Underwater Shock Wave Research Articles

Fundamental Investigation of Effects for Neutrophils Chemotaxis by Underwater Shockwave Stimulation

Fundamental Investigation of Effects for Neutrophils Chemotaxis by Underwater Shockwave Stimulation

Magnesium Alloy Forming using Underwater Shock Wave by Wire Electric Discharge

The magnesium alloy has advantage in strength per mass and it has been widely used on airplane, aerospace, computer, cellphone and automobile industries. However, forming of magnesium alloy plate at the room temperature is very difficult, because it has a dense hexagonal and the basal sliding is easy to happen conspicuously in comparison with other sliding system. We considered that those weak characteristics are reduced by high strain rate forming. Therefore, magnesium alloy forming using shock wave by metal wire electric discharge has been carried out. Thin aluminum alloy was used as the metal wire. Electricity is supplied to this wire from power supply with Marx circuit. The aluminum wire set underwater and it has instantly molten vaporization, then, the underwater shock wave was generated. The shock loading by the underwater shock wave acts to the magnesium alloy plate. The magnesium alloy plate was AZ31(Al 3%, Zn 1%). In this study, the target is bulge forming of the magnesium alloy plate. Then, some numerical simulations were carried out. These results will be discussed in this paper.

Design and production of pressure vessel for food processing machine using underwater shock using measurement of particle velocity and results of numerical analysis

Okinawa National College of Technology has developed a food processing machine using underwater shock waves. Several prototype machines were developed, and experimental results (sterilization, improvement of juice extraction, milling flour, emulsification etc.) were obtained. After deciding food materials to be processed and the desired processing results, we designed and manufactured a pressure vessel for experiments. In this report, the process flow for designing and manufacturing a pressure vessel for softening meat using underwater shock and its concept design are described. The relationships among the number of shock waves, the distance between the shock wave generation point and the meat, the backing material, and the amount of softening ware experimentally compared. We measured the velocity of the shock wave penetrating to the inside of the meat, from which we estimated the particle velocity. We developed computer simulation model using the estimated particle velocity in the meat. Using the results of the analysis obtained from the computer simulation model, we designed and fabricated the pressure vessel.

Micropunching large-area metal sheets using underwater shock wave: Experimental study and numerical simulation

Laser shock punching is a recently developed technique, which is very efficient for punching microholes in thin metal sheets. However, processing large areas with laser shock punching is difficult because the processing area is limited by the size of the laser spot. Moreover, as the duration of the laser-induced shock pressure is considerably less than that of the explosive used, the thickness of the punchable metal sheet is in the order of a few tenths of the punch diameter. In this paper, we report an efficient approach that enables micropunching over a large area of a metal sheet in a single step. This micropunching method uses an underwater shock wave generated by the explosion of a plastic explosive charge. This approach is successfully used to punch circular holes over a large area of a 0.1-mm thick A1100 sheet, forming multiple holes with a diameter of 300 μm each. The pressure profiles of the underwater shock waves measured using piezo film gauges are used to analyze the micropunching process using ANSYS Autodyn software. The punching process is numerically simulated, and it is observed that the simulation and experimental results are in good agreement. The proposed approach can be applied to high-strength materials and thick sheets that are difficult to process using laser-induced shock waves.

Multilayer weak shocks generated by restrike during underwater electrical explosion of Cu wires

Underwater electrical explosions of Cu wires were carried out on a microsecond time scale to produce underwater shock waves. Experimental results show that the radial density distribution of the water flow after restrike contains several oscillations, observed as ∼1 mm-spaced layers in the backlit streak images and laser shadowgraphs. The phenomenon is attributed to the partial reheating of the exploding product (EP) by an interior restrike arc, which stimulates a compression wave propagating back and forth radially in the EP. Simulations are used to support the interior breakdown scenario and to demonstrate that each reflection of the compression wave at the EP–water interface launches a weak shock into the water, forming a multilayer structure. As the surrounding metallic vapor is ionized due to radiation and thermal conduction from the arc, the highly conductive plasma channel continues to extend radially and launches the main compression wave, which drowns out the multilayers when the power injection is sufficiently high.

