Pressure pulse propagation

Li, J.K.-J. and A. Noordergraaf. Similar pressure pulse propagation and reflection characteristics in aortas of mammals. Am. ]. Physiol. 261 R519-R521,1991. 

Shock-compression processes are encountered when material bodies are subjected to rapid impulsive loading, whose time of load application is short compared to the time for the body to respond inertially. The inertial responses are stress pulses propagating through the body to communicate the presence of loads to interior points. In our everyday experience, such loadings are the result of impact or explosion. To the untrained observer, such events evoke an image of utter chaos and confusion. Nevertheless, what is experienced by the human senses are the rigid-body effects the time and pressure resolution are not sufficient to sense the wave phenomena. 

Throughout this book, a shock pulse (a steady compression wave followed by an expansion wave) will be represented as a profile, such as in Fig. 2.6. In Fig. 2.8 we show a series of P-x snapshots of pressure versus propagation distance x for an initially square pulse, at a series of times t. For a fluid with... 

Sonic wave propagation. Sonic waves differ from pressure pulses in two respects ... 

Grolmes, M. A., and H. K. Fauske, 1969, Propagation Characteristics of Compression and Rarefaction Pressure Pulses in One-Component Vapor-Liquid Mixtures, Nuclear Eng. Design 77 137-142. (3) Grolmes, M. A., and H. K. Fauske, 1970, Modeling of Sodium Expulsion of Freon-11, ASME Paper 70-HT-24, Fluids Engineering Heat Transfer and Lubrication Conf., Detroit, MI. (4)... 

Hsu, Y. Y., 1972, Review of Critical Flow Rate, Propagation of Pressure Pulse, and Sonic Velocity in Two-Phase Media, NASA TN D-6814, NASA Lewis Res. Ctr, Cleveland, OH. (3)... 

Fig 33, from Ref 17, is a schematic representation of the effects of a nearby surface on pressure pulse shapes at various distances below the water surface. It also shows the expected pulse shapes for acoustic rather than shock waves A shock wave in water will be reflected as a rarefaction wave when it encounters another medium less dense than water, eg, a water/air boundary. The rarefaction wave, generated by the reflection of the primary shock wave from the surface, propagates downward and relieves the pressure behind the primary shock wave. If the shock wave is treated as a weak (acoustic) wave, this interaction instantaneously decreases the pressure in the primary shock wave to a negative value, as shown by the broken line in Fig 33 (Ref 17), Point A. Cavitation occurs in seawater when its pressure decreases to a value somewhat above its vapor pressure. The pressure of the primary shock wave is, therefore, reduced to a value which is usually so close to ambient water pressure that the shock wave pulse appears to have been truncated... 

M. Mlejnek, E. M. Wright, J. V. Moloney, Femtosecond pulse propagation in argon A pressure dependence study, Physical Review E 58, 4903 (1998)... 

More rigorously, the current flowing in the external circuit during propagation of the pressure pulse across the sample (z-direction) is expressed by ... 

Most organic fuels show a pressure-Hemperature region in which their oxidation is accompanied by cool-flame formation. In static systems this feature is characterized by the occurrence of one or more pressure pulses, each of which is accompanied by a moderate temperature rise (< 200 °C) and the weak emission of radiation corresponding to the excited HCHO spectrum. The propagation velocity of cool flames is low (ca. 10 cm. sec ), and often they can be stabilized in flow systems. 

A complete model would embrace the cylinder flow, turbulence, flame propagation, and gas reaction, and, if they occur, autoignitions at hot spots and the associated interactive pressure pulses. No such model has been achieved, although there have been partial successes in marrying autoignition to engine combustion models. As will be shown later, the accurate modelling of pressure pulses presents formidable problems. 

This one-step expression for the reaction rate is adequate for a demonstration of some of the general principles involved in the generation of pressure pulses. The equations are used to show the effects of the temperature gradient around a hot spot and the volumetric heat release rate there upon the propagation of autoignition. 

Shock initiation of lead azide by an electron beam has been compared with that of potassium dinitrobenzofuroxan (KDNBF), lead styphnate, and lead mononitroresorcinate (LMNR) [49], An aluminum slab was heated rapidly by electron deposition, generating a pressure pulse that propagated through the slab and was transmitted to a specimen bonded to its rear. The mean energy of the electrons was in the range of 900 keV and produced a stress pulse in the aluminum with a duration of approximately 0.2 psec. 

The speed of propagation of a small pressure pulse or sound wave in a fluid, us- can be shown to be equal to... 

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