Coefficients of Time and Length Scales of Turbulent Eddies

Abstract

ABSTRACTThe turbulence time and length scales representing the energy containing eddies are by Tt = CtT k/ε and ℓt = Ctℓ k32/ε, respectively, while the Kolmogorov time and length scales representing the energy dissipative eddies are expressed by Tk = CkT (ν/ε)1/2 and ℓk = Ckℓ (ν3/ε)1/4, respectively. The available DNS data for fully developed channel flows with and without wall injection / suction are used to determine the coefficients. It is found that, with the typical values of CtT = Ctℓ = 1 which are usually adopted in the turbulence study, ckT = 2 and Ckℓ = 3. However, this set of coefficients lead to underprediction of the thickness of viscous sublayer . By relaxing the usual assumption of CtT = Ctℓ= 1, a new set of coefficients: CtT = Ctℓ = 0.8, CkT = 4, and Ckℓ = 9 is suggested. The calculated with this set of coefficients becomes more physically reasonable.