Shock Tube System Research Articles

Analysis of stagger effects on Busemann supersonic biplane airfoil in shock tube tests by point diffraction interferometer method

The Busemann biplane concept is proposed for low-boom low-drag supersonic aircraft. Studies on the supersonic biplane have been focused on supersonic flow, whereas the understanding of transonic aerodynamic characteristics is essential for aircraft design. Significantly, the complicated flow field with a shock and boundary layer interaction between Busemann biplane elements in transonic flow remains unclear. In the present study, the transonic aerodynamic characteristics of the two-dimensional Busemann biplane are investigated by shock tube tests and numerical simulations, focusing on the flow field between the biplane elements. In addition, the stagger effects, which change the relative position of the lower and upper elements in the freestream direction to avoid the choked flow between the biplane elements, are also analyzed. A shock tube system creates a test flow at Mach numbers of 0.6 to 0.8, and the Reynolds number is set at 2.85 × 105. The Point Diffraction Interferometer (PDI) method is applied to determine the density distribution around the model and the pressure coefficient on the surfaces of the biplane elements. Symmetrical density distribution is confirmed in the Busemann biplane (the baseline model, or the biplane with no stagger). A normal shock wave is generated between the biplane elements. When the Mach number increases, the normal shock wave moves downstream. The normal shock position is quantitatively stable with small fluctuation amplitudes. The fringes are strongly curved near the surfaces of the biplane elements due to the flow separation near the airfoil surfaces. When the Mach number increases, the separation area increases. When the Mach number increases, the peak value of the pressure coefficient on the surfaces of the biplane elements increases. On the other hand, the normal shock wave between the biplane elements is eliminated in the staggered models. The changes in density distribution between the biplane elements are minor compared to the case of the baseline model, which indicates that the stagger reduces the choked flow between the biplane elements. The peak value of the pressure coefficient on the wing surface increases when the stagger value increases. The stagger effects on reducing the total drag coefficient of the biplane models are confirmed.

Experimental study on pressure evolution of detonation waves penetrating into water

Propagation of detonation waves crossing the gas–liquid interface is a basic phenomenon worth studying for underwater detonation engines. In this work, the pressure evolution of detonation waves penetrating into water is theoretically and experimentally investigated. The one-dimensional shock wave theory is adopted to solve the pressure–velocity relations of the reflected and transmitted shock wave in different mediums. Experiments under different filling pressure are performed based on a two-phase shock tube system. Theoretical results show that the range of pressure rise ratios between the detonation and transmitted wave is 2.40–2.50. Its trend is determined by the total atoms number of fuel under low filling pressure, but dominated by the ratio of C/H atoms under high filling pressure. Experimental results demonstrate that pressure rise ratios are in good agreement with the theoretical values. There are similar attenuation laws (decay to 50% in 0.3 ms) for subsequent pressure development after those two waves. Under the interface effect, the transmitted wave is stretched and the pressure zone becomes wider. The difference of acoustic impedance between two phases leads to wave property changes at the interface and exit. These changes result in the reciprocating cavitation zones and reformed shock waves in the water, greatly influencing the water pressure.

Improved shock tube method for dynamic calibration of the sensitivity characteristic of piezoresistive pressure sensors

The dynamic calibration of pressure sensors with shock tube system are inevitably affected by the non-ideal shock wave characteristics and complex noise interferences, which limits the achievable accuracy of the dynamic pressure measurements. This paper proposes an improved shock tube (IST) method for identifying the sensitivity characteristic of piezoresistive pressure sensors. The incident shock wave (ISW) velocity attenuation model is first established by a distributed ISW velocity measurement combined with least squares fitting to compensate the shock wave pressure in shock tube. Besides, a signal correction method based on the hybrid adaptive mode decomposition is presented to eliminate the effects of complex noise on the response signals of pressure sensor. An accurate dynamic calibration result of the sensitivity characteristic is finally achieved with the compensated shock wave pressure and corrected response signal. A series of dynamic calibration experiments for a piezoresistive pressure sensor are carried out to verify the performance of the IST method. Results show that the IST method is able to effectively reduce the effects of the non-ideal shock wave and complex noises on the sensitivity calibration results. The mean relative error of sensitivity calibration results with the IST method is only 0.55%, which is about 1/7 times of the results obtained by the usual shock tube method. Furthermore, the sensitivity calibration uncertainty is evaluated and the smaller uncertainty results further verify the superiority of the IST method in high-accuracy dynamic calibration of piezoresistive pressure sensors.

