Open boundary condition for 1d euler equation?

Ashley · July 28, 2009, 18:19

What is the open outflow nonreflecting boundary condition for 1d Euler equations?
thank you

vinayender · July 29, 2009, 06:18

Sloving a local Reiman problem, or solving the Reiman Invarients along the there waves u,u+a and u-a at the eixt would work as a non reflective boundary condition.

Ashley · July 31, 2009, 13:34

Thank you very much.I have calculated the exact solution using method of characteristics.Did you mean that I can put those values as the outflow BC?
thanks alot

vinayender · August 3, 2009, 05:05

Yes right but, dont calculate them manually and give as the BC,,,
because you have the flow properties variying across the exit of the domain. That is
on left side state of the normal outward vector on the outlet will be varying and your right side state would be fixed by free stream conditions, so let your code calculate the exact fluxs on all the faces on the outlet bc in every iteration.

And rember this method would be good enough only if there is no wake passing through outlet. (As method of charatraristics is appicable only for isentropic flows). So incase you fell that some wake is moving out of the oulet then make your outlet bc very far such that by the time this wake reaches the outlet it would have smeared out removing all the graidients.

July 28, 2009, 18:19	Open boundary condition for 1d euler equation?	#1
Ashley New Member Join Date: Jul 2009 Posts: 6 Rep Power: 17	What is the open outflow nonreflecting boundary condition for 1d Euler equations? thank you

July 29, 2009, 06:18		#2
vinayender New Member Vinayender Join Date: Jul 2009 Location: India Posts: 24 Rep Power: 17	Sloving a local Reiman problem, or solving the Reiman Invarients along the there waves u,u+a and u-a at the eixt would work as a non reflective boundary condition. __________________ Thanks , Vinayender

August 3, 2009, 05:05		#4
vinayender New Member Vinayender Join Date: Jul 2009 Location: India Posts: 24 Rep Power: 17	Yes right but, dont calculate them manually and give as the BC,,, because you have the flow properties variying across the exit of the domain. That is on left side state of the normal outward vector on the outlet will be varying and your right side state would be fixed by free stream conditions, so let your code calculate the exact fluxs on all the faces on the outlet bc in every iteration. And rember this method would be good enough only if there is no wake passing through outlet. (As method of charatraristics is appicable only for isentropic flows). So incase you fell that some wake is moving out of the oulet then make your outlet bc very far such that by the time this wake reaches the outlet it would have smeared out removing all the graidients. __________________ Thanks , Vinayender

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July 31, 2009, 13:34		#3
Ashley New Member Join Date: Jul 2009 Posts: 6 Rep Power: 17	Thank you very much.I have calculated the exact solution using method of characteristics.Did you mean that I can put those values as the outflow BC? thanks alot