The problems about the turbulentDFSEMinlet method for non-reacting jet

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April 18, 2019, 13:30
The problems about the turbulentDFSEMinlet method for non-reacting jet
#1
New Member

lgz
Join Date: Apr 2019
Posts: 4
Rep Power: 6
Hi,

I have run a non-reacting case with the initial turbulent inlet boundary condition which was created by the turbulentDFSEM method. However, the results there are no velocity fluctuation (u') in the streamline. I don't know how to deal with this problem.

I would appreciate any help on this matter. Thanks in advance! The cases including the files: 0/ were attached.

The turbulentDFSEMinlet was introduced in this website:
https://www.openfoam.com/releases/op...conditions.php
Attached Files
 0.zip (65.6 KB, 35 views)

 January 27, 2020, 05:23 #2 Member   Marc Join Date: May 2017 Posts: 42 Rep Power: 8 Maybe it's a bit late but the line: Code: L uniform 0; In your 0/U file defines the lengthscale of your incomming eddies as zero - so there will be no turbulence! If you used a precursor RANS simulation there are correlations to obtain L from you data. For example for a simulation you have that: You can find similar correlations for the model you employed. If you didn't get that data from a precursor RANS, I would suggest looking a two-point correlations to obtain .

 May 20, 2020, 17:19 #3 New Member   Xiangjie Wang Join Date: Jul 2019 Posts: 26 Rep Power: 6 Hi Marc, I encountered the same problem. Could you please give me some suggestions on how to do the RANS precursor simulation? I set turbulentDFSEMInlet as my inlet velocity. My computational domain is a wind tunnel with a 50(streamwise)*27.5(width)*22.5(height). I have run my simulation with a uniform velocity inlet and the results showed that it could work. But when I changed my inlet boundary condition of U, it couldn't. After inputing blockMesh and decomposePar, I input: mpirun -np 12 pisoFoam -parallel. But it was stuck at the first time step, which showed: Time = 0.005 Courant Number mean: 0 max: 0 In my simulation, the simulation type is RAS, RAS model is KEpsilon. I only defined the mean velocity profile in ./constant/boundaryData/inlet directory, and for R and L, I set them to a fixed value. This is how my inlet boundary of U looks like: inlet { type turbulentDFSEMInlet; delta 12; nCellPerEddy 1; d 1; R uniform (0.5 0.1 0.1 0.03 0.01 0.01); L uniform 0.005; mapMethod nearestCell; value $internalField; } I will appreciate it if you can give me some suggestions! Thanks! Xiangjie July 20, 2023, 14:57 turbulentDFSEMInlet gets stuck #4 New Member Alireza Maleki Join Date: Aug 2017 Location: United State Posts: 20 Rep Power: 8 Quote:  Originally Posted by XJ_Wang Hi Marc, I encountered the same problem. Could you please give me some suggestions on how to do the RANS precursor simulation? I set turbulentDFSEMInlet as my inlet velocity. My computational domain is a wind tunnel with a 50(streamwise)*27.5(width)*22.5(height). I have run my simulation with a uniform velocity inlet and the results showed that it could work. But when I changed my inlet boundary condition of U, it couldn't. After inputing blockMesh and decomposePar, I input: mpirun -np 12 pisoFoam -parallel. But it was stuck at the first time step, which showed: Time = 0.005 Courant Number mean: 0 max: 0 In my simulation, the simulation type is RAS, RAS model is KEpsilon. I only defined the mean velocity profile in ./constant/boundaryData/inlet directory, and for R and L, I set them to a fixed value. This is how my inlet boundary of U looks like: inlet { type turbulentDFSEMInlet; delta 12; nCellPerEddy 1; d 1; R uniform (0.5 0.1 0.1 0.03 0.01 0.01); L uniform 0.005; mapMethod nearestCell; value$internalField; } I will appreciate it if you can give me some suggestions! Thanks! Xiangjie

Hi Wang,

It is late, but I have the same problem, it just got stuck in the first iteration and even it does not start making the turbulence and solving the velocity equation.
my simulation is a LES and I gave the R, L, and U, and I'm using the turbulentDFSEMInlet with the following setup

PHP Code:
     inlet     {         type            turbulentDFSEMInlet;         delta           0.0762;   // 0.0762(building width)   typically represents the characteristic scale of flow or flow domain                       U         {             type        mappedFile;             mapMethod   nearest;         }         R         {             type        mappedFile;             mapMethod   nearest;         }         L         {             type        mappedFile;             mapMethod   nearest;         }                           d               1;         nCellPerEddy    3;   // should be 3 to 5         scale           1;         value           $internalField; m 0.333333333333; // 0.3333 lead to a nondimensional c1 in Eq. 11 }  Another issue is that I'm getting the following warner as well that I don't know the problem of the turbulence generator caused by that or not! PHP Code:  Reynolds stress (0.50486214 0.50627394 0.61918657 -0.086360121 0.093858697 -0.042078017) at index 0 does not obey the constraint: Rxx*Ryy - sqr(Rxy) >= 0  July 20, 2023, 15:35 #5 New Member Xiangjie Wang Join Date: Jul 2019 Posts: 26 Rep Power: 6 Hi Alireza, I guess you have found out how to solve the problem. You are using an old version of Openfoam, am I right? Quote:  Originally Posted by alireza94 Hi Wang, It is late, but I have the same problem, it just got stuck in the first iteration and even it does not start making the turbulence and solving the velocity equation. my simulation is a LES and I gave the R, L, and U, and I'm using the turbulentDFSEMInlet with the following setup PHP Code:  inlet { type turbulentDFSEMInlet; delta 0.0762; // 0.0762(building width) typically represents the characteristic scale of flow or flow domain U { type mappedFile; mapMethod nearest; } R { type mappedFile; mapMethod nearest; } L { type mappedFile; mapMethod nearest; } d 1; nCellPerEddy 3; // should be 3 to 5 scale 1; value$internalField;         m                 0.333333333333; // 0.3333 lead to a nondimensional c1 in Eq. 11     }   Another issue is that I'm getting the following warner as well that I don't know the problem of the turbulence generator caused by that or not! PHP Code:  Reynolds stress (0.50486214 0.50627394 0.61918657 -0.086360121 0.093858697 -0.042078017) at index 0 does not obey the constraint: Rxx*Ryy - sqr(Rxy) >= 0  

July 20, 2023, 16:22
#6
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Alireza Maleki
Join Date: Aug 2017
Location: United State
Posts: 20
Rep Power: 8
Quote:
 Originally Posted by XJ_Wang Hi Alireza, I guess you have found out how to solve the problem. You are using an old version of Openfoam, am I right?
No, indeed I'm using the openFoam 2212, but still I have this problem!

July 20, 2023, 16:24
#7
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Xiangjie Wang
Join Date: Jul 2019
Posts: 26
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Then the Reynold stress tensor might not be correct or pyhsical. You can check the source code and find the corresponding line then you can substitute your reynold tensor to that code.

Quote:
 Originally Posted by alireza94 No, indeed I'm using the openFoam 2212, but still I have this problem!

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