Insights into the shockwave attenuation in miniature shock tubes

Miniature shock tubes are finding growing importance in a variety of interdisciplinary applications. There is a lack of experimental data to validate the existing shock tube flow models that explain the shockwave attenuation in pressure-driven miniature shock tubes. This paper gives insights into the shock formation and shock propagation phenomena in miniature shock tubes of 2, 6 and 10 mm square cross-sections operated at diaphragm rupture pressure ratios in the range 5–25 and driven section initially at ambient conditions. Pressure measurements and visualization studies are carried out in a new miniature table-top shock tube system using nitrogen and helium as driver gases. The experimental findings are validated using a shock tube model explained in terms of two regions: (i) the shock formation region, dominated by wave interactions due to the diaphragm's finite rupture time; and (ii) the shock propagation region, where the shockwave attenuation occurs mainly due to wall effects and boundary layer growth. Correlations to predict the variation of shock Mach number in the shock formation region and shock propagation region work well for the present findings and experimental data reported in the literature. Similar flow features are observed in the shock tubes at the same dimensionless time stamps. The formation of the planar shock front scales proportionally with the diameter of the shock tube. The peak Mach number attained by the shockwave is higher as the shock tube diameter increases.

Investigation of vibration effect on dynamic calibration of pressure sensors based on shock tube system

This paper devotes to investigate the influence of vibration on dynamic calibration of pressure sensors based on shock tube system. Two sensors with different types are separately calibrated under the same step pressure to distinguish the individual sensor’s dependent effect. To excavate how the sensor’s dynamic characteristics fluctuate under different vibration cases, support mounts and buffer rings of different materials are used in the experimental shock tube system. Vibrations from two main sources are expounded in detail and detected by an acceleration sensor installed near the pressure sensors. Based on the outputs of sensors, the influences of vibration on the repeatability, stability and dynamic characteristics of pressure sensors are analyzed qualitatively and quantitatively. Furthermore, a weighted scoring method based on the relative standard deviation of the calibration parameters is proposed to comprehensively assess the vibration effect on dynamic calibration results of pressure sensors. The experimental results show that the influence of vibration from the rupture of diaphragm on dynamic calibration can be avoided suitably by using the mount with high damping material or a shock tube with long driven section. The vibration from the instantaneous impact of shock wave has slight influence on the repeatability, rise time and resonant frequency, and significant influence on the stability, settling time, overshoot and uncertainty in working band of pressure sensors. Based on the weighted scores under different vibration cases, the combination of steel mount and aluminum ring produces the most reliable calibration result. These findings are also verified by another group of calibration experiments with a smaller amplitude of step pressure.

Blast load simulation using conical shock tube systems

With the increased frequency of accidental and deliberate explosions, evaluating the response of civil infrastructure systems to blast loading has been attracting the interests of the research and regulatory communities. However, with the high cost and complex safety and logistical issues associated with field explosives testing, North American blast-resistant construction standards (e.g. ASCE 59-11 and CSA S850-12) recommend the use of shock tubes to simulate blast loads and evaluate relevant structural response. This study first aims at developing a simplified two-dimensional axisymmetric shock tube model, implemented in ANSYS Fluent, a computational fluid dynamics software, and then validating the model using the classical Sod’s shock tube problem solution, as well as available shock tube experimental test results. Subsequently, the developed model is compared to a more complex three-dimensional model and the results show that there is negligible difference between the two models for axisymmetric shock tube performance simulation; however, the three-dimensional model is necessary to simulate non-axisymmetric shock tubes. Following the model validation, extensive analyses are performed to evaluate the influences of shock tube design parameters (e.g. the driver section pressure and length and the expansion section length) on blast wave characteristics to facilitate a shock tube design that would generate shock waves similar to those experienced by civil infrastructure components under blast loads. The results show that the peak reflected pressure increases as the driver pressure increases, while a decrease in the expansion length increases the peak reflected pressure. In addition, the positive phase duration increases as both the driver length and expansion length are increased. Finally, the developed two-dimensional axisymmetric model is used to optimize the dimensions of a physical large-scale conical shock tube system constructed for civil infrastructure component blast response evaluation applications. The capabilities of such shock tube system are further investigated by correlating its design parameters to a range of explosion threats identified by different hemispherical TNT charge weight and distance scenarios.

