초록 ▼

Streamwise ridges on a lifting wing intercept local flow consisting of free stream and spanwise crossflow to create a pattern of vortices over the wing and aligned with the ridge axes; the vortices act as suction pumps collecting low energy boundary layer fluid, ingesting such fluid into the core of

Streamwise ridges on a lifting wing intercept local flow consisting of free stream and spanwise crossflow to create a pattern of vortices over the wing and aligned with the ridge axes; the vortices act as suction pumps collecting low energy boundary layer fluid, ingesting such fluid into the core of the vortices, transporting it in the streamwise direction, and discharging it into the wake. Fresh fluid from the outer, free stream flow replaces the spent fluid withdrawn by the vortex array. This produces a favorable pressure gradient that maintains laminarity, avoiding the onset of boundary layer transition leading to turbulence. The favorable pressure gradient also suppresses separation on the back side of the wing, where the pressure gradient is normally positive and adverse. The accelerations of fluid resulting from the ridges is an order of magnitude greater than the usual streamwise accelerations produced by wing shape and friction resulting in low effective Reynolds\number dominating the boundary layer and corresponding to laminar flow. Close spacing of the ridges maximizes the interception of local flow. Each ridge is asymmetric in cross-section with a gentle ramp on its windward side and a steep bluff on its lee side to generate a standing vortex between two consecutive ridges. A slight inclination of the ridge with respect to the free stream direction at least aft of the wing\s maximum thickness taps the flow in the free stream direction to augment the acceleration produced by spanwise crossflow.

대표청구항 ▼

An improvement in an aircraft having a wing with a lower surface and an upper surface, the two surfaces being joined at a leading and a trailing edge, the thickness of the wing increasing from the leading edge to a maximum thickness and then decreasing to the trailing edge such that in flight the wi

An improvement in an aircraft having a wing with a lower surface and an upper surface, the two surfaces being joined at a leading and a trailing edge, the thickness of the wing increasing from the leading edge to a maximum thickness and then decreasing to the trailing edge such that in flight the wing generates a static pressure on the upper surface that is lower than on the lower surface to generate lift, the wing having a streamwise direction and a spanwise direction transverse to the streamwise direction, the improvement comprising: a plurality of substantially uninterrupted ridges on at least the upper of the surfaces, the ridges extending from in front of the maximum thickness and past the maximum thickness towards the trailing edge of the wing, generally in a parallel array and generally in the streamwise direction, the height, orientation and length of each ridge being such that the cross-coupling terms of the streamwise accelerations are an order of magnitude greater than the acceleration of the streamwise flow due to the wing shape and friction over substantially the entire wing, i.e., [Figure] whereby the spanwise flow over each of the ridges generates a standing vortex on its lee side, each vortex: (1) providing a suction source to collect low energy boundary layer fluid near the surface of the wing and formed from flow in the freestream direction, (2) providing a conduit to transport such spent fluid aft for discharge into the wake beyond the wing trailing edge, and (3) forcing continuous replenishment by fresh fluid from the outer stream to maintain laminar flow on the surface of the wing.