Hi @lv_wilove,

Ah. I assumed you wanted to determine the turbulence intensity factor at the outlet of the nozzle. Hence why I was asking for the goal. Determining that is much much more complex and RANS is not accurate enough as it tends to under predict.

So since now you have made your objective clear, I think I know how to proceed. But first, you will need to make some geometry changes which may be a little complicated.

First, you need to simplify your geometry so that we can run a slice of it rather than say, a quarter. Referto Jousef’s post on the Laval Nozzle Simulation.

Secondly, we need to take the model and mesh it in 2D. That will greatly reduce simulation time and resources as well as allowing us to refine the model to a high degree without incurring too much computational cost. This is a little complex as SimScale cannot mesh 2D but there is a workaround. Let us get to that after you’ve done the first step.

Lastly, we need to determine the boundary conditions. Seeing as your flow rate is sub-sonic, but compressible, I believe we can continue to use a pressure based solver. However, they tend to be not so cooperative and I have minimal experience with getting them to work properly, so we’ll figure it out when it comes.

No, not at all. As mentioned earlier, my assumption as to what you wanted to determine was wrong. As such, my runs are already invalid.

Yes that is the problem with this kind of compressible flow simulation. Would help if I was more familiar with the math but oh well. Lets see what we can do.

Cheers.

Regards,

Barry