A fast estimation of shock wave pressure based on trend identification

In this paper, a fast method based on trend identification is proposed to accurately estimate the shock wave pressure in a dynamic measurement. Firstly, the collected output signal of the pressure sensor is reconstructed by discrete cosine transform (DCT) to reduce the computational complexity for the subsequent steps. Secondly, the empirical mode decomposition (EMD) is applied to decompose the reconstructed signal into several components with different frequency-bands, and the last few low-frequency components are chosen to recover the trend of the reconstructed signal. In the meantime, the optimal component number is determined based on the correlation coefficient and the normalized Euclidean distance between the trend and the reconstructed signal. Thirdly, with the areas under the gradient curve of the trend signal, the stable interval that produces the minimum can be easily identified. As a result, the stable value of the output signal is achieved in this interval. Finally, the shock wave pressure can be estimated according to the stable value of the output signal and the sensitivity of the sensor in the dynamic measurement. A series of shock wave pressure measurements are carried out with a shock tube system to validate the performance of this method. The experimental results show that the proposed method works well in shock wave pressure estimation. Furthermore, comparative experiments also demonstrate the superiority of the proposed method over the existing approaches in both estimation accuracy and computational efficiency.

Lasting Retinal Injury in a Mouse Model of Blast-Induced Trauma

Traumatic brain injury due to blast exposure is currently the most prevalent of war injuries. Although secondary ocular blast injuries due to flying debris are more common, primary ocular blast exposure resulting from blast wave pressure has been reported among survivors of explosions, but with limited understanding of the resulting retinal pathologies. Using a compressed air-driven shock tube system, adult male and female C57BL/6 mice were exposed to blast wave pressure of 300 kPa (43.5 psi) per day for 3 successive days, and euthanized 30 days after injury. We assessed retinal tissues using immunofluorescence for glial fibrillary acidic protein, microglia-specific proteins Iba1 and CD68, and phosphorylated tau (AT-270 pThr181 and AT-180 pThr231). Primary blast wave pressure resulted in activation of Müller glia, loss of photoreceptor cells, and an increase in phosphorylated tau in retinal neurons and glia. We found that 300-kPa blasts yielded no detectable cognitive or motor deficits, and no neurochemical or biochemical evidence of injury in the striatum or prefrontal cortex, respectively. These changes were detected 30 days after blast exposure, suggesting the possibility of long-lasting retinal injury and neuronal inflammation afterprimary blast exposure.

G0500904 空中に浮遊した物体と衝撃波の干渉

From a safety engineering viewpoint, it is important to predict the motion of flying fragments generated during accidental explosions. In our previous work, a special shock tube system to study the shock-induced motion of a solid body suspended in the air was constructed, and then the shadowgraph images of the shock-induced motion of a solid body were acquired by using a high-speed camera. It was found from the previous work that the body's motion was affected by the flow between the body and the floor, and the initial attack angle of the solid body. In the present study, we have observed the shock-induced motion of a solid body with relatively large, initial attack angle by Schlieren photography technique. The present results show how the initial posture of the solid body and the flow field around the body influence the body's motion.

Characterization of a fiber-optic pressure sensor in a shock tube system for dynamic calibrations

Measurements of mechanical quantities such as pressure often take place under dynamic conditions, yet no traceable standards for the primary dynamic calibration of pressure sensors currently exist. In theory, shock tubes can provide a close to perfect step-function ideal for the calibration of pressure transducers. In this paper we investigate a system consisting of a shock tube and an ultra-fast fiber-optical sensor that is designed to be a future primary system for dynamic pressure calibrations. For reference, the fiber-optical sensor is compared to a piezoelectric sensor, and their corresponding frequency spectra are calculated. Furthermore, an investigation of the repeatability of the fiber-optical sensor, as well as a comparison with a second shock tube, is performed.

Weak and strong ignition of hydrogen/oxygen mixtures in shock-tube systems

Detailed simulations of hydrogen/oxygen mixtures are performed to study weak and strong ignition regimes in a shock-tube system. An adaptive mesh refinement (AMR) algorithm in conjunction with a detailed chemistry representation is used to resolve physically relevant features such as the viscous boundary layer, the shock bifurcation region, and ignition kernels. The simulations employ a second-order accurate Navier–Stokes equations solver that is modified to include finite-rate reaction chemistry, wall-heat transfer, and detailed mass, thermal, and viscous-diffusion-transport properties. The operating conditions considered in this study span the thermodynamic state-space in the weak and strong ignition regimes. The treatment of wall-heat transfer is found to significantly alter the characteristics of ignition. The computations show that the mixing of the thermally stratified fluid, which carries different momentum and enthalpy, introduces inhomogeneities in the core region behind the reflected shock. These inhomogeneities act as localized ignition kernels. During the induction period, these kernels slowly expand and eventually transition to a detonation wave, rapidly consuming the unburned mixture. Effects of the reaction chemistry on the ignition behavior are examined by considering two different reaction mechanisms. A detailed analysis is performed to show that the transition from ignition kernel to detonation is well described by the SWACER mechanism.

