Tube Waves Research Articles

Research on the Application Performance of the Helmholtz High-Efficiency Wave-Elimination Chamber in Gas Wave Tubes

A gas wave refrigerator is a device that uses gas pressure to expand and refrigerate; the moving shock wave in the gas wave tube is the key to cooling. If the shock wave is reflected to the open mouth of the gas wave tube, it will heat the expanded refrigeration gas at the open end, severely reducing the refrigeration efficiency. In order to reduce this effect, a Helmholtz middle wave chamber-type gas wave tube is presented here. This study describes the performance of this structure in the gas wave refrigeration process. The refrigeration performance of the structure’s gas wave tube use was evaluated experimentally and numerically using computational fluid dynamics (CFD). The function of the middle wave elimination chamber was studied and explained: the chamber turns the reflected shock wave back to the end section of the tube and converts part of the incoming shock wave to an expansion wave, which may counteract the reflected shock wave by escaping from wave elimination chamber. The experimental results showed that the structure increased refrigeration efficiency by about 2.9% (50 Hz), 2% (40 Hz), and 2.2% (25 Hz) at the corresponding ejection frequencies, and reduced the reflected shock wave intensity by 11%, which proves the high-efficiency energy dissipation performance and the significant increase in refrigeration efficiency of the Helmholtz-type gas wave tube.

Modeling of two-phase refrigerant distribution in brazed plate heat exchangers

This paper presents a mechanistic model that predicts two-phase refrigerant distribution in brazed plate heat exchangers. The modeling of two-phase distribution is based on the flow visualization in the inlet header, in which the flow regime is identified to be periodic and one cycle includes two or three flow stages, given a fully developed stratified/stratified-wavy flow is present at the heat exchanger entrance. To predict the vapor refrigerant distribution, this model considers two different flow stages in the inlet header: for the top corner vapor flow, the vapor refrigerant distribution is predicted by the balance between the suction force (radial pressure gradient) and the axial momentum of each phase; for the vapor jet flow, the vapor refrigerant is assumed to be distributed evenly among the channels. The time ratio of the two flow stages is estimated by assuming the irregular large-amplitude rolling waves in the feeding tube, which lead to the vapor jet flow in the header, to have the most dangerous wavelength and their traveling time can be related to the liquid slug frequency. The apparent vapor refrigerant distribution is the time average of the vapor distributions at the two stages. For the liquid refrigerant distribution, it is predicted by imposing an equal total pressure drop for each flow path. The proposed model is validated against the experimental results: quantified two-phase refrigerant distribution, heat exchanger capacities, pressure profiles in the headers, and surface temperature of the sidewalls.

Persistent fast kink magnetohydrodynamic waves detected in a quiescent prominence

Small-scale, cyclic, transverse motions of plasma threads are usually seen in solar prominences, which are often interpreted as magnetohydrodynamic (MHD) waves. Here, we observed small-scale decayless transverse oscillations in a quiescent prominence, and they appear to be omnipresent. The oscillatory periods of the emission intensity and a proxy for the line-of-sight Doppler shift are about half period of the displacement oscillations. This feature agrees well with the fast kink-mode waves in a flux tube. All the moving threads oscillate transversally spatially in phase and exhibit no significant damping throughout the visible segments, indicating that the fast kink MHD waves are persistently powered and ongoing dissipating energy is transferred to the ambient plasma in the quiet corona. However, our calculations suggest that the energy taken by the fast kink MHD waves alone can not support the coronal heating on the quiet Sun.

Numerical analysis and control of nonlinear traveling wave in cylindrical tube based on neo-Hookean material

In this paper, the nonlinear wave of a cylindrical tube composed of neo-Hookean material is analyzed. Firstly, the homoclinic orbit of the system not affected by external disturbance is analyzed and calculated by numerical method, then the chaos of the system containing disturbance is analyzed by bifurcation diagram and Lyapunov exponent spectrum, and finally the system is controlled by synchronous coupling control.

