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dynamic mesh motion (angularOscillatingDisplacement) in OF1.6 |
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#1 |
New Member
Tamás Baksa
Join Date: Dec 2009
Location: Budapest, Hungary
Posts: 2
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Dear Foamers,
I'd like to simulate the flow around an oscillating cross-section. The shape is very simple it is almost like a rectangle. I had to define very fine boundary layer resolution in order to stay below y+<1. The chord length of my shape is 1 [m] and the first cell next to the wall is 0.04e-3 [m]. My constant/dynamicMeshDict looks like: Code:
dynamicFvMesh dynamicMotionSolverFvMesh; solver displacementLaplacian; motionSolverLibs ("libfvMotionSolvers.so"); diffusivity quadratic inverseDistance 1(fixedWalls); // **************************************** // Code:
... boundaryField { [inlet, outlet, frontAndBack description] fixedWalls { type angularOscillatingDisplacement; // angle = angle0_ + amplitude_*sin(omega_*t.value()); axis (0 0 1); // direction origin (0 0 0); angle0 0; amplitude 0.17453; // 10 deg in rad omega 6.2832; // 1Hz * (2pi) value uniform (0 0 0); // ??? } } // ********************************************* // Code:
Mesh non-orthogonality Max: 179.989 average: 7.45988 *Number of severely non-orthogonal faces: 318. ***Number of non-orthogonality errors: 50. ***Error in face pyramids: 204 faces are incorrectly oriented. http://img526.imageshack.us/img526/7...edmesha183.png Do you have any idea how to avoid this? 1) Maybe using different diffusivity fields? According to Jasak and Tukovic paper [1] I should try diffusivity proportional to the distortion energy. But none of the available diffusivity keywords sound like dist. energy in OF1.6: Code:
10 ( uniform quadratic file motionDirectional inverseDistance inversePointDistance inverseFaceDistance directional inverseVolume exponential ) Code:
5 ( dynamicMotionSolverFvMesh // I'm using this one solidBodyMotionFvMesh dynamicRefineFvMesh dynamicInkJetFvMesh staticFvMesh // mesh has no motion ) ps: my time step is sufficiently small, I think: 2e-4 [1] http://powerlab.fsb.hr/ped/kturbo/Op...tionFAMENA.pdf [2] http://www.aero.lr.tudelft.nl/~frank/index.php?id=research/cfd/problems/2D_movingmesh_wing |
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#3 |
Senior Member
Kevin Smith
Join Date: Mar 2009
Posts: 104
Rep Power: 17 ![]() |
If you can conform your mesh around the body to a circle, you could use GGI to oscillate the body, which would avoid mesh deformation. Take a look at the mixerGGI example and code, it is fairly easy to change the driving function to a cosine signal.
If you don't want to change your mesh or simply cannot conform the mesh surrounding the body to a circle, I would look into the subset motion as Eric mentioned or RBF mesh motion. |
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#5 |
Senior Member
Kevin Smith
Join Date: Mar 2009
Posts: 104
Rep Power: 17 ![]() |
Ah, you are correct.
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