Wednesday, July 15, 2015

Calculate inlet conditions for k-epsilon

How to estimate k and epsilon for inlet

k=1.5*(I*U)^2
where I is turbulence intensity and U is velocity, k is turbulent kinetic energy

epsilon=C_mu^0.75*k^1.5/L
where C_mu=0.09, epsilon is dissipation rate, L is the mixing length

for OpenFOAM easy conditions to specify are

turbulentIntensityKineticEnergyInlet for k

inlet
    {
        type            turbulentIntensityKineticEnergyInlet;
        intensity            0.05 ;
        value           uniform .05; //dummy value
    }

turbulentMixingLengthDissipationRateInlet for epsilon

  inlet
    {
        type            turbulentMixingLengthDissipationRateInlet;
        mixingLength            0.01; //m
        value          uniform 0.01; // dummy
    }

see description by ESI
or https://en.wikipedia.org/wiki/Turbulence_kinetic_energy
http://www.cfd-online.com/Wiki/Turbulence_free-stream_boundary_conditions

No comments:

Post a Comment