Flow around a square prism between two parallel walls

A numerical investigation is conducted on the fluid flow around a square prism (of height d) symmetrically placed in a rectangular channel. The primary objective is to explore the effects of prism-wall gap spacing g* = g/d (= 0.5–12.0) on flow dynamics, vortex shedding, and aerodynamic forces at a fixed Reynolds number Re = 100, where g is the spacing between the prism and the channel wall. The Strouhal number, time-mean drag coefficient, and base pressure coefficient all exponentially increase when g* decreases from 12 to 0.5. The fluctuating lift coefficient, however, decreases for g* from 0.5 to 1.0, increases for g* from 1.0 to 2.2, and again decreases for g* = 2.2–12.0. It is inversely correlated with vortex formation length. Four distinct flow regimes are identified: (i) wall vortex street (g* < 0.9), (ii) reversed Kármán vortex street (0.9 < g* < 2.9), (iii) aligned vortex street (2.9 < g* < 4.2), and (iv) Kármán vortex street (g* > 4.2). Confinement by side walls accelerates the gap flow between the prism and walls, skewing the velocity profile, enhancing local dynamic pressure and viscous effects, and thereby increasing drag and Strouhal number, with their scaling closely linked to the gap velocities and effective Reynolds number under decreasing g*.