Proper orthogonal decomposition based dynamic modeling for the three-dimensional wake flow behind a rectangular prism building

Abstract

This paper presents the identification of the dynamic system for the K?rm?n-type vortex shedding, based on the mode analysis results of the turbulent structure around a rectangular prism building model. First, proper orthogonal decomposition (POD) was performed on the turbulent velocity data. In this case, the 2nd dominant POD mode (mode 2) was found to be controlled by the inflow fluctuation, and the 1st, 3rd and 4th dominant POD mode (mode 1, 3 and 4) depicted the main periodic vortex shedding phenomenon on the wake of the building. Then, the dynamics system of modes 1, 3 and 4 were fitted into a polynomial regression model, which showed an average trend of the trajectory of the state. The two limit cycles of the regression model were found to depict the two rotation directions of the K?rm?n-type vortex, which were the final states if the system is free of perturbations. Additionally, two characteristic periods were recognized from the trajectory generated from the regression model, which indicates a fast motion and a slow motion of the wake vortex.