DNS of compressible turbulent channel flow subject to strong temperature gradient

Abstract

A direct numerical simulation of compressible turbulent channel flow at low Mach number(Ma = 0.3) subject to strong temperature gradient is conducted. The wall temperature ratios which are defined by a temperature on the upper wall divided by that on the lower one, are set to 2 and 3. It is shown that the flow of high temperature wall side is laminarized as increasing the wall temperature ratio. Moreover, compressible and dilatational motions are induced on the low and high temperature wall sides, respectively. The identity of friction coefficient originally derived by Fukagata et al.(2002) (so-called ‘FIK identity’) is extended to those of friction coefficient and Nusselt number on the compressible channel flow. It is revealed that the viscous variation component attains to 16 % of the friction coefficient on the case of high temperature ratio. Furthermore, the pressure work component occupies about 20 % of the overall Nusselt number for the all cases. The pressure work has a redistributive effect between mean kinetic energy and internal energy. The energy transfer from mean kinetic energy to internal energy appears on the low temperature side whereas that toward the opposite direction on the high temperature side at the present low Mach number flow.

Keywords

• compressible effect
• turbulent channel flow
• strong temperature gradient
• low mach number
• direct numerical simulation