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1
HoIe, S. "Recent developments in the pressure wave propagation method". IEEE Electrical Insulation Magazine 25, n. 3 (maggio 2009): 7–20. http://dx.doi.org/10.1109/mei.2009.4976898.
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Miyazaki, Yusuke, Jon Farmer, Miki Morimatsu, Shota Ito, Séan Mitchell e Paul Sherratt. "Brain Pressure Wave Propagation during Baseball Impact". Proceedings 49, n. 1 (15 giugno 2020): 149. http://dx.doi.org/10.3390/proceedings2020049149.
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Tommasin, Caenen, Verhegghe, Greenwald e Segers. "Physics of Within-Tissue Wave Propagation Generated by Pulse Propagation in the Carotid Artery". Applied Sciences 9, n. 14 (18 luglio 2019): 2878. http://dx.doi.org/10.3390/app9142878.
Testo completoAbstract (sommario):
(1) Background: We aimed to assess the validity of laser Doppler vibrometry (LDV) as an emerging method to measure the local pulse wave velocity (PWV) from skin displacement generated by the pressure pulse inside an underlying artery. (2) Methods: A finite element model representing a simplified common carotid artery embedded within a soft tissue mimicking material was used to reproduce how tissue motions due to a wave propagation along the artery radiates to the skin surface. A parametric study was set up, varying: (i) the pressure conditions inside the artery (shock and traveling pressure impulse), (ii) the arterial depth and (iii) the geometry in a patient-specific artery model. (3) Results: under all conditions, the arterial pulse induced primary and secondary waves at the skin surface; of which the propagation speed deviated from the imposed PWV (deviations between −5.0% to 47.0% for the primary wave front). (4) Conclusions: the propagation of a short pressure impulse induced complex skin displacement patterns revealing a complicated link between PWV and measured propagation speeds at the skin surface. Wave propagation at the skin level may convey information about arterial PWV, however, advanced signal analysis techniques will be necessary to extract local PWV values.
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Zhang, Xiu Hua, e Yan Yan Wu. "Numerical Analysis of Shock Wave Propagation Law of Internal Gas Explosion". Applied Mechanics and Materials 105-107 (settembre 2011): 299–302. http://dx.doi.org/10.4028/www.scientific.net/amm.105-107.299.
Testo completoAbstract (sommario):
The purpose of this paper is to research on shock wave propagation law of internal gas explosion. The multi-material Eulerian and Lagrangian coupling algorithm was adopt. Using ANSYS/LS-DYNA dynamic analysis software to build frame structure, air and gas explosion models. Multiple ALE elements for simulating air and gas explosion material the analysis of blast shock wave propagation in a three-story steel frame structure and the characteristics of explosion pressure using fluid-structure coupling method are carried out. The conclusions show that fluid-structure coupling method can well simulated shock wave propagation of internal gas explosion, and the pressure peak of blast shock wave increased with the increasing of the blast air initial energy. Locality is the characteristic of explosion pressure in sealed space, and the pressure pass weakly when it propagates in solid.
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William-Louis, M. J. P., e C. Tournier. "Calculation of Pressure Wave Propagation Through a Tube Junction". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 210, n. 3 (maggio 1996): 239–44. http://dx.doi.org/10.1243/pime_proc_1996_210_193_02.
Testo completoAbstract (sommario):
This paper describes a new method for the calculation of pressure wave propagation through a junction. The unsteady model, valid for subsonic flow, takes into account the fluid compressibility and pressure losses according to the type of junction. A new method called the ‘branch superposition method’ is used for the numerical calculation, and consists of uncoupling the system of governing equations. During the propagation of pressure waves through a three-tube junction, two branches are inlet or outlet. Therefore, to uncouple the system, one of the two branches with incoming flow is modelled as a source or one of the two branches with outgoing flow as a sink. This method, combined with the method of characteristics, gives the possibility of predicting the propagation of pressure waves through a junction, where the fluid may be initially at rest or not. The model is validated by a comparison with experimental results.
