Micro-shock Waves Research Articles

Design, Fabrication, and Commissioning of Transonic Linear Cascade for Micro-Shock Wave Analysis

Understanding shock wave behavior in supersonic flow environments is critical for optimizing the aerodynamic performance of turbomachinery components. This study introduces a novel transonic linear cascade design, focusing on advanced blade manufacturing and experimental validation. Blades were 3D-printed using Inconel 625, enabling tight control over the geometry and surface quality, which were verified through extensive dimensional accuracy assessments and surface finish quality checks using coordinate measuring machines (CMMs). Numerical simulations were performed using Ansys CFX with an implicit pressure-based solver and high-order numerical schemes to accurately model the shock wave phenomena. To validate the simulations, experimental tests were conducted using Schlieren visualization, ensuring high fidelity in capturing the shock wave dynamics. A custom-designed test rig was commissioned to replicate the specific requirements of the cascade, enabling stable and repeatable testing conditions. Experiments were conducted at three different inlet pressures (0.7-bar, 0.8-bar, and 0.9-bar gauges) at a constant temperature of 21 °C. Results indicated that the shock wave intensity and position are highly sensitive to the inlet pressure, with higher pressures producing more intense and extensive shock waves. While the numerical simulations aligned broadly with the experimental observations, discrepancies at finer flow scales suggest the need for the further refinement of the computational models to capture detailed flow phenomena accurately.

Investigation of micro-shock waves in a planar magnetogasdynamic flow using the discontinuous Galerkin finite element method

The present work focuses on the numerical investigation of micro-shock wave propagation in a two-dimensional magnetogasdynamic flow in the framework of the Dis- continuous Galerkin-Finite Element Method (DG-FEM). The Lorentz force has been im- plemented in the compressible, viscous Navier–Stokes equations as a source term using first-order spatial and fourth-order temporal Runge–Kutta discretization schemes. To in- vestigate the effect of the electrical conductivity on the micro-shock wave propagation, a two-dimensional micro-shock channel problem with hydraulic diameter of 2.5 mm, length of 82 mm, and no-slip boundary conditions at the left and at the right wall is considered as a benchmark problem. In this case, acoustic waves are generated behind after the rupture of the membrane that separates two states of the same gas originally at different pressure and density and both initially at rest. The magnetic field is taken into account as uniform and stationary throughout the microchannel, and the numerical simulations are performed in a short physical time, before the reflection of the waves on the lateral wall. A detailed parametric study of the temperature, density, pressure, and u-velocity is carried out by a variation of the electrical conductivity of the magnetogasdynamic flow, under the assumption of low magnetic Reynolds numbers. It has been found that the jumps of the acoustic waves become significantly intensified when the electrical conductivity of the gas is increased. It has also been observed that the presence of the Lorentz force causes an acceleration in the gasflow towards the outlet section of the microchannel at the low Knudsen number of 0.05. The outcome of this research work could be relevant to biomedical applications where the ability to control the flow in a microchannel has a significant impact on the development of small devices aimed to deliver pharmaceutical drugs in specific locations.

A note on supersonic flow control with nanosecond plasma actuator

A concept study on supersonic flow control using nanosecond pulsed plasma actuator is conducted by means of numerical simulation. The nanosecond plasma discharge is characterized by the generation of a micro-shock wave in ambient air and a residual heat in the discharge volume arising from the rapid heating of near-surface gas by the quick discharge. The residual heat has been found to be essential for the flow separation control over aerodynamic bodies like airfoil and backward-facing step. In this study, novel experiment is designed to utilize the other flow feature from discharge, i.e., instant shock wave, to control supersonic flow through shock-shock interaction. Both bow shock in front of a blunt body and attached shock anchored at the tip of supersonic projectile are manipulated via the discharged-induced shock wave in an appropriate manner. It is observed that drag on the blunt body is reduced appreciably. Meanwhile, a lateral force on sharp-edged projectile is produced, which can steer the body and give it an effective angle of attack. This opens a promising possibility for extending the applicability of this flow control technique in supersonic flow regime.

Experimental Investigations on Microshock Waves and Contact Surfaces.

