Nose Bluntness for Side-Force Control on Circular Cones at High Incidence

Abstract

An experimental investigation has been car ked out to study the effect of nose bluntness on the characteristics of vortex asymmetry and induced side forces on slender cone models at low speeds. Two cone models with semi-apex angles of 8 and 12 deg were utilized, and on each model nose bluntness was varied up to 20% (based on base diameter).Measurements made consisted of six-component balance loads over a Widerange of Reynolds number from 0.4 x 10(6) to 5.4 x 10(6). The results show that the onset of vortex asymmetry with nose blunting correlates with geometrical parameters and is practically independent of Reynolds number. The (maximum) side-force levels decrease initially up to a certain bluntness ratio, then increase, followed by a gradual decrease for large values of bluntness ratios. This decrease or increase inside-force levels with nose blunting is associated with a corresponding increase or decrease, respectively, in the onset of vortex asymmetry.Whereas the increase in side-force level beyond the first minimum is qualitatively similar to that observed in earlier studies, the present data definitely indicate that there is a progressive decrease inside-force levels to relatively low values for large bluntness ratios,which could form an important design input. The bluntness ratio corresponding to the occurrence of the first minimum in (maximum) side force depends on the cone angle and is nearly independent of Reynolds number.