Karthik R
nTotal gauge pressure is still gauge pressure. It is simple the fluid pressure in isentropic conditions. Gauge pressure + Operating pressure = Absolute pressure. nIn most cases, you will be using the ideal gas law to model compressible flow. You should be able to set the operating pressure to 0. But, make sure that you appropriately adjust your total gauge pressure conditions to reflect the same absolute pressure. This is the most important step.nIf you are working on an external flow simulation, it is recommended that you use the 'Far Field Pressure BC'. This is a better physical representation of free-stream condition at infinity. However, there are some limitations:nIdeal-gas law must be chosen.nIncompatible with multiphase modelsnCannot apply this BC with constant density flows.nI hope this addresses your question. nThank you.nBest,nKarthikn