Simulating turbulent flow in rectangle pipe with rhoPimpleFoam

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 January 3, 2014, 20:23 Simulating turbulent flow in rectangle pipe with rhoPimpleFoam #1 Member   赵庆良 Join Date: Aug 2013 Posts: 56 Rep Power: 5 Hi foamers, I want to use rhoPimpleFoam to simulate turbulent flow in rectangle piple.here is my mesh,it is simple. mesh.jpg The length is 200mm,width and high is 25mm.The detail is in blockMeshdict. Code: ```FoamFile { version 2.0; format ascii; class dictionary; object blockMeshDict; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // convertToMeters 1; vertices ( (0 0 0) (0.2 0 0) (0.2 0.025 0) (0 0.025 0) (0 0 0.025) (0.2 0 0.025) (0.2 0.025 0.025) (0 0.025 0.025) ); blocks ( hex (0 1 2 3 4 5 6 7) (100 20 20) simpleGrading (1 1 1) ); edges ( ); boundary ( bottomWall { type wall; faces ((0 4 5 1)); } topWall { type wall; faces ((7 6 2 3)); } sides1 { type wall; faces ((7 4 5 6)); } sides2 { type wall; faces ((3 0 1 2)); } in { type patch; faces ((0 4 7 3)); } out { type patch; faces ((1 5 6 2)); } ); mergePatchPairs ( );``` The U initial condition is that x-direction is 1m/s,y and z direction are 0.As following: Code: ```dimensions [ 0 1 -1 0 0 0 0 ]; internalField uniform (0 0 0); boundaryField { bottomWall { type fixedValue; value uniform (0 0 0); } topWall { type fixedValue; value uniform (0 0 0); } sides1 { type fixedValue; value uniform (0 0 0); } sides2 { type fixedValue; value uniform (0 0 0); } in { type turbulentInlet; referenceField uniform (1 0 0); fluctuationScale (0.1 0.1 0.1); value uniform (1 0 0); } out { type inletOutlet; inletValue uniform (0 0 0); value uniform (0 0 0); } }``` The deltaT I used in controlDict is 1e-4.Picture "time0" is my U field at time=0. time0.jpg Then I run my case,and I write out a result at every 20 deltaT(The first result is time=0.002).Picture "time1" is U field at time=0.002. time1.jpg Please take a look at time1 picture carefully.Just after 0.002s,the outlet's velocity is nearly 1m/s,same as initial vilocity I defined firstly. Actually,it is unphysical.Because 1m/s*0.002s=2mm.And the mesh length is 200mm,it is impossible that after 0.002s,outlet's velocity is nearly 1m/s. Could some one tell me that where I was wrong?What cause the problem?

 January 6, 2014, 06:24 #2 Senior Member   HECKMANN Frédéric Join Date: Jul 2010 Posts: 237 Rep Power: 9 Put your full case here, it will be easier to check

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