How to set periodic boundaries with initial conditions?
I'm using openfoam to creat a pipe.
I want to realize a periodic fluid flowing within this pipe. I set inlet and outlet as cyclic, and a initial velocity in interfild. But after some timesteps the fluid's velocity become smaller and smaller. What i want is a stable fluid with constant velocity. Can anybody tell me why and how to fix this problem? Thanks a lot. |
there is no driving force for your flow therefore you see the flow decay to zero velocity. Look into using a pressure gradient driving force (pressureGradientExplicitSource) through using an fvOption. Search the forum for more details. Good luck.
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simply you can change your inlet BC to: type fixedValue; value uniform (1 0 0); for example at inlet with pressure BC as zeroGradient. then you can put outlet BC as zerGradient for velocity and for pressure: type fixedValue; value uniform 1; // note it is scalar while velocity is vector. value here for pressure/density. in this way to assure continues flow at pipe. could you please share your pipe mesh with me. good luck, |
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Hi, i may misunderstanding you. do you mean by periodic that you want exit flow to reentering your pipe? our you want fixed flow rate of fluid? I’m sorry if i confused you. |
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This is what I want to achieve. I've used "sourcesProperties".But it did not work. all { type pressureGradientExplicitSource; active on; //on/off switch timeStart 0.0; //start time duration 1e10; //duration selectionMode all; //cellSet // points //cellZone pressureGradientExplicitSourceCoeffs { UName U; fieldNames ( U ); // flowDir (0 1 0 ); // set Re=64,000 Ubar (0 1 0); // desired average velocity gradPini gradPini [0 1 -2 0 0] 0; // initial pressure gradient } } |
Here is my blockmesh.
convertToMeters 0.001; vertices ( ( 11.3137 0 11.3137) //0 (-11.3137 0 11.3137) //1 (-11.3137 0 -11.3137) //2 ( 11.3137 0 -11.3137) //3 ( 22.6274 0 22.6274) //4 (-22.6274 0 22.6274) //5 (-22.6274 0 -22.6274) //6 ( 22.6274 0 -22.6274) //7 ( 11.3137 100 11.3137) //8 (-11.3137 100 11.3137) //9 (-11.3137 100 -11.3137) //10 ( 11.3137 100 -11.3137) //11 ( 22.6274 100 22.6274) //12 (-22.6274 100 22.6274) //13 (-22.6274 100 -22.6274) //14 ( 22.6274 100 -22.6274) //15 ); blocks ( hex (2 3 11 10 1 0 8 9) (20 10 20) simpleGrading (1 1 1) hex (7 4 12 15 3 0 8 11) (20 10 20) simpleGrading (1 1 1) hex (4 5 13 12 0 1 9 8) (20 10 20) simpleGrading (1 1 1) hex (5 6 14 13 1 2 10 9) (20 10 20) simpleGrading (1 1 1) hex (6 7 15 14 2 3 11 10) (20 10 20) simpleGrading (1 1 1) ); edges ( arc 4 7 ( 32 0 0) //arc_0 arc 12 15 ( 32 100 0) //arc_1 arc 5 4 ( 0 0 32) //arc_2 arc 13 12 ( 0 100 32) //arc_3 arc 6 5 (-32 0 0) //arc_4 arc 14 13 (-32 100 0) //arc_5 arc 7 6 ( 0 0 -32) //arc_6 arc 15 14 ( 0 100 -32) //arc_7 ); boundary ( INLET { type cyclic; neighbourPatch OUTLET; faces ( (0 1 2 3) (0 4 7 3) (0 1 5 4) (1 2 6 5) (2 3 7 6) ); } OUTLET { type cyclic; neighbourPatch INLET; faces ( ( 8 9 10 11) ( 8 11 15 12) ( 8 12 13 9) ( 9 13 14 10) (10 14 15 11) ); } FIXEDWALL { type wall; faces ( (4 7 15 12) (4 5 13 12) (5 6 14 13) (6 7 15 14) ); } ); mergePatchPairs ( ); |
Hi,
thanks a lot for your mesh. it is quite easier from mine. i make my mesh lick triangle cheese. |
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