The present work reports on progress in the research of a microshock wave. Because of the lack of a good understanding of the propagation mechanism of the microshock flow system (shock wave, contact surface, and boundary layer), the current work concentrates on measuring microshock flows with special attention paid to the contact surface. A novel setup involving a glass capillary (with a 200 or 300 μm hydraulic diameter D) and a high-speed magnetic valve is applied to generate a shock wave with a maximum initial Mach number of 1.3. The current work applies a laser differential interferometer to perform noncontact measurements of the microshock flow's trajectory, velocity, and density. The current work presents microscale measurements of the shock-contact distance L that solves the problem of calculating the scaling factor Sc=Re×D/(4L) (introduced by Brouillette), which is a parameter characterizing the scaling effects of shock waves. The results show that in contrast to macroscopic shock waves, shock waves at the microscale have a different propagation or attenuation mechanism (key issue of this Letter) which cannot be described by the conventional "leaky piston" model. The main attenuation mechanism of microshock flow may be the ever slower moving contact surface, which drives the shock wave. Different from other measurements using pressure transducers, the current setup for density measurements resolves the whole microshock flow system.

Experimental observation of immediate focus of underwater shock wave by using concave emitter induced by nano-pulsed laser

Propagation of an underwater micro-shock wave induced by a single-pulsed laser was observed by the shadowgraph technique. To introduce the micro-shock wave into water, different types of shock wave emitters are designed using flat and concave glass coated with 100-nm-thick titanium metal. The experiment was carried out in low irradiation intensity range from 0 to 200 GW/m2, and the shock wave was produced by the thermo-elastic effect of the metal film. In this study, we proposed an immediate focusing technique using a concave surface. The focusing effect was confirmed by optical observation and pressure measurement. The velocity and Mach number of shock wave were calculated using a shadowgraph imaging technique. The result revealed that the laser-induced micro-shock wave propagated approximately at just under the sound of speed in water. From the pressure measurement, it was confirmed that the shock wave strength from the concave emitter was 1.5 times stronger than the flat one. The effective area of the focus was determined by the radius of curvature of the concave surface and the irradiation beam diameter.

Remotely triggered micro-shock wave responsive drug delivery system for resolving diabetic wound infection and controlling blood sugar levels

A novel, micro-shock wave responsive spermidine and dextran sulfate microparticle was developed.

Two-dimensional numerical modeling of interaction of micro-shock wave generated by nanosecond plasma actuators and transonic flow

The influence of nanosecond pulse-driven, surface-mounted dielectric barrier discharge (DBD) actuators on a transonic flow is studied numerically. An airfoil representing turbomachinery blades in transonic flow is considered as a test case. A two-dimensional fluid model of DBD is used to describe the plasma dynamics. The model couples fluid discharge equations with compressible Navier–Stokes equations. Simulations were conducted with an airfoil of NACA 3506 profile in a transonic condition of M=0.75. When a nanosecond pulse voltage is used, with a rise and a decay time of the order of nanoseconds, a significant amount of energy is transferred in a short time from the plasma to the fluid, which leads to the formation of micro-shock waves and therefore to the modification of flow features. Moreover, a plasma energy deposition model is developed and presented by using the results of the plasma discharge model.

Modelling of plasma aerodynamic actuation driven by nanosecond SDBD discharge

A two-dimensional air plasma kinetics model (16 species and 44 processes) for nanosecond discharge under atmospheric pressure was developed to reveal the spatial and temporal distribution of discharge characteristics of a surface dielectric barrier discharge (SDBD) actuator. An energy transfer model, including two channels for energy release from external power source to gas, was developed to couple plasma with hydrodynamics directly in the same dimension. The governing equations included the Poisson equation for the electric potential, continuity equations for each species, electron energy equations for electrons taking part in reactions, and Navier–Stokes equations for non-isothermal fluid. The model was validated through current–voltage profile and electron temperature obtained from experiments. Calculations for discharge characteristics as well as the responses of fluid field from tens of nanoseconds to tens of seconds were performed. Results have shown that local air is heated to 1170 K within tens of nanoseconds and then decreases to 310 K at the end of a discharge period. 30% of the total power is transferred from electric field to electrons while only 20% of this energy is then released to gas through quenching processes. 9% of the total energy is released through ion collision. A micro-shock wave is formed and propagates at the speed of sound. High local density gradient and dynamic viscosity induces vortexes which whirl the heated air downstream. The combined effects of heating convection and vortexes in repetitive pulse discharges lead to the formation of a steady jet, in agreement with experimental results.

