EP1156962B1 – Tangentially Directed Acoustic Jet Controlling Boundary Layers – Google Patents

Causas y tratamiento del dolor de espalda en los niños In Fig. 4, the tangential acoustic jet 31 of the invention is embodied at the entrance to a diffuser 32 of a centrifugal fan 34 having a volute (or scroll) 35 and a rotor 36 with blades 37. In accordance with the invention, a chamber 38 has a nozzle 39 feeding an orifice 40. The orifice 40 is located at the point where boundary layer energization is most effective, which may be just downstream of the cut-off 41 as shown in Fig. Disclosure of Invention Objects of the invention include: absolute adherence of a boundary layer of laminar or turbulent gaseous flow to an adjacent surface; improved boundary layer characteristics in turbulent flow; reduced boundary layer thickness; improved deterrence of gas flow boundary layer separation; increased efficiency of gas flow machinery; improved helicopter stability; improved effectiveness of fan, helicopter rotor and other blades, wings, other airfoils, fuselages and other aerodynamic structures; boundary layer control which is effective, efficient, having moderate initial cost and low operating costs; and boundary layer control which is relatively simple and provides little parasitic impact on the host structures and systems.

Background Art Boundary layer separation is a fundamentally limiting mechanism which constrains the design of gas flow systems. 1B illustrates unsteady flow 204 and the vortical structures 205 which form adjacent the suction surface 206 of an airfoil 207 in response to typical forcing, illustrated by arrow 208, applied near the point of onset of boundary layer separation, utilizing the dynamic separation control technique of the prior art described hereinbefore. In contrast with all of the prior art, the frequency of excitation of the tangential acoustic jet of the present invention is essentially unrelated to the flow and the surface (that is, independent of flow speed, length of separation and approaching boundary layer characteristics), and is, instead, a function of the characteristics of the acoustic jet itself, including the actuator resonant frequency.

Tipos De Dolor Dental

In Fig. 2A, the nozzle 3 of a tangential acoustic jet according to the present invention is directed substantially tangentially with respect to the surface or wall 4, adjacent to which is a gas flow which, without the present invention, would suffer severe boundary layer separation. If desired, tangential acoustic jets can be appropriately placed on the outer periphery of such a duct, as well. The invention may be practiced utilizing cavities in which the acoustic forcing energy is applied through a resilient member or a rigid member acting as a wall of the cavity, the member being vibrated by electric, magnetic or mechanical forcing, to induce pressure oscillations in the gas at an effective frequency, such as a loudspeaker, preferably with a high Q (quality factor, a measure of mechanical losses) centered at an effective frequency for boundary layer control, or other electroacoustic or mechanoacoustic transducer, such as simple vibrators attached to diaphragms or pistons, powered by rotary or linear devices, piezoelectric drivers, and the like.

It is seen that the particles being projected into the flow from the nozzle 3 are traveling substantially tangentially, thereby being essentially parallel with the upstream flow. The amplitude for a given frequency must be high enough with tangential injection of the particles into a flow, to ensure that gas particle displacement through the nozzle is sufficient to prevent the particles from being re-entrained into the slot. A similar approach is simply blowing high energy gas tangentially in the downstream direction through a slot to directly energize the flow adjacent to the surface.

8, the back of the gas pressure oscillation generator may be used to drive a chamber 79 to provide mass flow through a slot 90. Therein, as the gas pressure oscillation generator 81 oscillates back and forth, a positive pressure is formed in the chamber 78 and a complementary negative pressure is formed in the chamber 79, and then vice versa, in each cycle.

The fan 11 may be driven in a conventional way, such as by means of a belt driving a pulley 23 or a hub-mounted motor (not shown). 28, not only to impart higher momentum flux to the particles flowing along the wall, but also move particles having momentum flux some distance from the wall, closer to the wall so as to improve the momentum flux adjacent the wall. Not shown in Fig.

Tipos De Dolor De Espalda

In the embodiments hereinbefore, it is assumed that the gas pressure oscillation generators (such as 30, Fig. Each separate chamber 26 (if such are used) requires one or more gas pressure oscillation generators 30, unless each generator serves two chambers as described hereinafter. The tangential acoustic jets of the invention can be used around the entire periphery of the engine air inlets, in order to shorten the length of the diffuser (from the tip of the inlet to the first compressor rotor). Fig. 24 is a partially broken away, partially sectioned side elevation view of a commercial jet engine utilizing the present invention in the lower lip and side lips of the air inlet. Fig. Sintomas de dolor muscular en el pecho . 18 illustrates the results which are achievable with the present invention.

This is in contrast with the present invention illustrated in Fig. If the pressure rise is sufficiently large, the momentum and energy of the gas along the surface is consumed in overcoming this pressure rise, so that the gas particles are finally brought to rest and then flow begins to break away from the wall, resulting in boundary layer separation (Fig.

This near-wall, low-momentum fluid can be problematic for the case where the static pressure rises along the direction of the flow. This provides resonant motion for greatest efficiency. 18, at a frequency near the 50 Hertz resonant frequency of the actuator (including the “acoustic” mass in the nozzle). Other electroacoustic devices may similarly be utilized so as to create the pressure oscillations for the tangential acoustic jet of the invention. The vane 150 is driven by a crank disk 158 which has a pin 159 engaging a slot 161 on a bell crank 162. The bell crank 162 is joumated by a pivot 164 in a fixed pillow block 166. The bell crank 162 will oscillate about the pivot 164 as shown by the arrow 167 in response to north pole and south pole magnets 168, 169 rotating on a shaft 170 which may be driven by the shaft of a fan or other apparatus with which the tangential acoustic jet of the invention is to be utilized.

Dolor Muscular Piernas

Similarly, at takeoff and following takeoff, the tangential acoustic jets 198 driving the nozzles 199 may be energized, and then as thrust is reduced during climb, these jets can be turned off. Use of tangential acoustic jets 192 of the invention as shown allows shorter turning sections without separation of the boundary layer. As an example, it is known in the helicopter art that retreating blade stall (boundary layer separation from the leading edge of the rotor blade) establishes limits on rotor load and flight speed. It is known that boundary layer separation can be deterred by increasing the momentum flux of the gas particles flowing near the surface. 6, depending on the actual boundary layer separation point in the operating regime of interest.

Dolor Neuropático Pdf

In the art, the deterrence or reduction of boundary layer separation is typically referred to as “delaying the onset of boundary layer separation”. 7, at the beginning of the cross section reduction transition section 87. The slots 82 form the nozzles of acoustic jets, which are driven by any suitable gas pressure oscillation generator, such as that described with respect to Fig.

  • Menta piperita
  • ¼ de cucharadita de bicarbonato de sodio (1,2 g)
  • Nuevos hábitos
  • Los brazos y las piernas se vuelven rígidos por un breve lapso

Referring to Fig. Dolor en el musculo de la pierna . 25, the intermediate case 205 of an axial flow gas turbine engine, such as the commercial jet engine 196 of Fig. Fig. 12 is a photograph of a test rig having tangential acoustic jets according to the invention, in which boundary layer flow control of the invention for various momentum coefficients is illustrated in Figs.