reflected shock in a shock-tube
 

hello,
i'm working with ansys-cfx since few weeks and i try to simulate the pressure-distribution in a shock-tube after the origin shock and the second, wall-reflected, shock.
During i'm satisfied with the calculated pressure-values after the first shock, the pressure-distribution after the reflected shock shows bad-damped oscillations i can't avoid.:(

do you have any hints how i can improve my simulation?
thanks

Hi,

Avoiding oscillations in shock waves is a difficult issue. I assume you are using the high-res differencing scheme? That should minimise the oscillations but still give you second order accuracy in most regions of the flow. Also what time differencing scheme are you using?

Glenn Horrocks

Hi glenn,
in my very first calculations i used second-order-euler-equations with a high-res-scheme. I got very bad oscillations behind my first shock.
Changing to first order in euler equations improved the results for the first shock but with still unacceptable oscillations behind the reflected shock.
Changing between high-res and upwind-scheme didn't change the results very much while using first-order-euler

thanks for your answer
matt

Try switching on "high speed numerics" in the advanced panel of the solver control. This enables some numerical techniques specifically aimed at dealing with shock oscillations/instabilities (such as the carbuncle effect).

Hi timon,
thank you for the hint. I will try it soon and report then about my results.
thanks

Shock tube simulation
 

Hello,
I am new user of cfx and I want to simulate shocktube with two different gases, Is there any body could help me in defining the two different component of fluid which I have to use in this simulation?

Regards
Thanks

Hi
a question:
does the flow behind the reflected shock wave have a total pressure bigger than the original driver gas? is it correct?