Experimental investigation of the performance of a thermoacoustic refrigeration

Thermo-Acoustics is a phenomenon that involves the interplay of sound and thermal engines. Its most recent application is in the development of heat engines and pumps/refrigerators. One such occurrence is thermo-acoustic refrigeration, which employs high-intensity sound waves in a pressured gas tube to transport heat from one location to another and generate a cooling effect. In this paper, the design covers stack dimension, acoustic driver selection, and acoustic resonator selection. Acoustic resonator selection, stack dimension and acoustic driver selection are discussed in this paper. The investigation revealed that, the temperature control by thermal acoustics was found to be feasible, but inefficiency was not achieved because of material constraints. For this basic device, we acquired a temperature differential of 3 degrees Celsius. However, based on these constraints, various recommendations for improving the performance of thermoacoustic refrigerators were developed. In experiments, superior materials, such as materials with high heat capacity, and working fluids, such as inert gases, have been shown to improve efficiency.Heat is turned into sound energy in a thermoacoustic engine, and its energy is useful for practical work. By using this device, heat is transferred from a higher-to a lower-temperature sink. The preceding process is reversed by a thermo-acoustic refrigerator, which absorbs heat from a low-temperature medium and rejects it to a high-temperature medium by using acoustic power.

Nonequilibrium Vibrational, Rotational, and Translational Thermometry via Megahertz Laser Absorption of CO

A mid-infrared laser absorption strategy for simultaneously measuring translational, rotational, and vibrational temperatures of carbon monoxide (CO) at high speeds was developed for application to high-temperature nonequilibrium environments relevant to Mars atmosphere entry. Rapid-tuning scanned wavelength techniques were used to spectrally resolve the R(0,66), P(0,31), P(2,20), and P(3,14) lines of the CO fundamental vibrational bands at a rate of 1 MHz to infer multiple temperatures of CO behind incident and reflected shock waves in a shock tube. A distributed feedback quantum cascade laser was used to probe the P-branch transitions near and an external cavity quantum cascade laser was used to probe the R-branch transition near , both using bias-tee circuitry. The sensing method is shown to resolve each targeted transition with temporal and spectral resolution sufficient for quantitative multi-temperature measurements over a wide range of temperatures and pressures (2100–5500 K, 0.03–1.02 atm), including behind incident shock waves traveling up to 3.3 km/s. Measured temperature results were compared to equilibrium and nonequilibrium simulations.

The role of resonance radiation in the propagation of a positive pre-breakdown ionization wave in long discharge tubes

The work is devoted to calculating the flux of resonance photons towards the boundary of a cylindrical discharge tube of a finite size during the propagation of a pre-breakdown ionization wave of positive polarity. A cylindrical discharge tube of finite dimensions with argon at the pressure of p = 1 Torr is considered. The propagation mechanisms of metastable and resonance atoms are compared. For the considered discharge conditions, the space-time distributions of metastable and resonance atoms are calculated. The manuscript presents a technique for calculating the flux of resonance photons onto the discharge tube wall with the account of the radiation trapping. It is shown that for the studied conditions the photon flux density towards the longitudinal boundary of the tube ahead of the ionization wave can reach 1013 cm−2 s−1. The obtained results allow us to describe the appearance of seed electrons ahead of the positive ionization wavefront during their propagation due to the electron photoemission from the discharge tube wall.

Modeling of weak shock waves propagation in aqueous foam layer

Dynamics of low-intensity air shock waves in the shock tube containing an aqueous foam layer is theoretically investigated. Modeling of studied process is carried out using two-phase model of aqueous foam developed by the authors in single-pressure, single-speed and two-temperature approximations. The model takes into account the Ranz-Marshall interphase contact heat transfer, effective Herschel-Bulkley viscosity, which describes foam behavior as a non-Newtonian fluid, and elastic properties of aqueous foam under a weak shock impaction without destruction of foam structure. Properties of air and water as the foam components are described by realistic equations of state. Computer implementation of the aqueous foam model is carried out in the solver, developed by the authors in OpenFOAM software. The influence of aqueous foam viscoelastic properties on the intensity and structure of a shock wave has been investigated. When analyzing the obtained solutions, reliability of the proposed model and method of numerical modeling is estimated by comparative analysis of the found solutions and literature experimental data.

