Time-averaged near-wake of a yawed cylinder


NAJAFI L., FIRAT E., AKILLI H.

OCEAN ENGINEERING, cilt.113, ss.335-349, 2016 (SCI İndekslerine Giren Dergi) identifier identifier

Özet

The present study focused on time-averaged near-wake (up to four diameters downstream) of a cylinder with yaw angles from 0 degrees to 45 degrees by 5 degrees steps at a Reynolds number (Re) of 5000 based on the cylinder diameter. Two complementary techniques was employed to identify the flow patterns i.e. dye injection flow visualization and particle image velocimetry (PIV). Two different flow patterns with respect to the direction of streamlines between the cylinder and the bifurcation line in the near-wake, flow pattern A (FP-A) and B (FP-B), and one bistable pattern were observed in the near-wake as yaw angle is varied. The underlying mechanism of transition was demonstrated. The breakdown of the limited validity of the independence principle (IP) was attributed to this three-dimensional transition in the near-wake. The time-averaged and rms velocity distributions, time-averaged streamline topologies, parallel shedding phenomena, time-averaged vorticity patterns, time-averaged turbulent kinetic energy fields, drag estimations and vortex shedding frequencies have been experimentally investigated using the Ply technique in both streamwise-transverse (x-y) and streamwise-spanwise (x-z) planes. (C) 2015 Elsevier Ltd. All rights reserved.