- **Main CFD Forum**
(*https://www.cfd-online.com/Forums/main/*)

- - **Kolmogorov scale
**
(*https://www.cfd-online.com/Forums/main/4204-kolmogorov-scale.html*)

Kolmogorov scale
Hello all
Does any one know how to esitmate Kolmogorov micro scale? I know Kolmogorov scale can be obtained from viscosity and dissipation rate per unit mass. Should I obtain dissipation rate from DNS or experiment results ? Can I estimate Kolmogorov scale without DNS or experiments? |

Re: Kolmogorov scale
If you know the kinetic energy q/2 and the integral length scale L , you may used the following relationship for the dissipation rate eps :
eps ~ ((q/2)^3/2)/L Moreover, if you define a tridimensionnal spectrum E(K) by : E(K) = AK^s for (K<Kmax) E(K) = c_k eps^2/3 K^(-5/3) (K>=Kmax) E(K) = 0 (K>Kkol) where s is the slope of the spectrum for large scale (s=2 to 4). Then you can find A by continuity in Kmax and eps, L and q/2 from the following relationship : q/2 = int (E(K)dK) eps = 2 nu int (K^2E(K)dK) q/2 L = int(E(K)/KdK) (may be 2*pi somewhere) this could give you a good idea of the different equalities between all this quantities for turbulence near equilibrium. |

Re: Kolmogorov scale
It should have been :
Moreover, if you define a tridimensionnal spectrum E(K) by : E(K) = AK^s (K<=Kmax) E(K) = c_k eps^2/3 K^(-5/3) (Kkol>=K>=Kmax) E(K) = 0 (K>=Kkol) PS : for K>=Kmax, one can also used the Pao formulation. |

All times are GMT -4. The time now is 01:41. |