Abstract
ABSTRACTThe numerical simulations of flow over a spinning finned projectile at angles of attack ranging from to in supersonic conditions were carried out to investigate the flow mechanism of the Magnus effect. The finite volume method, a dual-time stepping method, and a transition model were combined to solve the Reynolds-averaged Navier-Stokes (RANS) equations. The validation of temporal resolution, grid independence, and turbulence models were conducted for the accuracy of the numerical method. The numerical results were in certain agreement with archival experimental data. A comparison of the transient lateral force and time-averaged Magnus force between the body of finned projectile and the nonfinned body, the projectile fin and single fin was given. The key lies in the analysis of the reasons for the production of the Magnus force. The simulation provided a profound insight into the flow structure and revealed the following. The fin leading edge shock contributes to the unsteady interference on body lateral force, while the time-averaged body Magnus force is similar to that of the nonfinned body. At , the shielding effect of body on crossflow weakens the time-averaged body Magnus force induced by asymmetrical flow separation, the magnitude of which is reduced to the value at . The leeward separation vortices and the resistance on wingroot flow are responsible for the nonlinear interference of the projectile body on fin Magnus force at different angles of attack. When the low pressure region of the vortex core is equivalent to the size and position of fin, leeward separation vortices contribute more the time-averaged Magnus force and induce high frequency variation to the transient fin lateral force.
Highlights
Many projectiles spin around their longitudinal axis during flight for advantages such as obtaining stability through the gyroscopic effect, eliminating or decreasing adverse effects caused by eccentricity, and simplifying the control system
At α = 30.3◦, the shielding effect of body on crossflow weakens the time-averaged body Magnus force induced by asymmetrical flow separation, the magnitude of which is reduced to the value at α = 8◦
Based on the Reynolds-averaged Navier-Stokes (RANS) equations, combining a dual-time stepping method and different turbulence models, the Magnus effect of a finned projectile in supersonic flows was investigated through numerical simulation
Summary
Many projectiles spin around their longitudinal axis during flight for advantages such as obtaining stability through the gyroscopic effect, eliminating or decreasing adverse effects caused by eccentricity, and simplifying the control system. Different from the quasi-steady Magnus effect of nonfinned projectile, the lateral force and yawing moment of finned projectile change with time and have obvious unsteady characteristics (Cayzac, Carette, Denis, & Guillen, 2011). The former study had certain limitations because the interference between the body and the fin was relatively small at small angles of attack and flow separation was not taken into consideration The latter was concentrated on the computation of aerodynamic coefficients while the insight of flow field structures was not involved in. The aforementioned studies neither include the comparison of the Magnus effect of a spinning finned projectile using different turbulence models, nor the analysis of the corresponding flow structures and the distribution characteristics of lateral force. The profound insight of the relationship between aerodynamic characteristics and flow structure can provide guidance for the design of projectile configuration and control system
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