SHEAR_SMAGORINSKY

[Fuxin He]

Dear OpenLB community,

I replaced “SmagorinskyForcedBGKdynamics” with “ShearSmagorinskyForcedBGKdynamics” in channel3d and it never runs successfully. I can’t get it to run successfully, is this based on the descriptor, because in nozzle3d it says “#ifdef USE_SHEAR_SMAGORINSKY”.
using DESCRIPTOR = D3Q19<AV_SHEAR>;” and I understand from the literature that I want to implement a dynamic smagorinsky model instead of a shear smagorinsky model, should I change the model to a channel in nozzle3d?

sincerely,
Fuxin He

[stephan]

Dear Fuxin He,

for using the shearSmagorinsky dynamics, please use the conforming descriptor as you suggested:
“#ifdef USE_SHEAR_SMAGORINSKY”.
using DESCRIPTOR = D3Q19<AV_SHEAR>;”

Best regards,
Stephan

[Rookie]

Rookie

• This reply was modified 1 week, 1 day ago by Rookie.
• This reply was modified 1 week, 1 day ago by Rookie.
• This reply was modified 1 week, 1 day ago by Rookie.

[Fuxin He]

Dear Stephan，

Thanks for writing back, I’m still using this descriptor“typedef WallFunctionForcedD3Q19Descriptor DESCRIPTOR;”and selected “ShearSmagorinskyForcedBGKdynamics”.It runs fine, so is this something I still need to change.

I also want to ask a question, I saw a post mentioned a mistake about Reynolds stress, but you only corrected half of the line 225 should be as said in this post：
https://www.openlb.net/forum/topic/correction-to-superlatticetimeaveragedcrosscorrelationf3d/
If I set after “SuperLatticeTimeAveragedCrossCorrelationF3D < T > sAveragedVelcc (sVel sVel);”Is the output “Time Averaged Corss Correlation physVelocity-physVelocity_2” Reynolds stress？

sincerely,
Fuxin He

[stephan]

Dear Fuxin He,

please note that the descriptor needs a tag …<AV_SHEAR> to make the shear Smagorinsky dynamics work correctly.

Please have a look at the doxygen to learn more about input and output of specific functors.
In your case, please consider:
https://www.openlb.net/DoxyGen/html/da/d58/classolb_1_1SuperLatticeTimeAveragedCrossCorrelationF3D.html

BR
Stephan

[Fuxin He]

Dear Stephan，

In this file I also think it should be changed to “_sDataMN.getBlock(iCloc).get(input+1,iDim)/_ensembles” because it is “(uv)_av – u_av v_av,” and there is no averaging of (uv)。After I output the original result and compare it with the literature, I find that the trend is correct, but the value is indeed too large

sincerely,
Fuxin He

[stephan]

Dear Fuxin He,

please specify the exact lines of the code you mean.
In case you have found a bug, please provide comparison to reference data in a plot or implementation for us to double-check.

Thank you and BR,
Stephan

[Fuxin He]

Dear Stephan，

I’m sorry for the late reply, because I just finished dealing with the result. The error is just as I said in the last post attached. In of this folder (/ olb1.6 r0 / SRC/functors/lattice timeAveraged/superLatticeTimeAveraged3D hh) line 225 should be “the output = [iDim] _sDataMN.getBlock(iCloc).get(input+1,iDim)-_sDataM.getBlock(iCloc).get(input+1,iDimM) *_sDataN.getBlock(iCloc).get(input+1,iDimN)/_ensembles/_ensembles;” Change to “output[iDim] = _sDataMN.getBlock(iCloc).get(input+1,iDim)/_ensembles-_sDataM.getBlock(iCloc).get(input+1,iDimM)” *_sDataN.getBlock(iCloc).get(input+1,iDimN)/_ensembles/_ensembles. In other words, you are missing an average of MN, which is the Reynolds stress processed after my modification. Although it is not in perfect agreement with Kim’s result, it is much better than the original data, which is 1000 times higher than the modified one.

Below is my output, compared to Kim’s literature：Kim J, Moin P, Moser R. Turbulence statistics in fully developed channel flow at low Reynolds number[J]. Journal of fluid mechanics, 1987, 177: 133-166.

https://postimg.cc/gallery/ZSHWS1h

sincerely,
Fuxin He

[Author]

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