Dynamics of laser induced micro-shock waves and hot core plasma in quiescent air

AbstractWe present our results on spatio-temporal evolution of laser plasma produced shockwaves (SWs) and hot core plasma (HCP) created by focused second harmonic (532 nm, 7 ns) of Nd-YAG laser in quiescent atmospheric air at f/#10 focusing geometry. Time resolved shadowgraphs imaged with the help of an ICCD camera with 1.5 ns temporal resolution revealed the presence of two co-existing sources simultaneously generating SWs. Each of the two sources independently led to a spherical SW following Sedov-Taylor theory along the laser propagation direction with a maximum velocity of 7.4 km/s and pressure of 57 MPa. While the interaction of SWs from the two sources led to a planar SW in the direction normal to the laser propagation direction. The SW detaches from the HCP and starts expanding into the ambient air at around 3 µs indicating the onset of asymmetric expansion of the HCP along the z-axis. The asymmetric expansion is observed till 10 µs beyond which the SW leaves the field of view followed by a deformation of the irradiated region in the XY-plane due to the penetration of surrounding colder air in to the HCP. The deformation in the XY-plane lasts till 600 µs. The dynamics of rapidly expanding HCP is observed to be analogous to that of cavitation bubble dynamics in fluids.

Development of micro-shock wave assisted dry particle and fluid jet delivery system

Small quantity of energetic material coated on the inner wall of a polymer tube is proposed as a new method to generate micro-shock waves in the laboratory. These micro-shock waves have been harnessed to develop a novel method of delivering dry particle and liquid jet into the target. We have generated micro-shock waves with the help of reactive explosive compound [high melting explosive (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine) and traces of aluminium] coated polymer tube, utilising ∼9J of energy. The detonation process is initiated electrically from one end of the tube, while the micro-shock wave followed by the products of detonation escape from the open end of the polymer tube. The energy available at the open end of the polymer tube is used to accelerate tungsten micro-particles coated on the other side of the diaphragm or force a liquid jet out of a small cavity filled with the liquid. The micro-particles deposited on a thin metal diaphragm (typically 100-μm thick) were accelerated to high velocity using micro-shock waves to penetrate the target. Tungsten particles of 0.7μm diameter have been successfully delivered into agarose gel targets of various strengths (0.6-1.0%). The device has been tested by delivering micro-particles into potato tuber and Arachis hypogaea Linnaeus (ground nut) stem tissue. Along similar lines, liquid jets of diameter ∼200-250μm (methylene blue, water and oils) have been successfully delivered into agarose gel targets of various strengths. Successful vaccination against murine salmonellosis was demonstrated as a biological application of this device. The penetration depths achieved in the experimental targets are very encouraging to develop a future device for biological and biomedical applications.

Characteristics of Micro Underwater Shock Waves Produced by Pulsed Electric Discharges for Medical Applications

The paper reports on the production and focusing of micro underwater shock waves for medical applications. Shock wave focusing has various scientific, industrial and medical applications. For precise shock wave therapies near sensitive organs, such as cranioplasty in the close vicinity of the brain, a micro-shock wave source is required. A half-ellipsoidal cavity with a 20.0 mm minor diameter and with a ratio of the major to the minor diameters of 1.41 was designed and constructed as an extracorporeal shock wave (ESW) source. Underwater shock waves were generated by using the electric discharge produced by a magnetic pulse compression circuit (MPC) and an electrode. The input voltage and the input current were measured by using an oscilloscope and a current monitor. The whole sequence of shock wave generation, propagation, and focusing was observed by using time-resolved high-speed shadowgraph visualization method. Pressure histories were measured at different stand-off distances by using PVDF needle and fiber-optic probe hydrophones. A wide range of peak overpressures from 10 to 200 MPa at the focus was obtained, and a small focal zone and focal energy flux density were measured. We conclude that the present compact extracorporeal shock wave generator has appropriate characteristics for application in precise and sensitive medical procedures.

