The isotropic forms of the transport equations for the mean turbulent kinetic energy and scalar variance dissipation rates, 〈∈〉and 〈x〉, suggest that the turbulent mixing (power-law) decay rates depend on the ratios G/R_λ_μ and G_θ/R_λ_μ, where G and G_θ are destruction coefficients of h_i and h_i, and R_λ_μ is the Taylor microscale Reynolds number. Present measurements and review data on grid turbulence show that, while G_θ/R_λ_μ is nearer to its asymptote than G/R_λ_μ, both ratios asymptote at R_λ~μ{approx=}10~3, which should correspond to a state of complete self-preservation for the velocity and the passive scalar fields.
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