scholarly journals Numerical Studies of Particle-Gas Two-Phase Flowing through Microshock Tubes

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Guang Zhang ◽  
Wei Wei Wang ◽  
Xiang Hui Su ◽  
Xiao Jun Li ◽  
Wen Hao Shen ◽  
...  
Keyword(s):  
Shock Wave ◽  
Drug Delivery ◽  
Shock Waves ◽  
Numerical Simulations ◽  
Free Drug ◽  
Reflected Shock Wave ◽  
Phase Method ◽  
Gas Flows ◽  
Sonic Nozzle ◽  
Reflected Shock

Microshock tubes are always used to induce shock waves and supersonic flows in aerospace and medical engineering fields. A needle-free drug delivery device including a microshock tube and an expanded nozzle is used for delivering solid drug powders through the skin surface without any injectors or pain. Therefore, to improve the performance of needle-free drug delivery devices, it is significantly important to investigate shock waves and particle-gas flows induced by microshock tubes. Even though shock waves and multiphase flows discharged from microshock tubes have been studied for several decades, the characteristics of unsteady particle-gas flows are not well known to date. In the present studies, three microshock tube models were used for numerical simulations. One microshock tube model with closed end was used to observe the reflected shock wave and flow characteristics behind it. The other two models are designed with a supersonic nozzle and a sonic nozzle at the exit of the driven section, respectively, to investigate particle-gas flows induced by different nozzles. Discrete phase method (DPM) was used to simulate unsteady particle-gas flows and the discrete random walk model was chosen to record the unsteady particle tracking. Numerical results were obtained for comparison with those from experimental pressure measurement and particle visualization. Shock wave propagation was observed to agree well with experimental results from numerical simulations. Particles were accelerated at the exit of microshock tube due to the reservoir pressure induced by reflected shock wave. Both sonic and supersonic nozzles were underexpanded at the end of microshock tubes. Particle velocity was calculated to be smaller than gas velocity, which results from larger drag of injected particles.

On the effectiveness of ventilation to mitigate the damage of spherical membrane vessels subjected to internal detonations

2020 ◽  
Vol 11 (3) ◽  
pp. 319-339
Author(s):  
Francisco Hernandez ◽  
Xihong Zhang ◽  
Hong Hao
Keyword(s):  
Shock Wave ◽  
Shock Waves ◽  
High Frequency ◽  
Arrival Time ◽  
Time Lag ◽  
Reflected Shock Wave ◽  
High Explosives ◽  
Element Analysis ◽  
Blast Overpressure ◽  
Reflected Shock

This article conducts a comparative study on the effectiveness of ventilation to mitigate blasting effects on spherical chambers subjected to internal detonations of high explosives through finite element analysis using the software package AUTODYN. Numerical simulations show that ventilation is ineffective in mitigating the damage of spherical chambers subjected to internal high explosives explosions because the chamber response is mainly described by high-frequency membrane modes. Openings do not reduce the chamber response despite they can reduce the blast overpressure after the chamber reaches its peak response. Worse still, openings lead to stress concentration, which weakens the structure. Therefore, small openings may reduce the capacity of the chamber to resist internal explosions. In addition, because large shock waves impose the chamber to respond to a reverberation frequency associated with the re-reflected shock wave pulses, secondary re-reflected shock waves can govern the chamber response, and plastic/elastic resonance can occur to the chamber. Simulations show that the time lag between the first and the second shock wave ranges from 3 to 7 times the arrival time of the first shock wave, implying that the current simplified design approach should be revised. The response of chambers subjected to eccentric detonations is also studied. Results show that due to asymmetric explosions, other membrane modes may govern the chamber response and causes localized damage, implying that ventilation is also ineffective to mitigate the damage of spherical chambers subjected to eccentric detonations.

Paper 14: On the Reflection of Shock Waves from Deflector Plates

1965 ◽  
Vol 180 (10) ◽  
pp. 245-259
Author(s):  
W. A. Woods
Keyword(s):  
Shock Wave ◽  
Shock Waves ◽  
Incident Shock ◽  
Incident Shock Wave ◽  
Reflected Shock Wave ◽  
Reflected Wave ◽  
Reflected Shock ◽  
Pressure Time ◽  
Wave Travel ◽  
Wave Region

The paper first explains the importance of the reflection of shock waves in the design of certain chemical plant. The theory of the reflection of shock waves is also discussed in the first part of the paper. It is shown that when a shock wave travelling along a pipe containing stationary gas reaches the outlet end of the pipe there may be ( a) a reflected expansion wave, ( b) a reflected shock wave, ( c) a reflected sound wave, ( d) no reflected wave at all, ( e) a standing shock wave situated at the end of the pipe, depending upon the strength of the incident shock wave and the amount of blockage present at the outlet end of the pipe. The conditions for each kind of reflection are determined, and in the case of the reflected shock wave region the strengths and speeds of the reflected shock waves are established throughout the region and the results are presented graphically. In the second part of the paper the results are given of experiments carried out on a shock tube fitted with various kinds of deflector plates. The experiments were performed to study the reflection of shock waves from the deflector plates by measuring pressure/time indicator diagrams near the outlet end of the pipe. The indicator diagrams revealed the approximate pressure amplitudes of the incident and reflected shock waves and also the wave travel times for the shock waves. This information was used in conjunction with the charts given in the first part of the paper to establish the deflector geometry and spacing needed in order to avoid the occurrence of a reflected shock wave.

