说明：  用于fluent软件模拟两相流，初始化气相为球形区域，适合传热流体专业
(The following interpreted UDF patches an initial volume fraction for a particular phase in a solution. It is executed once at the beginning of the solution process. The function sets up a spherical volume centered at 0.5, 0.5, 0.5 with a radius of 0.25. A secondary-phase volume fraction of 1 is then patched to the cells within the spherical volume, while the volume fraction for the secondary phase in all other cells is set to 0. )