A computational study of drug particle delivery through a shock tube

Transdermal powdered drug delivery is a recent concept which has been proposed as an alternative of the conventional drug delivery systems. The idea is to accelerate the drug particles behind a moving shock inside the shock tube so that particles can gain enough momentum to penetrate the outer layer of the skin (stratum corneum) and have a pharmaceutical effect. The drugs are delivered in a powdered form. While delivering the particles to the skin two important issues have to be taken care of. The particles should be delivered with uniform velocity and with spatial distribution. To fulfill these requirements different systems have been tried and tested . Among different systems the contoured shock tube (CST) system is the one to be mentioned. CST system can successfully produce uniform velocity and also with spatial distribution. However, future application of this system demands flexibility and capability to accommodate a wide range of drugs and doses. This paper aims at numerical investigation of particle transportation through the contoured shock tube. Computation fluid dynamics (CFD) has been used to model the flow field and analyze it in details. The unsteady DPM (discrete phase model) is adopted to model the particle transportation. The drug correlation proposed by Igra et al. is used instead of the standard drag correlation to predict the particle movement through the flow filed. The gas and particle dynamics inside the shock tube is closely monitored and analyzed. The effect of different particle features in the transportation process is also investigated.

A numerical study of the gas and particle dynamics in a needle free drug delivery device

In recent times, a unique drug delivery system known as transdermal drug delivery has been developed which can deliver drug to the human skin without using any external needle. A shock tube system is used to generate a moving shock wave which flows through the tube. The idea is to accelerate particles behind the moving shock so that it can attain sufficient momentum to penetrate the outer layer of the skin (stratum corneum) and have a pharmaceutical effect. The important issue while delivering drug to the skin is to deliver it with uniform velocity and spatial distribution. Among different tried and tested systems the contoured shock tube (CST) seems to fulfill this requirement successfully. This paper focuses on numerically investigating the flow field and analyzing the gas and particle interaction through the contoured shock tube. Computational fluid dynamics (CFD) has been used to simulate and further analyze the flow field. The important issues regarding the flow field and the gas particle interaction are discussed in details.

A study on the gas-solid particle flows in a needle-free drug delivery device

Different systems have been used over the years to deliver drug particles to the human skin for pharmaceutical effect. Research has been done to improve the performance and flexibility of these systems. In recent years a unique system called the transdermal drug delivery has been developed. Transdermal drug delivery opened a new door in the field of drug delivery as it is more flexible and offers better performance than the conventional systems. The principle of this system is to accelerate drug particles with a high speed gas flow. Among different transdermal drug delivery systems we will concentrate on the contour shock tube system in this paper. A contoured shock tube is consists of a rupture chamber, a shock tube and a supersonic nozzle section. The drug particles are retained between a set of bursting diaphragm. When the diaphragm is ruptured at a certain pressure, a high speed unsteady flow is initiated through the shock tube which accelerates the particles. Computational fluid dynamics is used to simulate and analyze the flow field. The DPM (discrete phase method) is used to model the particle flow. As an unsteady flow is initiated though the shock tube the drag correlation proposed by Igra et al is used other than the standard drag correlation. The particle velocities at different sections including the nozzle exit are investigated under different operating conditions. Static pressure histories in different sections in the shock tube are investigated to analyze the flow field. The important aspects of the gas and particle dynamics in the shock tube are discussed and analyzed in details.

Effect of Plate Curvature on Blast Response of Carbon/Epoxy Composite

Experimental and numerical studies wereconducted to understand the effect of plate curvature on the blast response ofcarbon/epoxy composite panels. A shock-tube system was utilized to impartcontrolled shock loading to quasi-isotropic composite panels with varying radiiof curvature. A 3D digital image correlation (DIC) technique coupled withhigh-speed photography was used to assess the out-of-plane deflection ofcomposite panels. A finite element (FE) model integrating fluid-structureinteraction to represent coupling between the air surrounding composite panels,shock wave and panels, was developed using a general-purpose FE softwareABAQUS/Explicit. The numerical results were compared to the experimental dataand showed a good correlation.

Blast response of curved carbon/epoxy composite panels: Experimental study and finite-element analysis

Experimental and numerical studies were conducted to understand the effect of plate curvature on blast response of carbon/epoxy composite panels. A shock-tube system was utilized to impart controlled shock loading to quasi-isotropic composite panels with differing range of radii of curvatures. A 3D Digital Image Correlation (DIC) technique coupled with high-speed photography was used to obtain out-of-plane deflection and velocity, as well as in-plane strain on the back face of the panels. Macroscopic post-mortem analysis was performed to compare yielding and deformation in these panels. A dynamic computational simulation that integrates fluid-structure interaction was conducted to evaluate the panel response in general purpose finite-element software ABAQUS/Explicit. The obtained numerical results were compared to the experimental data and showed a good correlation.

