Lamb dilatation and its hydrodynamic viscous flux in near-wall incompressible flows

Chen，Tao1; Liu，Tianshu2

2023-06-01

10.1016/j.physd.2023.133730

Physica D: Nonlinear Phenomena   Impact Factor & Quartile

0167-2789

In this paper, we introduce a new physical concept referred to as the wall-normal Lamb dilatation flux (WNLDF), which is defined as the wall-normal derivative of the Lamb dilatation (namely, the divergence of the Lamb vector) multiplied by the dynamic viscosity for incompressible viscous flows. It is proved that the boundary Lamb dilatation flux (BLDF, namely the wall-normal Lamb dilatation flux at the wall) is determined by the boundary enstrophy flux (BEF) and the surface curvature-induced contribution. As the first step to explore this new concept, the present study only considers flow past a stationary no-slip flat wall without curvature-fluid dynamic coupling effects. It is found that the temporal–spatial evolution rate of the WNLDF is contributed by four source terms, which can be explicitly expressed by using the fundamental surface quantities including skin friction (or surface vorticity) and surface pressure. Therefore, the instantaneous near-wall flow structures are directly related to the WNLDF in both laminar and turbulent flows. As an example, for the turbulent channel flow at Re=180, the intensification of the temporal–spatial evolution rate of the WNLDF is caused by the strong wall-normal velocity event (SWNVE) associated with quasi-streamwise vortices and high intermittency of the viscous sublayer. In addition, near the SWNVE, this evolution rate is mainly contributed by the dot product of skin friction and surface enstrophy gradient, as well as the coupling between the skin friction divergence and the boundary enstrophy. The exact results presented in this paper could provide new physical insights into complex near-wall flows.

Boundary enstrophy flux Lamb vector Near-wall flow Skin friction Turbulence

English

First

PHYSICS

2-s2.0-85151333352

Scopus

1.Department of Mechanics and Aerospace Engineering,Southern University of Science and Technology,Shenzhen,518055,China
2.Department of Mechanical and Aerospace Engineering,Western Michigan University,Kalamazoo,49008,United States

Chen，Tao,Liu，Tianshu. Lamb dilatation and its hydrodynamic viscous flux in near-wall incompressible flows[J]. Physica D: Nonlinear Phenomena,2023,448.

Chen，Tao,&Liu，Tianshu.(2023).Lamb dilatation and its hydrodynamic viscous flux in near-wall incompressible flows.Physica D: Nonlinear Phenomena,448.

Chen，Tao,et al."Lamb dilatation and its hydrodynamic viscous flux in near-wall incompressible flows".Physica D: Nonlinear Phenomena 448(2023).