Reynolds number effect on the wake of two staggered cylinders

This work aims to investigate, based on the measured/reported Strouhal number (St) and the flow structure, the Reynolds number (Re) effect on the wake of two identical cylinders with a diameter of d over P∗=P/d=1.2–4.0 and α=0°–90°, where P is the center-to-center spacing between the two cylinders and α is the angle of incident flow with respect to the line through the two cylinder centers. The Re range examined is from 1.5×103 to 2.0×104. Two hotwires were used to measure St simultaneously behind each of the two cylinders. The St-Re relationship is classified into four distinct types, i.e., types 1–4. Each is linked to distinct initial conditions, viz., interactions between the four shear layers around the cylinders. Type 1 occurs at small P∗, not exceeding 1.25. The two cylinders act like a single body, producing a single St across the wake throughout the range of Re examined. On the other hand, type 2 occurs at small α (<10°). Although single valued, the St in type 2 displays a sudden jump with increas...