US 3901277 A
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United States Patent 1 Viets [451 Aug. 26, 1975 1 VARIABLE FLUIDIC IMPEDANCE FEEDBACK LOOP FOR OSCILLATING JET NOZZLE  Inventor:
 Assignee: The United States of America as represented by the Secretary of the Air Force, Washington, DC.
 Filed: Aug. 14, 1974 121] App]. No.: 497,408
Hermann Viets, Dayton, Ohio  US. Cl. 137/829; 137/835; 251/126  Int. Cl. F15C 1/08  Field of Search 137/825, 826, 829, 830,
 7 References Cited UNITED STATES PATENTS 3,016.066 1/1962 Warren 137/835 X 3,504,689 4/1970 Lazar 137/832 3,529,612 9/1970 Rausch 3,724,504 4/1973 Matsui et a1. 251/126 Primary Examiner-William R. Cline Attorney, Agent, or Firm-Joseph E. Rusz; Richard J. Killoren 5 7] ABSTRACT A variable length feedback loop for an oscillating jet having a pair of plate members which are slidable with respect to each other. Each plate member has a plurality of holes with partial loop members connected between pairs of holes. A terminal member is attached to one hole on each plate member. The holes on the plate members are arranged to match loops on one plate member with different loop members on the other plate member so that the length of the feedback loop can be changed.
3 Claims, 5 Drawing Figures 'PATENTED AUG 2 6 I975.
sum .1 115 2 VARIABLE FLUIDIC IMPEDANCE FEEDBACK LOOP FOR OSCILLATING JET NOZZLE RIGHTS OF THE GOVERNMENT The invention described herein may be manufactured and used by or for the Government of the United States for all governmental purposes without the payment of any royalty.
BACKGROUND OF THE INVENTION In thrust augmentation systems, such as described in the inventors copending patent application, Thrust Augmentation System With Oscillating Jet nozzles, Ser. No. 492,078, filed July 26, 1974, the frequency of oscillation is a function of the length of the feedback loop. It is desirable to have some means for varying the length of the feedback loop so that the frequency of os cillation can be varied. There is no known system to accomplish this result.
BRIEF SUMMARY OF THE INVENTION According to this invention, apparatus is provided for varying the length of the feedback loop. Two plate members which are slidable with respect to each other have partial loops connected to a plurality of holes in the plate members. By aligning different numbers of partial loops on one plate member with a corresponding number of partial loops on the other plate member, the length of the feedback loop can be changed to set the frequency of oscillation of the jet from the nozzle, as desired.
IN THE DRAWING DETAILED DESCRIPTION OF THE INVENTION Reference is now made to FIG. 1 of the drawing, which shows a fluidic oscillating nozzle 10, such as used in the device of the referenced copending application, wherein the frequency of the oscillating jet is determined by the length of the feedback loop between the control ports 12 and 14. The variable fluidic impedance element 16 has a pair of plate members 18 and 20, as shown in FIGS. 2 and 3.
The plate member 18 has a plurality of holes 22 therein, with partial loop members 24 connected between pairs of holes. A terminal member 26 is attached to a hole at one end of the plate member 18.
The plate member 20 has a plurality of holes 28, with partial loop members 30 connected between pairs of holes. A terminal member 32 is attached to a hole at one end of plate member 20. The holes in plate member 18 and the holes in plate member 20 are positioned so that when the plates are juxtaposed, as shown in FIG. 1, the partial loops 24 and 30 form a continuous hollow tubular channel extending from terminal member 26 to terminal member 32.
By moving one plate laterally with respect to the other, the length of the tubular channel can be changed, with the minimum channel being, as shown in FIG. 4, wherein the holes with terminal members 26 and 32 are aligned. The terminal members 26 and 32 are secured to terminal connectors 34 and 36 of the fluidic oscillating nozzle 10.
One manner in which the plates 18 and 20 may be held together is shown in FIG. 5, wherein plate member 20' has a key slot 38. Plate member 18 is formed as a key memberfor sliding in the key slot 38. Indexing marks 39 may be provided, if desired, to aid in aligning the partial loops.
Other configurations for the variable fiuidic impedance element than that shown may be used, for example, for some applications the loops could be located in a circular configuration on circular disks or they could be located on tubular elements.
In the operation of the device, for any particular nozzle flow configuration, the gas jet leaving nozzle 10 oscillates at a frequency as determined by the length of the feedback loop. By aligning predetermined holes 22 with corresponding holes 28, a predetermined length of feedback loop is provided.
There is thus provided an apparatus for selecting the frequency of oscillation of a gas jet leaving a nozzle.
1. A variable fluidic impedance element in the feedback loop ofa fluidic oscillator, having a pair of control ports, comprising: a first plate member; a plurality of tubular partial loop elements supported on said first plate member; a second plate member positioned adjacent and movable with respect to said first plate member; a plurality of tubular partial loop elements supported on said second plate member; a first terminal member on said first plate member; a second terminal member on said second plate member; means for connecting the terminal member and certain predetermined partial loop elements on the first plate member to certain predetermined loop elements and the terminal member on the second plate member to thereby provide a predetermined length of feedback loop and means for connecting said first and second terminal members to the control ports of said fluidic oscillator.
2. The device as recited in claim 1 wherein said means for connecting the first terminal member and certain predetermined partial loop elements on the first plate member to certain predetermined loop elements and the terminal member on the second plate member includes a plurality of holes in the first plate member and a plurality of holes in the second plate member adapted to be aligned with corresponding holes in the first plate member.
3. The device as recited in claim 2 wherein said first plate member is shaped as a key member and said second plate member has a key slot thereon adapted to receive said first plate member.