killen and J.' Alma
Measurements are being made of drag and surface pressure fluctuation spectrum on the boundary of a cylinder rotating axially in a large tank as. influedced by the addition of various iolymers to the test water. Both smooth and rourh surfaces are used.
Little influence of drag reducing polymer is apparent on the high, frequency part of the surface pressure fluctuation spectra. The 16w frequency part correlates well with
surface shear and is reduced with the addition of polymer for smooth surfaces. Polyox WSR-301 has been found to redue drag. on a su±-face with 0.3 i glass heads bt requires higher concentration as the roughness increases .Detäilsof pressure fluctuation measurements are incomplete.
P-32
2. a) Injection of Polymer Additives into eJLatively Large Scale Boundary Larers
b) J.. M,. Wetzer and J F. Ripken
.c) Concentrated solutions of Polyox WSR-301 are being injected tangentially into the developing turbulent boundary layer of a large flowing stream. Concentration and velocity profiles are being measured fOr various injection rates and distance,s froth the slot.
d) Concentration and velocity profiles 'have been obtained at longitudinal distances of
16,28,
and IQ ft. from the injection slot at ReynoldS numbers, based on the dis-tance from the slot, up to about 7 x 107. Concentration profiles have been dimensionally correlated ith suitableparameters., Limited theasurements were made of the avePage and fluctuating wall shear components using a flush
mounted hot film probe..
e) P-62
UNIVSITY OF MISSOtJRI-ROLLA, DEPARTMENT OF CHEMICAL ENGINEER-ING, ROLLA, MISSOURI 6:5Iol
1. a) Turbulence Measurements in Polymer Solutions J. L. Zakin and G. K. Patterson
Hot-film and wire anemometer measurements of the fluctuating longitudinal velocities were measured at radial locations from pipe axis to na of 0.75 for solvents and polymer solutions at various levels of drag reduction. Comparisons of various type probes have been made. Hot-film probe frequency response characteristics have been measured for viscoelastjc fluids.
Turbulence intensities were higher than for normal fluids at both high and low Reynolds numbers with
slightly low intensities in an intermediate Reynolds number region. The degradation level of the dis-solved polymer strongly influenced its turbulence behavior. Little difference was fOund in energy spectra for polymer solutions and solvents. Cone and wedge film probes were found to behave similarly, but cylindrical film probesrneasired high inten-sities at high flO rates (not caused by eddy shed ding). No response attenuation was observed on the range studied (10-100 cps).
P-47
J. M. Rodriquez, G. K. Patterson, and J. L. Zakin, "Effects of Probe Geometry on Turbulence Measure-ments in Liquids Using Hot-Film Anemometry", sub-mitted to J. Hydronautics.
J. M. Rodriquez, J. L. Zakin,, and G. K. Patterson, "Response of Hot-Film Wedge Probes in Viscoelastic Fluids", to be presented at Symposium on Turbulence Measurements ih Liquids, University of Missouri
-Rolla, Sept. 1969.
2. a) Effect of Molecular Structure on D'ag Reducing
Characteristics of High Polymers J. L. Zakin
Polymer additives of various molecular structures were studied in capillary tube and pipe flow
exper-iments in hydrocarbon solvents to determine how
structure affects the drag ieducing capacity of these additives.
Based on critical pervaded volume fractions for the start of "concentrated" solution drag reduction be-havior, the effectiveness of the polymer additive
was observed to be. dependent on molecular flexibility, provided the polymer satisfied a minumum molecular weight criterion. "Dilute" and "concentrated" polymer solution correlations were obtained.
e) G. C. Liaw, J. L. Zakin, and G. K. Patterson, "The Effects of Molecular Characteristics of Polymers on Drag Reduction", submitted to A.I.Ch.E.J.
