Effect of vortex generators on hydrodynamic behavior of an underwater axisymmetric hull at high angles of attack

Underwater vehicles when yawed to free stream flow, like submarines in a turning maneuver, produce large vortical separated regions. This vortical flow affects acoustic, body drag, control effectiveness and maneuverability. A suitable way to reduce the effects of this separated flow is to use vortex generators. The main goal of this study is to investigate the effect of the vortex generator on the flow field around a standard underwater model employing the vortex generators by using the oil flow visualization method in wind tunnel only in yaw direction (0° ≤ β ≤ 30° angles of attack, due to the experimental cost) and the CFD method in the pitch direction (0° ≤ α ≤ 30° angles of attack) and the yaw direction (0° ≤ β ≤ 30° angles of attack). Numerical simulations are performed for the investigation of the DARPA SUBOFF bare hull geometry with the vortex generators placed on it. The cross-flow interaction between the pressure side and the suction side is studied in the presence of angle of attack. For this study, the standard k-ε model of turbulence is used for solving the Reynolds averaged Navier–Stokes equations (RANS). The effect of angle of attack on the flow structure, the force coefficients and the wall related flow variables are discussed in detail. The numerical simulations show that the strength of the separation is significantly reduced for the model with the vortex generators. The experimental method used for this study is the application of the oil flow visualizing method which can help one to precisely study the location of the flow separation and the cross-flow vortices around the SUBOFF submarine model. The results show that the vortex generators placed along the submarine do indeed significantly reduce the cross-flow separation on the submarine in a high incident angle. Graphical abstract