Shock wave characteristics in a conical water explosion shock tube under cylindrical charge condition

A conical shock tube is a kind of underwater explosive devices which uses small conical explosive charge to form high intensity shock pressure. Theoretically, the shock wave pressure in the conical shock tube is the same as that generated by a virtual spherical explosive charge in free field water. However, considering the effect of practical factors, the characteristics of shock wave in the actual device and the theoretical device are different to some extent. In order to investigate the shock wave characteristics in the conical water explosion shock tube under a cylindrical charge condition, and to obtain the variation rules of the peak pressure value, the specific impulse and the energy flux density, a series of numerical calculations with different cone angles and different quality of cylindrical charges were conducted. The reliability of the simulation methods was verified by comparing with the published experimental data. Through the analysis of the pressure data obtained by the validated simulation method, it is found that the shock wave in the tube follows the same scaling law as it is in the free field underwater explosion. The constants k and n of the empirical expressions for peak pressure, the impulse and the energy flux density for the shock wave in shock tube are obtained by data fitting. Furthermore, the relationships among the coefficient k, index n and cone angle α were deduced, and the result shows that the coefficients k have well linear relationship with constructed angle coefficient β, and the indexes n can be quantitatively expressed by cone angle α. Regarding the free field as a special case with a cone angle of 360°, it’s constants k and n also conform to the obtained relationships. It is also found that the secondary pulsation pressure period shows an anomalous change rule with explosive mass, which can be well explained by the significant increasement of the equivalent hydrostatic pressure depth. The ratio between the secondary impulse pressure peak and initial pressure peak is bigger than that in free field while the ratio between the secondary impulse pressure’s impulse to the initial pressure impulse is almost the same. These results can provide support for the application of conical shock tubes.

Flow Nonuniformities Behind Accelerating and Decelerating Shock Waves in Shock Tubes

Shock tubes are used to investigate the chemical kinetics and radiative properties of gasses. Analyses of the flow conditions produced in shock tubes typically assume a single, constant shock speed even though the shock speed varies due to driver effects, boundary-layer growth, and diaphragm rupture effects. This paper will investigate the dependence of flow properties upon the entire shock speed history for a 100-mm-diam, 8-m-long shock tube using the FROSST axisymmetric shock tube Navier–Stokes code. A perfect gas is applied to remove the complexity of thermochemistry and allow a focus upon the flow details. Shock speed profiles ranging from accelerating to decelerating are simulated to qualitatively represent different experimental conditions, and the resulting test slugs compared. All shocks reach the test section at the same final shock Mach number of 6.53. Pressure variations caused by the accelerating shock are found to combine with entropy gradients introduced by the changing shock strength, yielding differences in maximum temperature of the test slug by as much as 56%, and differences in maximum pressure as high as 22% despite the shared tube-end Mach number. Local temperature and pressure around gas packets in the test slug are found to relax significantly through time in response to changing postshock conditions. Test slug variations due to boundary-layer effects are found to be present, but overwhelmed by the relaxation processes under many conditions.

