[som87]

Hi,
I am asked to do acoustic analysis with RANS model for my thesis.
I am using inhouse k-omega sst model applied in overture. Since my flowfield is with very low mach number (vel=10, M=0.05) I am not sure whether there's any point on calculating spectra of SPL.
Can anyone please guide me regarding this?
I am attaching my instantaneous acoustic pressure contour here for oscillating S809 airfoil.

Please let me know if someone has any tips for this

[FMDenaro]

well, that sounds strange...using RANS for solving acoustic problem what kind of information you want to extract??

[som87]

Hi again,
As per theory phi_comp=phi_incomp+Phi_acoustic
where Phi=fluid property
When using RANS, I am assuming that I am getting the mean (time avg) value of phi

So by I concluded that Phi_acoustics==Phi_comp-Phi_incomp

I know it is not very accurate, but that's what I can do at max after being asked to add "acoustics result" before 1 month of my first presentation.


Am I wrong on my assumptions?
I compared my instantaneous acoustic pressure for naca0012 with C. Tam's JFM paper of 2012.It was "similar". So I am planning to just capture the instantaneous acoustic pressure contour (roughly..since it's impossible for me to write LES now) and leave it at that (I intend to target my solver description & overset grid as main "topic")

[tb_cfd]

Acoustics is depending on instationary effects (fluctuations). You can use your solution of the RANS-simulation as start solution for a transient CFD. Then it is possible to extract the fluctuations and you can calculate for example the acoustic spectra with FW-H analogy.

[som87]

I dont want to use FW-H.
Reason is:-
My airfoil is oscillating, so obviously the acoustic wave generating points at boundary layer will change position. So my mono/di/quadrapole's positions are NOT fixed over airfoil span

[FMDenaro]

well, therefore you should use URANS, isn't? I think that after solving the flow field you should resolve the acoustic field assuming to know the velocity field

[som87]

I am using URANS sir, and I just wanted some senior's comment on my approach, that's all.
What I am doing is:-
Running two separate simulations with URANS in compressible & incompressible model. After 20 cycles (of airfoil oscillation) on each I am capturing the data.
I did not intend to do acoustics at start (since URANS wouldn't be by choice if I wanted to), but now I HAVE to add some acoustics result.

[Shamoon Jamshed]

Dear Somdeb,

Although this is not relating to your issue of URANS. I am writing here because I emailed you on your gmail account for a paper issue. The paper you wrote on DES study over a transonic body. Could you please reply to me on that?

Regards,