Experimental investigation on wake characteristics behind a yawed square cylinder. (February 2016)

• Record Type: Journal Article
• Authors: Lou, X.; Zhou, T.; Zhou, Y.; Wang, H.; Cheng, L.
• Is Part Of: Journal of fluids and structures. Volume 61(2016:Feb.)
• Page Start: 274
• Page End: 294
• Publication Date: 2016-02
• Subjects: Yawed square cylinder -- Vortex shedding -- Phase-average method; Fluid-structure interaction -- Periodicals; Fluid mechanics -- Periodicals; Structural dynamics -- Periodicals; Structural analysis (Engineering) -- Periodicals; 620.106
• DOI: 10.1016/j.jfluidstructs.2015.11.017
• Languages: English
• ISSNs: 0889-9746

Abstract

Abstract: The wake vortical structures of a square cylinder at different yaw angles to the incoming flow ( α = 0°, 15°, 30° and 45°) are studied using a one-dimensional (1D) hot-wire vorticity probe at a Reynolds number (Re) of about 3600. The results are compared with those obtained in a yawed circular cylinder wake. The Strouhal number (St N ) as well as the mean drag coefficient ( C D N ), normalized by the velocity component normal to the cylinder axis, follow the independent principle (IP) satisfactorily up to α = 40°. Using the phase-averaging analysis, both the coherent and the remaining contributions of velocity and vorticity are quantified. The flow patterns of the coherent spanwise vorticity ( ω z ) display obvious Kármán vortex streets and their maximum concentrations decrease as α increases. Similar phenomena are also shown in the coherent contours of the streamwise ( u ) and transverse ( v ) velocities as well as the Reynolds shear stress ( u v ). The contours of the spanwise velocity ( w ) and Reynolds shear stress ( u w ), however, experience an increasing trend for the maximum concentrations with increasing yaw angle. These results indicate an enhancement of the three-dimensionality of the wake and the reduction of vortex shedding strength as α increases. While general similarities to the wake behind a yawed circular cylinder are found in terms of flow features, some differences between the two wakes at different yaw angles are highlighted. Highlights: IP in square cylinder wake is satisfied up to 40°. Three-dimensionality of the wake is enhanced as yaw angle increases. Vortex shedding in the square cylinder wake at α =60° is completely suppressed. Vortices decay faster in the square cylinder wake than that in the circular one.