Base Region Topology of Turbulent Wake around Finite Wall-Mounted Cylinder with Application of Low Order Flow Representation

Abstract

Turbulent flow topology around a rectangular cylinder with h/d=8 is characterized by either dipole or quadrupole mean wake depending on the turbulent boundary layer thickness. This study investigates the physical and mathematical mechanisms giving rise to the two distinct types of flow by considering the phase-averaged velocity field. It was found that the vortex stretching and tilting and the time-averaged representation of tilted vortex shedding are the key terms distinguishing between the dipole and quadrupole wake structures. The other objective is to develop a procedure to estimate the higher-rank low order flow based on Extended Proper Orthogonal Decomposition. Within this technique, the global velocity flow can be reconstructed with correlated surface pressure sensors to have a closer look at the mechanisms leading to dipole and quadrupole wakes. It was observed that optimum choice of sensor locations needs analytical considerations to improve the ability of pressure probes in capturing the coherent structures of interest.