Parallel spectral-element—Fourier simulation of turbulent flow over riblet-mounted surfaces

The flow in a channel with its lower wall mounted with streamwise V-shaped riblets is simulated using a highly efficient spectral-element—Fourier method. The range of Reynolds numbers investigated is 500 to 4000, which corresponds to laminar, transitional, and turbulent flow states. Our results suggest that in the laminar regime there is no drag reduction, while in the transitional and turbulent regimes drag reduction up to 10% exists for the riblet-mounted wall in comparison with the smooth wall of the channel. For the first time, we present detailed turbulent statistics in a complex geometry. These results are in good agreement with available experimental data and provide a quantitative picture of the drag-reduction mechanism of the riblets.This work was supported by National Science Foundation Grants CTS-8906432, CTS-8906911, and CTS-8914422, AFOSR Grant No. AFOSR-90-0124, and DARPA Grant No. N00014-86-K-0759. The computations were performed on the Cray Y/MP's of NAS at NASA Ames and the Pittsburgh Supercomputing Center, and on the Intel 32-node iPSC/860 hypercube at Princeton University.