Oblique Detonation Waves

An experimental arrangement is illustrated in Fig 1. on p 381 of Ref 93. A metal plate thickness , is bent thru an angle fj, by means of a deton wave, velocity DQ travelling thru a layer of explosive. When the plate was deflected, it hit at an angle of incidence i a block of expl, density p.Q The thicknesses were sufficiently small compared to the other quantities so that the flow could be considered as plane two-dimensional and stationary. The reference system R had its origin at the point of impact I and was under uhiform linear motion. Theoretical and experimental studies of the flow were carried ont in the vicinity of the noinr nf impact 

Fig 5 (shown here) shows experimental layout and the type of recording made on photographic plates. In the experiments, copper was projected by means of an explosive of detonation velocity D, of initial density pQ which varied from experiment to experiment. Photographs of luminosity produced when using simplified method are given in Plates 1 2 of p 385 (These plates are not reproduced here) 

The experiments of David et al showed that overdetonation took place at impact. The simplified method seemed to give a reasonable account of observation within experimental error, in so far as a solution was possible. 

When this method offered no solution, experiments diowed that the overdetonation shock was very strong and it seemed that the shock suffered a large discontinuity as investigators went from the determinate to the indeterminate case. 

No observation could be made of the prestressing shock in the photographs and this was probably due to the smallness of the induction region 

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Detonation, Oblique Impact of a Layer of Explosive by a Metal Plate in. David et al (Ref) conducted experiments on initiation of explosives by impacts upon them of metal plates. When the metal plate came in contact with the layer of explosive, not all at once but gradually, an oblique detonation wave was initiated. In experimental arrangement shown in Fig 1, a metal plate (such as of Cu), was bent thru an angle

[Pg.461]

David et al (Ref 93) obtained overdetonation when investigating oblique detonation waves (See under Detonation Waves, Oblique)... 

Ibid 55, 315 (1947) (Flow of detonation products in the case of oblique deton waves) 15)Ya. B. Zel(dovich K.P. Stanyukovich,... 

D. Piacesi, "Interaction of Oblique Detonation Waves in Iron, Ibid, p 153 (Abstract) Complete paper published in the PhysFluids 9, 1307 (1966) 92) S.D. Gardner J. 

Munson, "The Influence of Mechanical Properties on Wave Propagation in Elastic-Plastic Materials, Ibid, pp 295-304 93) F. David et al, "Oblique Impact of a Layer of Explosive by a Metal Plate , Ibid, pp 381-85 (Formation of oblique deton wave and of over-detonation wave by such impact)... 

This keynote paper gives a general discussion of blast waves developed by high explosive detonations, their effects on structures and people, and risk assessment methods. The properties of free-field waves and normally and obliquely reflected waves are reviewed. Diffraction around block shapes and slender obstacles is covered next. Blast and gas pressures from explosions within vented structures are sumnarized. 

Detonation Waves, Oblique. Under this term are known waves formed on the initiation of an explosive chge by the oblique impact of a metal plate... 

Sternberg Piacesi (Ref 91a) investigated interaction of such waves with iron David et al (Ref 93) investigated formation of oblique and overdriven deton waves... 

The detonation process, at least in insensitive LE, can bae visualized as follows (Ref 17a) Microinhomogeneities in the LE (eg, fluctuation in density or composition) result in non-uniform reaction rates in the shocked LE. Because reaction rates are so strongly dependent on temp, these perturbations do not attenuate and eventually reach the shock front of the detonation wave and bend it, thus creating oblique shocks at its leading edge. 

The results obtained must be interpreted from the point of view of the modern theory of spin detonation [4, 5]. In the works cited only the region in which ignition of the gas occurs (the so-called head of the spin or shock wave kink ) was considered. The conditions were found—the speed of the oblique shock wave and corresponding pressure p2 and temperature T2—at the spin head, i.e., the conditions under which ignition occurs in spin detonation. The size of the head b2 and the reaction time r2 at the spin head under these conditions were considered quite small the question of conditions for the existence/feasibility of spin detonation was not posed. 

Normal Reflection of Shock and Rarefaction Waves (82-4) Types of Interaction (86) Normal Reflection of Rarefaction (86-7) Normal Refraction of Shock and Rarefaction Waves (87-8) Head-on Collisions (88-9) Oblique Intersections (89 90) Oblique Interactions (90-1) Spherical Shock Waves (97-8) Distinction Between Shock and Detonation Fronts (163-66) Application to Solid Explosives (166-68) Principle of Similarity and Its Application to Shock Waves (307-10) Effects of Ionization in the Shock Front (387-90)... 

Stanyukovich. (Ref 14) obtd oblique waves and investigated flow of deton products in the case of such waves. 

Fig. 10.32 Diagram of the flow behind the detonation complex in a layer of a combustible mixture (a) [54] and the explosion products velocity field, (b) [55] 1 - combustible mixture 2 - noncombustible surrounding 3 - attached oblique wave 4 - contact surface between explosion products and surrounding interface 5 - fan of attached and reflected rarefaction waves (Prandtl-Meyer expansion fan)...

Angles of product flow rotation ro and attached oblique wave angle 0 are calculated based on the flow characteristics [54]. The explosion products expand in a rarefaction wave fan attached to the detonation complex for Pe3, pressure, and further, in the system of reflected rarefaction waves, to P, - pressure. 

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