Array nRead the ANSYS Help in the Mechanical APDL section, Element Library, for the HSFLD242 element. You will find that a node labeled Q is the node that holds the pressure for the fluid volume. You can assign a pressure to that node.nHSFLD242 Input SummaryntNodesnI, J, K, L, M, N, O, P, QntDegrees of FreedomnUX, UY, UZ for surface nodes (I, J, K, L, M, N, O, P)nHSDP and PRES for pressure node (Q)ntReal ConstantsnPREF - Reference pressure (for compressible gas defined via TB command with Lab = FLUID and TBOPT = GAS)n