P-I
NAVAL POSTGRADUATE SCHOOL, DEPARTMENT OF MECHANICAL ENGINEER-ING, MONTEREY, CALIFORNIA 9394O
a) Resistance to the. Flow of Dilute Aqueous Polymer
Solutions
b) Dr. Turgut Sarpkaya
c) The purpose of the investigation was to acquire an
understanding of the phenomenon of polymerturbulence. interaction through the study of the resistance to the flow of dilute aqueous polymer soliitions under various types of closely related nd specifically designed flow conditions.
d) The first six months of the investigation was devoted (a) to the design and construction of a water tunnel and (b) to a theoretical investigation of the be-hav±or of a second-order fluid and its applicability as a model to the prediotion of the ciaracteristics of dilute polymer solutions.
The water tunnel has been designed and constructed spcificaily for the purpose of studying the char-acteristics of separated tuibulent flow about bluff bodies. The 50 H pump has a very low r.p.m. (300) so as to minimize the effect of pump on the quality and degradation of the polymer The tunnel has a
working section of 8 by iii. inches. Full scale
ex-periments are expected to tart in July, 1969, usIig Dextran and Polyox WSR-301 as the working polymers. The first phase of the theoretical aspects of the.
investegation has been completed In summary, it has been found that:
the viscoelasticity incieases the shear stress at the wall and causes oscillations in the velocity Profile;
as the Weissenberg number increases, the maximum value of the overshoot in the velocity profile increases and the damping of the oscillations decreases;
the consti,tut'ive equation desOribing the behavior of the viscoelastic-fluid mOdel is not valid for
Weissenberg numbers larger than 0.33; and that the boundary layer thickness for stagnation
point flow rapidly increases as the critical Weis-senberg number is approached.
NAVAL RESEARCH LABORATORY, SURFACE CHISThY BRAIWH, WASH-INGTON, D. C. 20390
Drag Reduction Studies in Aqueous and Nonaqueous Solvents
R.. C. Little, R. J. Hansen and P. Peyser.
Experimental investigations are being made of the drag-reducing ability of polymers and association colloids in aqueous and nonaqueous. environments. Association colloids in concentrations are low as 0.01% in toluene yield drag reductions of over 70% up to the experimental Reynolds number limit of 12,000 in a capillary tube. Monomeric units of these materials associate to form long chain polymer-like structures by association rather than by chemical bonds. Should the drag reducing species be fragmented upon passing through a region of intense shear the original species will be regenerated by re-association of the fragments under less intense conditions.
Dilute solutions of high molecular weight polymers show structural turbulence in laminar flows through small tubes. The onset of structural turbulence is Characterized by a wall shear stress somewhat greater than that observed for the onset of drag reduction
in larger tubes. The fact that the structural tur-bulence flow regime persists to Reynolds numbers
well above R (with a consequent drag reducing effect) suggests some similarity between polymer behavior during structural turbulence and in the viscous
sublayer during normal drag reduction at high Reynolds numbers in larger tubes.
Little,R. C., "A Note on the Flow Properties of Polyox Solutions", to be published in the August issue of I and EC Fundamentals.
Little, R. C., "Displacement of Aqueous Drag-Reducing Polymer Solutions", to be published in the August issue of I and EC Fundamentals.
NAVAL SHIP R & D CENTER, HYDROMECHANICS LABORATORY, WASHINGTON, D. C. 20007
Effects of High Polymers on Hydrofoils J. H. Wolff and R. Cahn
strut system were performed at the Langley High
Speed Basin. The foil system load characteristics were determined with and without air venting. Polymer
solutions of Poly(ethyleneoxide) of 1, 3, 9, 18, and 27 parts per million by weight were etablished in the tank and the foil load characteristics were determined at each polymer concetration.
d) Differences in lift and drag performance between the tests with and without polymer were found. Tests with polymer solutions of 18 and 27 ppmw concentration
showed strut drag reductions of approximately 145%.
Following the experiments, the effects of the polymer in the basin were completely dissipated by dissolving
500 pounds of swimming pool disinfectant (calcium hypoci-ilorite) in the
5.6 x
io6
gallon tank facility.Tests with the strut before and after application of calcium hypochiorite showed a return to clear water test results.
