Drag reduction for axisymmetric boattail model by longitudinal groove cavity under low-speed conditions

The effect of longitudinal groove cavities on drag and flow behavior was investigated for the axisymmetric model acquired by different conical boattail models. The angle of the boattail was changed from 0 to 22° to understand the influence of cavities on the aerodynamic drag and flow behaviors. The Reynolds averaged Navier-Stokes (RANS) equation with turbulent model k-ω SST was used for the investigation. The simulation was conducted at a velocity of 22 m/s by Ansys Fluent software. Numerical results of the boundary layer, velocity fields, pressure, and drag were first validated by experiments at the same flow conditions. Our results indicate that the grooved cavity allows a reduction of aerodynamic drag up to 24 % for the boattail model of 22°. Additionally, a 6 % drag reduction was also observed for the boattail model of around 14°, where the drag is minimal. The decreasing drag is connected to an increasing base pressure, which is from shortening wake structure and increasing boattail pressure around the shoulder. The longitudinal grooves are found an effective passive control device for narrowing flow separation on the boattail. The details of pressure distributions, flow structure at the surface, and near-wake structure were investigated.