Can somebody offer a simple explanation of the difference between static and total pressure when used as an input in SimCFD and advise when the use of each is most appropriate? For years I have used total pressure as the input in many studies and static as the output (because when starting out with the program I was advised that this was correct) but I have found with a study I am currently running that in some cases using total pressure for the input results in divergence and/or a less accurate result, and changing to a static input seems to correct the problem.
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For incompressible analyses, static pressure is the recommended inlet condition when simulating a pressure drop. Total pressure is the sum of the static and dynamic pressure, and is often useful as an inlet for compressible simulations.
using static pressure boundary conditions will enhance your stability. When total pressure is used as a boundary condition, then P_total = P_static + 0.5 * density *V^2. From a computational standpoint, we impose P_static on those boundaries, so P_static = P_total - 0.5 * density * V^2. Having to subtract off the 0.5 *density * V^2 makes this a more non-linear computation. As the velocities change on the BC surface, we then update the P_static using these velocities and compute the pressure field based on static pressures. Using P_static on you BC planes allows for a constant prescribed pressure and eliminates the 0.5 * density * V^2 term being factored in.
Dave.