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March 30, 2020, 22:50 |
TKE production and Dissipation for DNS
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#1 |
Member
Akshay Patil
Join Date: Nov 2015
Location: Pune, India
Posts: 35
Rep Power: 10 |
Hi guys,
I am working on a DNS calculation and would like to confirm if the TKE production and Dissipation calculations on the fly make sense. I am constantly getting about one order of magnitude difference between production term and dissipation term. in my code Production is defined as (Production = -ui'uj'dui/dxj) Code:
volSymmTensorField gradU = symm(fvc::grad(U)); volScalarField prod = -((U - u_bar)*(U - u_bar)) && gradU; //Take the volume average in the domain dimensionedScalar production = average(prod); Code:
volTensorField gradUprime = fvc::grad(U-u_bar); volScalarField eps = nu*(gradUprime && gradUprime); //Take the volume average in the domain dimensionedScalar dissipation = average(eps); When I do this the TKE production < dissipation by about an order of magnitude. I have checked the dependence of the mesh on this and it is consistently the same so I am wondering if I did something wrong here. I am using C-N for the viscous temporal discretisation while all other settings are second order. I have also switched off the extra phi term in the Piso algorithm which stabilises the solver. Would be grateful to hear what you think. Thanks! Regards, Akshay Patil |
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October 8, 2023, 10:00 |
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#2 |
New Member
Xingguang Zhou
Join Date: May 2022
Location: CHINA
Posts: 14
Rep Power: 4 |
Hi Patil, maybe you can make the validation with Kim, Moin, and Moser (1987) DNS data for TKE production rate and dissipation rate. Nowadays, I also dedicate myself to quasi-DNS with OpenFOAM. The equations of TKE production rate and dissipate rate are both same to yours. However, I try to post-process these two physical quantities in the way to make the modification of solver and utilities, ie pisoFoam and postChannel (OpenFOAM v2006).
The case is running on HPC, and I will make the comparation with MKM (1987) to verify whether these methd is correct or not. Best regards. Xingguang Zhou. |
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April 29, 2024, 12:01 |
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#3 | |
New Member
shiyu
Join Date: Mar 2018
Location: london
Posts: 9
Rep Power: 8 |
Quote:
I am wondering if you have got any good results and I am also quite interested in this topic. Thanks. |
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April 29, 2024, 12:21 |
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#4 |
Member
Akshay Patil
Join Date: Nov 2015
Location: Pune, India
Posts: 35
Rep Power: 10 |
Hi,
I stopped using OpenFOAM for simple Channel Flow type DNS since its not fast enough compared to some existing spectral and/or finite difference solvers. Initially my aim was to extend it for non-flat channel walls but it was easier to implement an immersed boundary method as opposed to using OpenFOAM. Hope this helps and sorry I cannot be of much help with regards to this. |
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Tags |
dissipation, dns, production, tke |
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