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Recent Advances in Energy, Environment, Economics and Technological Innovation

Comparative study on the spread of petroleum products on the water surface IONUT VOICU1, FĂNEL VIOREL PANAITESCU2, NICOLAE VALERIU PANAITESCU3, MARIANA PANAITESCU4 Engineering Sciences in the Mechanical Field and Environmental1,2,4 Hydraulics, Hydraulics Equipment and Environmental Engineering3 Constanta Maritime University1,2,4;University Politehnica of Bucharest3 Mircea cel Bătrân Street, no. 104, Constanta1,2,4; Splaiul Independentei, no 313, Bucharest3 ROMANIA1,2,3,4 [email protected], [email protected], [email protected], [email protected] Abstract: - This paper presents the comparative study on the spread of petroleum products on the water surface. Authors compare the results obtained in the laboratory with the results of a computer simulation in the same environmental conditions - the simulation is performed with PISCES II, a computational model used by specialists to assess the consequences of water pollution with oil. Key-Words: - oil, spill, pollution, environment, simulation, Pisces II - the kinematic viscosity of the oil product (ν p ),

1 Introduction The objective of this paper is to determine the physical properties of the oil product which is later used in the laboratory study for development of oil spill on the water surface. Laboratory results are compared with the results of a computer simulation performed on the simulator Pisces II, under the same environmental conditions. The petroleum product used in the practical experiment is a crude, not distilled oil, obtained from S.C. Oil Terminal S.A. The sample was extracted from Western Siberia and the accompanying analysis report indicates the following characteristics: - Water and sediment content: maximum 1.2 %; - Sulphur content: maximum 1.8 %; - Paraffin content: maximum 6 %; - Chloride content: maximum 0.05 %; - Concentration of salts: maximum 100 [mg/l]. The following measurements were performed in the S.C. Oil Terminal S.A. laboratory in Constanta, where authors determined the properties of the specific crude oil sample, at 20 [ºC] (the value of temperature): - the density ( ρ p ) was determined by using a

was determined using an Ubbelohde type capillary viscousimeter with suspended-level (ν p = 14.6 ⋅ 10−6 [m2/s]). The dynamic viscosity of the oil product (η p ) was determined by using the following relation

η p = ν p ⋅ ρ p . [kg/m·s]

From relation (1), authors obtained the value of the dynamic viscosity: η p = 0.013 kg/m·s. - the surface tension of the oil product ( σ p ), was determined by the drop method, using a stalagmometer

σ p = σa

na ρ p , [kg/s2] n p ρa

(2)

where σ p , σ a is the surface tension of oil respectively water; (the water surface tension at temperature 20 [ºC] is σ a = 72.75 ⋅ 10−3 [kg/s2]); n p and na are the number of oil and water droplets leaking from the stalagmometer’s constant volume tank; ρ p and ρ a are the densities of oil and water

digital densimeter DMA 48, operating under the principles given by the law of harmonic oscillations. The obtained value of density is ρ p = 888.77

at temperature 20 [ºC]. Solving (2), authors obtained the surface tension of the oil product: σ p = 30.22 ⋅ 10−3 [kg/s2].

[kg/m3];

ISBN: 978-960-474-343-8

(1)

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it authors placed a digital camera, fixed in an immobilization system, and a halogen lamp which produced an uniform illumination, necessary to obtain a high contrast between water and oil product. In the range of the camera was set a timer that measures tenths of a second. At the bottom of the tank, below the water surface, it was connected a tube with a syringe, that was used to inject almost instantaneously welldefined different volumes of oil. This process is similar to an accidental instant oil pollution, at time t = 0. For these measurements authors used tap water and oil product (whose characteristics have been previously determined) at 20 ± 0.5 [ºC] ambient temperature [2]. Photographs taken from experimental work (Fig. 2) were further processed using image analysis software Sigma Scan Pro (Fig. 3) [8], which can clearly differentiate oil spill, by using a color filter method [2]. The area of the oil spill evolution in time (Fig. 4) was identified by analysing the photographs.

- the surface tension at the oil-water interface ( σ p− a ), was determined by using the relation

σ p −a = σ a

na ∆ρ , n p ρa

[kg/s2]

(3)

where σ p− a is the surface tension at oil-water interface; σ a is the surface tension of water; ∆ρ is the density difference of the two liquids, water and oil; n p , na is the number of oil respectively the number of water drops. Following equation (3), the surface tension at the oil-water interface is σ p − a = 18.34 ⋅ 10−3 [kg/s2].the net scattering coefficient of oil spill on the water surface ( σ ) was determined by the relation [kg/s2] (4) σ = σ a − σ p −a − σ p . Net scattering coefficient is σ = 24.19 ⋅ 10−3 [kg/s2].

