Acoustic resonance

Pulsation can be problematic and difficult to predict. Pulsations are also dependent on acoustic resonance charac teristics. 

When a pulsation frequency coincides with a mechanical or acoustic resonance, severe vibration can result. A common cause for pulsation is the presence of flow control valves or pressure regulators. These often operate with high pressure drops (i.e., high flow velocities), which can result in the generation of severe pulsation. Flashing and cavitation can also contribute. 

Acoustic Coupling When the shell-side fluid is a low-density gas, acoustic resonance or coupling develops when the standing waves in the shell are in phase with vortex shedding from the tubes. The standing waves are perpendicular to the axis of the tubes and to the direction of cross-flow. Damage to the tubes is rare. However, the noise can be extremely painful. 

The control of acoustic resonances should always he considered in piping design. That is, acoustic resonant frequencies of piping elements should he separated from the frequencies of prominent engine harmonics as much as pos-... 

The more important techniques for controlling acoustic resonance are selected depending on the required purpose. 

L. O. Bowen, Nuclear magnetic acoustic resonance and Debye vibration potentials in non-viscous liquids, Proc. Phys. Soc., 1966, 87, 717-720. 

Axial and swirling air streams in the combustor issued from a circular chamber through a conical nozzle. The chamber was utilized both as an acoustic resonator and a settling chamber. It contained a honeycomb to straighten the how and two acoustic drivers to apply acoustic excitation to the jet. The nozzle exit diameter was 3.8 cm and the maximum Reynolds number based on this diameter and the exit velocity with and without air forcing was 4800 and 1400, respectively. The tests were performed with total air how rate of 85 1/min, and fuel how rate of 0.063 1/min. The swirl was applied with tangential air injection and the maximum swirl number tested was Ns = 0.30. 

The use of acoustic resonances for increasing sound amplitude from an OA cell was first described by A. G. Bell, Phil. Mag., 11, 510 (1881). Recent experiments with resonant OA cells are described by C. F. Dewey, Jr., R. D. Kamm, and C. E. Hackett, Appl. Phys. Lett. 23, 633 (1973). 

Miller and Bolef (1968) treated the quartz oscillator and coating system as a single-dimensional, coherent acoustic resonator. Lu and Lewis (1972) developed the simplified Z match equation on that basis. Simultaneous advances in electronics, particularly the microprocessor, made it possible to solve the Z match equation in real time. Most coating process control units sold today use this sophisticated equation, which takes into account the acoustic properties of the quartz oscillator/coating system ... 

Sensitivity Enhancement by the use of Acoustic Resonators in cw Ultrasonic Spectroscopy. 

Pulsation can be problematic ancfdifficult to predict. Pulsations are also dependent on acoustic resonance characteristics. For reciprocating equipment, such as reciprocating compressors and pumps, in some cases, an analog (digital) study needs to be performed to identify the deficiency in the piping and pipe support systems as well as to evaluate the performance ofthe machine during operation. The study will also provide recommendations on how to improve the machine and piping system s performance. 

Young, JChemPhys 27(5), 1149-55(1957) (Measurement of vibrational relaxation time in nitrogen by means of an acoustical resonance cavity) 4) Dunkle s Syllabus (1957-1958), pp 57-8 389 5) M. Saikoff... 

F tuidic Explosive Initiator. A new fluidic explosive initiator operates on compressed gas and utilizes acoustic resonance instead of electricity to initiate an explosive charge. Current applications are in various military... 

The most essential properly of acoustic vibrations in a nanoparticle is the existence of minimum size-quantized frequencies corresponding to acoustic resonances of the particle. In dielectric nanociystals, the Debye model is not valid for evaluation of the PDOS if the radius of the nanociystal is less than 10 nm. The vibrational modes of a finite sphere were analyzed previously by Lamb (1882) and Tamura (1995). A stress-free boundary condition at the surface and a finiteness condition on both elastic displacements and stresses at the center are assumed. These boundary conditions yield the spheroidal modes and torsional modes, determined by the following eigenvalue equations ... 

Terhune and Anderson [144] measured N02 sensitivities of better than 0.1 ppb during in situ measurements of aerosols using an acoustically resonant spectrophone and a 514.5-nm Ar+-ion laser. By constructing a nonmetal cell to minimize surface adsorption, Crane [145] was able to use a C02 laser (9.6 p,m) to obtain optoacoustic absorption spectra of EGDN, DNT, and NG vapors with LODs of 8.26,0.23, and 0.50 ppb, respectively. 

The pulsation amplitude for different pump speeds have been computed at three testpoints (TP 1, TP 2, TP 3). The computation indicates, that nearly over the whole speed range the pressure pulsations remain below 3 %. At a speed of 45 rpm the pulsation amplitudes pass a maximum which indicates an acoustical resonance (Fig. 6)... 

Have you ever been sitting in a quiet room when suddenly a fixed pitch noise (sound waves) causes a nearby object to vibrate in sympathy This is an example of acoustic resonance, in which the frequency of the sound waves exactly matches the frequency with which the object naturally vibrates. If the pitch of the sound changes, the resonance ceases. 

Resonant US in liquids. Measurements of ultrasonic resonance in liquids involve using a resonator cell comprising two major elements, namely a resonator chamber, where acoustic resonance forms and two transducers (usually piezoelectric), which excite and detect ultrasonic vibrations. 

The evolution of US-induced crystallization around the glass transition temperature for metallic glass was monitored by electromagnetic acoustic resonance, which allowed resonance frequencies and internal frictions to be measured. In an as-cast glassy sample, such frequencies jumped up just above the glass temperature transition at the beginning of the process under ultrasonic vibration this was ascribed to nano-crystallization as confirmed by an X-ray diffraction profile, which was absent in the absence of US. Irregular A-shaped internal-friction peaks were also observed prior to abrupt crystallization [48]. 

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