An experimental study on dynamic response of polyurea coated metal plates under intense underwater impulsive loading

Polyurea coating provides a new method to improve the underwater shock resistance of ships. In this study, high-strength shock wave was loaded on the polyurea coated 6061 aluminum target plate through impact-type underwater shock wave loading device, and the dynamic deformation process was recorded by three-dimensional digital imaging correlation (DIC) method. Then, the influences of the shock wave peak, polyurea coating thickness and coating method were investigated. The experimental results confirmed that the underwater shock resistance performance of polyurea coated aluminum plate was improved as the peak of initial loading pulse and the polyurea coating thickness increased. In the meanwhile, it was found that under the same polyurea content, the underwater shock resistance of the aluminum plate with polyurea coated on the front surface was basically the same as that of the aluminum plate with polyurea coated on the rear surface, both of which were better than that of the aluminum plate with polyurea coated on both surfaces. Finally, the quantitative relationships of the residual deformation of the polyurea coated aluminum plate with the peak of initial loading pulse and the polyurea coating thickness were concluded.

Inactivation of Cyanobacteria by Underwater Shock Wave

A treatment of underwater shock wave was proposed to solve this problems which the harm caused by cyanobacteria blooms. Underwater shock wave technology has the features of energy saving, environmental protection, safe and efficient. The underwater shock wave technology effective performance for the removal of cyanobacteria was investigated. The results obtained from on-site algae water showed that the initial chlorophyll-a content of Taihu Lake wild algae is 216.22 μg/L, after applying with the optimum working conditions treatment, the chlorophyll-a of the treated group is only 3.84μg/L at the ninth day, while the concentration of chlorophyll-a was 209.87μg/L in control group after 9 days of culture, the average removal rate was 98.22%. The initial algal toxin level in the wild algae in Taihu Lake was 4.23 μg/L, after treatment with underwater shock wave, the concentration of algae toxin in the treatment group decrease below the limit of detection (0.1 μg/L) after 1 day of algae culture, meanwhile, the control group increased to 4.36 μg/L. The contents of TN, TP and COD in the treatment group were lower than the control group with the underwater shock wave treatment. The results indicated that the underwater shock wave cannot only inactivated the wild cyanobacteria, but also can improve water quality.

Underwater explosion of slender explosives: Directional effects of shock waves and structure responses

The shape of a high-explosive is an important factor to consider in the near-field and contact explosion, but this has been rarely studied previously. In this paper, we first conduct experiments to study the directional effects of the underwater explosion shock wave of slender explosives. A numerical model based on the multi-material arbitrary Lagrangian Eulerian (MM–ALE) technique is then developed to study the influence of the explosive slender ratio on the generated shock waves. The numerical model is validated by experiment data. Then, tests are conducted with constant-mass cylindrical explosives with slender ratios ranging from 2.0 to 9.2. By comparing with the center-detonated spherical explosive, the peak pressure, pulse duration, impulse and energy flux of the underwater explosion of slender explosives are analyzed in detail. Furthermore, the effectiveness of the fluid-structure interaction algorithm is verified through the experimental data of a plate subjected to underwater contact explosion. Finally, the response of plates subjected to the underwater explosion of a slender explosive at different azimuths is studied. The interaction between the plate and the directional loads is analyzed. We conclude that the loads and structure responses of the near-field underwater explosion of slender explosives are different from those of spherical explosives. The analyses and results provide a reference for the near-field underwater explosion loads and structural response studies.

Dynamic response of closed cell PVC foams subjected to underwater shock loading

A dynamic loading facility is developed to investigate the underwater shock response of poly vinyl chloride foams of varying densities. The shock loading facility consists of a water filled hollow cylindrical structure, with one end fully closed and the other end fitted with a nylon piston. A rigid striker is used to impact the piston, which creates an underwater shockwave. The facility is comprised of four separate sections, where the middle section is an optically clear acrylic window, and the other three sections are aluminum. The optically clear acrylic window is utilized for the employment of three-dimensional Digital Image Correlation in conjunction with high-speed photography (90,000–100,000 frames per second) to obtain full-field deformation data of the foams during shock loading. Pressure data is recorded using piezoelectric pressure sensors at different locations along the underwater shock tube. Peak pressures in the range of 1–10 MPa with exponential decays are generated by changing the striker velocity. Furthermore, quasi-static hydrostatic response of pre shocked foams is evaluated using a previously developed underwater loading facility. Strain rate of 103s − 1 is obtained in foam specimens during the experiments. Findings showed substantial delay between the underwater shock loading and material response. Polyvinyl chloride foams recovered 80–90% of their original shape after underwater shock loading and also retained much of their energy absorption capacity.

