Far field boudary conditions in FDM

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 July 14, 2005, 16:29 Far field boudary conditions in FDM #1 James Guest   Posts: n/a Hi, I have a simple shear flow with complicated interface conditions and am struggling to formulate far field boundary conditions for a staggered type grid. Applying du/dx=dv/dx=0 on the boundary I still have an unknown pressure term outside my domain. Any ideas? Also at the boundaries should I apply the boundary conditions above to the equations (Stokes) or simply disretise them and use them instead of the normal equations? Thanks James

 July 15, 2005, 12:19 Re: Far field boudary conditions in FDM #2 agg Guest   Posts: n/a This is for incompressible flow" For velocities just set u(N) = u(N-1) {along X) v(N) = v(N-1) (along X) For pressure set pressure such that pressure at boundary to be zero P(N+1) = - P(N-1) Where N+1 is pressure point just ouside of domain and N-1 is point just inside domain (for staggered grid)

 July 15, 2005, 12:47 Re: Far field boudary conditions in FDM #3 james Guest   Posts: n/a Thanks, thats great. One final thing, would you substitute u(N)=u(N-1) into the discretised Stokes equations (so that dp/dx=d2u/dy2 etc) or would you simply use u(N)=u(N-1) instead of the bulk equations? Also do you know of any good books/sites on FDM and in particular staggered grid arrangements as on the whole I have found the literature average. Thanks again James

 July 20, 2005, 02:44 Re: Far field boudary conditions in FDM #4 yuan Guest   Posts: n/a At outflow boundary the zero-gradient condition for (u,v,p) may work well. But you need fix something of the inflow.

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