Preliminary Report on Sheared Cellular Motion as a Qualitative Model of Homogeneous Turbulent Shear Flow.

摘要

In the hope of gaining some insight into homogeneous turbulent shear flow dynamics, the motion of a three-dimensional cellular velocity field under a constant mean strain-rate has been computed. Navier-Stokes velocity and pressure fields are calculated as power series in time with coefficients periodic in space. The results are used to compute various instantaneous fields, including vorticity, velocity products and presssure/strain-rate products. The cell-averaged results show rough agreeement with statistical experiments on nearly homogeneous turbulent shear flow, although the total mean strain is limited by the computer time available to us. The instantaneous fields allow a search for explicit hydrodynamic mechanisms of energy transfer, both from mean flow to 'fluctuations,' and (especially) between orthogonal velocity 'fluctuation' components. The dominant 'right way' intercomponent transfer paradigm is a kind of local stagnation point flow; local regions of 'wrong way' transfer include reduced pressure swirls with particular relative orientations of local vorticity and strain-rate tensor. Although the effective Reynolds number is modest, most of the intercomponent transfer is contained in a rather small fraction of the cell. (Author)