I am trying to simulate flow over an object in simscale. For a compressible flow simuilation in transonic regions I am having trouble getting succesful and accurate solutiongs for the expected flow. Specifically, I am measuring “accuracy” as the expected stagnation pressure (the flow is over a pitot tube). There seems to be a diverging trend from the expected value (caculated from stagnation/dynamic pressure mach relation equation) as flow increases to transonic speeds. Eventually, around 0.8-0.9 Mach, the solution diverges.

Here is a link to my project (only compressible 9 is important ignore the other simulations) SimScale

Is there is anything I am doing wrong with my setup? or are there things I can change to get a better setup?

Hello @noahl310,

Here are some comments on Compressible 9:

- Firstly, we are currently working on a transonic solver (see the public roadmap here), which should ease the setup/convergence for this particular simulation.
- Secondly, for 0.8-0.9 Mach you are likely to still get a successful simulation, but you need to be cautious with the initialization of the velocity. For instance, check the section 2.2.D from the compressible airflow around a wing tutorial. Ramping the velocity will give you a more stable configuration/help with convergence.

Cheers

Hi,

Thanks for the reply. Is a table like this going to linearly increase the velocity for each timestep t ={0, 600} or will it apply V at 0 and then V at 600?

Hello,

The first option is correct, the velocity varies linearly. There’s an image in the tutorial (Figure 42), which shows the resulting velocity:

Cheers

I was able to apply the velocity ramp however the solution still isnt converging.

this time the failure was diverging temperature at the back end pressure outlet. It was at a single point, what could be the cause of this issue?

Here is just inside the back edge