Lifting body with reduced-strength trailing vortices
AssigneeBritish Technology Group USA Inc.
InventorsDaniel M. Nosenchuck, Garry L. Brown
Life of this patent
Estimating the term…
Abstract
A lifting body moves relative to a fluid, thereby creating a vortex field in the fluid downstream of the lifting body. The lifting body has a predetermined lift distribution along the length thereof which enhances the velocity component of the fluid flow directed outwardly from the centroid of the vortex field to reduce the strength of trailing vortices. In a preferred embodiment, the lifting body is a wing with a perturbation proximate to the tip end of the wing planform trailing edge.
Claims19
In a predetermined lifting body for moving relative to a fluid medium, the relative motion being in an x-direction defined as the direction of a velocity vector of the fluid medium relative to said lifting body upstream thereof, wherein said lifting body has a predetermined planform with a chord length in the x-direction, said chord length being defined as a predetermined function c(y) that provides a predetermined lift distribution in a y-direction normal to the x-direction to create in the fluid medium a vortex field having a predetermined total vorticity at any given location downstream of said lifting body, wherein such total vorticity is represented by an equivalent vortex with a center at a centroid of the vortex field and a radius in a plane normal to the x-direction, the equivalent vortex having the same total vorticity as the vortex field at the same given location and the radius having a rate of growth in the x-direction depending on a fluid velocity component of the equivalent vortex directed outwardly from the centroid of the vortex field, the improvement comprising:
- a perturbation in said lifting body that changes the periphery of said predetermined planform to vary c(y) only in a region of said lifting body and thereby alter said predetermined lift distribution to enhance the fluid velocity component of the equivalent vortex directed outwardly from the centroid of the vortex field and increase the rate of growth of the radius of the equivalent vortex in the x-direction.
In a predetermined lifting body for moving relative to a fluid medium, the relative motion being in an x-direction defined as the direction of a velocity vector of the fluid medium relative to said lifting body upstream thereof, wherein said lifting body and a velocity vector of the fluid medium form a predetermined angle of attack .alpha. between a chord of said lifting body and a velocity vector of the fluid medium in the x-direction, said angle of attack being defined as a predetermined function .alpha.(y) that provides a predetermined lift distribution in a y-direction normal to the x-direction to create in the fluid medium a vortex field having a predetermined total vorticity at any given location downstream of said lifting body, wherein such total vorticity is represented by an equivalent vortex with a center at a centroid of the vortex field and a radius in a plane normal to the x-direction, the equivalent vortex having the same total vorticity as the vortex filed at the same given location and the radius having a rate of growth in the x-direction depending on a fluid velocity component of the equivalent vortex directed outwardly from the centroid of the vortex field, the improvement comprising:
- a twist in said lifting body that changes said predetermined angle of attack to vary .alpha.(y) only in a region of said lifting body and thereby alter said predetermined lift distribution to enhance the fluid velocity component of the equivalent vortex directed outwardly from the centroid of the vortex field and increase the rate of growth of the radius of the equivalent vortex in the x-direction.
Dependencies are inferred from the claim text.