| ERROR #002100048 has occurred in subroutine SU_BNEXT. Message: All vertices for a fluid domain lie on a boundary. The solver considers this to be a fatal error because control volume gradients cannot be calculated, leading to serious discretization error. | This error may arise for two-dimensional simulations when a free slip boundary condition is applied to the end planes. In this situation a symmetry condition should be applied to the end planes . | Execution is terminating. This error message can be bypassed by setting the expert parameter 'boundary vertex check = f'.

I simualte fluid in a thin board,error as above.Can someone give me some suggestion?

You have a 1-cell thickness domain? Your lateral planes should be set to symmetry planes, otherwise the "CV gradients cannot be calculated", is it clear? F