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We present a numerical study of the flow past a spinning bullet-shaped body of length-to-diameter ratio L/D=2, focusing on the evolution of the forces and flow regimes that appear depending on the values of the two governing parameters, namely the Reynolds number, Re = rho w(infinity)D/mu, and the dimensionless angular velocity, Omega = omega D/(2w(infinity)), where rho,mu and w(infinity) are the free-stream density, viscosity and velocity, respectively, and omega is the angular velocity of the body. The parametric study covers the range 0 <=Omega <= 0.4 for Re < 450, corresponding to laminar flow and moderate rotation velocities. It is shown that the (Re, Omega) parameter plane can be divided into four regions, corresponding to the destabilization of several instability modes. In the range 0 <=Omega less than or similar to 0.2, three different flow regimes take place as Re increases keeping constant Omega: axisymmetric, frozen and spiral flow regimes respectively; the latter leading to a swirling configuration of vortices curling up around the axis, caused by a combination of the frozen mode and the vortex shedding. However, at Omega similar or equal to 0.2, a new frozen spiral mode takes place for large enough values of Re, where two counter-rotating vortices spiral around the axis, as a result of a lock-in process of the vortex shedding associated to the unsteady spiral regime, being this mode the single unstable one existent for Omega >= 0.225. An exhaustive study of the dependence of the drag and lift forces on D and Re is also presented. (C) 2013 Elsevier Ltd. All rights reserved.
rotation body; wake instability; spiral mode; frozen regime; bifurcation; reynolds-numbers; bluff-body; wake transition; sphere; stability; unsteadiness; instability; equations; dynamics; bodies