Table-top Shock Tube Research Articles

Acoustic shock-pulse-induced tunable structural and optical properties of L-Histidine maleate single crystals for photonic applications

In this paper, a single crystal of L-histidine maleate (LHM) was grown using a slow evaporation solution process. A tabletop shock tube is used to generate shock pulses. Shock waves' impact on the optical and structural characteristics of the LHM single crystal was studied for 0, 1, 2, and 3 shock pulses with a Mach number of 1.7. Analytical methods such as Powder X-ray diffraction, Raman, UV–visible spectroscopy, and optical microscopic techniques were utilized to get a deep understanding of the shock pulse impact of the title crystals. The crystalline nature is observed to be increased at the third shocked condition, as shown by the Raman and PXRD data. The UV-visible studies infer the enhancement of the crystal's optical-transmittance at 3rd shocked condition. It is to be noted that, the difference between optical transmittance at the impact of 2nd and 3rd shock is almost 30 %. It is evident from the data that, the applied shock waves are capable of tuning the local crystalline perfection and the optical transmittance of the test crystals. The shock wave induced higher crystalline perfection and optical transmittance LHM crystal is strongly suggested to the non-linear optical applications.

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.

Exploration of shockwaves on polymeric membranephysical properties and performance

The Commercial polymeric membranes like Polysulfone (PSF), Polyvinylidene difluoride (PVDF) and Polyacrylonitrile (PAN) which are an integral part of water purification investigation were chosen for the shockwave (SW) exposure experiment. These membranes were prepared by blending polymer (wt. %) / DMF (solvent) followed by phaseinversion casting technique. Shockwaves are generated by using Reddy Tube lab module (Table-top Shocktube) with range of pressure (1.5, 2.5 and 5 bar). Understanding the changes in membrane before and after shock wave treatment by parameters, i.e., pure water flux (PWF), rejection (%), porosity, surface roughness (AFM), morphology (SEM) and contact angle which can significantly affect the membrane's performance. Flux values PSf membranes shows increase, 465 (pristine) to 524 (1.5wt%) LMH at 50 Psi pressure and similar enhancement was observed at 100Psi (625 to 696 LMH). Porosity also shows improvement from 73.6% to 76.84% for 15wt% PSf membranes. It was observed that membranes made of polymers such as PAN and PSF (of high w/w %) exhibits some resistance against shockwaves impact and are stable compared to other membranes. Shockwave pressure of up to 1.5 bar was sufficient enough to change properties which are crucial for performance. Membranes exposed to a maximum pressure of 5 bar completely scratched the surface and with minimum pressure of 1.5bar is optimum enough to improve the water flux and other parameters. Initial results proved that SW may be suitable alternative route to minimize/control membrane fouling and improve efficiency.

Force Calibration of a Hemispherical Model Using Reddy Shock Tube

Shock tube study is done to understand the characteristic behavior of various types of shock wave, pressure and temperature variations observed at hypersonic speed. To study these characteristics in an inexpensive and simplified way, an instrument called Reddy Shock tube was designed, also known as Table-Top shock tube. Shock waves are generated purely by the application of manual force. In the test section, a flow of Mach upto 6.5 is generated. The attempt here was made to calculate force acting on a hemispherical model at hypersonic flow regime. It is an impulse facility, where the flow operates only for a fractional second. The pressure transducers were used to characterize the shock wave properties. Similarly, an accelerometer was connected to the model, which determined the acceleration value required to find the axial force.

Effect of Shock Waves on Structural, Thermophysical and Dielectric Properties of Glycine Phosphate (GPI) Crystal

In this article, the authors investigate the structural, thermophysical and dielectric properties of glycine phosphate (GPI) crystals for pre- and post-shock wave loaded conditions. The supersonic shock waves were generated by a table-top shock tube with corresponding Mach number of 1.7. The applied shock wave has 1.048 MPa transient pressure and 644 K temperature, respectively. The changes observed in the structural properties for pre- and post-shock loaded sample were confirmed using a powder x-ray diffractometer. Thermophysical properties such as thermal diffusivity, thermal conductivity and thermal effusivity were elucidated by photoacoustic spectrometer. The impedance analyzer is employed to determine the electrical properties and domain stabilities of the GPI crystal in the frequency range from 1 Hz to 1 MHz at ambient temperature. From this investigation we conclude that the GPI crystal can be used for devices that work in high vibration and extreme environments.

