US6109566A – Vibration-driven Acoustic Jet Controlling Boundary Layer Separation – Google Patents

Dolores lumbares y "core" - ITRAMED The negative pressure portion of the acoustic jet cycle creates a flow of low momentum flux fluid particles perpendicular to the surface, entering the chamber, thereby removing low momentum flux fluid particles from the approaching boundary layer. Similar boundary layer problems attend other aerodynamic surfaces, such as fuselages, compressor and turbine blades, wings, and so forth. 1, the nozzles 20 may be elongated, and there may be several nozzles disposed along substantially the entire length of each blade, each nozzle or group of nozzles being driven by one or more acoustic jets. Referring to FIGS. 12 and 13, a wind energy electric power generator 70 includes a structure 71 supporting a generator 73 driven by blades 75-77 mounted on a hub 79. A plurality of leading slots 80 each comprise the nozzle of an acoustic jet having a chamber 81, and a plurality of trailing slots 83 each comprise the nozzle of an acoustic jet having a chamber 84, both chambers driven by the same mass/membrane resonant system 86. If desired in any case, the resonant system 86 could be mounted to oscillate in a direction other than normal to the cord of the blade as shown, such as parallel to the cord of the blade, or otherwise.

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Experto Universitario en Neurocirugía y Cirugía.. 4 and 5. Therein, a pair of wall structures 32, 33 support a combined mass and membrane 34 that will produce a positive pressure in a chamber 35 which drives a slot-shaped nozzle 37 and a negative pressure in a chamber 36 which evacuates a slot-shaped nozzle 38 which is separated spanwise (cross-stream) from the nozzle 37; the mass/membrane 34 will alternately provide a negative pressure in the chamber 35 and a positive pressure in the chamber 36. Of course, each chamber of an acoustic jet could drive a plurality of nozzles, the nozzles being separated streamwise and/or spanwise from other nozzles driven by the same chamber, as well as other nozzles driven by other chambers, in any configuration within the scope of the invention. Each of the blades have at least a pair of slots 55, 56 which comprise the nozzles for a two chamber acoustic jet having a membrane 58 and a mass 59, which is shown in more detail in FIGS.

However, such perturbations must be actively controlled as a function of all of the flow and geometric parameters, dynamically, requiring expensive modeling of complex unsteady flow structures and/or significant testing to provide information for adapting to flow changes either through open loop scheduling or in response to feedback from sensors in the flow. This approach has been reported as being highly parameter dependent, thus also requiring dynamic control; and, the results achieved to date have not been sufficient to merit the cost and complexity thereof. On the other hand, the chamber 15 may also be used for providing mass flow through a slot, as illustrated in FIG.

Dolor Muscular Bayer

BEST MODE FOR CARRYING OUT THE INVENTION Referring to FIGS. The simplest and most common method for overcoming boundary layer separation includes small vortex generators, which may typically be tabs extending outwardly from the surface (such as the upper surface of an airplane wing), which shed an array of streamwise vortices along the surface. It is known that boundary layer separation can be deterred by increasing the momentum flux of the fluid particles flowing near the surface. The energized fluid particles, having higher momentum flux, injected preferably essentially tangentially into the boundary layer, provide adequate momentum flux in the boundary layer to deter the onset of boundary layer separation downstream thereof. A wall suction upstream of the boundary separation line (that is the line at which the onset of full boundary layer separation occurs across the surface of an airfoil or a diffuser) simply removes low momentum flux fluid particles from the flow adjacent to the surface, the void created thereby being filled by higher momentum flux particles drawn in from the flow further out from the surface.

Dolores Musculares Generalizados

This invention is predicated in part on the fact that the outflowing jet stream of an acoustic jet will clear the orifice or nozzle area sufficiently before the onset of negative pressure, which therefore will cause replenishment of fluid mass within the jet cavity with molecules which are other than those in the emitted jet stream. In the art, the deterrence or elimination of boundary layer separation is typically referred to as “delaying the onset of boundary layer separation”. The nozzle 20 is preferably oriented at a small acute angle with respect to the suction surface 22, so that air particles will be injected substantially tangentially into the boundary layer on the suction surface 22, thereby to deter or prevent boundary layer separation. TECHNICAL FIELD This invention relates to use of the vibration of a structure having a surface with an aerodynamic profile to drive an acoustic jet having a nozzle directed, preferably essentially tangentially, into the boundary layer of the surface to control boundary layer separation.

