reflected shock in a shock-tube

matt · April 8, 2009, 08:34

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

ghorrocks · April 8, 2009, 20:33

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

matt · April 9, 2009, 10:07

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

Timon · April 9, 2009, 10:18

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).

matt · April 9, 2009, 12:13

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

wind.cfd · January 24, 2013, 20:15

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

immortality · February 4, 2014, 17:43

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

April 8, 2009, 08:34	reflected shock in a shock-tube	#1
matt New Member mathias kiesel Join Date: Apr 2009 Posts: 3 Rep Power: 17	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

January 24, 2013, 20:15	Shock tube simulation	#6
wind.cfd New Member cfd Join Date: Oct 2011 Posts: 17 Rep Power: 14	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

February 4, 2014, 17:43		#7
immortality Senior Member Ehsan Join Date: Oct 2012 Location: Iran Posts: 2,208 Rep Power: 26	Hi a question: does the flow behind the reflected shock wave have a total pressure bigger than the original driver gas? is it correct? __________________ Injustice Anywhere is a Threat for Justice Everywhere.Martin Luther King. To Be or Not To Be,Thats the Question! The Only Stupid Question Is the One that Goes Unasked.

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April 8, 2009, 20:33		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,701 Rep Power: 143	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

April 9, 2009, 10:07		#3
matt New Member mathias kiesel Join Date: Apr 2009 Posts: 3 Rep Power: 17	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

April 9, 2009, 10:18		#4
Timon Member Join Date: Mar 2009 Posts: 44 Rep Power: 17	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).

April 9, 2009, 12:13		#5
matt New Member mathias kiesel Join Date: Apr 2009 Posts: 3 Rep Power: 17	Hi timon, thank you for the hint. I will try it soon and report then about my results. thanks