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Wei, Kang, Yuangui Mei, Qi Sun e Xiao Hu. "Propagation Characteristics of Initial Compression Wave Induced by 400 km/h High-Speed Trains Passing through Very Long Tunnels". Applied Sciences 14, n. 13 (8 luglio 2024): 5946. http://dx.doi.org/10.3390/app14135946.
Testo completoAbstract (sommario):
When high-speed trains enter tunnels, an initial compression wave is generated. As the compression wave propagates at the local speed of sound to the tunnel exit, it radiates into the surrounding environment, forming micro-pressure waves (MPWs). MPWs create sonic booms, resulting in significant environmental issues. The magnitude of the micro-pressure waves is directly proportional to the pressure gradient of the compression wave at the tunnel exit. The nonlinear effects of the initial compression wave during propagation lead to a significant increase in pressure gradient. Therefore, the propagation characteristics of the initial compression wave during the tunnel are the crucial factor affecting the amplitude of MPWs. Based on the one-dimensional compressible unsteady non-isentropic flow model and the improved generalized Riemann variable characteristic method, this paper researched the propagation and evolution characteristics of an initial compression wave generated when 400 km/h high-speed trains enter tunnels with three portal shapes: (no tunnel entrance hood (no hood), an oblique, enlarged tunnel entrance hood (type A), an enlarged equal-section non-uniform opening hole tunnel entrance hood (type B)). The results show that when the initial compression wave propagates inside very long tunnels, the pressure gradient of the compression wave exhibits a trend of initially increasing and then decreasing with the increase in propagation distance. When the pressure gradient of the compression wave reaches its maximum value, the corresponding propagation distance is the steepening critical distance. For no tunnel entrance hoods, type A tunnel entrance hoods, and type B tunnel entrance hoods, the steepening critical distances are 5 km, 6 km, and 16 km, respectively. The steepening critical distance shortens with increasing train speed. Steady friction and unsteady friction effects mainly affect the pressure amplitude and pressure gradient during compression wave propagation, respectively. At lower ambient temperatures, the nonlinear effects in compression wave propagation are significantly enhanced. The mitigation effects of type A tunnel entrance hoods and type B tunnel entrance hoods on pressure gradient reduction are mainly concentrated within 4 km and 12 km, respectively. It is necessary to determine the optimal matching relationship between the tunnel entrance hood and tunnel length based on the characteristics of compression wave propagation to ensure their mitigating performance is maximized.
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Sun, Yali, Feihu Zheng, Zhenlian An, Yewen Zhang, Stephane Hole, Zhien Zhu, Liming Yang et al. "Pressure wave propagation method for space charge measurement in coaxial geometry". IEEE Transactions on Dielectrics and Electrical Insulation 25, n. 6 (dicembre 2018): 2139–46. http://dx.doi.org/10.1109/tdei.2018.007234.
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Yang, Jun, Junhua He, Dezhi Zhang, Haibin Xu, Guokai Shi, Min Zhang, Wenxiang Liu e Yang Zhang. "Local Phase-Amplitude Joint Correction for Free Surface Velocity of Hopkinson Pressure Bar". Applied Sciences 10, n. 15 (4 agosto 2020): 5390. http://dx.doi.org/10.3390/app10155390.
Testo completoAbstract (sommario):
The Hopkinson pressure bar is widely used to measure the reflected pressure of blast waves over a short distance. However, dispersion effects will occur when the elastic stress waves propagate in the pressure bar due to lateral inertia, and there will be errors between the signals obtained from the sensors and the actual loading. For the free surface velocity measured in our system, we developed a local phase-amplitude joint correction method to convert the measured velocity into the average reflected pressure of a shock wave at the impact end of the bar, considering factors such as propagation modes of the elastic wave, the frequency components’ time of arrival, velocity variation over the bar axis, and the stress–velocity relationship. Firstly, the Pochhammer–Chree frequency equation is calculated numerically, and the first to fourth orders of phase velocity, group velocity, normalized frequency, and propagation time curves of elastic wave propagation in 35CrMnSiA steel are obtained. Secondly, the phase and amplitude correction formulas for calculating average reflected pressure from center velocity are derived based on the propagation mode of the axial elastic wave in the pressure bar by analyzing the time-frequency combined spectrum obtained by short-time Fourier transform. Thirdly, a local phase-amplitude joint correction algorithm based on propagation mode is proposed in detail. The experimental tests and data analyses are carried out for eight sets of pressure bar. The results show that this method can identify the propagation mode of elastic waves in the bar intuitively and clearly. The first three orders of propagation modes are stimulated in the bar 04, while only the first order of propagation is stimulated in the other eight bars. The local phase-amplitude joint correction algorithm can avoid correcting the component of the non-axial elastic wave. The rising edge of the average stress curve on the impact surface of bar 01 and bar 04 is corrected from 4.13 μs and 4.09 μs to 2.70 μs, respectively.
