Quantitative analysis of coherent structures affecting instantaneous fluctuation of point-source plumes based on PIV-POD method

Abstract

Abstract For an enclosed space like an industrial plant where devices and equipment generate a large amount of heat, the fluctuation characteristics of thermal plume become more crucial. This paper aims to study the unique air distribution of the point-source plume by shutting down all valves in a thermostatic chamber. 250 consecutive instantaneous flow fields (in each zone) were measured by a two-dimensional particle image velocimetry (PIV) system at a sampling frequency of 3 Hz to quantify the air distribution of the plume. Based on the experimental data, the indoor instantaneous velocity and vorticity fields were analyzed, and the transient velocity fluctuation characteristics of typical points were discussed. The fluctuation periods of the plume at different heights were initially estimated. Through the proper orthogonal decomposition (POD) analysis, the dominant coherent structures in complex instantaneous flow fields were excavated, and the turbulent kinetic energy of coherent structures was calculated. In addition, POD analysis provided a new method for validating and improving transient numerical simulation models.