On propagation of waves in pressurized fiber-reinforced hyperelastic tubes based on a reduced model

A refined dynamic finite-strain shell theory for incompressible hyperelastic materials was developed by the authors recently. In this paper, we first derive the associated linearized incremental theory, and then use it to investigate wave propagation in a fiber-reinforced hyperelastic tube that is subjected to an axial pre-stretch and internal pressure. We obtain the dispersion relations for both axisymmetric and non-axisymmetric waves and discuss their accuracy by comparing them with the exact dispersion relations. The bending effect is also examined by comparing the dispersion curves based on the present theory and membrane theory. It is shown that the present theory is more accurate than the membrane theory in studying wave propagation and the bending effect plays an important role in some wave modes for relatively large wavenumbers. The effects of the pressure, axial pre-stretch and fiber angle on the dispersion relations are displayed. These results provide the necessary validation for using the refined dynamic finite-strain shell theory and wave propagation to determine arterial properties.

Influence of diaphragm fragments on the flow in a conical shock tube

In experimental study of spherical shock waves in a conical shock tube, it was found that the amplitude of the shock wave turns out to be less than that calculated on the assumption of instantaneous removal of the diaphragm separating the high and low pressure chambers. To interpret the revealed effect, we analyzed the results of numerical modeling, taking into account the effect of diaphragm fragments on the formation and propagation of a shock wave.

Beam propagation of the 15‐degree equation and prestack depth migration in tilted transversely isotropic media using a ray‐centred coordinate system

ABSTRACTSeismic wave imaging in complex media requires an accurate wavefield simulation method that can accurately describethe wave propagation in realistic media. Reverse time‐depth migration is the preferred method for seismic wave imaging in complex media. Although it is relatively expensive, its imaging accuracy is usually better than migrations based on the ray method. Migration of primary reflection data requires a wave propagation simulation method that can accurately describe primary reflected/scattered wave energy and incorporate anisotropy. Accordingly, we propose the simulation of wave propagation in tilted transversely isotropic media using a 15° one‐way wave equation in a ray‐centred coordinate system, combining the flexibility of ray theory and the accuracy of wave theory. We use this equation to describe the propagation of body waves in a single ray tube, a ‘beam’. The wavefield along the beam, guided by its central raypath, has an angle limit defined only by the ray angle; therefore, wave propagation in complex and steeply dipping media can be simulated with a 15° one‐way wave equation. Numerical experiments show that the simulation results for beam propagation using the 15° equation in the ray‐centred coordinate system have good accuracy. For prestack depth migration in tilted transversely isotropic media, we built a beam imaging method using this propagator, and this migration method yielded accurate images with greater efficiency than reverse time‐depth migration.

On the compressible biglobal stability of the mean flow motion in porous tubes

In this work, a compressible biglobal stability approach is used to investigate the growth characteristics of hydrodynamic and vorticoacoustic waves in porous tubes with uniform wall injection. The retention of compressibility effects enables us to construct a physics-based formulation that is capable of predicting both hydrodynamic and vorticoacoustic wave motions simultaneously with no need for mode decomposition. At first, we show that, in the absence of a mean flow, the stability framework reproduces traditional Helmholtz frequencies and modal shapes. This confirms the embedment of the wave equation within the compressible Navier–Stokes framework. We then proceed to simulate the idealized motion in solid rocket motors, often modeled as porous tubes, where a mean flow expression is available. Specifically, using the compressible Taylor–Culick profile as a base flow, our solver produces a comprehensive frequency spectrum that returns both hydrodynamic and vorticoacoustic modes in one swoop with the added benefit of pinpointing the flow-induced longitudinal, radial, and mixed frequencies at user-prescribed tangential modes. Moreover, we find that increasing the flow Mach number leads to a slight reduction in the vorticoacoustic frequencies relative to their strictly acoustic counterparts. Similar results are obtained while increasing the Reynolds number and aspect ratio, thus affirming the origin of frequency shifts often observed in motor firings. Finally, the vorticoacoustic velocity fluctuations are shown to resemble those obtained asymptotically. Particularly, their depths of penetration appear to be controlled by the penetration number, a dimensionless parameter that combines the effects of sidewall injection, oscillatory frequency, viscosity, and chamber radius.