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Akkas, N., e F. Erdogan. "The Residual Variable Method Applied to Acoustic Wave Propagation from a Spherical Surface". Journal of Vibration and Acoustics 115, n. 1 (1 gennaio 1993): 75–80. http://dx.doi.org/10.1115/1.2930318.
Testo completoAbstract (sommario):
The classical wave equation in spherical coordinates is expressed in terms of a residual potential applying the Residual Variable Method. This method essentially eliminates the second derivative of the potential with respect to the radial coordinate from the wave equation. Thus, the dynamic pressure distribution on the surface of a spherical cavity can be studied by considering the cavity surface only. Moreover, the Residual Variable Method, being amenable to “marching” solutions in a finite-difference implementation, is very suitable for the analysis of acoustic wave propagation into the finite medium from the cavity surface. The propagation of the wave from the internal surface can be followed numerically. There is no need to discretize the infinite domain in its entirety at all. The propagation analysis can be terminated at any point in the radial direction without having to consider the rest.
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Shatalova, N., T. Apasov, Al Shatalov e B. Grigoriev. "Renovation method of restoring well productivity using wavefields". Journal of Mining Institute 258 (30 dicembre 2022): 986–97. http://dx.doi.org/10.31897/pmi.2022.108.
Testo completoAbstract (sommario):
A stagewise theoretical substantiation of the renovation vibrowave method of influencing the near-wellbore zone of reservoir for restoring well productivity is presented. The area of treatment by the proposed method covers the reservoir with a heterogeneous permeability with fractures formed by fracking. In this method a decrease in concentration of colmatants occurs due to a change in direction of contaminants migration. Under the influence of pressure pulses, they move deep into the reservoir and disperse through the proppant pack. The results of mathematical modelling of the propagation of pressure wave and velocity wave and the calculations of particles entrainment in wave motion are presented.
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CHANDRA, R., e S. SINGH. "Propagation of Laser Generated Shock Waves through Heterogeneous Metallic Mediums". Journal of Ultra Scientist of Physical Sciences Section B 36, n. 3 (24 giugno 2024): 19–27. http://dx.doi.org/10.22147/jusps-b/360301.
Testo completoAbstract (sommario):
This paper deals with an analytical study of shock waves propagating in heterogeneous metallic mediums. A shock wave travels through most media at a speed higher than ordinary wave. The propagation of a shock wave created by a laser impact over a metallic surface is considered here. In the process of Shock wave generation, a high-pressure surface level is reached using a nanosecond laser pulse that heats the surface of the material and generates adense plasma expansion. The pressure reaches few GPa so that shockwaves are generated and propagated in the bulk of the material. Whitham method, a powerful analytical method for shock waves, has been employed to obtain the analytical relations for shock velocity, shock strength and pressure behind the freely propagating shock. Numerical calculations have been performed for shock velocity, shock strength, pressure, adiabatic sound velocity, and compression behind the shock () and their variation with propagation distance have been discussed. A sharp decrease in shock velocity and pressure behind the shock whereas a steadily increasing shock strength with propagation distance has been observed. Particle velocity, adiabatic sound velocity and compression parameter also show a gradual decrease as the shock advances in the medium. Effect of overtaking disturbances has been evaluated by considering Yadav’s approach.
