• boundary-layer separation
• drag reduction
• grooves

The present work describes the results of a numerical investigation aimed at characterizing the performance of a passive control method to delay boundary layer separation and reduce drag. It consists in the introduction of transverse grooves on the surface of two-dimensional boat-tailed bluff body. The grooves start with a sharp edge, have an upstream part with a circular arc shape and end with a spline leading to a point on the original boat-tail contour.
In previous works this technique has shown to be able to reduce drag in axisymmetric boat-tails, due to the relaxation of the no-slip condition in the small recirculation region inside the groove. In this way the near-wall momentum losses is reduced and the flow separation is delayed.
The scope is now to evaluate the performance of a similar device even in the presence of a strong vortex-shedding, which is a peculiar characteristic of two-dimensional body.
It has been studied the flow around the rear part of a model with a boat-tail that is half-diameter long.
The effectiveness of the device has been assessed through RANS simulation.