Dynamics of Large-Scale Structures and Heat Transfer in Turbulent Mixed Convection

Abstract — Low frequency oscillations in the heat transfer of mixed convection in a rectangular cav-ity with an aspect ratio of Γxz = 1 and Γyz = 5 have been observed. Mixed convective flow at Ra = 2.4 × 108, Re = 1.0 × 104, Ar = 3.3 and Pr ≈ 0.7 was studied to determine the nature of these oscillations. Therefore Particle Image Velocimetry (PIV) and temperature measurements have been performed under ambient and heigh pressure conditions. The PIV results have been analysed using Proper Orthogonal Decomposion (POD) to identify the characteristic frequencies of the coherent large-scale structures dynamics and compared their dynamics with the low frequency oscillations found in the heat transfer. 1