NAVAL UNDERSEA R & D CENTER, PASADENA, CALIFORNIA 91107
a) Polymer supply rates for Friction Reduction in High-Shear Flows
'c) Andrew G. Fábula
A combined analytical and experimental study of poly-meric additive supply rates for friction reduction
in high shear flows is underway. The object is the prediction of friction reduction and additive supply requirements in external flows on the basis of pipe
flow experiments and boundary layer theory.
In recent work, the far-domstream scaling laws of dilution of a passive scalar injected into a
two-dimensional, constant-pressure turbulent boundary layer on a flat plate were treated. The intermit-tency of turbulence and scalar concentration, as well as the effects of friction-reducing polymer on the boundary-layer mean velocity profile, were considered. The "negative roughness" analogy of.polymeric friction reduction was invoked to justify the assumption that all sig±iificant properties of the outer layer (i.e., outside the viscous layer) satisfy the Newtonian-fluid outer layer similarity laws, including those for velocity-defect, intermittency and normalized mean concentration profile. (The assumption is ex-pected to be valid in cases of low polymer concen-tration and moderate wall shear stresses.) Thus the polymer is treated like a passive scalar in the outer layer. A notable feature of the predicted dilution scaling law for the mean concentration near the wall
(cw) is that cl.3 ct, where
is the turbulent-fluid volume-flwc average concentration in theboundary layer.
A comparison with preliminary experimental results suggests that the dilution scaling-law predictions of the negative-roughness analpy are useful.
e) P-l7, P-i8
2. a) Elongational Flows of Friction-Reducing Fluids Andrew G. Fabula
Greater understanding of the basic mechanism of the Toms effect is the aim of this work. The approach taken is to study the rheological properties of friction-reducing fluids in elongational flows.
In recent work, emphasis has shifted from experimental studies (e.g., "Indian-rope" and orifice flow)
to related analytical investigations
in continuum mechanics. Various well-known vis-coelastic-fluid equations of state have been compared by considering their responses to extensional flow with a step-function history of principal strain rates. This type of flow can be. called "start-ex-tension" flow.
A seemingly significant finding concerns those models which show a critical extensional strain rate. In such cases, as is well known, no valid solutiOn for extensional viscosity exists for steady-state
ex-tension at or above the critical strain rate. This behavior has been taken to be an obvious deficiency of such fluid models. However, the new work shows that such models yield valid solutions for all finite
strain rates and all finite times in start-extension
flow. Thus, since only finite times are of interest in the real world, the behavior of such fluids for critical or supercritical strain rates is of interest and possibly has some conterparts in the physical world. Indian-rope flow seems to be such a case..
For supercritical extensional strain rates, such fluid models imply very high extensional viscosities. It
seems to be a reasonable conjecture that such models may be capable Of providing a continuum-mechanical in
terpretation of Toms effect. Such models so far seem to be restricted to two principal types: the Oldroyd stress-relaxation type and the Lodge network type. It
is notable that such models do not show. any critical behavior in simple shear flow, which is consistent with the known viscometric and optical properties of friction-reducing solutions.
3. a) Scale Effects of Macromolecules on Cavitation
J. G. Waugh (NUC, Pasadena) and A. T. Ellis (UCSD) A cooperative NUC-UCSD (University of California, San Diego) program has been established to study theoretically and experimenta1l the scale effects of macromoleaules on cavitation. Experiments were carried out in the Blow-Down Water Tunnel at UCSD to study the effect Of dilute aqueous polymer sol-utions on flow-generated cavitation inception. These included Polyox WSR=301 (20, 32, 50, and 100 ppm), guar gum J2FP (300 ppm), and Porphyridium aerugineum algae exudate (concentration unknown). Tests were made using l/ and 1/2-inch diameter cylindrical models with hemisphere noses.
