In-silico experiments on characteristic time scale at a shear-free gas-liquid interface in fully developed turbulence
Journal of Physics, Conference Series
The purpose of this study is to model scalar transfer mechanisms in a fully developed turbulence for accurate predictions of the turbulent scalar flux across a shear-free gas-liquid interface. The concept of the surface-renewal approximation (Dankwerts, 1951) is introduced in this study to establish the predictive models for the interfacial scalar flux. Turbulent flow realizations obtained by a direct numerical simulation technique are employed to prepare details of three-dimensional
... ensional information on turbulence in the region very close to the interface. Two characteristic time scales at the interface have been examined for exact prediction of the scalar transfer flux. One is the time scale which is reciprocal of the rootmean-square surface divergence, Tγ = γγ −1/2 , where γ is the surface divergence. The other time scale to be examined is TS = Λ/V , where Λ is the zero-correlation length of the surface divergence as the interfacial length scale, and V is the root-mean-square velocity fluctuation in the streamwise direction as the interfacial velocity scale. The results of this study suggests that Tγ is slightly unsatisfactory to correlate the turbulent scalar flux at the gas-liquid interface based on the surface-renewal approximation. It is also found that the proportionality constant appear to be 0.19, which is different with that observed in the laboratory experiments, 0.34 (Komori, Murakami, & Ueda, 1989) . It is concluded that the time scale, Tγ, is considered a different kind of the time scale observed in the laboratory experiments. On the other hand, the present in-silico experiments indicate that TS predicts the turbulent scalar flux based on the surfacerenewal approximation in a satisfactory manner. It is also elucidated that the proportionality constant for TS is approximately 0.36, which is very close to that found by the laboratory experiments. This fact shows that the time scale TS appears to be essentially the same as the time scale the laboratory experiments observed.