Dynamics of large-scale structures and heat transfer in turbulent mixed convection

Abstract

Low frequency oscillations have been observed in the heat transfer of mixed convection in a rectangular cavity with an aspect ratio of $\Gamma_{\mathrm{xz}} = 1$ and $\Gamma_{\mathrm{yz}} = 5$.~Mixed convective flow at $Ra = 2.4 \times 10^8$, $Re = 1.0 \times 10^{4}$, $Ar = 3.3$ and $Pr \approx 0.7$ has been studied to determine the nature of these oscillations. Therefore Particle Image Velocimetry (PIV) and temperature measurements have been performed under ambient and high pressure conditions. The PIV results have been analysed using Proper Orthogonal Decomposion (POD) to identify the characteristic frequencies of the coherent large-scale structures and their dynamics have been compared with the low frequency oscillations found in the heat transfer.