Shock tube species transport divergence
I'm modeling a 2D shock tube, in fluent, as a rectangle (1meter long by 6cm diameter) with 2 separated sections, a high-pressure one called driver and a low pressure one called driven. Im using density-based solver with transient analysis, inviscid with energy eq. and species transport with hydrogen-ar mixture with both as ideal gas. I set the operating pressure inside to 0 pa. After this i Initialize with 10 bar in the driver section and 1 bar in the driven section and value 1 of hydrogen for the driver section. I run the calculations for 50 time steps of 20 iterations each with a time step of 7e-06s and i do all of this with 4 solver processes and double precision.
When I model it for 10 bar, it all goes smooth and the solution converges but when i change the driver pressure to 20bar or higher the solution diverges a lot and presents results like 0 pressure along the shock-tube. The reason i am doing this is to see the temperate and density behaviour for different pressures inside the shock-tube and then test if the length of the tube will have any effect on them.
I think this is a very simple problem but i just can't seem to get it right. If anyone can help, i would be very grateful.