Simulation of a jet of air into a shock tube
I am simulating the resulting turbulent flow generated from injecting air at a supply (absolute) pressure of 202.65 kPa through an inlet of diameter 0.5", into a shock tube that has an initial (absolute) pressure of 101.325 kPa. The dimensions of the rectangular shock tube's cross section are 2.5"x1.5". I am only modelling a portion of the length of the shock tube, shown below. When I hit Calculate, the residuals start off below 1, and then the x, y, z equations shoot up to the order of 10's and 100's. I hope somebody can help me troubleshoot what is supposed to be a simple turbulence simulation.
My flow is compressible so I selected the density-based solver. Transient flow is selected as well. I am using the k-omega model to model the turbulence, and my solution method is implicit. I set 3 boundary conditions:
1) inlet: pressure-inlet --> Gauge pressure total pressure is set to 101325 Pa, and supersonic/initial gauge pressure is set to 0 (i also tried different pressures here)
2) left and right planes indicated in the diagram: both set as pressure-outlet --> gauge pressure is set to 0 as that is the gauge pressure in my shock tube at those two locations
Are the boundary conditions correctly set? Is anything missing?
In the solution initialization, I am computing from inlet, where the Y-velocity is automatically set to -329 m/s2.
The below attached images are of the shock tube, the fluid domain (air) that I am modelling, the mesh, and the set boundary conditions in FLUENT.