Effect of Obstacle Shape on Natural Convection in Partially Open Square Enclosure

Abstract

The present study reports a real-time experimental analysis of natural convection of air using a noninvasive technique (Mach-Zehnder interferometry). The experiments are conducted in a partially open square cavity with a centrally placed adiabatic obstacle and a heat source positioned at the center of the bottom horizontal wall. The left vertical wall has a partial opening occupying 50% of the wall height. The effect of obstacle shapes (square, circular, and triangular) and Rayleigh number on natural convection is evaluated. The interferograms obtained from the experiments give temperature field in the cavity. Air velocity at the opening is measured using an air velocity transducer. The experimental results are compared with numerical findings obtained using ANSYS Fluent 2020. The fringe density in the cavity enhances with increase in Rayleigh number. The temperature gradient, average Nusselt number, and average exit velocity of the flowing fluid are higher for triangular obstacle, whereas minimum for square obstacle. For Rayleigh numbers in the range of 107 to 108, an average increment in Nusselt number and average exit velocity is up to 15% and 16%, respectively. The maximum temperature in the enclosure is higher for square obstacle, whereas it is lower for triangular obstacle.