Exploring the underlying mechanism of acoustic radiation force on a sphere in a fluid-filled rigid tube

The propagation of sound waves in a fluid-filled rigid tube has potential application in acoustic particle-positioning, valuable reagent recovery, and noninvasive manipulation of targets. The interaction between sound waves and targets causes momentum transport, and the acoustic radiation force is motivated to move and rotate the targets. Generally, acoustic radiation force is related to sound scattering of the target. The relationship between acoustic radiation force and the scattering pattern will play a positive role in better explaining the phenomenon of and changed trend in acoustic radiation force acting on a particle in a tube and in predicting the acoustic control system in a tube. This paper studies the interactions between a plane sound wave and a sphere in a fluid-filled rigid tube and tries to explore the relationship between acoustic radiation force and the dimensionless complex scattering pattern. The spherical particle with different materials is studied for Rayleigh scattering and Mie-like scattering. Simulation results show that there is a certain relationship between the acoustic radiation force and the scattering pattern for a spherical particle. At the resonance frequency, which corresponds to the natural frequencies of the vibration of fluid filled in the cavity with the rigid wall, both acoustic radiation force and the backscattering form function show identical resonance characteristics. At Rayleigh scattering and Mie-like scattering regimes, when the backscattering is greater than the forward scattering, acoustic radiation forces show an increasing trend compared with the dimensional frequency. However, with the increase in dimensionless frequency, the acoustic radiation force does not respond to the forward scattering except the resonance positions in the transition region from Mie-like scattering regimes to the geometric scattering regimes. When a negative force occurs near the resonance position, the scattering in the back hemisphere is weaker than that of the front hemisphere. This study will help predict the various behaviors of radiation force using the measured backscattering echo and the forward scattering wave, and it can provide reference to the control of the acoustic manipulation system effectively and precisely.

Thermal Decomposition of 2-Methyltetrahydrofuran behind Reflected Shock Waves over the Temperature Range of 1179–1361 K

The thermal unimolecular decomposition of 2-methyltetrahydrofuran (2-MTHF) was studied behind reflected shock waves in a single-pulse shock tube over the temperature range of 1179-1361 K and pressure range of 9-17 atm. Methane, ethylene, ethane, 1,3-butadiene, propylene, acetaldehyde, and acetylene were identified as products in the decomposition of 2-MTHF. A reaction scheme was proposed to explain the mechanism for the observed products. The experimentally determined rate coefficients were best fit to an Arrhenius expression for the overall decomposition and is represented as ktotalexp(1179-1361 K) = (3.23 ± 0.59) × 1011 s-1 exp(-51.3 ± 1.4 kcal mol-1/RT). Quantum chemistry methods were used to calculate the energetics and kinetics of various possible unimolecular dissociation pathways involved in the thermal decomposition of 2-MTHF. The initial decomposition of 2-MTHF occurs predominantly via ring-methyl (C-CH3) single bond fission, leading to the formation of tetrahydrofuran (C4H7O) radical, and methyl radical was found to be the major reaction compared to all the possible initial bond fission, ring opening, and molecular elimination channels. The temperature-dependent rate coefficients for the unimolecular dissociation of 2-MTHF were calculated using the RRKM (Rice-Ramsperger-Kassel-Marcus) theory in combination with the CCSD(T)/cc-pVTZ//B3LYP/cc-pVTZ level of electronic structure calculations over the temperature range of 800-1500 K. The computed high-pressure limiting rate coefficients for the initial decomposition of 2-MTHF through C-CH3 single bond fission channel were found to be ∼2 times higher in the temperatures between 800 and 900 K, and above this temperature, they agree well with the values reported in the literature.

