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 June 27, 2006, 06:43 Re: Steady state #42 diaw Guest   Posts: n/a Ruben OP: I'm writting a code for solving the Euler equations of compressible flow. I'm interested in state state solutions and I have problems with the oscillations. Even in the subsonic case I have spurious oscillations and the convergence is too slow. I think that I need a time integration scheme with damping. What scheme can I use? ------ diaw comments: After all has been said & argued on this thread, & after spending a while reviewing both Euler & Potential derivations & equations forms, I must say that I fail to see a useful valid connection between the two. Potential flow: Irrotational flow => transform via u=d(phi)/dx ; v=d(phi)/dy => d2(phi)/dx2 + d2(phi)/dy2 =0 Euler flow (weak form): d()/dt + u.d()/dx + v.d()/dy = f(x,y,t) The two are completely different animals: 1. The Laplace equation is going to either decay/grow in time, if a d(phi)/dt is bolted on & dependent on the sign used & possibly some forcing function. If in steady form, then we have a nice smooth shape. 2. Euler eqn is a convection flow which is inherently unstable & wants to produce instability, waves & the like. Not too smooth at all... If you really begin to look deeply into the physics of what these forms actually represent, they are very different. I have no doubt that the OP sees waves - & so he should with a good algorithm. It is a poor algorithm that adds unwanted numeric viscosity. diaw...

 June 27, 2006, 17:17 Re: Steady state #43 Ruben Guest   Posts: n/a Thnaks for your comments diaw.

 May 7, 2011, 03:32 #44 New Member   m p Join Date: Nov 2010 Posts: 15 Rep Power: 8 what are the correct boundary conditions for this problem? we need 4 in 2D .among them one is extrapolation which I use riemann invariant extrapolation,but what are the others when we have the inlet mach number?

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