Projectile with reduced base drag
First Claim
1. A projectile adapted to travel through a fluid in an upstream direction, said projectile having an external surface which is substantially a surface of revolution about an axis extending in the upstream direction, said projectile having a blunt, downstream facing end surface, said surface of revolution terminating at said end surface, a plurality of circumferentially spaced apart downstream extending troughs formed in said surface of revolution, each trough being smoothly U-shaped in cross section along its length, having zero depth at its upstream end and blending smoothly at its upstream end with said external surface of revolution, and intersecting said end surface to form a smoothly U-shaped trough outlet, each of said troughs increasing in depth to a maximum depth at its outlet, wherein the contour and dimensions of said troughs are selected to ensure that each trough flows full throughout its length and generates a pair of large-scale, counterrotating vortices downstream of the trough outlet, the axes of the vortices extending in the downstream direction, whereby fluid is caused to flow into the space immediately downstream of said blunt end surface to reduce base drag.
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Accused Products
Abstract
A projectile having a downstream extending surface of revolution which terminates as a blunt base has a plurality of circumferentially spaced apart U-shaped, downstream extending troughs in its surface. Each trough is essentially aligned with the direction of the bulk fluid flow adjacent the surface in the vicinity of the trough, and intersects the blunt base to form a trough outlet therein. The troughs are appropriately spaced apart, sized and configured to flow full over their entire length and to cause fluid to flow into the space immediately behind the blunt base, thereby reducing base drag on the projectile.
71 Citations
8 Claims
- 1. A projectile adapted to travel through a fluid in an upstream direction, said projectile having an external surface which is substantially a surface of revolution about an axis extending in the upstream direction, said projectile having a blunt, downstream facing end surface, said surface of revolution terminating at said end surface, a plurality of circumferentially spaced apart downstream extending troughs formed in said surface of revolution, each trough being smoothly U-shaped in cross section along its length, having zero depth at its upstream end and blending smoothly at its upstream end with said external surface of revolution, and intersecting said end surface to form a smoothly U-shaped trough outlet, each of said troughs increasing in depth to a maximum depth at its outlet, wherein the contour and dimensions of said troughs are selected to ensure that each trough flows full throughout its length and generates a pair of large-scale, counterrotating vortices downstream of the trough outlet, the axes of the vortices extending in the downstream direction, whereby fluid is caused to flow into the space immediately downstream of said blunt end surface to reduce base drag.
Specification