Acoustic oscillations

Structure of installation enter the source-receiver of acoustic oscillations, block of ultrasonic transducers, system of scanning, control system engines, block of the analysis and registration. 

The electronic block, which includes block of the analysis and registration and control system engines, and block of the source-receiver of acoustic oscillations are universal for any installations of this type. As the source-receiver of acoustic oscillations the ultrasonic flow detector is usually use. It s, as a rule, the serial devices for example y/f2-12. The electronic block contains the microprocessor device or PC, device of the power supply and management of engines... 

Bergles, A. E., P. Goldberg, and J. S. Maulbetsch, 1967a, Acoustic Oscillations in a High Pressure Single Channel Boiling System, EUR ATOM Rep., Proc. Symp. on Two-Phase Flow Dynamics, Eindhoven, pp. 525-550. (6)... 

Culick, F. E. C. 1971. Nonlinear growth and hmiting amplitude of acoustic oscillations in combustion chamber. Combustion Science Technology 3 1-16. 

Manson (Ref a) showed that transverse acoustic oscillations of the burned gas of the lowest permitted frequencies with none or one or two (fixed) nodal meridional planes agreed reasonably well with the observed frequencies. 

The first theoretical predictions of AT/T = 10-2 (Sachs and Wolfe, 1967) and A T/T = 10-3 5 (Silk, 1968) were superseded by predictions based on cold dark matter (Peebles, 1982, Bond and Efstathiou, 1987). These CDM predictions were consistent with the small anisotropy seen by COBE and furthermore predicted a large peak at a particular angular scale due to acoustic oscillations in the baryon/photon fluid prior to recombination. The position... 

Combustion Stability. Although burning without acoustic oscillations is partly a motor design concern, the propellant may be modified by the addition of refractory particles to dampen such vibrations. If uncorrected, pressure oscillations from combustion instability may be large enough to destroy a motor during firing. 

Steady state acoustic response of the unit cell occurred for the composites considered after the passage of some five acoustic oscillations. Patterns of direct stress, and shear stress as shown in Figures 2 and 3 were obtained. As expected, the corners of the cavities concentrated the stresses. Viscoelastic energy loss calculations, not discussed here, also show that the corners of the cavities are concentrations of energy losses. 

More thorough derivations of formulas equivalent to equation (42) may be found in the literature [42], [43]. The result here shows that the dimensionless decay rate, — a/m, vanishes as cot approaches zero or infinity and attains a maximum value of (ajola Q — l)/4 at cot = I. Thus the dissipation rate is greatest when the reciprocal of the relaxation time equals the frequency of the acoustic oscillations and is negligible for long or short relaxation times (that is, for frozen or equilibrium behavior, respectively compare Section 4.3.4.4). Most vibrational relaxations are too rapid to contribute significantly to a, and most chemical times are either too short or too long values of af /a Q for the few that are not typically produce a —10 co,... 

F. T. McClure, R. W. Hart, and J. F. Bird, Solid Propellant Rocket Motors as Acoustic Oscillators, in Solid Propellant Rocket Research, vol. 1 of Progress in... 

The low NO production for combustion in a refractory tube apparently results from the short residence times of 2-5 msec at high temperature and from the minimal back-mixing caused by the planar fiame front and the absence of acoustical oscillations. Bernstein and Churchill showed that the observed decrease in NO. and increase in CO with decreased residence time are consistent with kinetic considerations. 

The phenomenon of unstable combustion results from a self-amplifying interaction between combustion processes and the. acoustic oscillations of the gas within the rocket motor. The unexpected appearance of combustion instability in any rocket generally terminates its mission thru motor case rupture from overpressure, disruption of guidance systems by severe vibration, or thrust malalignment. Both axial mode and transverse mode instabilities are observed (Ref 45). In the case of the transverse mode the characteristic wave time is usually that required to travel radially around the proplnt cavity whereas the characteristic time for the axial mode is the time for the wave to travel from end to end in the combustion chamber. Double-base proplnts predominantly are prone to transverse wave instabilities and infrequently to those in the axial mode, while composite proplnts appear to go unstable mostly in the axial mode. In the case of transverse instability chamber pressures have been known o double whereas in axial mode instabilities artificially induced by pulsing the chamber pressure at lOOOpsi, the pressure excursion may reach 300—400psi. A review of recent theoretical combustion modeling for combustion instability has been made by Price (Ref 47)... 

Phonon excitations are dependent on the condition that the temporal width of the excitation pulses, Tp, is short compared to the single acoustic oscillation periods (1 /Tp> 1 /Ta)- Hence the interaction term "impulsive" is incorporated into the name ISLS. Material modes where Xp > T A will not be efficiently excited. The acoustic wavelength and wave vectors describing the two coherently excited elastic waves are (A,, k ) where... 

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