Parameter regulation of underwater shock waves based on exploding-wire-ignited energetic materials

This paper proposed and verified a method for adjusting parameters of underwater shock waves. In the experiments, a metal wire with an energetic material coat was exploded by applying a pulsed current on it. Under different matches of size/material of wire, mass/type of energetic material, and injected pulsed current, characteristics of shock waves were obtained. It has been proven that peak pressure, impulse, and energy of shock waves can be conveniently regulated by simply changing the explosion of either the wire or its energetic material coat. Finally, the mechanisms of this method were analyzed and potential applications discussed.

Local discontinuous Galerkin method for far-field underwater explosion shock wave and cavitation

The shock wave and cavitation are main effects in the far-field underwater explosion, which could cause serious damage to marine structures. In this paper, the fluid mechanical behavior of blast load is described by the propagation of pressure wave. The acoustic pressure caused by far-field explosion is determined by solving the wave equation, where a strongly discontinuous axisymmetric numerical model is established with the local discontinuous Galerkin (LDG) method. The model can calculate the dynamic pressure in the fluid field and capture the high-resolution shock wave. The pressure cutoff model is employed to deal with the cavitation effect due to the reflection of the shock wave. The numerical model is verified by comparing with the analytical solution of the cavitation effect near the structure in one dimension. With the same mesh discretization, the present model shows higher precision than the results calculated by the acoustic finite element method. In addition, the propagation of shock wave in the cylindrical water column is studied. Finally, the formation, growth and collapse of the cavitation region near the free surface are simulated. The LDG model can remove the spurious oscillations behind the shock front and it’s more accurate than the results of the acoustic finite element method, in terms of capturing the sharpness of shock wave and calculating the shock and cavitation loading. And the present model can be applied to calculate the structural damage caused by shock wave in three dimensions.

Evaluation of anti-explosion performance of Shuibuya concrete-faced rockfill dam slabs subjected to strong shock waves caused by an underwater explosion

A concrete plastic-damage model, the extended Drucker–Prager model for rockfill, and acoustic elements for water were introduced and applied to the impact fracture analysis of a concrete-faced rockfill dam–water three-dimensional system. The plastic-damage dynamic analysis process was used in combination with the concrete compressive and tensile damage model. The 223-m high Shuibuya concrete-faced rockfill dam was analyzed using an explicit integration. Numerical simulations of the damage threshold, rockfill modeling, and interface processing were conducted to research the effect of the anti-explosion performance that occurs when a concrete slab is subjected to an underwater shock wave. The simulation results indicate that the main regions of weakness in the slabs during an underwater shock wave are determined by the tensile damage. The slab’s anti-knock weak areas appear in the right dam abutment and the top of the left dam. The anti-knock performance in the upper slab is inferior to that of the lower slab. Specific local optimization steps should be applied at these locations to improve the slabs’ anti-knock capabilities, which are important for designing concrete-faced rockfill dams.

Research on Calibration Method of Underwater Shock Wave Pressure Measurement Sensor Systemt

Underwater explosions are distinguished from explosions in the air, and their environment is complex, making sensor systems more difficult to calibrate. In this paper, the calibration method of underwater shock wave pressure sensor system is studied. The dynamic pressure calibration method based on water shock tube is proposed to calibrate the system. The propagation characteristics of the pulse pressure signal in the water shock tube are studied. The water shock tube device suitable for the calibration of the underwater shock wave pressure sensor system is designed. In the end, the advantages of the water shock tube in measuring the underwater shock wave pressure are summarized.

