Fluids

Fluids

Total Turb. Kinetic Energy and Dissipation Rate

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    • NimaNZ
      Subscriber

      Hi everyone

      As in LES the TKE and TDR are not provided I have to calculate them through the CFF for the sampling process.

      I can calculate the resolved TKE by: (rmse-x-velocity ^ 2 + rmse-y-velocity ^ 2 + rmse-z-velocity ^ 2) / 2

      But how can I calculate the modeled TKE in the WALE SGS model to obtain the total TKE as TKE_tot=TKE_resolved+TKE_modeled

      And how about the TDR?

      I want these two values for obtaining the Lenght Scale of Turbulence as L=(K^3/2)/epsilon


      I would appreciate any help or suggestion.

      Thanks

    • DrAmine
      Ansys Employee
      TKE modeled can be estimated from
      S is the strain rate magnitude.

      TDR is proportional to S^2. Proportionality constant is mu+mu_t.
    • NimaNZ
      Subscriber

      Thanks a million for your reply. Can I calculate it through the following If so, is l_sgs the Ls in the ANSYS formulation? which is the following in the WALE model. And is the length scale of turbulence that I need for grid resolution assessment as L/delta?
      *EDITED by DrAmine: Removed Picture*


    • DrAmine
      Ansys Employee
      What about just using the formula I posted to be independent from the length scale (sma constant * cube root of volume the default is 0.1 and 0.325 for wale)? I will remove the picture from the help you are referring to. The length should be the
    • NimaNZ
      Subscriber
      Sure, if I use that formula, should I add the CFF for sampling? or I can use the results of default sampling variables?
    • DrAmine
      Ansys Employee
      Yes to get the time average value. Unsteady statistics are anyhow required to get the RMSE to build-up the resolved part.
    • NimaNZ
      Subscriber
      Thanks a million
    • DrAmine
      Ansys Employee
      You want to give me a million :) ?
    • NimaNZ
      Subscriber
      well if I get this project published, why not? :))
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