Experimental and numerical study of thermal structure of turbulent thermal convection

Abstract

This study presents results of experimental numerical investigation of turbulent thermal convection in air placed between two horizontal plates and heated below. The experiments covered a range of Rayeigh numbers between $3\times10^6$ and $1.5\times10^7$. The test results indicate that the heat transfer coefficients investigated may be determined from the relationship $$Nu = 0.111\,Ra^{0.298}$$ With increasing the vertical distance from the bottomplate, it was found that the mean temperature gradient profiles follow $Z^0$ law of the lower conduction region, $Z^{-2}$ law in transition region, and thence the $Z^{-4/3}$ law of the convective region, successibely. These agree with Kraichnen``s (1962) theoretical expection. More over, it was found that a law of the wake-like mean temperature profule exists in the core layer. Also, numerical study was carried out by using Zeman and Lumley (1976)``s bouyancy transport model to investigate the higher order structure of the thermal convection problems.