To provide a method, a program and an apparatus for performing a simulation of variations in oil for improving accuracy and a processing speed of the whole of the simulation.

A simulation condition is determined (step 1). An area is divided to set a plurality of segmentized sections composed of squares with same size and shape (step S2), and the distributions of oil at each of the plurality of segmentized sections are defined by the oil sections shaped in square or rectangle, respectively (step S3). The variations in the oil sections due to time elapse are calculated respectively (step S4). The oil distributions at each segmentized section are re-defined by the square-shaped oil sections, respectively, in accordance with variations in the oil sections obtained in the step 4 (step 5). The steps S4, S5 are repeated by a prescribed number of times at prescribed time intervals.