2 Experimental determination Experimental works were conducted in the research laboratory at the Fire Officers Faculty ,,Alexandru Ioan Cuza” Police Academy (Fig. 1) and are aimed at quantifying the changes in the geometric parameters of the oil spill instantly discharged on the water surface.

Fig. 2 Photo with the state of the spreading oil spill

Fig. 1 Experimental laboratory stand used to visualize an oil spill on the water surface The geometrical parameters of the oil spill were determined by using photo processing software [2], applied on the pictures that were taken during the physical process of mechanical scattering, in order to identify its characteristic regimes. The experimental stand consists in a metal tank with a length of 1.5 [m] and a width of 1 [m]; above

ISBN: 978-960-474-343-8

Fig. 3 Results obtained with software Sigma Scan Pro

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Recent Advances in Energy, Environment, Economics and Technological Innovation

Laboratory works were conducted on a well defined 2 [ml] volume of oil with the physical previously established properties. For analysis and identification of the scattering regimes of the Fay model, authors define the following geometrical parameters [1], [2], [4]:

2500

2

Oil spill area [cm ]

- average thickness of the film (Fig. 5), h =

3000

V , A

2000 1500 1000 500

where V is the volume of oil introduced and A is the area of the spill; - the approximate radius of the spill (Fig. 6),

0 1

2

3

4

5

6

7

8

9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Time [s]

Fig. 4. Variation of the oil spill area

V l= , where V is the volume of oil and h is π ⋅h

0,5

the average thickness of the spill;

0,45 0,4

- the scattering speed (Fig. 7), v(t ) =

Oil spill thickness [mm]

dl , where dt l is the approximate radius of the spill and t is time. The following studies determined the geometrical parameters of the oil spill in Table 1.

0,35 0,3 0,25 0,2 0,15 0,1 0,05 0

Table 1. Laboratory results for a volume of 2 [ml] of oil

1

2

3

4

5

6

7

8

9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Time [s]

Fig. 5 Variation of the oil spill thickness

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

41 159 320 540 811 1 178 1 478 1 773 2 064 2 188 2 367 2 523 2 640 2 680 2 706 2 716 2 723 2 728 2 733 2 741 2 750 2 762 2 775 2 789

ISBN: 978-960-474-343-8

The spreading speed [m/s] 2.47 3.51 2.98 3.00 2.96 3.29 2.32 2.06 1.88 0.75 1.05 0.89 0.64 0.21 0.14 0.05 0.04 0.02 0.02 0.04 0.04 0.06 0.06 0.07

35 30

Approximative oil spill radius [cm]

Spill area [cm2]

Radius of the spill [cm] 3.6 7.1 10.1 13.1 16.0 19.3 21.6 23.7 25.6 26.3 27.4 28.3 28.9 29.2 29.3 29.4 29.4 29.4 29.5 29.5 29.6 29.6 29.7 29.8

25 20 15 10 5 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Time [s]

Fig. 6 Variation of the approximate oil spill radius 4 3,5

Oil spill scattering speed [cm/s]

Time [s]

Average spill thickness [mm] 0.488 0.125 0.062 0.037 0.024 0.016 0.013 0.011 0.009 0.009 0.008 0.007 0.007 0.007 0.007 0.007 0.007 0.007 0.007 0.007 0.007 0.007 0.007 0.007

3 2,5 2 1,5 1 0,5 0 1

2

3

4

5

6

7

8

9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Time [s]

Fig. 7 Variation of the oil spill scattering speed

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Recent Advances in Energy, Environment, Economics and Technological Innovation

University [5], [6]. The results are presented in table 2 below.

The results show that the oil film thickness is directly proportional to the scattering speed and inversely proportional to the spill area and radius. For a more accurate determination of the scattering stages authors derived the relations describing the range of oil film in the three modes of the Fay scattering model [1], [2], [4]. Thus, one obtained the scattering rate dl/dt [2], [3]: - for the inertial regime, by using the relationship

Table 2. Computer simulation results for an oil discharge of 524 [m3]

dl 1 ≈ ( g∆V )1 4 t −1 2 (5) dt 2

l ≈ ( g∆V )1 4 t1 2 ⇒

ρa − ρ p is the fraction of oil that floats ρa above the water level; ρ a and ρ p are the water where ∆ =

respectively the oil densities. - for the viscous regime, by using the relationship

l ≈ ν −p1 12 (g∆ )1 6V 1 3t1 4 ⇓ dl 1 −1 12 ≈ ν p ( g∆ )1 6V 1 3t −3 4 , dt 4

(6)

where ν is the kinematic viscosity of the oil product, g is the gravitational acceleration, V is the volume of oil spilled, t is time. - for the regime produced by the surface tension of oil-water interface, by using the relationship

l ≈σ

12

where σ

dl 3 1 2 t −1 4 ≈ σ ⇒ dt 4 ρ1p 8η1p 4 ρ1p 8η1p 4 t3 4

Time [h]

Spill area [m2]

