The wake of two staggered circular cylinders

The work aims to study experimentally the flow structure, heat and momentum transport in the wake of two staggered circular cylinders. The cylinder center-to-center pitch ranged from 1.2 to 4.0, and the angle between the incident flow and the direction through the two cylinder axes was between 0 degrees and 90 degrees. In order to characterize the heat transport of this flow, both cylinders were slightly heated so that heat generated could be considered to be a passive scalar. The velocity and temperature fluctuations were measured using a movable three-wire (one X-wire plus a cold wire) probe across the wake and a fixed X-wire, which acted to provide a reference signal. Measurements were conducted at x/d = 10 and 20 and a Reynolds number of 7000, where d is the cylinder diameter and x is the longitudinal distance from the mid point between the cylinders. Based on phase-averaged vorticity contours and sectional streamlines, the flow structure behind two staggered cylinders is classified into five typical patterns. The flow behaviours for each pattern are examined in detail, including its topology, vortex strength, stability and decay rate. The different behaviours; between the patterns are further linked to the different initial conditions. The momentum and heat transport are not presented due to limited space.