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NONLOCAL TRANSPORT OF PASSIVE SCALAR IN TURBULENT CHANNEL FLOW

Fujihiro Hamba
Institute of Industrial Science, University of Tokyo Komaba, Meguro-ku, Tokyo 153-8505, Japan

Аннотация

A nonlocal expression for the scalar flux was derived using the Green's function for the scalar. The nonlocal diffusivity in the expression represents a contribution to the scalar flux from the mean scalar gradient at remote points in space and time. Direct numerical simulation (DNS) of channel flow was carried out to validate the nonlocal expression. The velocity and scalar fields as well as the Green's function were calculated in the cases of the one- and two-dimensional mean scalar. It was shown that the nonlocal expression exactly holds in both cases. The local expression for the scalar flux was also examined to show that the local approximation is not accurate enough and that nonlocal effects are important. The nonlocal expression evaluated in DNS is expected to gain insight into modeling the scalar transport.