Dynamic Analysis of Wake Characteristics of the Circular Cylinder with a Dimpled Surface

Abstract

In order to understand the wake characteristics for the circular cylinder with the dimpled structure, particle image velocimetry (PIV) and proper orthogonal decomposition (POD) method are used to measure and analyze the flow field velocity and the flow characteristic of the wake flow of the circular cylinder with the dimpled surface. This study focuses on the distribution of Reynolds stress and turbulent kinetic energy, the velocity profiles and recirculation zones, and the velocity fluctuating characteristics of flow field with POD technology. It is found that the equivalent high-intensity Reynolds stress and turbulent kinetic energy regions of the circular cylinder with the dimpled surface are smaller, and the peak values are lower, and the velocity gradient in the wake region of the circular cylinder with the dimpled surface is larger. Otherwise, the energy contained by the dominant modes of the smooth cylinder is larger than that contained by the dominant modes of the circular cylinders with the dimpled surface, which means the energy of the dimpled cylinder is more distributed. At the same time, it is observed that the dimpled structure will decrease the vortex shedding intensity, but may increase the vortex shedding frequency, and destroy the inherent flow mode of the flow field around the cylinder.

Experimental Study on the Wake Characteristics of Composite Secondary Grooved Cylinder

“…At x/D = −1.2 and y/D = 0.6, the spectrum S v of the velocity component u for all three cases was calculated. As shown in Figure 12a, the peak power spectrum on the smooth cylindrical tail has a frequency of 4 Hz and the Strouhal number can be expressed as St = f D/U = 0.21, which is consistent with the results of Qi and Oruç [31,43]. The Strouhal44 number is the ratio of the inertial force of motion to the inertial force of a non-constant fluid and can be used to describe the flow state of a non-constant fluid.…”