Effects of Streamlining a Bluff Body in the Laminar Vortex Shedding Regime

Abstract

Two-dimensional flow over bluff bodies is studied in the unsteady laminar flow regime using numerical simulations. In previous investigations, lift and drag forces have been studied over different cross-sectional shapes like circles, squares, and ellipses. We aim to extend the previous research by studying the variation of hydrodynamic forces as the shape of the body changes from a circular cylinder to a more streamlined or a bluffer body. The different body shapes are created by modifying the downstream circular arc of a circular cylinder into an ellipse, hence elongating or compressing the rear part of the body. The precise geometry of the body is quantified by defining a shape factor. Two distinct ranges of shape factors with fundamentally different behavior of lift and drag are identified. The geometry constituting the limit is where the rear part ellipse has a semi-minor axis of half the radius of the original circle, independent of the Reynolds number. On the other hand, the vortex shedding frequency decreases linearly over the whole range of shape factors. Furthermore, the variation of the forces and frequency with Reynolds number, and how the relations vary with the shape factor are reported.

Flow-induced vibrations of elastically coupled tandem cylinders

“…Similar behaviour of decreasing with increasing length of afterbody of stationary cylinders has also been reported by Dobriyal et al. (2020) and Sharma et al. (2022 b ).…”

“…This wake frequency is also present in the UB regime (figure 10c,d), apart from the dominant lock-in frequencies. Figure S11 shows that this single-body wake mode frequency increases with decreasing G. Similar behaviour of decreasing St 0 with increasing length of afterbody of stationary cylinders has also been reported by Dobriyal et al (2020) and Sharma et al (2022b).…”

Aerodynamic Free-Flight Conditions in Wind Tunnel Modelling through Reduced-Order Wall Inserts

“…The occurrence of the compression shock in the wind tunnel, which was later denoted as 'transonic blockage', was resolved based on the principle of wall streamlining [8]. In this method, a streamline is selected to separate the flow around the wing and the theoretical infinite region encountered in free-flight conditions, thereby the real infinite flow field is split into two parts with a streamtube (ignoring the boundary-layer (BL) growth on the test-section walls) [9].…”