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wall shear stress determination

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Old   February 11, 2020, 05:12
Post wall shear stress determination
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Hello all,
how can I find the wall shear stress in post-processing?
In my case, I have a 3D column(4 mm gap) which has a single bubble having a diameter (3 mm or more) collides when it rises. I have to determine the wall shear stress generated by that bubble on the wall.
is there any algorithm or inbuild way to do so?
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Old   February 11, 2020, 05:25
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A 3 mm bubble in a 4 mm gap is not a bubble but a slug. You have to use multiphase model, VOF, to predict the shear stress.
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Old   February 11, 2020, 05:44
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Quote:
Originally Posted by vinerm View Post
A 3 mm bubble in a 4 mm gap is not a bubble but a slug. You have to use multiphase model, VOF, to predict the shear stress.
Dear Vinerm,
Thanks for replying
the column is wide in the lateral direction.besides that this study is conducted on a smaller bubble diameter than 3 mm too. Yes VOF simulations are already done now I only want an algorithm to find the WSS.

Thanks
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Old   February 11, 2020, 05:51
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If you wish to extract shear stress from VOF simulations, then you do not need any extra work. Shear Stress is reported directly under Wall Fluxes.

However, if you wish to determine shear stress due to particle impingement within a DPM, then you have to do some work; not just on the algorithm or the code but studying some literature on which model can be used to predict quantitative value of shear stress due to particle impingement. It won't be easy because you have to assume wall as a particle and then use mechanical properties of both, particles and wall, to predict the shear stress.

Since the particles in your case are bubbles, I don't think there would be any extra stresses on the walls, rather bubbles will be pushed away due to wall lubrication.
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Old   February 11, 2020, 05:57
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Quote:
Originally Posted by vinerm View Post
If you wish to extract shear stress from VOF simulations, then you do not need any extra work. Shear Stress is reported directly under Wall Fluxes.

However, if you wish to determine shear stress due to particle impingement within a DPM, then you have to do some work; not just on the algorithm or the code but studying some literature on which model can be used to predict quantitative value of shear stress due to particle impingement. It won't be easy because you have to assume wall as a particle and then use mechanical properties of both, particles and wall, to predict the shear stress.

Since the particles in your case are bubbles, I don't think there would be any extra stresses on the walls, rather bubbles will be pushed away due to wall lubrication.
Great
Thanks for the prompt reply vinerm.I will be back to you soon.

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