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Zhang, Gang. "Experimental Study on Shock Wave Propagation of the Explosion in a Pipe with Holes by High-Speed Schlieren Method". Shock and Vibration 2020 (12 settembre 2020): 1–9. http://dx.doi.org/10.1155/2020/8850443.
Testo completoAbstract (sommario):
The shock wave propagation of the explosion in a pipe with holes was studied by a high-speed schlieren experimental system. In the experiments, schlieren images in the explosion were recorded by a high-speed camera from parallel and perpendicular orientations, respectively, and the pressure in the air was measured by an overpressure test system. In parallel orientation, it is observed that the steel pipe blocks the propagation of blast gases, but it allows the propagation of shock waves with a symmetrical shape. In perpendicular orientation, oblique shock wave fronts were observed, indicating the propagation of explosion detonation along the charge. Shock wave velocity in the hole direction is larger than that in the nonhole direction, indicating the function of holes in controlling blast energy, that is, leading blast energy to hole direction. Furthermore, the function of holes is verified by overpressure measurements in which peak overpressure in the hole direction is 0.87 KPa, 2.8 times larger than that in the nonhole direction. Finally, the variation of pressure around the explosion in a pipe with holes was analyzed by numerical simulation, qualitatively agreeing with high-speed schlieren experiments.
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Tanaka, A., M. Maeda e T. Takada. "Observation of charge behavior in organic photoconductor using pressure-wave propagation method". IEEE Transactions on Electrical Insulation 27, n. 3 (giugno 1992): 440–44. http://dx.doi.org/10.1109/14.142704.
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Leontyeva, I. V., I. A. Kovalev, M. A. Shkolnikova, Yu S. Isayeva, A. N. Putintsev, E. N. Dudinskaya, O. N. Tkacheva e L. V. Machekhina. "Early diagnosis of increased stiffness of great vessels in adolescents with functional pathology of vegetative genesis". Rossiyskiy Vestnik Perinatologii i Pediatrii (Russian Bulletin of Perinatology and Pediatrics) 66, n. 3 (1 luglio 2021): 52–61. http://dx.doi.org/10.21508/1027-4065-2021-66-3-52-61.
Testo completoAbstract (sommario):
40 adolescents aged 15–17 years with functional cardiovascular pathology of vegetative origin underwent a 24-hour blood pressure monitoring (using the oscillometric method BPLabVasotens, Peter Telegin LLC, Nizhny Novgorod) with an assessment of central blood pressure parameters and rigidity of the main arteries.The scientists found significantly higher values of central systolic pressure during the day and night hours in the group of adolescents with arterial hypertension (n=13) compared to adolescents with normal blood pressure (n=27). They determined significantly higher values of the pulse wave velocity both during 24 hours and in the day and night hours in the group with arterial hypertension compared to the group of adolescents with normal blood pressure. No differences were found in the parameters of the propagation time of the reflected pulse wave and the augmentation index. The time of the reflected pulse wave propagation was significantly lower at nighttime compared to the daytime. In the group with arterial hypertension, the rate of pulse wave propagation in the aorta correlated only with the values of diastolic pressure over 24 hours and diastolic pressure in the daytime. In the adolescents with normal blood pressure, the pulse wave velocity correlated with systolic and pulse blood pressure. The augmentation index in the group of adolescents with arterial hypertension correlated with diastolic pressure, in contrast to the group of adolescents with normal blood pressure, where such a correlation was not detected.
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Li, Zhan Hui, Yun Xin Wu e Zhi Li Long. "Effect of Contact Interface Pressure on Higher-Order Harmonic Wave and Bond Strength". Advanced Materials Research 148-149 (ottobre 2010): 36–39. http://dx.doi.org/10.4028/www.scientific.net/amr.148-149.36.
