I’m having some trouble looking at a wave propagation problem using the transient compressible flow analysis in simscale. The project is here https://www.simscale.com/workbench/?pid=2218239081399080106&mi=spec%3A88b7d823-b459-44db-a6e1-2fe24198750a%2Cservice%3ASIMULATION%2Cstrategy%3A31 and the best study in it to highlight the problem is the one titled “mesh study”.
I am looking at wave propagation in air contained within a two metre long pipe. In my simulation, I have set up probe points at 0.5m, 1m, and 1.5m along the length of the tube, and am exciting the tube at the inlet at 0cm with a sinusoidal pressure source (given from a .csv file).
Using a speed of sound of 340 m/s, the pulse should arrive at each probe point at 0.0015s, 0.0029 s, and 0.0044 s. The simulation is recording the pulse arriving at each probe point at around 0.0009s, 0.0018 s, and 0.0027 s, which corresponds to a speed of sound around 550 m/s. This result appears to be consistent with finer resolution meshes and time steps (from deltat = 1e-5s to 1e-7s). I haven’t tried different solvers yet but I don’t believe they should affect the speed of sound this way.
The material properties of air were taken straight from the SimScale library. I tried adjusting the amount of substance (default 1 mole) to what would be the actual amount, thinking this may have an effect on density, and therefore speed of sound, but this had no noticeable affect on the output.
If anyone has any suggestions on how to fix this problem or on how to test it further, I’d be grateful to hear your thoughts.