Research on detection technology of squeezed branch and disk pile under boulder geological condition

The detection methods of the cavity and cavity size and pile quality of squeezed branch and disk pile are not perfect. Based on the 65 pier of a viaduct in Zhongshan City, this paper uses caliper, cross hole acoustic wave method, core pulling method and tube wave method to detect the squeezed branch and disk pile, and compares and analyzes the advantages and disadvantages, applicable conditions and detection results of each method. It can be seen from the test results that both caliper and cross hole acoustic wave method can detect the length of squeezed branch pile, while core pulling method and tube wave method can detect the quality of pile body and the thickness of sediment at the bottom of pile. The test results are basically consistent and verified with each other, and the specific data such as the length of branch and the thickness of sediment are slightly different. In this paper, caliper, cross hole acoustic method, core pulling method and tube wave method are verified and analyzed to provide ideas and support for the later detection of squeezed branch and disk pile.

Mesoscopic kinetic approach for studying nonequilibrium hydrodynamic and thermodynamic effects of shock wave, contact discontinuity, and rarefaction wave in the unsteady shock tube.

This paper presents a detailed description of a molecular velocity distribution-based mesoscopic kinetic approach that enables a better understanding of various nonequilibrium hydrodynamic and thermodynamic effects in shock waves, contact discontinuities, and rarefaction waves. This builds on the mesoscopic kinetic approach in a previous investigation into regular reflection shocks by further addressing the mesoscopic physical meaning of kinetic moments from the view of kinetics and the implications of the magnitude and sign of nonequilibrium kinetic moments. To deepen understanding of nonequilibrium effects, this work focuses on the one-dimensional unsteady shock tube problem, which contains the typical and essential features of the discontinuous flows, and has no interference of two-dimensional flow direction. The approach uses a lattice Boltzmann method to solve the flow field, and describes nonequilibrium effects through the nonequilibrium kinetic moments of molecular velocity distribution functions. The mechanism of nonequilibrium effect in discontinuous flows is further probed. This work develops the mesoscopic kinetic approach and clarifies the mesoscopic physics of shock waves, contact discontinuities, and rarefaction waves.

Experimental and Numerical Study for the Representation of Standing Waves in a Kundt's Tube

The study of the behavior of a standing wave inside a resonant cavity, such as a closed tube, has always been of great revelation in the manufacture of wind musical instruments, in addition to research carried out on the transfer and absorption of heat, energy and pressure for the acoustic characterization of materials by injecting sound waves at one end of the Kundt’s tube. In this work, we did the implementation of two experiments for measure the speed of sound, using a Kundt’s tube where also we obtained the bellies and nodes of the sound wave and we verified with a computational code that was written for us in Python, in which we made simulation of the temporal evolution was achieved of the wave that vibrated inside the tube. Also, we show the wave profile for the first four harmonics with computational simulations and we presented the experimental results by two different methods, these were compared with the obtained using the equations modeled by the undulatory theory of physics. Finally, we show in this article, the respective errors obtained from these two experimental configurations, which were made with the purpose of showing university students the importance of being able to visualize the wave phenomenon of sound inside a Kundt’s tube.

Fluid resonance in elastic-walled englacial transport networks

AbstractEnglacial water transport is an integral part of the glacial hydrologic system, yet the geometry of englacial structures remains largely unknown. In this study, we explore the excitation of fluid resonance by small amplitude waves as a probe of englacial geometry. We model a hydraulic network consisting of one or more tabular cracks that intersect a cylindrical conduit, subject to oscillatory wave motion initiated at the water surface. Resulting resonant frequencies and quality factors are diagnostic of fluid properties and geometry of the englacial system. For a single crack–conduit system, the fundamental mode involves gravity-driven fluid sloshing between the conduit and the crack, at frequencies between 0.02 and 10 Hz for typical glacial parameters. Higher frequency modes include dispersive Krauklis waves generated within the crack and tube waves in the conduit. But we find that crack lengths are often well constrained by fundamental mode frequency and damping rate alone for settings that include alpine glaciers and ice sheets. Branching crack geometry and dip, ice thickness and source excitation function help define limits of crack detectability for this mode. In general, we suggest that identification of eigenmodes associated with wave motion in time series data may provide a pathway toward inferring englacial hydrologic structures.