Abstract
Developing compressible viscous fluid flow in a curved duct, especially mechanism of the voritical flow field due to the curvature, is studied numerically by means of DNS. The Dean number of Dn=271 and the Mach number of M=0.7 are chosen to investigate the curvature effects on the compressible viscous flow. The secondary flow is defined as the helicity density structure, which leads to a clear relationship between the secondary flow pattern and the three-dimensional structure downstream. Higher Mach number flow yields more complicated secondary flows, a pair or two pairs of Dean vortices are generated downstream at the same Dean number. DNS results show a developing helicity density flow of the herical structure. Convection terms in the Navier-Stokes equations are visualized as vector plots, as well as the pressure gradient. This visualization leads a clear understanding of the role of viscous terms near the outer wall. Numerical unsteady motions responding to random disturbances show temporal periodic oscillation of the spanwise velocity component near the outer wall of z=0.
