Simulation of Oil Core-Flows by a Modified VOF Method. A basic study on spilled heavy oil on the sea. (3rd Report).

In this paper, two-phase flows of oil and water were considered numerically. For a description of a sharp interface between oil and water, the original VOF method was modified by means of an inclined line-segment in a numerical cell. Continuous and separated core-annular flows (CAF) in a two-dimensional channel were simulated by the modified VOF method in combination with a κ-ε turbulent model. Some of main results are as follows : 1) In comparison with the original VOF method, the modified method gave satisfactory conservation of mass and shape to the Zalesak's problem. 2) The modified method is applicable to a complex flow in which merging and separation of fluid lumps occur. 3) Time averaged pressure gradients of continuos core- annular flows were slightly higher than those of water flows in both the simulation and experiments. 4) Pressure gradients of separated core flows fluctuated largely due to distortion of the core; however, time averaged pressure gradients of them were close to those of the continuous CAF.