Standard initialization with an expected pressure

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 March 26, 2013, 15:08 Standard initialization with an expected pressure #1 New Member   Join Date: Mar 2013 Posts: 1 Rep Power: 0 I'm using the SIMPLE solver to find the area-weighted average of static pressure at the inlet of a laminar, steady-state, incompressible flow within a porous material. My boundary conditions are a velocity inlet and a pressure outlet. From theory, I know what the pressure inlet should roughly be. However, if I try to initialize the problem with this theoretical pressure inlet, the solver gives me worse convergence and the pressure starts diverging at a high rate (though I did not keep running the simulation for long due to this initial observation). If I standard initialize using the default values at the velocity inlet, the convergence trend is much more re-assuring and the values do not tend toward divergence. Also, hybrid initialization with default settings also gives me worse convergence. Is there a better way to specify an expected solution at the initialization stage to speed up the convergence process? What are the exact steps? Thank you!

 March 27, 2013, 09:30 #2 Senior Member   OJ Join Date: Apr 2012 Location: United Kindom Posts: 473 Rep Power: 19 Often it takes a bit of experimentation to deduce the right approach for initialization strategy. As long as you get a converged solution, it doesn't exactly matter how you initialized it, but right initialization yields faster convergence. In your case, in addition to standard initialization, you can also "patch" the inlet pressure to your inlet boundary. Also, have a look at FMG initialization, wherein your geometry is meshed with virtually with coarse mesh and the Euler inviscid equations are solved. Be aware that FMG doesn't initialize turbulence quantities (k, etc). So it is important to specify appropriate quantities at boundaries. The solution is then applied to successive meshes until the final fine mesh. Process takes few minutes but provides a good initialization. Another way is to start having a coarse mesh solution as initial solution. This is possible in CFX, but not sure about FLUENT. OJ

 September 4, 2013, 01:18 #3 New Member   Jalay Shukla Join Date: Aug 2013 Posts: 11 Rep Power: 12 i get smooth curve while going with hybrid initialization when i go for air in with standard initialization it continuously converge diverse .. why this would be happening?

 March 11, 2020, 07:43 #4 New Member   Muhammad Lutfi Aziz Join Date: Mar 2020 Posts: 15 Rep Power: 5