Cavitation nception was inhibited at Reynolds numbers from 1 x l0' to 3 x and a maximum reduction of the incipient cavitation number to 50% of its value for
tap water was observed. Flow visualization was
obtained by optical techniques which were also used to measure fluid velocities, thereby providing a check
on values obtained from the venturi pressure drops. Possible mechanisms to explain cavitation inhibition are being investigated, and further studies will be conducted in the Blow-Down Water Tunnel. Tests will be made at higher Reynolds numbers to ensure fully turbulent flow, aM other model configurations will be considered.
a) Flow Noise - Pipe Flow Studies
J. M. Caraher
Instalation of the 4-inch pipe flow facility has been completed. This blowdown facility will be used with both plain water and polymer solutions to study the effects on bounary layer pressure fluctuations. Manufacture of piezo-electric transducers for measuring wall pres-sure fluctuations has been completed and the trans-ducers have undergone a prelimiiiary calibration.
Sound damping material has been applied to the pipe and isolating washers have been installed to reduce the structure-borne noise reaching the hydrophones. Design has been started on a transducer with several sensing crystals for obtaining longitudinal cross
correlation of the boundary layer pressure fluctuations. A computer program for digital analysis of these data has been prepared that will give auto and cross cor-relation and power spectral density functions.
A number of runs have been made with water, and wall pressure fluctuations and pipe pressure losses were
measured. Experience has been gained in using the Robertshaw pneumatic flow control system on the water tunnel and constant velocity runs at low flow rates can be made consistently. Careful calibrations
show, however, that the venturi in the pipe does not give accurate values of average flow velocity. A new method is being sought for determining that par-ameter with sufficient accuracy.
5. a) Polymer Secreting Organisms
Paul H. Kenis
Bacterial polysaccharides were tested for drag-reducing effectiveness in a search for more effective materials. Polysaccharides from many bacteria were found to be ef-fective. A pOlysaccharide from Pseudomonas sp.
reduced drag 60% at 60 ppm; Neisseria sp., 60% at 100 ppm; and Athrobacter viscosüs 145% at 250 ppm. The polysaceharide from anthomonas campestris reduced drag 60% at 50 ppm, and is the most effective poly-saccharide found to date; however, the synthetic
polymers, poly(ethylene oxide) and polyacrylamide, are much more effective on a weight basis.
Drag reduction measurements were made at different pH values to study molecular conformational changes or
cross-linking effects on the drag-reducing properties of bacterial polysaccharides. Polysaccharides from Xanthomonas canipestris, Pseudonionas sp., Ne-isseria
sp , and Arthrobacter viscosus exhibited altered
drag-reducing properties under various pH units. When pH values were changed, irreversible, partially
rever-sible, and other drag-reducing effects occurred. P-27, P-30, P-31
6.
a) Drag Reduction in the Cardiovascular System W. D. White and J. W. HoytThe pressure drop of human blood flowing through a short length of hodermic tubing was measured as a function of velocity in a miniature pipe-flow apparatus.
The addition of very small amounts of polymers (50 ppm of Polyox and 122 ppm of DNA) was shown to reduce the pressure drop by as much as 50% under normally turbulent flow conditions.
The saie eerimental apparatus had previously been ised to investigate a wide variety of polymer solutions,
including some experiments with poly(ethyiene oxide), Po-lyox WSR-30l dissolved in various infusion fluids. The experiments with human blood were carried out as
an extension of that program. The blood used in these tests was pooled from citrated samples that had been drawn from a large number of subjects in routine physi-cal examinations. The hematocrit was adjusted to about 30% by adding human plasma to reduce the viscosity, which insured that the transition to turbulent flow would occur well within the velocity capability of the apparatus.
The pressure drop of blood as a function of fluid velocity was compared with the pressure drop of an
identical sample containing 122 ppm of DNA (highly polymerized deoxyribonucleic acid derived from calf thymus, Sia Chemical CO.). DNA was selected because
it was known to give a significant pressure drop re-duction and had been reported to be non-antigenic in blood and to be absorbed quite rapidly. In these experiments, the blood displayed a normal transition from laminar to turbuJ.ent flow at around 37 ft/sec
(Reynolds number: 2,700). The blood containing DNA maintained what appeared to be laminar flow up to at least 60 ft/sec (Reynolds number: 5,000). At 60 ft/sec, the pressure drop was about half that of the control sample.