Bacterial transformation using micro-shock waves

Shock waves are one of the most competent mechanisms of energy dissipation observed in nature. We have developed a novel device to generate controlled micro-shock waves using an explosive-coated polymer tube. In this study, we harnessed these controlled micro-shock waves to develop a unique bacterial transformation method. The conditions were optimized for the maximum transformation efficiency in Escherichia coli. The maximum transformation efficiency was obtained when we used a 30 cm length polymer tube, 100 μm thick metal foil, 200 mM CaCl 2, 1 ng/μl plasmid DNA concentration, and 1 × 10 9 cell density. The highest transformation efficiency achieved (1 × 10 −5 transformants/cell) was at least 10 times greater than the previously reported ultrasound-mediated transformation (1 × 10 −6 transformants/cell). This method was also successfully employed for the efficient and reproducible transformation of Pseudomonas aeruginosa and Salmonella typhimurium. This novel method of transformation was shown to be as efficient as electroporation with the added advantage of better recovery of cells, reduced cost (40 times cheaper than a commercial electroporator), and growth phase independent transformation.

Needleless Vaccine Delivery Using Micro-Shock Waves

Shock waves are one of the most efficient mechanisms of energy dissipation observed in nature. In this study, utilizing the instantaneous mechanical impulse generated behind a micro-shock wave during a controlled explosion, a novel nonintrusive needleless vaccine delivery system has been developed. It is well-known that antigens in the epidermis are efficiently presented by resident Langerhans cells, eliciting the requisite immune response, making them a good target for vaccine delivery. Unfortunately, needle-free devices for epidermal delivery have inherent problems from the perspective of the safety and comfort of the patient. The penetration depth of less than 100 μm in the skin can elicit higher immune response without any pain. Here we show the efficient utilization of our needleless device (that uses micro-shock waves) for vaccination. The production of liquid jet was confirmed by high-speed microscopy, and the penetration in acrylamide gel and mouse skin was observed by confocal microscopy. Salmonella enterica serovar Typhimurium vaccine strain pmrG-HM-D (DV-STM-07) was delivered using our device in the murine salmonellosis model, and the effectiveness of the delivery system for vaccination was compared with other routes of vaccination. Vaccination using our device elicits better protection and an IgG response even at a lower vaccine dose (10-fold less) compared to other routes of vaccination. We anticipate that our novel method can be utilized for effective, cheap, and safe vaccination in the near future.

Experimental and numerical study of weak shock wave transmissions through minitubes

The aim of this letter is to present an original experimental technique to study weak shock wave in a minitube. Thus, we designed an apparatus that can be connected to any classical shock tube in order to characterize high speed flows induced by the shock wave transmission in minitubes. We proposed appropriated measurements based on high speed strioscopy coupled with pressure sensors. Two minitube diameters are considered: 1.020±0.010 and 0.480±0.010 mm. We realized preliminary experimental and numerical campaigns with an incident shock wave Mach number at 1.12±0.01. The generation of a microshock wave was observable in the two minitubes. For the smallest minitube, we found an attenuation of the strength of the shock wave with a decrease of 1.8% of the Mach number.

Applications of Shock Waves in Agriculture Research

Controlled shock waves can be generated in any medium of interest in the laboratory using various methods. The instantaneous increase in pressure and temperature, in the medium of propagation behind a shock wave, can be used for many novel industrial applications. In this paper we describe two new applications of shock waves developed for the agriculture research. An underwater shock wave generator has been used designed, calibrated and successfully used to generate under water shock waves. About 100 J of energy is deposited between two stainless steel electrodes immersed in water for about 350 ns for generating the micro-shock waves in water. Utilizing the instantaneous jumps in pressure and temperature behind these spherical micro-shock waves in water, desired DNA has been successfully injected inside (Agrobacterium tumefaciens) cells at a measured overpressure level of 50 bar. Reporter gene assay were also recorded in tomato plants to confirm the successful transformation of the naked plasmid DNA. Thes...

