Experimental Investigation of Transitional Natural Convection in a Cube Using Particle Image Velocimetry—Part II: Turbulence Quantities and Proper Orthogonal Decomposition

An experimental investigation of transitional natural convection in an air filled cube was conducted in this research. The characteristic dimension of the enclosure was H = 0.35 m, and data were collected in the middle plane of the cavity. The Rayleigh number range examined was $5.0×107≤Ra≤3.4×108$⁠. In Part I, the authors presented the mean velocity profiles in the enclosure and conducted heat transfer measurements on the hot wall. An expression between Nu and Ra numbers was concluded and compared against other correlations available in literature. In the present work, the authors present a complete description of the flow in the enclosure by quantifying the low turbulence regime developed in the cavity. This was accomplished by estimating Reynolds stresses, turbulent kinetic energy, vorticity, and swirling strength. Proper orthogonal decomposition (POD) was employed to analyze the flow fields obtained from the experimental data and retain the most salient features of the flow field. This study attempts to close the gap of available experimental data in the literature and provide experimental benchmark data that can be used to validate CFD codes since the estimated error from particle image velocimetry (PIV) measurements is within 1–2%.