Testing of a oil spill mathematical model contained in PISCES II simulator

Transcription

1 Scientific Journals Maritime University of Szczecin Zeszyty Naukowe Akademia Morska w Szczecinie 212, 32(14) z. 2 pp , 32(14) z. 2 s 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 7-5 Szczecin, ul. Wały Chrobrego 1 2, 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 Fig. 1. The processes following the oil spill [1] Zeszyty Naukowe 32(14) z. 2 15

2 ":" "19:" "38:" "57:" "76:" "95:" "114:" "133:" "152:" "171:" "19:" "29:" "228:" "247:" "266:" "285:" "34:" "323:" "342:" "361:" "38:" Duration of simulation [h] Kinga Łazuga compounds, oxygen and nitrogen. Due to the diversity 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 filling is determined by physical and chemical properties of spilled substance and external conditions that accompany this spills. Oil can also undergo a process such as evaporation, emulsification, dissolution, microbial degradation, 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 simulations. In the case study of the impact of wind on the processes taking place in oil slick 1 tons of IFO 3 were used (in form of slick on the surface of the initial.1 km 2 and a maximum initial thickness 3.3 mm). In each simulation the wind direction was north, and its speed was 5 3 m/s. In the current case study of the impact of surface processes occurring in the stain 5 and 1 tons of IFO 3 belongs to a group of medium-sized marine fuels were used. All simulations were carried out for total annihilation of spilled material from the surface of water or until the simulation duration exceeded 1 hours. Fig. 2. Properties of fuel oil IFO 3 Wind effect One of the main factors influencing the movement of the oil slick is the wind force, which mainly affects the speed of some physical processes occurring in the oil slick. In the following simulations the winds of 5, 1, 15, 2, 25 and 3 m/s and wind direction Kw = were taken into account. Simulations results are presented in next subsections. 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 Ts [h] Wind speed [m/s] 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 intensively in the first hours after the oil spillage. With increasing of wind force and air temperature 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 Vw=5 m/s Fig. 4. Evaporation of oil during the simulation for wind speeds of 5 m/s 16 Scientific Journals 32(14) z. 2

3 Amount [t] ":" "3:" "6:" "9:" "12:" "15:" "18:" "21:" "24:" "27:" "3:" "33:" "36:" "39:" "42:" Dispersion [t] ":" "3:" "6:" "9:" "12:" "15:" "18:" "21:" "24:" "27:" "3:" "33:" "36:" "39:" "42:" ":" "19:" "38:" "57:" "76:" "95:" "114:" "133:" "152:" "171:" "19:" "29:" "228:" "247:" "266:" "285:" "34:" "323:" "342:" "361:" "38:" Dispersion [t] Testing of a oil spill mathematical model contained in PISCES II simulator Vw=5 m/s Fig. 6. Dispersion of crude oil at wind speeds of 5 m/s Fig. 5. Evaporation of oil during the simulation for wind speeds of 1 3 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 temperature 2 C and wind speed 15 m/s. Current Impact Vw=1 m/s Vw=2 m/s Vw=3 m/s Vw=15 m/s Vw=25 m/s Another of the main factors influencing the behavior of the oil slick in water is a surface current, or tidal current. Current parameters affect mainly the direction and speed of movement of oil slick. Influence of surface current on the processes occurring in the spot crude oil If on the oil slick has influance only a surface current (in this case 1 m/s) and wind speed is 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 direction of current is caused by coastline shape Vw=1 m/s Vw=2 m/s Vw=3 m/s Vw=15 m/s Vw=25 m/s Fig. 7. Dispersion of oil in the wind speeds of 1 3 m/s Floating amount [t] Evaporated amount [t] Dispersed amount [t] Fig. 8. Processes occurring after oil spillage at a wind speed of 15 m/s Zeszyty Naukowe 32(14) z. 2 17

4 Kinga Łazuga Fig. 9. The movement of oil slicks at the current speed of 1 m/s 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. 1. The direction of movement of oil slick under influence on current (V c = 1 m/s) and wind (V w = 1 m/s) 18 Scientific Journals 32(14) z. 2

5 Amount [t] Testing of a oil spill mathematical model contained in PISCES II simulator 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 2 C and the water temperature was 15 C Floating amount [t] Evaporated amount [t] Dispersed amount [t] Conclusions Reported results relate only to simulations of the physical processes occurring after spillage of IFO 3 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 sinking, 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 PISCES II User Manual. Transas Ltd., Specyfication for PISCES II. Transas Ltd., 27. Fig. 11. Processes occurring in the oil slick when exposed to current and wind Zeszyty Naukowe 32(14) z. 2 19