P-70
NAVAL UNDERWATER WEAPONS RESEARCH & ENGINEERING STATION, NEWPORT, RHODE ISLAND O2840
Drag and Noise Reduction R. J. Grady, R. H. Nadolink
The primary objective is to develop the technology nec-essary to utilize dilute polymer solutions for drag reduction. Ejection of these solutions into the bound-ary layer has been shown to be feasible means of re-ducing frictional drag (and thereby propulsive power and energy) by 30-50%. A secondary objective of the research has been to obtain a better insight into the mechanism of this drag reduction and optimize the polymer formulation and application techniques for po-tentially greater drag reductions..
1. Pipe Flow Experiments
Pressure drop measurements were made in 3/1k inch and 1-1/2 inch diameter smooth wall tubes as a function of flow rate and polymer concentration. The resulting Reynolds number/friction factor data correlates wl with that published by other investigators. A max-imum reduction in friction factor of .80% was obtained. In an effort to obtain further information on how
the dissolved polymer affects the structure of the near-wall flow, heat transfer coefficients to these dilute polymer solutions were measured, and the analogy be-tween heat and momentum transport invoked to draw inference about the wall layer. It was found that the heat transfer coefficients are as drastically re-duced as the friction factors. Also, a series of pressure drop measurements were made in a rough wall pipe (coarse sand cemented to the inside of the tube). An attempt is now being made to formulate a theory which will explain the smooth and rough wall friction
drag as well as the heat transfer data. Drop Tank Experiments
A series of experiments was conducted using small, (3" x 15"), streamlined bodies of revolution falling in a 20 ft. high tank of water containing sFiall
concentrations of polymer. The time required to fall a fixed distance was recorded and used to compute the terminal velocity and drag coefficient for a range of
Reynolds numbers and solution concentrations. Re-ductions of drag coefficient up to 30% were observed. Several attempts were made to apply the polymer dir-ectly to the body in the form of a paint or gelatin film which would ablate and dissolve during the
descent. None of these proved successful in reducing the drag.
High speed motion pictures of the falling body were taken with dye solution being ejected through small
holes near the nose. A dramatic differei,ce in the degree of turbulence in the boundary layer can be
observed between the body falling in water and a 30 part per million solution of polymer.
On-Board Mixer Laboratory Evaluations
A complete laboratory facility has been built to eval-uate new polymer slurry and mixing configurations. The facility consists of a large water supply to feed the intake of a polymer ejection nose, a calibrated turbulent pipe flow apparatus, into which the output of the polymer ejection nose is introduced.
Pressure Drop -- friction factor measurements are made on the turbulent pipe flow containing the polymer ejection products and the drag reducing effectiveness of the ejection products can be quickly determined. In this way, new polymer slurry formulations and mixing techniques can be evaluated before installation on test vehicles.
. improved Polymer Slurry and Mixing Techniques
mix an effective polymer solution aboard from O% polymer pastes or slurries have not proven successful. The current effort is directed toward modifying the polymer concentrate and/or on-board mixer to improve the rate of solution. A 20% Separan AP-30 slurry is now being tested in conjunction with mixing elements which provide increased turbulence in the mixing chamber. Chemical means of increasing the rate of polymer slurry/water solution are also being explored. A new method has been discovered to substantially increase the rate of polymer solution with water.
A patent is being sought which exploits this mechanism.
5.
TheoreticalThe classical problem of the decay of rectilinear vortex due to the action of viscosity was extended to include the diffusion of vorticity in a viscoelastic fluids formed by dilute solutions of high molecular weight polymers.
The motivation for this work was the supposition that suppression of propeller-tip cavitation may be obtained by seeding the propulsor intake-field with a polymer solution.
e) (1) McNally, W. A., 'Heat and Momentum Transport in Dilute Polyethylene Oxide Solutions," NUWS TB
No. i;i, June
1968.
Nadolink, R. H., "Drag Reduction Characteristics of Streamline Models with Polyox-WSR-3O1," IWWS
ITN 3-68,
Jan.1968.
