Hydrodynamic Feedback Oscillators
John V. Bouyoucos · The Journal of the Acoustical Society of America · 1954
The conversion of fluid-flow energy to acoustic energy by means of a controlled, variable-area orifice is described. Such an orifice acts as a variable flow-impedance device, and it is shown that for small variations of area a simple circuit representation may be obtained which involves an acoustic pressure or volume velocity “source” of finite internal impedance. Although such a mechanism is actually a “displacement-controlled” device, the area-variation can be “sound pressure-actuated.” Thus the network representation of the system can have the form of a four-terminal, unilateral, acoustic transducer which is, in many respects, similar to the vacuum tube. Acoustic feedback may be employed between these terminal pairs to originate and sustain the energy conversion process, thus giving rise to self-excited oscillations. Most of this converted energy is available to be dissipated in an acoustic load, since only a small fraction must be returned to the system to maintain the excitation. A number of oscillator configurations are illustrated, some of which are analogous to common vacuum-tube systems. (This research has been aided by funds made available under a contract with the U.S. Office of Naval Research.)