Dear Rob,nI really appreciate your suggestion. Yes, you are right, the star,k and z0 are constant and z is the coordinate under mesh.nAs I know, the Custom Field Function cannot give me the right hand side of above equation since the height z is unable to get.nAs I mentioned in the first post, I write the above wind profile in my udf and load it as z-velocity in inlet-velocity boundary condition. Can it be utilized in some way?.