Phase-Averaged Analysis of Three-Dimensional Vorticity in the Wake of Two Yawed Side-By-Side Circular Cylinders

Thewake flow behind two yawed side-by-sidecircular cylinders is investigated using athree-dimensional vorticity probe. Four yaw angles (α), namely, 0°, 15°, 30° and 45° and twocylinder spacing ratios T of 1.7 and 3.0 were tested. For T = 3.0, there exist two vortex streets and the cylinders behave as independent and isolated ones. The maximum contour value of the coherent streamwise vorticity * ~ x ω is only about 10% of that of the spanwise vorticity * ~ z ω . With the increase of α, * ~ x ω increases whereas * ~ z ω decreases. At α = 45°, * ~ x ω is about 67% of * ~ z ω .For T* = 1.7, only a single peak is detected in the energy spectrum. The spanwise vorticity contours have an organized pattern only at α = 0°. The maximum coherent vorticity contours of * ~ x ω and * ~ z ω for T * = 1.7 are about 30% and 7% of those for T = 3.0.The independence principle (IP)in terms of Strouhal numbers is applicable in both wakes when α< 40°. Keywords—Circular cylinder wake, vorticity, vortex shedding.