函数名为pressure_profile,数组x通过函数F_CENTROID得到面f的质心，loop循环扫描整个定义的边界，计算每个网格面边界条件的值。对于初学fluent udf编程的同学来说，是很好的练习案例(Function called pressure_profile, array x surface is obtained by function F_CENTROID f centroid, scanning the entire loop cycle defined boundary, calculating the value of each grid surface boundary conditions. Udf programming for beginners fluent students, it is good practice case)