ABSTRACT
Wrap around fins (WAF) have been used on tube launched missiles and dispenser launched projectiles. Modern
advances in stealth technology have made the use of missiles equipped with WAFs desirable because they can be
stowed to reduce the radar cross section of the aircraft. Recent studies have identified several roll –and pitch–
moment instabilities. The rolling moment of the WASF is positive at subsonic velocities (defined here to means
that the missile rolls towards the concave side of fin). A roll reversal occurring at M=1.0 indicates that the
magnitude of the rolling moment decreases with increasing Mach number and that a second rolling moment
reversal may occur at high supersonic speed. Tillman et al and Bower sox examined experimentally and
numerically the flow structure in the vicinity of a single fin mounted onto blended cylindrical body at Mach 3.00
and 5.00 Those studies indicated that the flow field was highly asymmetric about WAF, with a stronger bow–
shock structure on the concave side of the fin. This resulted in creating a very high-pressure region between the fin
and its center of curvature, which resulted in relatively high surface pressures near the mid span of the fin. In
contrast, on the convex side of the fin, surface pressure was relatively independent of location along the span.
This resulted in asymmetric pressure loading on the fin, which caused generation of out-of-plane moment at angle
of attack; it is suspected that this side moment is symptomatic of WAF configurations. When testing such
configurations, the test engineer should ensure that this side moment is obtained and stability boundaries are
computed. This side moment can have a dramatic effect on trajectory computation based on the conventional
aerodynamic coefficients and derivatives.
Experiments have been conducted to study the effect of fin shapes on generation induced rolling moment and out
of-plane moment coefficients. Four sets of WAF configuration were tested. The results were then compared wi