Molinski, J., Patent Application, "Polymer Sol-ubility Mechanism." dtd
15 July
1968.
(1) Trottier, C. H., Patent Application, "Polymer Slurry Formulation," dtd Jan.
1968
Nadolink, R. H., Patent Application, "Boundary Layer Foam Injection Using Polymer/Gas Aerosol," March
1969.
Lessmann, R. C., "Diffusion of a Rectilinear Vortex in an Incompressible Viscoelastic Fluid," NUWS
ITN No.
131-68,
Nov1968.
Lagasse, A. R.., "Method of Calculating Effects of Drag Reduction Techniques," NUWS ITN No.
152-68,
Nov1968
OHIO STATE UNIVERSITY, DEPARTMBNT OF CIMICAL ENGINEING COLUMBUS, OHIO
432lO
Visual studies of the flow in the sublayer of drag reducing polymer and soap solutions
Professor Harry C. Hershey
Visual studies of the wall area during turbulent flow
using high speed photography and. tracer particles. Also the flow around a probe will be photographed using both a solvent and a drag reducing solution.
d) The criticai or onset Reynolds number has been higher than we are able to photograph for all drag reducing agents tried so far.
UNIVERSITY OF OKLAHOMA, SCHOOL OF AEROSPACE AND MECHANICAL ENGINEERING, NORMAN,OKLAHOMA 73069
Aerodynamic Skin Friction Reduction Edward F. Buck
1. Turbulent skin friction on polyurethane foam-PVC compliant surfaces in wind tunnels.
2. Skin friction of dusty air in pipes and wind tunnel.
a) 1. Polyurethane forms covered with thin polyvinyl chloride sheets had up to 38 per cent less turbulent skin friction than smooth hard plates for speeds between 15 fps to6230 fps (Reynolds number from
x 10 to 5 x 10 ).
2. Skin friction reductions of up to 50 percent below that of clear air, at the same speed, were recorded for dusty air in pipes and wind tunnel. The largest reductions occurred for the snialles "dust particles"
(2p.glass beads) and reductions occurred only in turbulent flow. The skin friction IncreaSed if the flow were laminar. The particle sizes tested ranged from 2to i68O,&z
e) 0-2, 0-3, 0-5
THE PENNSYLVANIA STATE UNIVERSITY, DEPARTINT OF AEROSPACE ENGINEERING, UNIVERSITY PARK, PENNSYLVANIA 16802
1. a) Turbulence measurement in polymer solutions by Doppler scattering.
W. George and J. Luinley.
The Doppler shift is measured incoherent (Laser) radiation scattered from tracer particles in homogen-eous turbulent flow, by homodyning scattered and unscattered rediation on a photocell. Flows of both polymer solutions and solvent alone are investigated. The intent is to measure the instantaneous fluctuating velocity, and consequently such quantities as spectra and probability densities.
None as yet. System is operative; electronics currently undergoing redesign for better extraction of signal noise.
e) Luinley, J. L., "A Brief Analysis of the Influence of Doppler Ambiguity on the Measurement of Turbulent
Spectra by Laser-Doppler Velocimetry." Prepared for publication.
2. a) Streaming birefringence measurement in axisymmetric emension of dilute solution of high molecular weight linear polymers.
S. Stanic and J. Luniley.
In a blow-down apparatus a high intensity axisyuxrnetric pure strain field is produced in a polymer solution. A laser beam is passed successively through: a
pol-arizer, the flow, an analyzer, a quarter wave plate, and and is detected by a photocell. The optical system is rotated about the optical axis at 1500 rpm. A sector rotating with the system produces a
signal having twice the frequency of rotation, which is used to synchronously demodulate the photocell signal, producing a voltage proportional to
birefring-ence. Concentration and strain rate are varied.
