[PeterShi]

Hello Foamers,

Does anyone have an idea about how to fix the transition point in the OF? I know the transition points at both suction side and pressure side from the experiment. BTW, I implemented a transitional model named KomegsSSTLM in my OF 4.1.

Thanks for your help in advance.

Best regards,
Peter

[PeterShi]

This issue has been solved

[ashishmagar600]

Hello Peter.

Can you please share how you were able to fix the transition point.

It would be of great help.

Thanks in advance.

[fra76]

Hi Peter,

It would be really interesting to understand what was your strategy to impose the laminar to turbulent transition point.
It is just a matter of splitting the patch and assigning some boundary conditions? Or have you added any source term in the volume above the laminar part of the surface to kill the production term in the turbulence model? Or what else?

Thanks,
Francesco

[PeterShi]

Hello both,

Sorry for the late reply. Please shoot me an email and I can show your guys more.

Best,
Peter

[ashishmagar600]

Hello guys.

I tried this method:
1. using toposet divide the mesh for laminar and turbulent regions (cellZones)
2. use fvOptions to define fields respective of zones

But this method is not giving a satisfactory solution. Can anyone help with something else ?

[PeterShi]

Hi,

Please look at the attached slides for my strategies. I got quite satisfactory results. However, you should realize you need to move the designated transition location to upstream in your program a little bit by using method 1, since transition occurs gradually, not suddenly. For example, if you want the transition occurs at 6.5%c, maybe you can try 5%c in your program.

Method 2 is good as well and easy to employ.

Good luck.

Best,
Peter

[ashishmagar600]

hello,

one more question. Do we have to refine the mesh near the wall (y+<1) for getting results?? The solution is not converging for me the same mesh I used for free transition.

Thanks.

[PeterShi]

Originally Posted by ashishmagar600

hello,

one more question. Do we have to refine the mesh near the wall (y+<1) for getting results?? The solution is not converging for me the same mesh I used for free transition.

Thanks.

y+ <1 is needed to get accurate CL at least. I do not know what is your case. Have you achieved the fixed transition, do my methods work well?

Best regards,
Peter

[ashishmagar600]

Hello,

I am working on cases where cd matters more than cl.. I am afraid of following method2.

I have followed method 1, talking about achieving fixed transition... yes we have achieved it. (not exactly at the interface, but some further delay).

[Clément_G]

Hello dear Foamers,

I'm trying to find again the performances of an academic profil like NACA0012 at medium Reynolds number (130000) that you can find in this paper https://www.sciencedirect.com/scienc...29801814002637 (Graf, 2014).


1) I have performed 2 unsteady simulations of the of the NACA0012 with a komega-SST turbulence model with Tu=1% and Tu=8% and only the 2d one matches properly with the reference (Graf paper) although I don't respect the turbulence intensity of 1%. This observation
lets me think that the problem is linked to the laminar-turbulent
transition. For e.g. the energy of the boundary layer for Tu=1% case seems to be too low because the stall occurs too early and the laminar bubble separation are shedded. Moreover, the Graf's paper mentions that the flow is "fully turbulent". So, I need to trigger the boundary layer transition at the leading edge while satisfying the turbulence intensity level of the original paper (Tu=1%).



Does someone has any comment on my results in low Reynolds number flow (around 100000)?


2) In order to trigger the boundary layer transition with a komega SSTLM model, I found the interesting "method 1" of Peter Shi explained in this slide (see picture 2). Unfortunately, I failed in defining a right zone in topoSetDict where k=0 and nut=0 in front of the leading edge of the airfoil represented in the 3rd picture. It seems that the x-abscissa of the 2d point of the box (topoSetDict below) isn't taken in account, but I don't know why?!


My topoSetDict file is defined below:

actions
(
    {
        name    laminar;
        type    cellSet;
        action  new;
        source  boxToCell;
        sourceInfo
        {
                box (-4 -4 0.08)(0.005 4 0.085);
        }
    }

);

and the fvOptions file:

source1
{
        type    scalarFixedValueConstraint;
        active  yes;
        scalarFixedValueConstraintCoeffs
        {
                selectionMode   cellSet;
                cellSet         laminar;
                fieldValues
                {
                        k       0;
                        nut     0;
                }
        }

}

Does somebody has any hint to help me to get the right distribution of k and nut shown in the last picture (4th picture)?


Thank you in advance


Clément