Effect of base elongation of circular cylinder on its wake characteristics

The present numerical study aims at the control of vortex shedding and drag reduction by shaping the rear geometry of a circular cylinder. The ratio of the semi-major/minor axis dimension (A) of the rear half to the radius of the circular part (R) is varied over a range of values between 0.0 and 4.0. A two-dimensional flow solver has been developed using body-fitting coordinate transformation with Cartesian velocity components as dependent variables and solved using a modified MAC algorithm. The flow solver offers a fast and accurate procedure for modelling viscous incompressible flows in complex geometries. The effect of elongation on the wake characteristics and hydrodynamic coefficients has been investigated for different values of Reynolds number (Re) ranging from 40 to 200. The predicted results indicate that vortex suppression occurs primarily due to reduction in the amplitude of fluctuation than by reduction in the vortex shedding frequency. The critical value of Re for the onset of vortex shedding has been correlated with elongation ratio ER, based on the numerical predictions.