Maritime University of Szczecin
Akademia Morska w Szczecinie
2012, 32(104) z. 2 pp. 105–109 2012, 32(104) z. 2 s. 105–109
Testing of a oil spill mathematical model contained
in PISCES II simulator
Kinga Łazuga
Maritime University of Szczecin, Faculty of Navigation, Institute of Marine Traffic Engineering 70-500 Szczecin, ul. Wały Chrobrego 1–2, e-mail: k.lazuga@am.szczecin.pl
Key words: SAR, wind, current, oil Abstract
PISCES II is a simulator designed to conduct research and training related to the rescue operation in the event of an oil spill on any of the world region. The program includes a built-in mathematical model, enables the oil spill of crude oil to observe the interaction in user-specified external conditions. This paper presents the results of the analysis of mathematical model simulation Pisces II, the behavior of the oil slick in selected hydrometeorological conditions.
PISCES II – oil spill simulator
Simulator PISCES II is designed to prepare and conduct rescue action in the case of an oil spill. The program dive into a comprehensive environmental information, based on mathematical modeling of oil spill and its interaction with geographical restrictions, environmental phenomena, and the spillage fighting.
Simulator PISCES II is used to predict the behavior of the oil spill spreading on sea surface,
observing the processes taking place during the interaction beetween oil, sea water and air. Also simulator is used to coordinate rescue operations in the case of oil spill and training.
Oil and processes occurring during the oil spill
Crude oil is a substance heterogeneous in terms of both, physical and chemical properities. It is a mixture of many hydrocarbons and sulfur
compounds, oxygen and nitrogen. Due to the diver-sity of chemical composition of different types of oil, forecasting the behavior of this substance on contact centers, such as water and air, is difficult. Behaviour of oil and its products at the time of fill-ing is determined by physical and chemical proper-ties of spilled substance and external conditions that accompany this spills.
Oil can also undergo a process such as evapora-tion, emulsificaevapora-tion, dissoluevapora-tion, microbial degrada-tion, which may alter the physical properties of spilled substance (Fig. 1).
Influance of hydrometeorological conditions on the simulation results
To see the properties of the simulator PISCES II model, two points (one point on the Atlantic Ocean and one point in the North Sea) were taken to simu-lations.
In the case study of the impact of wind on the processes taking place in oil slick 100 tons of IFO 300 were used (in form of slick on the surface of the initial 0.1 km2 and a maximum initial thickness
3.3 mm). In each simulation the wind direction was north, and its speed was 5–30 m/s.
In the current case study of the impact of surface processes occurring in the stain 50 and 100 tons of IFO 300 belongs to a group of medium-sized ma-rine fuels were used.
All simulations were carried out for total annihi-lation of spilled material from the surface of water or until the simulation duration exceeded 100 hours.
Fig. 2. Properties of fuel oil IFO 300
Wind effect
One of the main factors influencing the move-ment of the oil slick is the wind force, which main-ly affects the speed of some physical processes occurring in the oil slick. In the following
simula-tions the winds of 5, 10, 15, 20, 25 and 30 m/s and wind direction Kw = 000° were taken into account. Simulations results are presented in next subsec-tions.
The impact of wind speed for the duration of the simulation
Wind force has mainly affected the speed of movement of oil slick on the surface. The figure below shows the dependence of the duration of the simulation on wind speed.
Fig. 3. The duration of the simulation depending on wind speed
Effect of wind speed on evaporation
Evaporation spill (volatilization light fractions of oil) is very intense. Within one to three weeks of the uprising even shed about 1/3 of the spilled oil can evaporate. Oxidation takes place most inten-sively in the first hours after the oil spillage.
With increasing of wind force and air tempera-ture evaporation is increasing too. Evaporation of the fraction of light causes an increase in density and viscosity of spilled oil. Evaporation process, depending on wind speeds present figures 4 and 5.
Fig. 4. Evaporation of oil during the simulation for wind speeds of 5 m/s 393.00 150.00 26.53 7.80 3.23 1.67 0 10 20 30 40 50 60 70 80 90 100 5 10 15 20 25 30 Du ra ti on o f sim ulatio n [h ] Wind speed [m/s] Ts [h] 0 2 4 6 8 10 12 14 16 18 20 "0 :0 0" "1 9: 00 " "3 8: 00 " "5 7: 00 " "7 6: 00 " "9 5: 00 " "1 14 :0 0" "1 33 :0 0" "1 52 :0 0" "1 71 :0 0" "1 90 :0 0" "2 09 :0 0" "2 28 :0 0" "2 47 :0 0" "2 66 :0 0" "2 85 :0 0" "3 04 :0 0" "3 23 :0 0" "3 42 :0 0" "3 61 :0 0" "3 80 :0 0" Ev ap ora ti on [ t] Vw=5 m/s
Fig. 5. Evaporation of oil during the simulation for wind speeds of 10–30 m/s
Effect of wind speed on the dispersion
Under certain conditions, oil can be dispersed (the formation of a suspension of microparticles of oil in water) by mechanical activity of the sea. The size of dispersion is a function of sea state and oil properties. Dispersion begins shortly after oil spillage.
