DIRECT NUMERICAL SIMULATION OF SQUARE DUCT FLOWS: ANALYSIS OF SECONDARY FLOWS

摘要

A DNS solver is developed for the numerical analysis of square duct flows. The solver uses the fully-implicit decoupling procedure proposed by Kim et at. (2002). The multigrid algorithm is employed to accelerate the convergence in solving the Poisson equation. The solver is validated through comparisons with the DNS data from Gavrilakis (1992): It is found from simulated results that two counter-rotating secondary flows are made around the duct corner and they are important to momentum transfer between duct center and corner. The conditional quadrant analysis is performed at the region where the wall shear stress shows local maximum and minimum, and the pattern of mean secondary flows are illustrated.