Direct numerical simulation of flow over circular cylinders for large-eddy simulation modeling.

摘要

Flow over a circular cylinder at a Reynolds number of 1500 is studied using a three-dimensional direct numerical simulation (DNS). At this condition, the shear layer is unstable. However, previous direct numerical simulations of this flow have been limited to Reynolds numbers of 1000 or less, where the shear layer is stable or only weakly unstable. The computational method uses a Fourier-Chebyshev spectral collocation for the spatial discretization, and boundary conditions that account for the displacement effect of the cylindrical body. The results of the simulation are analyzed and we find good comparison with mean and root-mean-square statistics of both experiments and large-eddy simulations. The peaks in the Reynolds stresses also agree with past results over varying Reynolds number. A number of views of the instantaneous velocity and vorticity fields are presented both at varying spanwise location and at a fixed x-y or x-z plane over time. These provide high-resolution snapshots of various structures in the streamwise and spanwise vorticity. Three-dimensional views of the swirling strength are also shown to illustrate the instability and rollup of the shear layer, as well as the breakdown to small scales. Finally, the optimal large-eddy simulation (LES) formulation is applied to the current problem and some results are obtained for the error estimates.