Effect of rear-base curvature on hydrodynamic loading and wake transition of a sharp-nosed bluff body at low Reynolds numbers

The stabilization of bluff-body wakes and subsequent reduction of hydrodynamic loading are often achieved by rear-end shaping but this behavior is not always true for sharp-nosed bodies. The current study explores the effect of swapping a sharp rear-base with a semi-circular base while maintaining the same sharp-nosed forebody. Two-dimensional finite-volume simulations are conducted for sharp-nose-sharp-base (SNSB) and sharp-nose-semi-circular-base (SNSCB) cylinders over Reynolds number, R e = 5 – 300. The results reveal that the SNSCB geometry produces marginally higher drag than the SNSB cylinder owing to the pressure redistribution in the vicinity of the rear-base and wake region. Sustained oscillations in lift response, meaningful Strouhal frequency, non-zero lift fluctuations and closed loop phase-portraits appear earlier for the SNSCB body than the SNSB body. The wake- and pressure-field analyses unveil earlier shear roll-up, stronger rear-pressure asymmetry and advanced vortex formation for the SNSCB case. The findings reveal that the semi-circular rear-end is not always a stabilizing modification. The interpretation of the observations at higher Reynolds numbers are strictly within the bounds of the adopted two-dimensional framework.