Stability of Weak Confined Wake Behind a Cylinder in Fully Developed Turbulent Channel Flow

The motivation for the study of instability of turbulent wake flow in a confined turbulent channel was multi-fold. First, the instability of confined wake flows has not been studied much. Second, confined wakes are found to retain their mean velocity profile for a considerable downstream distance. Third, wakes have two points of inflection, one each on either side of the centre line. The basic aim of the present study was to investigate the correlation between the turbulence in the wake region and the inflection points in the wake region using stability theory. The wake behind a cylinder of diameter d in a turbulent channel with half width h, is a weak confined wake when d/h ≈ 0.2. Thus, d/h = 0.2 was chosen for the present work. Experimental results are obtained by introducing organized disturbances in the wake and tracking these downstream. Theoretical results were obtained by solving the Orr-Sommerfeld equation by numerical methods.