0 6 12 18 24 30 36 42 48 54 60 66 72 78 84 90 96

10 445 101 333 158 605 202 286 238 335 269 649 297 539 323 244 347 111 368 413 389 208 408 409 426 503 443 675 459 338 474 344 488 432

Average spill thickness [mm] 50.16 5.17 3.30 2.59 2.19 1.94 1.76 1.62 1.50 1.42 1.34 1.28 1.22 1.18 1.14 1.10 1.07

Radius of the spill [m] 57.6 179.6 224.7 253.8 275.5 293.0 307.8 320.8 332.4 342.5 352 360.6 368.5 375.8 382.4 388.6 394.4

The spreading speed [m/s] 0.929 0.161 0.092 0.064 0.051 0.044 0.038 0.032 0.029 0.027 0.024 0.021 0.020 0.019 0.017 0.016 -

The following figures (from 8 to 11) present graphic results of the simulation [7].

(7)

is net scattering coefficient, η p is

dynamic viscosity of the oil product, ρ p is the petroleum product density.

3 Measurements obtained with Pisces Simulator II Fig. 8 Variation of the oil spill area To check the results of laboratory measurements authors have simulated instantaneous discharge of a volume of 524 [m3] of oil. The properties and environmental conditions in the simulation were considered similar to the laboratory ones. The simulation was performed with the Simulator for Emergencies Pisces II (Potential Incident Simulation Control and Evaluation System), situated inside the Environmental Engineering Department at the Constanta Maritime

ISBN: 978-960-474-343-8

To find out the thickness of the oil spill, authors used the relation

h=

V A

(8)

where V is the oil spill volume and A is the area of the oil spill.

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A=f(t), h=f(t), l=f(t), v=f(t) for laboratory and computer determination. This means that measurements made with Pisces Simulator II confirms the results obtained in the laboratory and vice versa.

4 Conclusion As shown in the laboratory research at small scale, the scattering phenomenon is qualitatively similar to that which occurs on a large scale (actual discharges) with large amounts of oil. As shown by Fay model [1], in the surface tension regime, the scattering rate of the spill becomes independent of the volume of pollutant discharged. Therefore, in the last phase of pollution the scattering speed is very low and the initial quantity of oil discharged is not of importance. By analysing the graphs obtained from both laboratory and computer measurements the authors can say that the predictive model largely reflects the situation simulated in the laboratory. Under these circumstances one can say with certainty that the Pisces II simulator can be successfully used to assess data needed for rapid intervention in emergency oil sea water surface pollution. Also it can be used to prevent environmental accidents by simulating a large number of scenarios to establish different possible consequences. These consequences are influenced by the quantity of oil spilled, by the distance to the shore and many other possible inputs. Using computer simulation, the authorities having jurisdiction can make quick and thorough assessments, avoiding this way, real environmental disasters.

Fig. 9 Variation of the oil spill thickness in time To find out the radius, authors used the relation

l=

V π ⋅h

(9)

where V is the oil volume and h is the medium thickness of the oil spill.

Fig. 10 Variation of the oil spill radius in time The scattering speed was calculated by using relation

v(t ) =

dl dt

(10)

where l is the radius of the spill and t is the time.

References: [1] Fay J.A., Physical processes in the spread of oil on a water surface, Proceedings On Prevention and Control of Oil Spill, American Petroleum Institute - Washington, 1971, pp. 463-467. [2] Pincovschi I., Gogoaşe Nistoran D., Modeling of Oil Spreading on Still Water Surface - Part 2 Experiments, International Conference of Energy and Environment, Bucharest, 2003.

Fig. 11 Variation of the oil spill scattering speed in time Following the interpretation of the results, authors noticed similarities between the curves

ISBN: 978-960-474-343-8

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[3] Popescu D. M., Gogoaşe Nistoran D. E., Oil spill modeling of river - an efficient forecast tool. Part 1: Physico-chemical processes, International Conference of Energy and Environment, Bucharest, 2005. [4] Popescu D. M., Evolution of the interface between two viscous immiscible fluids with application to oil pollution on open channel flows, PhD Thesis, University Politehnica of Bucharest, 2008, pp. 145-154. [5] Voicu I., Panaitescu F. V., Panaitescu M., Panaitescu V. N., Oil leakage simulation and spill prediction from sunk ship Paris, near Constanta harbor, 7th International Conference

ISBN: 978-960-474-343-8

on Management of Tehnological Changes, Alexandroupolis, Greece, 2011, pp. 765-768. [6] Voicu I., Panaitescu V. N., Popa C., Computer Simulation of an Emergency Situation – accidental discharge of hydrocarbons in the Black Sea, The International Conference on Water Resources and Wetlands, Tulcea 14-16 september 2012, Editura Transversal, 2012, pp. 408-413. [7] ***, PISCES29-PL Specifications, ver. 1.0, 2008. [8] ***, SigmaScan Pro 5.

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