Since the cascade is here being used only to assist in the propulsion of the fluid in which the cascade is positioned, flutter and critical velocity are not important factors. However, the cascade can also be mechanically oscillated so that the energy of the moving fluid stream is utilized to increase its own propulsion. The subsystems may be mechanically interconnected to move 180° out of phase or may be interconnected solely with oppositely acting mechanical oscillators which maintain and enhance the flutter oscillations and also provide the initial disturbance of the airfoils within the fluid stream.
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Thus if the wind should die down to a velocity which is too low for the control system, which will be explained below, to maintain the system at critical velocity, the mechanical oscillators will keep the airfoils oscillating, until the velocity increases sufficiently to reestablish flow at critical velocity. U.S. Pat. No. 3,995,972 discloses a device including a stack of rigidly interconnected airfoils positioned in the wind.
The airfoils are preferably arranged in two subsystems, the airfoils of each subsystem being interconnected to oscillate in phase. Pat. 4,595,336. It is a device that draws energy from moving fluids by means of a set of two wings performing a reciprocating motion. In 1936, I. E. Garrick reported that by oscillating a single airfoil in a moving fluid, a negative drag is produced. It can be shown that a single airfoil which is equally spaced between a pair of flat plates when in an undisturbed state acts as an infinite cascade. From the foregoing, it will be apparent that the two subsystems are free to oscillate in pitch and plunge relative to each other and that when the energy converting device 10 is subjected to the wind at a critical velocity, the adjacent airfoils will oscillate approximately 180° out of phase as shown in FIG.
Dolores Musculares Piernas
The use of a cascade provides a distinct advantage over a single airfoil subjected to flutter. FIG. 2 is a graph illustrating advantage of the cascade. Dolor de espalda baja intenso . The same type of flow results if, instead of a cascade of airfoils, a flat plate is positioned at s/2 both above and below the airfoil.
Fisioterapia A Domicilio
Each energy converter 10 includes a support structure 16 open at both ends to permit free passage of the wind therethrough and has a plurality of equally spaced thin airfoils 181. For example, flaps may be provided in combination with airfoils which are freely movable in both pitch and plunge to provide an energy converter 10 having three degrees of freedom. Similarly it will be appreciated that all of the foregoing embodiments may be constructed to permit three or more degrees of freedom since the invention is not intended to be limited to only two degrees of freedom. 6, namely, airfoils 184 -187 although all of the airfoils will be referred to hereinafter.
One alternative to the windmill is disclosed in U.S. Since the rods do not support the airfoils in this embodiment, a single set of rods, adjacent one side of the energy converter is sufficient to interconnect each subsystem. FIG. 14 is a graph illustrating this phenomenon. The present invention, however, is able to utilize the flutter phenomenon because there is provided a control system which prevents the instability and destruction which normally result in wing flutter situations. In operation, the energy converter 10 is positioned at a location where it will be subject to the action of the wind. Thereafter, based on the velocity of the wind, various parameters are adjusted so that the wind velocity will be a critical velocity for the system.