Hello, I believe that this question might be more towards OpenFoam use than SIMSCALE but I figured I would swing it by the community and see if you could help. I am having some issues related to convergence of a K-W SST model and am in the process of checking my BCs and ICs. So far I was having goo…

Hi oscarcorripio Initial/Inlet turbulence is not easy to define. But you also want to pay attention to the sensitivity of your results to these inlet values. Some models are more sensitive than others in a number of flow fields. There are a number of ways to define inlet turbulence, some involving…

No problem! [image] dylan: The turbulent viscosity is the result of turbulence modelling. So how can I calculate or find the value of this so that I know I am within the 0.1-2 range?

Hi @dylan and good to see you back! The SA 1 equation turbulence model is adapted for flows around an airfoil and as you know boussinesq approximations to not behave super accurate (whatever you define as accurate in this case), but a contracting section is a good example as the eddies loose their …

Wow, Sydney, Florida and Germany all at the same time :smiley::smiley::smiley:

From Spalart and Rumsey , you have [image] Calculate k and omega using a length scale of your choice. From this link Turbulence free-stream boundary conditions -- CFD-Wiki, the free CFD reference , you have [image] where, [image] is the turbulent viscosity ratio; [image] is air density; [imag…

@jousefm I exclusively use SpalartAllmaras, RealizableKE, and SST as RANS. In fact, I find SpalartAllmaras very useful for external aerodynamics with mild separation, such as a plane or a wing. I think @DaleKramer ’s problem can be very well solved by SA, because I have done similar projects.

Aha, I finally see it, I can just back it out from known values. And this means I really need to go to bed now … Thanks. Dale

Hi @dylan , I totally agree here but as SA is not implemented on our platform we have to work with another turbulence model. Best, Jousef

@dylan Just curious as to why you suggest calculating ut/u from the cfd_online.com formula rather than from the Spalart and Rumsey recommendation of 2e-7 * Re ? There is a 20% difference in my case. And by the way, I did have to change my reference length from a fuselage length of 5m to a value …

Did you use the same length scale in Reynolds number?

Yes [k-omegaCORRECTED-forumpost] EDIT: corrected the value for u (dynamic viscosity) which is equal to SimScale Kinematic Viscosity * Density This makes ut/u smaller than the original post…

SimScale CAE Forum

Initial Values for Turbulence Coefficients

Using SimScale Fluid Flow / CFD

dylan September 4, 2018, 9:49am 34

Turbulent viscosity and eddy viscosity are the same thing. However, nut = mut/rho, where nut is commonly used in incompressible flow, and mut in compressible flow.

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