A Numerical Study of the Performance of a Contoured Shock Tube for Needle-free Drug Delivery

In recent years a unique drug delivery system named as the transdermal drug delivery system has been developed which can deliver drug particles to the human skin without using any external needle. The solid drug particles are accelerated by means of high speed gas flow through a shock tube imparting enough momentum so that particles can penetrate through the outer layer of the skin. Different systems have been tried and tested in order to make it more convenient for clinical use. One of them is the contoured shock tube system (CST). The contoured shock tube consists of a classical shock tube connected with a correctly expanded supersonic nozzle. A set of bursting membrane are placed upstream of the nozzle section which retains the drug particle as well as initiates the gas flow (act as a diaphragm in a shock tube). The key feature of the CST system is it can deliver particles with a controllable velocity and spatial distribution. The flow dynamics of the contoured shock tube is analyzed numerically using computational fluid dynamics (CFD). To validate the numerical approach pressure histories in different sections on the CST are compared with the experimental results. The key features of the flow field have been studied and analyzed in details. To investigate the performance of the CST system flow behavior through the shock tube under different operating conditions are also observed.

点回折干渉計による衝撃波管翼型流れの試験気体の影響に関する研究

In the present study, flow visualizations and quantitative measurements around a NACA0012 airfoil are performed under air and CO2 operation modes. A diaphragmless shock tube system is used for a high-subsonic airfoil testing. This system has the possibility of efficient aerodynamic experiments as an intermittent wind tunnel. A point diffraction interferometry (PDI) is used for a flow measurement technique. Moreover, the comparison with numerical results by the OpenFOAM is performed. The driver tube of this shock tube is the circular cross section with a diameter of 150mm. The driven tube is the rectangular cross section with a width of 60mm and a height of 150mm. The hot gas Mach number (uniform high-subsonic flow condition) is M2 = 0.65. The angle of attack is α = 0° and 2°, and the range of the Reynolds number is Re = 1.7–7.4 × 105. The results of the present study are as follows. In the present Reynolds numbers, if the shock wave does not generate, the shock tube airfoil flows of CO2 mode showed almost the same trend as the case of air mode quantitatively. The difference of operation gas was confirmed when the shock wave generated on the airfoil surface. In the high-subsonic flow, the pressure coefficients Cp by the PDI are in relatively agreement with the CFD results. The numerical results by the OpenFOAM give useful results for the comparison with aerodynamic data. Therefore, this shock tube system with a PDI measurement technique is considered as one of useful facilities for different operational modes.

D111 フォーカシングシュリーレン法による遷音速衝撃波管翼型回りの観察

In this study, the focusing schleren system was designed to visualize the flow field around the double wedge airfoil model in the test section of the shock tube. The focusing schlieren system was developed by Weinstein. It is perpendicular to the test beam path of the optical system and can be used to examine three-dimensional flow field in the wind tunnel testing. As a first step, we made the measurement gauge for the investigation of characteristics of this system, location of image plane and depth of focus. And we understood the depth of focus in the present test section of shock tube system. Also, the visualization of shock tube airfoil flow was performed by this system to investigate the three-dimensional airfoil flow.

Infrared emission from high-temperature H2O(nu2) - A diagnostic for concentration and temperature

A shock tube system was used to produce known concentrations of water at combustion temperatures so that the infrared radiance from a portion of the H 2 O(v 2 ) band could be measured as a function of temperature and wavelength. The resulting data set was used to determine the efficacy of a spectral emission diagnostic for H 2 O temperature and column density at the exit plane of a supersonic combustor. Temporally and spectrally resolved, optically thin infrared emission, at 13 wavelengths between 6.5 and 9.5 μm, was observed from shock-heated H 2 O/N 2 , H 2 /O 2 /N 2 , and H 2 /O 2 /Ar mixtures, at pressures of 1 and 5 atm and temperatures between 1400 and 3000 K. Least-squares analysis of the temperature-dependent intensities for each wavelength channel gave parameters that accurately describe the radiance as a function of wavelength and temperature over the entire temperature range of the measurements. The accuracy to which temperatures and H 2 O column densities can be determined from these parameters was then estimated. Radiometric data were compared with predictions from a widely used band model, corrections for optically thick systems were explored, and the relationship between optically thin radiance and the optical cross section produced. Column densities at which corrections for optical thickness are required were also calculated.