Explosion near the ground: a solution to the multi-shock problem in cylindrical symmetry by the particle trajectory method

1977 ◽  
Vol 358 (1692) ◽  
pp. 31-46 ◽  
Keyword(s):  
Shock Wave ◽  
Shock Waves ◽  
Flow Field ◽  
Ground Surface ◽  
Cylindrical Symmetry ◽  
Theoretical Development ◽  
Reflected Shock Wave ◽  
Particle Trajectories ◽  
Reflected Shock ◽  
Cylindrically Symmetric

A theoretical development is described whereby cylindrically symmetric flows involving multiple shock waves may be mapped in both time and space. The theory is an extension of earlier work by Dewey which was restricted to flows with spherical symmetry and in which only one shock wave was present. The method requires a knowledge of the trajectories of individual air elements from which the density can be calculated by using the Lagrangian form of the equation of continuity. The other thermodynamic variables can be derived by assuming that, except in the shock waves, the flow is reversible and adiabatic. The theory has been applied to an investigation of the flow field associated with the explosion of 479 kg of TNT placed 22 m above the ground surface. The flow field is spherically symmetric until the initial shock wave is reflected from the ground after which it is symmetrical in azimuth but not in elevation. The presence of the reflected shock wave introduces a second shock wave into the problem which must be included in the analysis in order to obtain a complete description of the flow. The particle trajectories were obtained by using an array of smoke puffs whose motions were followed photographically. The results obtained by analysing the particle trajectories by the theoretical approach described in this paper have been compared with the results obtained from piezo-electric pressure transducers at several points in the flow field and strikingly good correlation has been noted. A brief discussion is included on the effects of certain simplifications introduced into the analysis for reasons of practical convenience. It has been concluded that the theory proposed is a valid one having general application to situations where gasdynamic effects are preponderant.

Dispersion of Shock Wave Transmitted Into Non-Uniform Materials

2017 ◽  
Author(s):  
Susumu Kobayashi ◽  
Hiroki Henmi
Keyword(s):  
Shock Wave ◽  
Shock Waves ◽  
Human Brain ◽  
Reflected Shock Wave ◽  
Severe Damage ◽  
Reflected Shock ◽  
Sintered Metal ◽  
Materials Used ◽  
D Model ◽  
Transmitted Shock Wave

When a shock wave is incident on an obstacle, it is not only reflected back but also transmitted into the obstacle itself. The transmitted shock wave has not been fully investigated so far, compared with the reflected shock wave. In actual situations, the behavior and the characteristics of the transmitted shock wave are also of importance. In battlefields, human bodies are often subject to explosions and resulting shock waves. In particular, severe damage can be caused when a shock wave is transmitted into the human brain. In the present study, we conducted experiments to investigate the behavior and intensity of a shock wave, after it is transmitted into various materials. The materials used were sintered metal, silicone, and polyethylene foam. They were fixed on a specially devised model with a cavity, by which the resulting wave after a shock wave is transmitted could be observed. In order to understand what is happening in sintered metal, a 2-D model made of straws was devised and used.

Temperature measurements for powdered solids in reflected shock waves

1964 ◽  
Vol 282 (1389) ◽  
pp. 265-274 ◽  
Keyword(s):  
Shock Wave ◽  
Shock Waves ◽  
Short Duration ◽  
Thermodynamic Equilibrium ◽  
Powdered Material ◽  
Reflected Shock Wave ◽  
Excitation Energies ◽  
Time Resolved ◽  
Reflected Shock ◽  
Atomic Excitation

Measurements have been made to determine the temperature behind reflected shock waves from an aerodynamic shock in argon containing a sample of powdered material. Time-resolved temperatures were measured photoelectrically by the brightness-emissivity method which employs a short duration flash tube. The measured temperatures were consistent, and about 10% lower than the calculated temperature for pure argon, over a 9 eV range of atomic excitation energies, indicating that thermodynamic equilibrium has been achieved. Calculated and measured densities for the atoms of the powder indicate that approximately 40% of the sample was uniformly distributed behind the reflected shock wave.

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