Open boundary condition for 1d euler equation?
What is the open outflow nonreflecting boundary condition for 1d Euler equations?
thank you 
Sloving a local Reiman problem, or solving the Reiman Invarients along the there waves u,u+a and ua at the eixt would work as a non reflective boundary condition.

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 
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. 
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