studying a valve case
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Hi all,
I'm studing a simple case which is a box with circular inlet (velocity 5,3 m/s) and an outlet (pressure =0) with walls and a valve (which is also wall). I simulate with air and using simpleFoam. Attached the pictures of the geometry and in the next post i will attach the problem pictures. |
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My problem is that using internal field, I have elements with high pressure at the interface between the inlet and the wall. Taking in consideration that I use feature edge: P { margin-bottom: 0.21cm; }
surfaceFeatureExtract -includedAngle 150 -writeObj constant/triSurface/surfacemesh.stl surfacemesh. Can anybody help me to solve this issue? |
it may return to your mesh, first check your mesh with checkMesh
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Dear Nima Sam,
I already check the mesh, & I think there is no problem. Code:
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well, did you consider uniform velocity at inlet and fixedValue for walls ?
if yes, you may want to try a profile for inlet velocity to make it much smooth near wall :) However you should provide more details until we can help you :) |
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Dear Nima Sam,
yes I consider uniform velocity with fixedValue at inlet (0 0 5.3) and a fixed value wich is also uniform of (0 0 0) at walls attached are the U, P, boundary files. taking in consideration that: stlSurface_mur --> wall stlSurface_clapet --> valve stlSurface_entree ---> inlet stlSurface_sortie --->outlet best regards, Mina |
well, its some how reasonable :), you assign a uniform fixed value velocity for inlet and also :) you assigned a no slip condition on wall :),consider just cells in edges, on those cells should be imposed both above conditions :), or in other words when fluid enters geometry with a uniform velocity, it should be compatible with no slip conditions on wall, so it should become zero :) so in one or two inlet cells you observed a high-pressure :) as i said in previous post you can assign a non-uniform velocity at inlet, for example parabolic one, then you would not see those high pressure
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I see, thanks a lot NimaSam for your help i will try now to search about non uniform velocity at inlet.
Regards, Mina Quote:
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But when i tried another geometry for inlet for example a rectangular surface instead of circular one.. I didn't realize these strange elements with high pressure !!!
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Greetings to all!
@Mina: I got your PM some time ago, but only today did I manage to look into this. I only have a few comments to make:
Bruno edit: Looks like the untrained readers are not able to understand which is which, in the attached images. It's simple:
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for more clarification,
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Hi Ehsan,
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I can't believe I'm going to have to explain this :( ... OK, in ParaView there are three basic geometrical types of representation:
Is it clear enough now? :confused: Best regards, Bruno |
very good description dear Bruno.there is one cfd-online and one Bruno Santos!
I don't know what I could do if you were not here. ;) another non related question! how do you write lists in your posts? |
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First of all, my STL file was in "mm" so after blockMesh and snappyhexMesh, I use transfomPoints to change from millimetres to metres. Is there any problems related to this? Here are some pictures using cells/faces representation I used these residuals values residualControl { p 1e-2; U 1e-3; "(k|epsilon|omega)" 1e-3; } and I put the endTime in controlDIct file to 3000 but in fact the solution didn't converge and it stops while attending the 3000 and it didn't converge before. I think i can't make the endTime more than 3000 because it took a lot of time to calculate. and in the next post i will attach other pictures using slice fliter Regards, Mina |
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These are other pictures, you can see these strange cells with high pressure .
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Hi Mina,
OK, there are several issues that seem to be possibly be occurring here:
Best regards, Bruno |
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Thank you so much for your reply. I created a very simple case which is a simple cylinder with inlet (velocity =5.3), walls , outlet (P=0). I used the solver simpleFoam with turbulent. I tried to vary the mesh with different values, increasing and reducing also i tried to apply a filled but the same problem is still there. I'm so surprise, I attached some pictures which explain this issue. |
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Could you post here the test case? This is strange behavior indeed :) I am guessing that it is caused due an inconsistent boundary conditions or due the numerical pressure singularity phenomena (e.g."L" problem or squeeze flow issue). Btw. It is usual to use pressure driven flow. In the test case that can be interpreted as PRESSURE driven flow in cylindrical pipe there exists an analytical solution. You can find it as Poiseuille fluid flow. It could help you to set the model properly. Best regards Martin |
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here is the test case |
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