None as yet. Apparatus is being constructed. UNIVERSITY OF SOUTHAMPTON, DEPARTMENT OF AERONAUTICS MID ASTRONAUTI CS, SOUHAIVTON, ENGLAND
Thrbulent pressure fluctuations in water with additives G. M. Lilley & A. Millwa±d
The purpose of the investigation is to measure the effect of long chain molecule polymer additives in Newtoiian flow by measuri1g the wall pressure fluc-tuations beneath a turbulent boundary layer in pipe flow.
The apparatus used in the investigation is non-con-. tinuous in operation consisting of a large header reservoir from which the homogeneous dilute polymer solution is released to flow through a 2" pipe, in which the experimental measurements are made, and then exhausts into a lower catcbmnent reservoir. A piezo electric pressure transducer is installed in the working section and the data obtained is stored on magnetic tape and subsequently analysed using an analogue-digital computer. Measurements of the static pressure and flow velocity in the pipe are recorded during
each experiment.
Prior .to the maifi experiments a number of ancilliary problems have been investigated. It has been suggested by other investigators that there could be errors
in the indicated velocity obtained from pitot-static probe readings and calibration experiments on severe.. pitot-static probes in various polymer solutions were
made. It was discovered that the indicated velocity errors were closely related to the age-of the polymer solution and that the pitot-static probe would indicate the expected velocity, except perhaps in a shear
layer, with the method of preparation of polymer sol-utions that has been adopted.
A further problem that has been investigated is the measurement of samples of a polymer solution being
used in an experiment to determine whether there has been any change in drag reduction effect such as can be caused by degradation. An instrument has been
developed, in effect a miniature pipe flow apparatus, which uses samples of approximately 1 pint (500 cc). Values of drag reduction against concentration for various polymers have been obtained in order to provide calibration curves for the instrument which has
also been found useful for determining the basic drag reduction properties of different polymers. it has been shown that a general curve can be obtained for numerous polymers relating the drag reduction to the polymer concentration, molecular weight and char-acteristic length of the molecule. A copy of this instrument was made available, with permission, and acknowledgement of the contract sponsorship, to the International Yacht Racing Union at the 1968 Olympic Games in order to determine whether competitions were infringing the rule banning the release of drag
reduction polymers in the yachting events.
ADMIRALTY UNDERWATER WEAPONS ESTABLISIENT, PORTLAND, ENGLAND
1. a) Drag Reduction with Fibre Suspensiors.
Dr. H. D. Ellis
Test in turbulent pipe flow using asbestos fibre suspensions.
58% drag reduction achieved, with 500 wppm suspension. (Polyox WSR 301 gives 60% at 25 wpprn).
"Drag Reduction with Suspensions of Fibres" Dr. H. D. Ellis and Jennifer A. Jeanes. AWE Tech Note No 3)42/69.
2. a) Reduction of Turbulent Flow Noise by the use of Drag
Reducing Fluids.
ID. R. R. Gawler.
3. a) Reduction of cavitation noise.
b) ID. R. R. Gawler.
Cavitation produced in a Venturi orifice.
Partial suppression and up to 30 dB noise reduction
HYDRONAUTICS, INCORPORATED, LAUREL, MARYLAIfl) 20810 Hydrodynamics of Disperse Systems
Marshall P. Thlin
-The research over the past year consisted of: The effect of high_molecular_weight additives on pitot-. tube readings; determination of drag reduction in external flows of additive solutions; drag reduction with additive solutions on a rough surface and prac-tical techniques of applying additives in external flows
The deficiency of the irrpac-t. pressure, registered
by the pitot tube in the visco-elastic '1üid, is shown to be governed by the ratio of the two time scales involved: one derived from the hydrodynamical flow condition (the ratio between the tube diameter and the flow velocity), and the other characterizing the
strain response of additive molecules (the relaxation
time.). Our experimental studies of drag reduction in
external flows show that the additive solution, ejected into the pure water boundary layer, is mixing very poorly with its surroundings. The results suggest that relatively small quantities, comparable with the viscous-sublayer discharge, of di-lute additive solution are needed for efficient drag reduction. P-72
BIBLIOGRAPHY - FRICTIONAL DRAG REDUCTION SUMMER 1968 TO SUMMER 1969
Polymer Additives
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