TURBULENT PRANDTL NUMBER IN THE NEAR-WALL REGION: STUDY OF THE EFFECT OF THE MOLECULAR PRANDTL NUMBER, TRANSPIRATION AND LONGITUDINAL PRESSURE GRADIENT

摘要

A numerical modeling of a subsonic flow at a permeable plate in the presence of a flow pressure gradient is carried out using a differential turbulence model, supplemented with the transport equation for the turbulent heat flux. The dependences of the turbulent Prandtl number from the molecular Prandtl number, injection (suction) intensity of the gas through the permeable wall and the acceleration parameter of the flow are presented. The air, mixtures of helium with xenon and argon are selected as the gas heat carriers and the mercury, water and transformer oil are selected as the liquid heat carriers respectively. The effect of the variability of the turbulent Prandtl number on heat transfer characteristics, in particular, on the Nusselt number is studied. It is shown that the difference of Nusselt number obtained in condition of the constant turbulent Prandtl number from the results obtained in the calculations with the equation for the turbulent heat flux increases under low and high molecular Prandtl number. The injection, suction and pressure gradient also increase this difference.