Quick Scheme for supersonic reacting flows

aravind vashista · March 9, 2018, 03:01

Hii all
i am solving a problem on 3d supersonic flow with flamelet model for chemical kinetics with 10 species and k-e turbulence model. i employ coupled solver to solve for pressure. i had initially employed second order for all other variables (energy, density,momentum, turbulent kinetic energy, mixture fraction) then later on after few thousand iterations i changed my solution methods to quick scheme for (density, momentum, energy) and retained second order for (turbulent kinetic energy, and mixture fraction). indoing so my mass imbalance and residuals have increased. is it beacuse of quick scheme ? is quick scheme be used for this complex flows? please let me know on this
thank u for your time

LuckyTran · March 9, 2018, 19:01

You should mention that you are using Fluent because QUICK is not the same in all codes.

Residuals are higher, but the solution is still stable right? And do you mean the residuals converged to higher values or they just spiked after you changed settings? You should expect a spike in residuals whenever you change anything.

My first guess which be to keep density discretization as before to help stabilize the p-v coupling. In general, QUICK is slightly higher order and hence more unstable than 2nd order upwind.

aravind vashista · March 10, 2018, 16:40

Thank u for the reply
Yes I am using fluent. Yes the residuals hv spiked up n came back , the solution is not stable yet . The mass imbalance has also increased. N residuals r getting stable at higher value as compared to second order in terms of magnitude

March 9, 2018, 03:01	Quick Scheme for supersonic reacting flows	#1
aravind vashista Member ARAVIND SRIDHARA Join Date: Jan 2017 Posts: 32 Rep Power: 9	Hii all i am solving a problem on 3d supersonic flow with flamelet model for chemical kinetics with 10 species and k-e turbulence model. i employ coupled solver to solve for pressure. i had initially employed second order for all other variables (energy, density,momentum, turbulent kinetic energy, mixture fraction) then later on after few thousand iterations i changed my solution methods to quick scheme for (density, momentum, energy) and retained second order for (turbulent kinetic energy, and mixture fraction). indoing so my mass imbalance and residuals have increased. is it beacuse of quick scheme ? is quick scheme be used for this complex flows? please let me know on this thank u for your time

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March 9, 2018, 19:01		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,754 Rep Power: 66	You should mention that you are using Fluent because QUICK is not the same in all codes. Residuals are higher, but the solution is still stable right? And do you mean the residuals converged to higher values or they just spiked after you changed settings? You should expect a spike in residuals whenever you change anything. My first guess which be to keep density discretization as before to help stabilize the p-v coupling. In general, QUICK is slightly higher order and hence more unstable than 2nd order upwind.

March 10, 2018, 16:40		#3
aravind vashista Member ARAVIND SRIDHARA Join Date: Jan 2017 Posts: 32 Rep Power: 9	Thank u for the reply Yes I am using fluent. Yes the residuals hv spiked up n came back , the solution is not stable yet . The mass imbalance has also increased. N residuals r getting stable at higher value as compared to second order in terms of magnitude