Statistical Analysis for Characteristic POD and DMD Modes in DNS of Oscillating Grid Turbulence Subjected to System Rotation

Abstract

Turbulence subjected to system rotation provides significant insights into real-world flow phenomena. Therefore, it is indispensable to better understand the effects of rotation on turbulence. In order to investigate the effect of rotation on turbulence diffusion under the other effects being eliminated, our previous study performed a set of DNS of oscillating grid turbulence in systems at rest and subjected to rotation. Also, two mode analysis methods, Proper Orthogonal Decomposition (POD) and Dynamic Mode Decomposition (DMD) methods, were applied to the velocity data to extract dominant flow structures. However, these mode analyses provided the insight into flow structures in a qualitative manner. Therefore, for the sake of the quantitative evaluations, this study applies the idea of the statistical analysis based on turbulence kinetic energy to the POD and DMD modes. The results show that the statistics well express the characteristics of the flow structure, which had previously been evaluated qualitatively, in terms of turbulence production, diffusion, and dissipation.