These techniques introduce cyclic vortical disturbances into the boundary layer which are amplified in the unstable shear layer into large vortical structures that convect momentum toward the surface; the separation is thereby limited to an extent, but the boundary layer is far from attached. These devices introduce a periodic disturbance in vorticity to the flow, the vortices being amplified in the unstable separating shear layer into large, spanwise vortical structures which convect high momentum flow toward the surface, thereby enabling pressure recovery. Dolor de espalda cambio de tiempo . FIG. 5 is a sectioned, side elevation view of an aerodynamic structure employing two-chambers and two spanwise slots, taken on the line 5–5 in FIG.

FIGS. 6 and 7 illustrate the invention applied to the fuselage of an aerodynamic vehicle 40, which may comprise a rocket powered vehicle, or otherwise. FIG. 9 is a fanciful, schematic illustration of the arrangement of the invention applied to the blade of FIG. FIG. 11 is a fanciful, schematic illustration of the arrangement of the invention viewed from the leading edge of the blade. FIG. 3 is a sectioned, side elevation view of a helicopter blade employing a two-chamber, two-nozzle embodiment of the present invention. Other frequencies may be used to suit any particular implementation of the present invention. FIG. 12 is a partially broken away perspective view of a wind energy electric power generator employing the invention. Dolor muscular en el esternon . Boundary layer separation typically results in the termination of pressure rise (recovery) and hence loss in performance (e.g., airfoil lift) and dramatic decrease in system efficiency, due to conversion of flow energy into turbulence, and eventually into heat.

In accordance with the invention, the jet effect on the boundary layer is not frequency dependent, other than to maximize mass flow through the nozzle. According to the present invention, an acoustic jet directed into the boundary layer of fluid flow (such as air) along the surface of a vibrating structure having an aerodynamic profile, to control the boundary layer thereof, is powered by a resiliently supported mass forming one wall of an acoustic chamber, oscillations of the mass as a result of vibration of the structure causing commensurate air pressure variations to drive the acoustic jet.

Dolor De Garganta

A recent variation on the dynamic separation control is the utilization of a so-called “synthetic jet” (also referred to as “acoustic jet” or “streaming”) directed perpendicular to the surface upstream of the boundary separation line of the surface. The momentum and energy of the fluid along the surface is consumed in overcoming the pressure rise and friction so that the fluid particles are finally brought to rest and the flow begins to break away from the wall, resulting in boundary layer separation. Use of the vibration energy can result in a smoother, quieter system. Stall boundaries define the maximum blade loads, which impact maneuverability and agility as well as speed and payload. This invention is also predicated in part on the discovery that a synthetic jet directed tangentially into a boundary layer of a fluid flow will produce a net negative flow averaged over time which is generally perpendicular to the surface and a net positive flow averaged over time which is generally parallel to the surface.

Dolor Muscular En El Pecho

Other objects, features and advantages of the present invention will become more apparent in the light of the following detailed description of exemplary embodiments thereof, as illustrated in the accompanying drawing. Thus, although the invention has been shown and described with respect to exemplary embodiments thereof, it should be understood by those skilled in the art that the foregoing and various other changes, omissions and additions may be made therein and thereto, without departing from the spirit and scope of the invention. This greatly increases the cost, weight and complexity of any such systems which have not as yet been found to be sufficiently effective to justify use. Pat. No. 5,209,438. These include: pivotal flaps which oscillate from being flush with the surface to having a downstream edge thereof extending out from the surface; ribbons parallel to the surface, the mean position of which is oscillated between being within the surface and extending outwardly into the flow; perpendicular obstructions that oscillate in and out of the flow; and rotating vanes (microturbines) that provide periodic obstruction to the flow, and oscillatory blowing.