Shock wave source with a coil carrier having a non-circular contour

The free shock wave has particular advantages as a source for seismic survey. Its physical parameters can be precisely defined and its interaction with the rock environment predicted. In particular, the wave mode conversion which occurs leads to the simultaneous generation of both strong compression and shear waves in the rock matrix. The first part of the present study outlines the basic principles of design for a source that will generate, repetitively, free shock waves with associated pressure fields that range over two orders of magnitude (measured in bars). The second part of the paper describes the wave system which develops when shocks, generated by such a source, interact with water in, for example, a water-filled surface bore-hole. The multiplication of incident shock pressure in water, which is characteristic of the operational performance of the shock-wave source, is shown to be a consequence of the complex interactions that take place between wave systems transmitted and reflected at the gas-water interface and those that are reflected at the water-solid interface. The third part of the paper illustrates the behaviour of compressional and shear waves generated by the shock-wave source in both sedimentary rock and granite. It is shown that the mode conversion to compressional and shear waves in granite leads to near-ideal behaviour in terms of the ratio of velocities of propagation for the two types of wave in the rock.

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Normal Reflection Characteristics of One-Dimensional Unsteady Flow Shock Waves on Rigid Walls from Pulse Discharge in Water

Shock and Vibration ◽

10.1155/2017/6958085 ◽

2017 ◽

Vol 2017 ◽

pp. 1-12

Author(s):

Dong Yan ◽

Jinchang Zhao ◽

Shaoqing Niu

Keyword(s):

Shock Wave ◽

Hydrostatic Pressure ◽

Shock Waves ◽

Pulse Discharge ◽

Weak Shock ◽

Rigid Wall ◽

Wave Source ◽

One Dimensional ◽

Normal Reflection ◽

Rigid Walls

Strong shock waves can be generated by pulse discharge in water, and the characteristics due to the shock wave normal reflection from rigid walls have important significance to many fields, such as industrial production and defense construction. This paper investigates the effects of hydrostatic pressures and perturbation of wave source (i.e., charging voltage) on normal reflection of one-dimensional unsteady flow shock waves. Basic properties of the incidence and reflection waves were analyzed theoretically and experimentally to identify the reflection mechanisms and hence the influencing factors and characteristics. The results indicated that increased perturbation (i.e., charging voltage) leads to increased peak pressure and velocity of the reflected shock wave, whereas increased hydrostatic pressure obviously inhibited superposition of the reflection waves close to the rigid wall. The perturbation of wave source influence on the reflected wave was much lower than that on the incident wave, while the hydrostatic pressure obviously affected both incident and reflection waves. The reflection wave from the rigid wall in water exhibited the characteristics of a weak shock wave, and with increased hydrostatic pressure, these weak shock wave characteristics became more obvious.

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Numerical Simulation on Underwater Shock Wave Focusing

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.105-107.121 ◽

2011 ◽

Vol 105-107 ◽

pp. 121-126

Author(s):

Zhen Fu Zhang ◽

Xin Wu Zeng ◽

Qing Yu Cai ◽

Kai Feng Han

Keyword(s):

Shock Wave ◽

Time History ◽

Element Model ◽

Numerical Results ◽

Axial Position ◽

Focal Region ◽

Underwater Shock Wave ◽

Wave Source ◽

Wave Focusing ◽

Shock Wave Focusing

Shock wave focusing by an ellipsoidal reflector can produce higher pressure in the focal region. The focusing process of shock wave was studied by theory analyses and numerical results. Base on the experimental observation the shock wave source is equivalent to the explosion of an underwater explosive. A finite element model was set up to investigate the shock wave focusing behaviors. Both the pressure-time history and the peak pressure along the axial position were presented. The shock wave focusing process was shown. The interactions of waves in the focal region are shown. A modified EOS of water was applied, which can be used to analyze the negative pressure observed; the numerical results based on the modified EOS agree well with the experimental data.

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