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The model of ultrasonic propagation at a solid-solid contact interface was established. Higher-order harmonic wave generation and waveform distortion take place when the ultrasonic wave propagation at the solid-solid contact interface. Aluminum wire bond experiments were performed on a laboratory test bench. The relation of bond strength, nonlinear coefficient and contact interface pressure was studied. The experiment results show that when contact interface pressure is less than 6 kPa, higher-order harmonic wave component and the nonlinear coefficient decrease and bond strength increases with contact interface pressure increasing, when contact interface pressure is in range of 6 kPa to 10 kPa, higher harmonic wave and the nonlinear coefficient is the least and bond strength is the highest, however, when contact interface pressure is more than 10 kPa, the nonlinear coefficient increases and bond strength decreases with pressure increasing. The nonlinear coefficient of ultrasonic is a method of forecast bond strength.
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Butt, Hafiz Sana Ullah, e Pu Xue. "Wave Dispersion and Attenuation in Viscoelastic Split Hopkinson Pressure Bar". Key Engineering Materials 535-536 (gennaio 2013): 547–50. http://dx.doi.org/10.4028/www.scientific.net/kem.535-536.547.
Testo completoAbstract (sommario):
The Split Hopkinson Pressure Bar (SHPB) is most commonly used facility to obtain material properties at high strain rates. Testing of soft materials using this method requires that bars made of low impedance material should be used, in order to improve signal-to-noise ratio of transmitted stress. However, utilization of such bars poses some difficulties in data processing as the wave dispersion and attenuation becomes noticeable due to their viscoelastic nature. Wave propagation coefficients of a viscoelastic pressure bar are evaluated using incident and reflected strain waves generated through impact of two different length striker bars. Two approaches are proposed for propagation coefficient measurement in this study, namely direct and waves-overlap. Using two approaches, it is found that the calculated attenuation coefficients are same, while the wave numbers are different. The difference in wave number in the case of two approaches is due to the difference in calculated phase change of incident and reflected waves, which is found as integer multiple of 2Π. Moreover, propagation coefficients calculated through different striker impacts are found different. The propagation coefficient found through long striker impact, when used for propagation response prediction of waves generated by short striker impact, resulted in high oscillations in predicted waves.
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Zhang, Yongjian, Peng Peng, Tao Lin, Aiwei Lou, Dahai Li e Changan Di. "Research on the Shock Wave Overpressure Peak Measurement Method Based on Equilateral Ternary Array". Sensors 24, n. 6 (14 marzo 2024): 1860. http://dx.doi.org/10.3390/s24061860.
Testo completoAbstract (sommario):
The measurement process of ground shock wave overpressure is influenced by complex field conditions, leading to notable errors in peak measurements. This study introduces a novel pressure measurement model that utilizes the Rankine−Hugoniot relation and an equilateral ternary array. The research delves into examining the influence of three key parameters (array size, shock wave incidence angle, and velocity) on the precision of pressure measurement through detailed simulations. The accuracy is compared with that of a dual-sensor array under the same conditions. Static explosion tests were conducted using bare charges of 0.3 kg and 3 kg TNT to verify the numerical simulation results. The findings indicate that the equilateral ternary array shock wave pressure measurement method demonstrates a strong anti-interference capability. It effectively reduces the peak overpressure error measured directly by the shock wave pressure sensor from 17.73% to 1.25% in the test environment. Furthermore, this method allows for velocity-based measurement of shock wave overpressure peaks in all propagation direction, with a maximum measurement error of 3.59% for shock wave overpressure peaks ≤ 9.08 MPa.
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Hou, Qingmin, Liang Ren, Wenling Jiao, Pinghua Zou e Gangbing Song. "An Improved Negative Pressure Wave Method for Natural Gas Pipeline Leak Location Using FBG Based Strain Sensor and Wavelet Transform". Mathematical Problems in Engineering 2013 (2013): 1–8. http://dx.doi.org/10.1155/2013/278794.
