Blockage effect on wakes of various bluff bodies: A review of confined flow

In many industrial applications, fluid flow around bluff bodies is confined between two parallel walls. This paper provides a thorough review of the studies on the confined flow around bluff bodies of different cross-sections including circular, square, and rectangular. Particular emphasis is put on the effect of blockage ratio on the steady-unsteady wake transition, shear layer transition, boundary layer transition, Strouhal number, aerodynamic forces, vortex formation length, and vortex inversion length. An increase in blockage ratio postpones steady-unsteady wake transition, hastens the shear layer transition, and increases the drag and Strouhal number. With increasing blockage ratio, fluctuating lift force for circular cylinder reduces in shear layer transition I but enhances in shear layer transition III. A square cylinder undergoes a greater blockage effect than a circular cylinder. The research gap in the literature is pinpointed and put forward for future investigations.