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Fluids

Fluids

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Help: About the expression of turbulent viscosity in Realizable k-e model

    • Max
      Subscriber

      Dear Experts,

      I am trying to make 2-dimension UDF code for turbulent viscosity of the realizable k-e model. I want to ask about the expression term U* (See the attached figure).

      I wonder what the eijk in the equation to estimate the mean rate-of -rotation is.

      Since the mean rate-of rotation and the angular speed have unit 1/s. The eijk here should be the constant not the turbulent dissipation rate?

      Thank you very much.

      Here is the UDF code:

      DEFINE_PROPERTY(tur_vis,c,t)
      {
        real mu_tur;
        real S11, S12, S22, W12, W12r;
        real SMU, WAS, PHI, USTAR;
        real AS;
        real CMU, y, a1, a2, a3, a4, a5, a6, ;/***
        real betas=0.09;
        real A0=4.04;
        real rho=C_R(c,t);
        real k=C_K(c,t);
        real w=C_D(c,t);
        real CMUL=C_MU_L(c,t)
        real y=C_WALL_DIST(c,t);
        real S=C_STRAIN_RATE_MAG(c,t);

      /***
        S11=0.5*(C_DUDX(c,t)+C_DUDX(c,t));
        S12=0.5*(C_DUDY(c,t)+C_DVDX(c,t));
        S22=0.5*(C_DVDY(c,t)+C_DVDY(c,t));

        W12=0.5*(C_DVDX(c,t)-C_DUDY(c,t));

      /*** Cal vorticity with rotation ***/

        W12r=W12-wr*ce;

      /*** Cal U*  ***/

        USTAR=sqrt(S11*S11+2*S12*S12+S22*S22+W12r*W12r);

      /*** Cal Phi ***/

        SMU=sqrt(S11*S11+2*S12*S12+S22*S22);
        WAS=(pow(S11,3)+pow(S22,3)+3*pow(S12,2)*(S11+S22))/pow(SMU,3);
        PHI=1/3*acos(sqrt(6)*WAS);

      /*** Cal As ***/

        AS = sqrt(6)*cos(PHI);

      /*** Cal CMU ***/

        CMU=1/(A0+AS*USTAR/betas/w);

      ....

       

    • abhishek.roy
      Ansys Employee

      here eijk is a constant 

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