Testo completoAbstract (sommario):
Methods that more quickly locate leakages in natural gas pipelines are urgently required. In this paper, an improved negative pressure wave method based on FBG based strain sensors and wavelet analysis is proposed. This method takes into account the variation in the negative pressure wave propagation velocity and the gas velocity variation, uses the traditional leak location formula, and employs Compound Simpson and Dichotomy Searching for solving this formula. In addition, a FBG based strain sensor instead of a traditional pressure sensor was developed for detecting the negative pressure wave signal produced by leakage. Unlike traditional sensors, FBG sensors can be installed anywhere along the pipeline, thus leading to high positioning accuracy through more frequent installment of the sensors. Finally, a wavelet transform method was employed to locate the pressure drop points within the FBG signals. Experiment results show good positioning accuracy for natural gas pipeline leakage, using this new method.
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Zienkiewicz, Aleksandra, Michelle Favre, Hany Ferdinando, Stephanie Iring, Jorge Serrador e Teemu Myllylä. "Blood pressure wave propagation—a multisensor setup for cerebral autoregulation studies". Physiological Measurement 42, n. 11 (1 novembre 2021): 115007. http://dx.doi.org/10.1088/1361-6579/ac3629.
Testo completoAbstract (sommario):
Abstract Objective. Cerebral autoregulation is critically important to maintain proper brain perfusion and supply the brain with oxygenated blood. Non-invasive measures of blood pressure (BP) are critical in assessing cerebral autoregulation. Wave propagation velocity may be a useful technique to estimate BP but the effect of the location of the sensors on the readings has not been thoroughly examined. In this paper, we were interested in studying whether the propagation velocity of a pressure wave in the direction from the heart to the brain may differ compared with propagation from the heart to the periphery, as well as across different physiological tasks and/or health conditions. Using non-invasive sensors simultaneously placed at different locations of the human body allows for the study of how the propagation velocity of the pressure wave, based on pulse transit time (PTT), varies across different directions. Approach. We present a multi-sensor BP wave propagation measurement setup intended for cerebral autoregulation studies. The presented sensor setup consists of three sensors, one placed on each of the neck, chest and finger, allowing simultaneous measurement of changes in BP propagation velocity towards the brain and to the periphery. We show how commonly tested physiological tasks affect the relative changes of PTT and correlations with BP. Main results. We observed that during maximal blow, valsalva and breath hold breathing tasks, the relative changes of PTT were higher when PTT was measured in the direction from the heart to the brain than from the heart to the peripherals. In contrast, during a deep breathing task, the relative change in PTT from the heart to the brain was lower. In addition, we present a short literature review of the PTT methods used in brain research. Significance. These preliminary data suggest that the physiological task and direction of PTT measurement may affect relative PTT changes. The presented three-sensor setup provides an easy and neuroimaging compatible method for cerebral autoregulation studies by allowing measurement of BP wave propagation velocity towards the brain versus towards the periphery.
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Qiu, Xiao, Jue Ding, Zhong Jie Wang e Pei Feng Weng. "The Similarity Law of Internal-Blast Wave Propagation in the Concrete". Advanced Materials Research 1065-1069 (dicembre 2014): 1143–46. http://dx.doi.org/10.4028/www.scientific.net/amr.1065-1069.1143.
Testo completoAbstract (sommario):
Concrete mechanical properties under dynamic load such as blast and impact are very complex. Shock wave propagation law and damage effect in the concrete were studied numerically in the paper by using TNT explosive ignition and growth model, concrete dynamic damage model, and SPH method. And shock wave properties of different mass explosives in the concrete were analyzed with the similarity theory. The result shows that TNT shock wave propagation law meets the internal-blast similarity law. Peak pressure, positive pressure impulse, maximum velocity and maximum acceleration in the concrete decrease with the increase of scaled distance. And time needed for reaching peak pressure increases linearly with the increase of scaled distance. A theoretical basis of structure and protection design for constructions is achieved in the paper.
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Zhang, Haotian, Linjian Ma, Zongmu Luo e Ning Zhang. "Wave Attenuation and Dispersion in a 6 mm Diameter Viscoelastic Split Hopkinson Pressure Bar and Its Correction Method". Shock and Vibration 2020 (16 novembre 2020): 1–10. http://dx.doi.org/10.1155/2020/8888445.
