Underwater explosion shock wave propagation law ofexperiment researchAbstract:Using PCB138 pressure sensor of dynamite underwater explosion shock wave pressure far field measurements, underwater explosion shock wave peak pressure and decay time constant.Calculated on the basis of explosion shock wave in explosive liquid medicine of similarity constants k and a .Preliminary mastered the experiment method of underwater explosion shock wave of underwater explosion of explosive shock wave propagation law had the further understanding.Keywords:underwater explosion;the shock wave;similar to the rate1 The introductionUnderwater explosion of explosive weapon design techniques is the water, the basis of studying the damage effect of problems.Underwater explosion can be roughly divided into three stages: explosive detonation, the generation of shock wave and propagation, the formation of air bubbles, and pulse.The strong action of shock waves characterize the dynamite explosion, at close range within the scope of damage to the target plays a decisive role.Research especially cylindrical propellant explosive underwater explosion shock wave propagation rule and performance parameters of underwater explosion have important practical significance, for the water weapon warhead design and provide important reference basis for the selection of explosives.Cole systematically summarizes the research achievements of Explosion in water since world war ii, published in 1948, the classic works in the field of the Underwater Explosion.Bocksteiner by two experiments of PBXW - 115 to assess the performance of cylindrical dynamite, gives the PBXW - 115 explosive underwater explosion performance parameters and similar constant.With the other underwater explosion of explosive performance parameters comparison, suggests PBXW - 115 has is better than other explosive underwater explosion properties of explosive, a superior blast kinetic energy weapons used in the water.This article according to the experimental measurement of CB - 01 explosive liquid medicine in the explosion shock wave pressure and the time history and have underwater explosion shock wave pressure peak and decay time constant, calculated by the shock wave peak pressure and time constant, CB - 01 of explosion shock wave in explosive liquid similarity constants k and a.2 The basic theory of underwater explosion shock wave propagationUnderwater explosion shock wave propagation process has four important parameters: p m , decay time constant θ, impulse I , peak pressure and energy flow density of E.By the measured pressure time curve, peak stress and attenuation time constant, has been further impulse and energy flow density.Decay time constant is defined as θ shock wave pressure from Pm peak pressure attenuation to p m /e of the time.E is a base of natural logarithms, e = 2.72.In θ time period, the change in pressure decay exponentially()()θ/t m e p t p -= (1) I was defined as pressure with time integral, integral limit from 0 to 5θ⎰=θ50)(dt t p I (2) After considering the creep flow of water, defined as E dt t p c p p E m m )())(10031.110422.21(502100284⎰---⨯-⨯-=θρ (3)ρ0c 0 is the acoustic impedance of the water.A large number of experimental results show that the underwater explosion shock wave propagation exists similarity.Sums up the law of similarity, people get the experience formula.aR w k Param ete ⎪⎪⎪⎭⎫ ⎝⎛=31(4) Type: k and is similar to a constant, w as the explosive charge, R is the distance from blasting center.Parameter corresponding to underwater explosion parameters: Pm peak pressure, compare the time constant θ/w 1/3, contrast impulse I/w 1/3, contrast energy flow density of E/w 1/3 four parameters.R a w a k Parameter ln ln )3/(ln )ln(-+=3 The experimental deviceExperimental apparatus as shown in figure l.At the bottom of the tank framework with Angle steel welded together, for steel plate, for around 5 mm thick glass.Tank size is 2 m * 0.6 m * 0.6 m, 0.57 m water depth.Test pieces of JH - 9005 (CB - OI) booster column, the grain size of 20 mm x 20 mm, the quality of about 10 g.Test pieces are fixed on the device, the grain the distance from the tank bottom is 0.3 m.Using pressure sensor test of tourmaline PCBI38 explosive underwater explosion far-field shock wave pressure.Four sensors and its column in the same horizontal plane and in a straight line, and the distance of the test pieces were 0.3, 0.6, 0.9, and 1.2 m, respectively named 1 #, 2 #, 3 # and 4# sensor.4 The experimental results and analysisThe process experiment of pressure time curve has a good consistency, repeatability of test results is very good, the test results are reliable.Typical pressure time history curve is shown in figure 2.The figure 2 shows, with the increase of the distance between the sensor and its column, gradually reduce the peak pressure.1 #, 2 # and 3 # sensor test results and forecasts the peak pressure of comparison.1 # test of pressure sensor in the later there is an obvious jump, may be the effects of the reflected shock wave tank on the side and underside of the results.And the test results of 4 # sensor than forecast peak pressure is low, may be due to the result of the surface reflection rarefaction wave action.As a result, the data processing, with 1 #, 2 # and 3 # sensor records of the results are analyzed.After some processing of measured pressure time curve can get Pm peak pressure and decay time constant θ.Underwater explosion shock wave are obtained by the basic theory of shock wave propagation in all kinds of parameters of the calculation results are shown in table 1.Results indicate that the peak pressure of shock wave, the energy flow density and pulse were reduced gradually, and the time constant is increased gradually.Time constant increase of shock wave peak pressure attenuation rate is gradually slow down.Is based on the shock wave peak pressure, time constant and the calculation parameters, the similarity law of similarity constant k and shown in table 2 a.The results of this paper comparedwith the literature [2] (see table 2), it can be seen that due to the explosive used for booster, the underwater explosion performance obviously on the low side.Therefore, CB - 01 booster is not suitable for used as a weapon in water main charge.Because only conducted two experiments, the measurement data points is limited, validated by experimental results remains to be further and perfect.In addition, due to the limited size of water tank, side and underside sensor reflected shock waves and the water reflected the influence of the rarefaction wave, causing pressure in the abrupt and sudden drop, and gives the analysis of experimental results.In the later work, will continue to carry out different length to diameter ratio and the quality of the aluminized explosive underwater explosion experiment, reduce the influence of boundary conditions on the shock wave propagation pressure test, in order to obtain knowledge of underwater explosion of explosive performance more fully.5 conclusionFrom two underwater explosion experiment of CB - 01 explosive underwater explosion shock wave pressure at that time, was obtained by analyzing the CB - 01 explosive liquid explosion shock wave parameters and basic similar constant.Shock waves in the process of transmission, peak pressure, time constant, impulse and energy flow density change are approximately obey the law of similarity.CB - 01 explosive liquid explosive performance is low, not suitable for used as a main charge of the underwater weapons.Preliminary mastered the experiment method of underwater explosion shock wave, the propagation law of underwater explosion of explosives have the further understanding.Reference：[1] CoIe R H．Unclex'water Explosions．New Jersey：nceton Uuiversity Press．1948.[2] Bocksteiner G．Evaluation of Underwater Explosive Performance of OBXW．1l5(AUST)．Melbourne Victoria 3001：Weapons System Division Aronautic and Maritime Research Laboratory．1996．[3] Sstemberg H M．Underwater Detonation of Pentolite c~inders．Physics of Fluids，1995，30(3)：761—769.[4] Swisdak M M．Ex plosion Efects and Properties：Part II-Explosion Ef ect in Water，Naval Surface Weapons Center rechnical Report．NSWC／N0L IR 76一ll6．1978．。