Numerical analysis of the effect of convex and concave shape modifications to a bluff body with/without rear cavities on the laminar steady to unsteady channel flow dynamics transition

Abstract Aerohydrodynamics in laminar flow channels is of interest in engineering applications such as passive micromixers and heat exchangers or even in studying the motion of underwater vehicles in confined spaces. The present investigation analyzes the impact of convex and concave shape modifications on a square object with/without rear cavities in a laminar channel flow. The effect on the flow behavior has been analyzed in the transition regime (steady to unsteady, with Reynolds numbers from 50 to 150, based on the side of the object, B), aiming to study the harmonic agitation and reduce drag, because of the possible applications of these geometries in vortex shedding-based engineering problems. The appearance of harmonic components and a transition from a simple periodic to a complex periodic flow with harmonics was observed in certain cases with concave region depths in the range 0.10B–0.30B at Re = 150. In these configurations, it was also found that the presence and depth of a rear cavity can induce or suppress such harmonic behavior. Among the configurations studied, the case with a depth of 0.20B and a rear cavity of 0.50B is the one that presented the highest number of harmonic components. However, in convex geometries, the configuration of convexity 0.15B with/without a rear cavity of 0.50B stood out, as they exhibit the lowest drag coefficients without significantly reducing vortex size. This work highlights that by selecting the appropriate convex/concave/cavity modifications, engineers can tune the frequency and intensity of flow oscillations, enabling an alternative form in passive control with low drag forces.