Shock waves energy transfer

The observation that the reaction requires an induction time of tens of picoseconds can be used to differentiate between proposed mechanisms of how shock wave energy localizes to cause chemical reaction. This induction time is expected for mechanisms that involve vibrational energy transfer, such as multiphonon up-pumping [107], where the shock wave excites low frequency phonons that multiply annihilate to excite the higher frequency modes involved in dissociation. It is also consistent with electronic excitation relaxing into highly excited vibrational states before dissociation, and experiments are underway to search for electronic excitations. On the other hand, prompt mechanisms, such as direct high frequency vibrational excitation by the shock wave, or direct electronic excitation and prompt excited state dissociation, should occur on sub-picosecond time scales, in contrast to the data presented here. 

Energy transfer from the hot spot to the surroundings is therefore presumed to occur entirely by shock and rarefaction waves. 

The propagation of pressure waves such as acoustic wave, shock wave, and Prandtl-Meyer expansion through a gas-solid suspension is a phenomenon associated primarily with the transfer of momentum although certain processes of energy transfer such as kinetic energy dissipation and heat transfer between gas and solids almost always occur. Typical applications of the pressure wave propagation include the measurements of the solids concentration and flow rate by use of acoustic devices as well as detonation combustion such as in a rocket propellant combustor or in the barrel of a gun. 

Sato, Tsuchiya, and Kuratani [216] have solved the relaxation equation for the vibrational energies of two diatomic gases A and B diluted in an inert monatomic gas M, and have applied the solution to shock-wave relaxation profiles in order to obtain V-V transfer rates. Their solution shows that the relaxation of each of the component molecules proceeds as if it possessed two relaxation times. At the onset of the relaxation process, both components begin to relax with their respective V-T rates, whereupon the relaxation rate of that component having the smaller V-T relaxation time begins to decrease, while the relaxation rate of the other component increases. Finally, both components relax with the same rate toward their equilibrium states. By observed infrared emission from the CO fundamental behind shock waves in mixtures of CO-N2, C0-02, CO-D2, and CO-H2, they were able to determine Pil as a function of temperature. Argon was used as inert buffer gas. 

The unique properties of underwater explosions are due to the high velocity of sound in water meaning that the pressure-wave travels approximately four times faster in water than it does in air. Furthermore, due to the high density and low compressibility of water, the destructive energy (from the explosion) can be efficiently transferred over relatively large distances. The most important effects caused by an underwater explosion are the corresponding shock-wave and the gas bubble pulsations. 

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