Effect of shock waves on thermophysical properties of ADP and KDP crystals

Ammonium Dihydrogen Phosphate (ADP) and Potassium Dihydrogen Phosphate (KDP) crystals are grown by slow evaporation method at ambient temperature. The said crystals are utilized as a test specimen and subjected to one-dimensional ‘loading of shock waves’ generated by rupturing a paper diaphragm with Mach number of 1.9 using supersonic low energy table-top shock tube. Thermal diffusivity of crystal is measured using Photoacoustic spectrometer (PAS) for the normal and shock loaded crystals, thermal conductivity and thermal effusivity are computed for the given volumetric specific heat capacity of the crystals. XRD characterization studies reveals that KDP crystal has better immunity to shock wave than ADP crystal.

Effect of Shock Waves on Dielectric Properties of KDP Crystal

An alternative non-destructive approach is proposed and demonstrated for modifying electrical properties of crystal using shock-waves. The method alters dielectric properties of a potassium dihydrogen phosphate (KDP) crystal by loading shock-waves generated by a table-top shock tube. The experiment involves launching the shock-waves perpendicular to the (100) plane of the crystal using a pressure driven table-top shock tube with Mach number 1.9. Electrical properties of dielectric constant, dielectric loss, permittivity, impedance, AC conductivity, DC conductivity and capacitance as a function of spectrum of frequency from 1 Hz to 1 MHz are reported for both pre- and post-shock wave loaded conditions of the KDP crystal. The experimental results reveal that dielectric constant of KDP crystal is sensitive to the shock waves such that the value decreases for the shock-loaded KDP sample from 158 to 147. The advantage of the proposed approach is that it is an alternative to the conventional doping process for tailoring dielectric properties of this type of crystal.

Modeling clinically relevant blast parameters based on scaling principles produces functional & histological deficits in rats

Blast-induced traumatic brain injury represents a leading cause of injury in modern warfare with injury pathogenesis poorly understood. Preclinical models of blast injury remain poorly standardized across laboratories and the clinical relevance unclear based upon pulmonary injury scaling laws. Models capable of high peak overpressures and of short duration may better replicate clinical exposure when scaling principles are considered. In this work we demonstrate a tabletop shock tube model capable of high peak overpressures and of short duration. By varying the thickness of the polyester membrane, peak overpressure can be controlled. We used membranes with a thickness of 0.003, 0.005, 0.007, and 0.010in to generate peak reflected overpressures of 31.47, 50.72, 72.05, and 90.10 PSI, respectively. Blast exposure was shown to decrease total activity and produce neural degeneration as indicated by fluoro-jade B staining. Similarly, blast exposure resulted in increased glial activation as indicated by an increase in the number of glial fibrillary acidic protein expressing astrocytes compared to control within the corpus callosum, the region of greatest apparent injury following blast exposure. Similar findings were observed with regard to activated microglia, some of which displayed phagocytic-like morphology within the corpus callosum following blast exposure, particularly with higher peak overpressures. Furthermore, hematoxylin and eosin staining showed the presence of red blood cells within the parenchyma and red, swollen neurons following blast injury. Exposure to blast with 90.10 PSI peak reflected overpressure resulted in immediate mortality associated with extensive intracranial bleeding. This work demonstrates one of the first examples of blast-induced brain injury in the rodent when exposed to a blast wave scaled from human exposure based on scaling principles derived from pulmonary injury lethality curves.

Note: A table-top blast driven shock tube

The prevalence of blast-induced traumatic brain injury in conflicts in Iraq and Afghanistan has motivated laboratory scale experiments on biomedical effects of blast waves and studies of blast wave transmission properties of various materials in hopes of improving armor design to mitigate these injuries. This paper describes the design and performance of a table-top shock tube that is more convenient and widely accessible than traditional compression driven and blast driven shock tubes. The design is simple: it is an explosive driven shock tube employing a rifle primer that explodes when impacted by the firing pin. The firearm barrel acts as the shock tube, and the shock wave emerges from the muzzle. The small size of this shock tube can facilitate localized application of a blast wave to a subject, tissue, or material under test.