Numerical Simulation Of Three-dimensional Flow Past Circular Cylinders At High Reynolds Numbers

In this paper, Three-dimensional flow over circular cylinders isnumerically simulated using DES method based on Spalart-Allmaras turbulencemodel. Flow patterns, lift and drag coefficients, and vortex shedding frequencies aremainly investigated. Two main parts are included in the contents.Firstly, the simulations were performed for high Reynolds numbers range105~106. The numerical simulation focused on investigating the flow patterns, thetime histories of drag and lift coefficients, and spectrum of lift coefficients.Compared with experimental data and results obtained from other methods, thecomputational results shows that they have a good agreement with experimentalresults and better than the results obtained from other methods. We also get the dragcoefficients crisis phenomenon at high Reynolds numbers. Accordance with proviousdata, the critical Reynolds number has been found to be2×105and the dragcoefficient raise back at5×105. All the flow distributions show vivid3D characters.Secondly, flow over two side-by-side circular cylinders is numerically simulatedfor varied spacing ratios at Re=10000. The computational simulations wereperformed for five different gap ratios T/D=1.1,1.5,2.0,3.0and4.0. The numericalsimulation focused on investigating flow patterns, time histories of lift and dragcoefficients, and spectrum of lift coefficients. The results show that flow patters arebased on the spacing ratios. We Analyse different flow patterns and the forceconditions and both them show vivid3D characters. Also, we find that there are flowlongitudinally behind the cylinders and form vortexes on the suface crossing themidline of the cylinder and parallel to the direction of incoming flow.This paper simulated the characteristics flowing over circular cylinders.Meanwhile, all these verify the calculation accuracy of DES method for cylindergroups at high Reynolds numbers.