Enhanced atomic short-range ordering of the alloy Fe–15 at. % Cr caused by ion irradiation at elevated temperature and thermal effects only

A solid solution of 15 at. % Cr in α-Fe was prepared by rapid quenching from 1200 °C and cold plastic deformation (foils 30-μm thick). Under ion irradiation at a temperature of 450 °C with the use of 20-keV Ar+ and 40-keV Fe+ ions, this metastable alloy undergoes partial decomposition. The corresponding short-range-order parameter was determined by transmission Mossbauer spectroscopy. It ranges between 0.07 and 0.14 depending on the irradiation conditions. By comparison with an annealing treatment using the same temperature of 450 °C, it was proved that the effect of short-range-order formation is mainly caused by the irradiation and not by the elevated temperature. The time dependence of the decomposition shows a saturation effect after the first minutes of ion irradiation. Conversion electron Mossbauer spectroscopy (CEMS) data have shown that transformation of the initially disordered homogeneous solid solution is not limited to the penetration depths of the ions but extends over the whole sample thickness. This effect is explained by the radiation-dynamic action of the accelerated ions: probably propagation of after-cascade microshock waves, becoming non-attenuating in metastable media and driving phase transformations or correlated atom regrouping at their front.

Micro-Shock Waves Generated Inside a Fluid Jet Impinging on Plane Wall

An Nd:glass laser pulse (18 ns, 1.38 J) is focused in a tiny area of about 100-mum diam under ambient conditions to produce micro-shock waves. The laser is focused above a planar surface with a typical standoff distance of about 4 mm, The laser energy is focused inside a supersonic circular jet of carbon dioxide gas produced by a nozzle with internal diameter of 2.9 mm and external diameter of 8 mm, Nominal value of the Mach number of the jet is around 2 with the corresponding pressure ratio of 7.5 (stagnation pressure/static pressure at the exit of the nozzle), The interaction process of the micro-shock wave generated inside the supersonic jet with the plane wall is investigated using double-pulse holographic interferometry. A strong surface vortex field with subsequent generation of a side jet propagating outward along the plane wail is observed. The interaction of the micro-shock wave with the cellular structure of the supersonic jet does not seem to influence the near surface features of the flowfield. The development of the coherent structures near the nozzle exit due to the upstream propagation of pressure waves seems to be affected by the outward propagating micro-shock wave. Mach reflection is observed when the micro-shock wave interacts with the plane wall at a standoff distance of 4 mm, The Mach stem is slightly deflected, indicating strong boundary-layer and viscous effects near the wall. The interaction process is also simulated numerically using an axisymmetric transient laminar Navier-Stokes solver. Qualitative agreement between experimental and numerical results is good.

Cluster-surface impact dissociation of halogen molecules in large inert gas clusters

Molecular dynamics simulations of the dissociation of I 2 embedded in large Ar n ( n = 319, 553) clusters, which impact at high velocities (ν = 7–15 km s −1 1 ) on Pt surfaces, result in information on heterogeneous and homogeneous dissociation mechanisms. A broad distribution of dissociation lifetimes is exhibited, which can be attributed to prompt and retarded heterogeneous dissociation and to prompt, retarded and outbound homogeneous dissociation events. The propagation of a microshock wave within a large cluster can be interrogated by the homogeneous dissociation of a chemical probe, with the velocity of the propagation of the dissociation front being close to the cluster impact velocity.

Microshock wave propagation in molecular clusters

Microshock wave propagation in ArN (N=55–555) clusters generated by high-energy cluster-Pt surface impact (cluster velocities v=1–10 km s−1) is explored by molecular dynamics simulations. The gross features of the dynamics of the intracluster microshock wave propagation at this impact velocity range are not sensitive to the details of the repulsive potential (i.e., the Lennard-Jones or the exp-6 form). The propagation of the microshock within the cluster was quantified by the time dependence of the first moment of the total energy. A linear dependence between the microshock (compression) velocity us and the cluster impact velocity v is observed and for sufficiently large clusters (N≥321) us≊v. For large clusters (N≳321), the cluster Hugoniot temperature–pressure relations are qualitatively similar to those for the compression of macroscopic fluid Ar.