In view of the fact that the sea state is closely dependent on the wind force dispersion acting most rapidly with high wind speed [1]. Dispersion process depending on wind speed present figures 6 and 7.
Speed processes in the oil stain, depending on the wind
Figure 8 shows the processes taking place after the oil spill on the water surface at 15°C, air tem-perature 20°C and wind speed 15 m/s.
Current Impact
Another of the main factors influencing the behavior of the oil slick in water is a surface cur-rent, or tidal current. Current parameters affect mainly the direction and speed of movement of oil slick.
Influence of surface current on the processes occur-ring in the spot crude oil
If on the oil slick has influance only a surface current (in this case 10 m/s) and wind speed is 0 m/s, the only process resulting from the action of this current is the movement of oil slick according to the current direction (Fig. 9). Changing the direc-tion of current is caused by coastline shape.
Fig. 6. Dispersion of crude oil at wind speeds of 5 m/s
Fig. 7. Dispersion of oil in the wind speeds of 10–30 m/s
Fig. 8. Processes occurring after oil spillage at a wind speed of 15 m/s 7.4 4.9 2.4 1.3 0.7 0 0.2 0.4 0.6 0.8 1 1.2 1.4 0 1 2 3 4 5 6 7 8 "0 :0 0" "3 :0 0" "6 :0 0" "9 :0 0" "1 2: 00 " "1 5: 00 " "1 8: 00 " "2 1: 00 " "2 4: 00 " "2 7: 00 " "3 0: 00 " "3 3: 00 " "3 6: 00 " "3 9: 00 " "4 2: 00 " Ev ap ora ti on [ t] Ev ap ora tio n [t] Vw=10 m/s Vw=15 m/s Vw=20 m/s Vw=25 m/s Vw=30 m/s 0 5 10 15 20 25 30 "0 :0 0" "1 9: 00 " "3 8: 00 " "5 7: 00 " "7 6: 00 " "9 5: 00 " "1 14 :0 0" "1 33 :0 0" "1 52 :0 0" "1 71 :0 0" "1 90 :0 0" "2 09 :0 0" "2 28 :0 0" "2 47 :0 0" "2 66 :0 0" "2 85 :0 0" "3 04 :0 0" "3 23 :0 0" "3 42 :0 0" "3 61 :0 0" "3 80 :0 0" D isp ersio n [t] Vw=5 m/s 0 20 40 60 80 100 120 "0 :0 0" "3 :0 0" "6 :0 0" "9 :0 0" "1 2: 00 " "1 5: 00 " "1 8: 00 " "2 1: 00 " "2 4: 00 " "2 7: 00 " "3 0: 00 " "3 3: 00 " "3 6: 00 " "3 9: 00 " "4 2: 00 " Disp ersio n [ t] Vw=10 m/s Vw=15 m/s Vw=20 m/s Vw=25 m/s Vw=30 m/s 0 20 40 60 80 100 120 1 5 9 13 17 21 25 A m ou nt [t] Floating amount [t] Evaporated amount [t] Dispersed amount [t]
Impact of current and wind on the behavior of the oil slick
When on the oil slick in the same time acting current and wind, movement of this oil slick is
mainly determined by the current parameters. Wind direction has little effect (3%) to the direction of movement of oil slick, while the wind speed determines the speed of most physical processes occurring in the oil slick.
Fig. 9. The movement of oil slicks at the current speed of 10 m/s
The intensity of evaporation of light petroleum fractions is dependent on air temperature and wind force. In the case described below the simulation temperature was 20°C and the water temperature was 15°C.
Fig. 11. Processes occurring in the oil slick when exposed to current and wind
Conclusions
Reported results relate only to simulations of the physical processes occurring after spillage of IFO 300 oil on the sea surface. Simulations show that the movement of the slick is mainly influence by the direction and speed of current. On physical processes such as evaporation, dispersion, or sink-ing, the greatest impact has the force of the wind. It is difficult to determine how fast these processes will occur after the spillage, because they are affected by other factors such as air and water temperature and density of the water. Therefore, this research will continue.
References
1. The national plan to combat hazards and pollution of the marine environment. Maritime Search and Rescue, Gdynia 2005.
2. PISCES II User Manual. Transas Ltd., 2008. 3. Specyfication for PISCES II. Transas Ltd., 2007. 0 10 20 30 40 50 60 70 80 90 100 A m ou nt [t] Floating amount [t] Evaporated amount [t] Dispersed amount [t]