Plastic deformation behavior of Mg alloys by underwater shock wave using air pressure

Plastic deformation behavior of Mg alloys by underwater shock wave using air pressure

1P4-3 A cylindrical waveguide with different diameters for extracting high-intensity pressure pulse of underwater spark-induced shock wave and for suppressing the impact of cavitation

1P4-3 A cylindrical waveguide with different diameters for extracting high-intensity pressure pulse of underwater spark-induced shock wave and for suppressing the impact of cavitation

Effect of Number of Discharge Shot on Pit of Gelatin Simulating Biomaterial Attached with Microbubbles Subjected to Underwater Shock Wave Loading Induced by Electrical Discharge

Effect of Number of Discharge Shot on Pit of Gelatin Simulating Biomaterial Attached with Microbubbles Subjected to Underwater Shock Wave Loading Induced by Electrical Discharge

Study on Underwater Shock Wave Phenomena in a Tube Made of Materials with Different Acoustic Impedance

Study on Underwater Shock Wave Phenomena in a Tube Made of Materials with Different Acoustic Impedance

Study of sterilization effects on marine Vibrio sp. using interaction of cavitation with shock wave in a narrow water chamber

Cavitation bubbles could also be called as inertial bubbles because of their oscillation due to the pressure difference between inside and outside. After the passage of an underwater shock wave, the violent collapses of the bubbles are induced and could produce stronger mechanical and biochemical actions so that the marine bacteria around them are inactivated by those productions. In the present study, cavitation inertial bubbles are observed behind multiple waves in a narrow water chamber after an electric discharge is triggered and then interacts with underwater reflected shock waves from the water chamber. The sterilization effects of only these oscillating bubbles and cavitation-shock interaction are investigated by bio-experiments of marine Vibrio sp. The results show that a high sterilization is obtained in the case of the cavitation-shock interaction. Furthermore, the chemical action of free radicals mainly contributes to inactivating the marine bacteria. The generation of the hydroxyl (OH) radicals is clarified by measuring the concentration of H2O2. Subsequently, we focus on a theoretical analysis of the generation condition of the OH radicals by a bubble dynamic model consisting of an oscillation model and an impact model. Finally, the theoretical estimation by the bubble dynamic model is discussed under the conditions of the present experiments. As a result, there is a possibility of effective sterilization by the cavitation-shock interaction without the supply of air microbubbles.

Underwater shock wave weldability window for Sn-Cu plates

In this paper, the effects of the heat input and depth of water (d) on the welding interface of tin − copper are discussed using underwater explosive welding technique. An increase in the water depth caused a reduction in the parameters of wavy morphology at the interface. The welding window which certifies the quality of welding was determined for welded Sn − Cu plates based on numerical analysis using AUTODYN – 2D software. The velocity of the flyer plate (Vp) and kinetic energy lost (ΔKE) at the interface was found to be decreased when the increase in water depth was pronounced. The Sn and Cu plates successfully welded using underwater shock wave method under moderate condition, and the experimental parameters were discussed based on the welding window.

Shock wave generation by collapse of an explosive bubble in water

Shock wave generation by collapse of a single explosive bubble exposed to an underwater shock wave in water has been studied experimentally and numerically. The explosive bubble was made of a stoichiometric ethylene-oxygen mixture and its initial volume-equivalent radius was varied from 1.0 to 2.9 mm. The underwater shock wave, whose strength ranged from 7 to 19 MPa, was driven by gasous detonation in a vertical detonation tube. It was found that after passage of the underwater shock wave, the bubble starts to shrink, resulting in explosion just before reaching the minimum radius. In the bubble rebound phase a shock wave is generated whose strength is about twice as compared to that for the air bubble. The maximum pressure of the shock wave nondimensionalized by the ambient pressure behind the underwater shock wave was found to be inversely proportional to the non-dimensional distance. The conversion rate of the bubble energy to the shock energy was estimated to be 0.10, regardless of chemical heat release. Simple numerical analysis of bubble dynamics including compressibility of water was performed. The calculated bubble motion and the shock propagation agree with the experimental results, although the calculated shock strength is overestimated mainly because of non-sphericity of the initial shape of the bubble floating up in water. There is also a good agreement between the experimental and the calculated results in regard to the ratio of the shock pressure for the explosive bubble to that for the air bubble.