Shock wave generator

Fig. 7. The impingement of this jet can create a localized erosion (and even melting) responsible for surface pitting and ultrasonic cleaning (68-70). A second contribution to erosion created by cavitation involves the impact of shock waves generated by cavitational collapse. The magnitude of such shock waves can be as high as 104 atmospheres, which will easily produce plastic deformation of malleable metals (77). The relative magnitudes of these two effects depends heavily on the specific system under consideration.

Fig 2 - Aspect ef the detonation zone in explosive and the shock wave generated in surrounding medium... 

Lasers have been used to initiate deton in RDX. Three types of initiation mechanisms have been described (Ref 102) (1) instantaneous deton caused by a shock wave in a thin metallic film (deposited on the expl) with the shock wave generated by a Q-switched laser pulse (2) instantaneous deton by direct interaction of a Q switched laser pulse and the test expl and (3) DDT produced by free-running laser pulses. Coarse RDX cannot be initiated, but milled RDX (particle size less than 40 microns) is readily initiated at various packing densities. The threshold fluences for the initiation of 1.18g/cc l,52g/cc milled RDX via mechanism (1) are 45,3J/cm2 and 127.9J/cm2, respectively. Detons are either essentially instantaneous or the sample bums without deton. For direct initiation [mechanism (2)], the threshold laser energy for 1.18g/cc RDX was 0.8J, or the same as in thin film initiation. However, deton was no longer instantaneous but required about 2 microsec for build-up. The 1.52g/cc RDX was initiated directly without delay (laser energy not given)... 

Thus the pressure of any shock wave generated in a pipeline would continue to rise if it were not for the fact that at a time 2Lie a return unloading pressure wave reaches the valve and stops the pressure rise at a value of about 53 ft, as contrasted with about three times that value if this were not the case. Subsequent pressure changes as elastic waves travel back and forth are very complex and require a detailed step-by-step analysis that is beyond the scope of this text. In brief, the method consists of assuming that the valve movement takes place in a series of steps each of which produces a pressure p proportional to each V. Other texts contain details of computing successive pressures for slow valve closure and further explanation of much of this condensed treatment [47-49]. 

The arc temperature profile is appreciably modified in this mode, becoming narrower with appreciably higher peak axis temperatures. More radiation from sodium lines arising from higher excited states and from the continuum results. Disadvantages of this approach are the need for special pulsing circuitry to operate the lamps and specially constructed arc tubes to withstand fracture from the acoustic shock waves generated by the pulses. 

Picture a circular flyer impacting a slab of explosive. The shock wave generated at impact travels forward axially into the explosive. The edges of the shock are at ambient pressure hence a rarefaction forms at the edge and propagates radially inward, relieving the shock pressure from the sides. This effect is shown in Figure 22.7. 

More recent lithotripters do not require patients to be lowered into a bath or to lie on a bed of water. Rather, the water is located inside the shock wave generator under the table on which the patient lies. This keeps the patient and water apart, permitting doctors to more easily position patients on the table to treat kidney stones, and increases the ability of physicians to target and destroy them. 

On the other hand, shock waves generate high pressures as well as high temperatures, and, consequently, some fector in addition to heat must be involved in the shock reactioa Drickamer [145], for example, has suggested a close relationship between photochemistry and liigh-pressure chemistry. He experimentally showed that high-pressure conditions promoted the formation of pentacene dimers with cross-linked structure, the formation of which usually occurred in the photochemical reaction. If the shock reaction is a type of some reactions in excited states such as a photochemical reaction, many valence isomers such as Dewar benzene and benzvalene would be generated from benzene by shock waves, and the interaction between these isomers would produce various com-poimds such as derivatives of fiilvene. Such valence isomers are imstable and would not have been detected in our study. 

Ultrasound exposure in the therapeutic range causes cavitation in the keratinocytes of the stratum corneum. Oscillations of the ultrasound-induced cavitation bubbles near the keratinocyte-lipid bilayer interfaces may, in turn, cause oscillations in the lipid bilayers, thereby causing structural disorder of the SC lipids (Fig. 4). Shock waves generated by the collapse of cavitation bubbles at the interfaces may also contribute to the structure-disordering effect. 

The airborne acoustic or shock wave generated by an explosion - Detonation, -> Fuel Air Explosives, - Thermobaric Explosives. 

A plot of P vs. Up has the slope poDs and passes through the origin. If the Hugoniot curve for the detonation products of lead azide at the C-J point were known (the curve for unreacted RDX is known [40]), it would be possible to determine the strength of the shock wave generated in RDX by the detonation wave from lead azide. It is to be recalled that the Chapman-Jouget model as modified calls for a reaction zone at the end of which the reactants have been completely converted to products in equilibrium and travel at the local sonic velocity. The end of the reaction zone is often called the C-J plane, and the associated pressure and temperature called the C-J pressure and temperature. 

At hypervelocities (e.g. in hypersonic aircraft or rockets), the Impact of particle matter on a plastic surface transfers a tremendous amount of kinetic energy within a small region. This energy is partitioned into heat, light, explosive mass ejection, and shock wave generations. The temperatures are of sufficient... 

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