Helical-groove and circular-trip effects on side force

When a slender body, such as a missile, is pitched at high angle of attack to an oncoming flow, it may experience a large side force due to the asymmetric shedding of the tip vortices. The side force is well known to be highly detrimental to the performance of the flight vehicle. We assess the effectiveness of two control devices, namely, the circular trips and the helical grooves, in alleviating the side force on a tangent ogive nose cylinder. Simultaneous side force and pressure measurements taken in a wind tunnel show that the circular trip is generally more effective in reducing the side force than the helical grooves over a wide range of angle of attack. Detailed findings of their performances are reported.