Investigation on the compressibility characteristics of laminar flow in rotating channel

Abstract

In high-speed rotating channels, significant compressive effects are observed, resulting in distinct flow characteristics compared to incompressible flows. This study employs a finite volume method, based on the implicit formulation, to solve for low-speed compressible laminar flow in rotating channels using an orthogonal uniform grid. The governing equations include the full Navier–Stokes equations and the energy equation. The alterations in flow within rotating channel are primarily influenced by the compressive effects of centrifugal force and the compressibility of fluid within the flow's normal section. The first effect involves a reduction in the velocity due to centrifugal force, leading to an increasing influence of the Coriolis force compared to inertial forces. This trend change aligns closely with the increase in rotation speed. The second effect arises from the increase in the rotating Mach number and the Coriolis compression, resulting in slight density differences within the cross section. Strong centrifugal forces generate significant centrifugal additional force (buoyancy force). Consequently, under the same local rotation number, the velocity profiles of the mainstream experience considerable changes. Additionally, a higher rotating Mach number significantly impacts wall shear stress, with the leading side being notably affected. For instance, at cross-sectional Ro = 0.6 and MaΩ = 2.1, the dimensionless shear stress on the leading side decreased by 13%. Furthermore, while an increase in the rotating Mach number has minimal impact on the cross-sectional secondary flow structure, changes in mainstream velocity profiles influence secondary flow intensity, resulting in an enhanced velocity peak and a shift toward the trailing side.