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*** Guidelines on Boundary Layer Meshing ***

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Old   March 18, 2008, 10:27
Default *** Guidelines on Boundary Layer Meshing ***
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I am about to mesh a large vehicle with a boundary layer mesh but I don't know what parameters to put in. I have no problems creating the b.l. mesh but I'm unsure how many layers to use, what height to put the first cell for a y+ of 30-50 and what expansion factor to use.

Has anybody used these before, can you give me your suggestions, maybe with a reference or two? In the past people have suggested 5 layers but I am happy to listen to any advice.

Any advice would be greatly appreciated as this represents the final stage of my PhD work and I only have 6 months left! So I want to get it right. As i said, any references would be very helpful.

Many thanks for your help,

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Old   March 18, 2008, 23:19
Default Re: *** Guidelines on Boundary Layer Meshing ***
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5-7 layer is sufficient,expansion ratio should be 1.1 - 1.2.
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Old   March 19, 2008, 06:44
Default Re: *** Guidelines on Boundary Layer Meshing ***
Ralf Schmidt
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the expansion ratio of 1.1 to 1.2 is ok... but i would take more BL rows!

Depending on the results you are interested in, i would choose the turb. model and therfor set y+. For calculation of heat or mass transfer and draq i would suggest the sst k-w model with y+ between 1 and 5.

The total thickness of the BL cells should be about the same size as the real velocity bl - the area, where the vel. is below 99 % of the free stream vel.

Hope, that helps Ralf
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Old   March 19, 2008, 08:29
Default Re: *** Guidelines on Boundary Layer Meshing ***
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for a 2D analysis of wing with fowler flap, I used expansion 1.2 and 25 layers.I didn't try with fewer layers. With Spalart-Almaras turb. model I get a mean value of y+ of 0.7.

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