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David February 15, 2004 01:25

Dynamic mesh update problem.

I use dynamic mesh model to simulate the motion of a flexible beam acted by wind based on DEFINE_GRID_MOTION() macro. The UDF is complied correctly and the motions of the dynamic boudaryies is proper according to the predefined condition. But I met a mesh update problem.My case is structural mesh.

According to the guide, the User-Defined motion type must be chosen when this macro was employed. The spring-based smoothing mesh update option is selected. But this mesh update method is seemed disabled because I find the cell near the dyanmic boundary does not deform to fit the moving boundary in the process of time steps. This results Fluent prompts:

"WARNING: non-positive volumes exist.

Error: Update-Dynamic-Mesh failed. Negative cell volume detected. Error Object: ()"

I had adjusted the parameters of smoothing method, and also tried the dynamic layering method, but no better results were produced. It seemed that, in my case, it is difficult to move the neighboring cell zone although the dynamic boundary moves properly. who can explain this problem?thanks.

cip dany February 20, 2004 13:57

Re: Dynamic mesh update problem.
i've worked most of my time in dynamic mesh. ok. my advise. make a small mash close to your beem(preferable a dinamic layer for 2d or a size function for 3d) after you've done this associate the udf with this zone of fluid. use local remeshing by calculating the parameters that it's asking. i've done this so many times so certenly works

Spring.s March 15, 2012 00:50

layering method
Also this post is old but i have one problem in layering method.
I want do the modeling that the body move at one direction in the channel with the circular section. I use the same UDF that be in UDF Manual of fluent 6.3. There is one problem during simulation of this case, that the behind cells of body do not split correctly and those stretched, while the cells in front of body, colapse correctly. Despite i change the split and colapse coefficients, do not vary in solution. I will thankful everyone that help me for this problem.

rezacfd1361 March 15, 2012 06:02

Time plot of the history of wave elevation in a defined point in NWT in Fluent
Dear friends

I m working with fluent 6.3 ,I modelled a wave tank in fluent and I want to get time plot about the history of wave elevation at a specified point for example x=7.5,y=0.5 (in fluent I accentuate this matter again) in a wave tank with these dimensions: L=15m, H=0.8m for a detemined time domain which is smaller than wave tank modeling time domain.

if any friend know, plz guide me and give me the tips and tricks about it.

With kind regards.

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