Near-wake structure behind two circular cylinders in a side-by-side configuration with heat release

Flow around two circular cylinders in a side-by-side arrangement normal to the free stream with heat release from one of the cylinders is studied experimentally. This flow, with no heat release, is known to exhibit a range of flow regimes at different cylinder spacings. In particular, the wake exhibits well-known intermittently bistable behavior in the center-to-center spacing (normalized by cylinder diameter) range of 1.2-2.0. We present, for the first time, the effect of heat release from one of the cylinders on the near-wake structure of the two cylinder configuration. The experiments are performed at spacing ratios of 1.1, 1.7, and 3.0, Reynolds numbers of 250, 350, and 450 and Richardson number less than 0.14. The investigations are carried out in a water tunnel using hydrogen bubble technique for flow visualization and particle-image-velocimetry for quantitative measurements. The bistability of the wake at a spacing ratio of 1.7 is controlled with a threshold heat release from one of the cylinders resulting in a stable narrow wake behind the heated cylinder and a wider wake behind the unheated cylinder. The heat release resulted in deflection of the gap-bleeding flow toward the heated cylinder at spacing ratio of S/D=1.1 and did not produce any visual changes in the near-wake structure at spacing ratio of 3.0.