Testo completoAbstract (sommario):
The propagation characteristics of viscoelastic waves have been investigated with a 6 mm diameter split Hopkinson pressure bar (SHPB) made of polymethyl methacrylate (PMMA). The strain signals in SHPB tests were improved by the pulse shaping technique. Based on the experimentally determined propagation coefficients, the amplitude attenuation and wave dispersion induced by viscoelastic effects at different impact velocities were quantitatively analyzed. The results indicate that the high-frequency harmonics attenuate faster in a higher phase velocity. With an increase in the impact velocity, the amplitude attenuation of the viscoelastic wave changes slightly during propagation, while the waveform dispersion gradually intensifies. A feasible method by waveform prediction was proposed to verify the validity and applicability of the propagation coefficient. The results indicate that the strain obtained from the small diameter viscoelastic SHPB can be effectively modified by utilizing the propagation coefficient. Furthermore, it is preferred to adopt the propagation coefficient obtained at low impact velocity for correction when the impact velocity varies. Moreover, the PMMA-steel bar impact test was performed to further illustrate the accuracy of the propagation coefficient and the effectiveness of the correction method.
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Nurprasetio, Ignatius Pulung, Bentang Arief Budiman, Farid Triawan e Muhammad Hafid. "Measurement of pressure wave speed in stainless-steel pipe generated by water hammer". MATEC Web of Conferences 197 (2018): 08020. http://dx.doi.org/10.1051/matecconf/201819708020.
Testo completoAbstract (sommario):
This paper aims to demonstrate a measurement method of pressure wave speed in stainless-steel pipe filled with water caused by water hammer phenomenon. The pressure wave is generated using a self-developed drop impact testing equipment. An impactor is dropped to collide a buffer which then induces the water hammer phenomenon. The generated pressure and its propagation speed in the water are carefully measured here. Pressure measurement is conducted by a pressure transducer, while pressure wave speed is measured by two methods, which utilize peak time of the pressure recorded by pressure transducer and peak time of strains recorded by two strain gages positioned in a different location. These strain gages are oriented to the circumferential direction of the pipe. Measurement result shows that at 1.5 m height, impact pressure of between 0.86 to 1.16 MPa and wave velocity of 1250 m/s were obtained. From the experimental results, the characteristic of pressure wave in the water was able to be observed.
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Resch, Janelle, Lilia Krivodonova e John Vanderkooy. "A Two-Dimensional Study of Finite Amplitude Sound Waves in a Trumpet Using the Discontinuous Galerkin Method". Journal of Computational Acoustics 22, n. 03 (16 luglio 2014): 1450007. http://dx.doi.org/10.1142/s0218396x14500076.
Testo completoAbstract (sommario):
A model for nonlinear sound wave propagation for the trumpet is proposed. Experiments have been carried out to measure the sound pressure waveforms of the [Formula: see text] and [Formula: see text] notes played forte. We use these pressure measurements at the mouthpiece as an input for the proposed model. The compressible Euler equations are used to incorporate nonlinear wave propagation and compressibility effects. The equations of motion are solved using the discontinuous Galerkin method (DGM) and the suitability of this method is assessed. The third spatial dimension is neglected and the consequences for such an assumption are examined. The numerical experiments demonstrate the validity of this approach. We obtain a good match between experimental and numerical data after the dimensionality of the problem is taken into account.
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Cheng, Z. Q., J. R. Crandall e W. D. Pilkey. "Wave Dispersion and Attenuation in Viscoelastic Split Hopkinson Pressure Bar". Shock and Vibration 5, n. 5-6 (1998): 307–15. http://dx.doi.org/10.1155/1998/906291.
Testo completoAbstract (sommario):
A viscoelastic split Hopkinson pressure bar intended for testing soft materials with low acoustic impedance is studied. Using one-dimensional linear viscoelastic wave propagation theory, the basic equations have been established for the determination of the stress—strain—strain rate relationship for the tested material. A method, based on the spectral analysis of wave motion and using measured wave signals along the split Hopkinson pressure bar, is developed for the correction of the dispersion and attenuation of viscoelastic waves. Computational simulations are performed to show the feasibility of the method.
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Xu, Min, Melad Olaimat, Tao Tang, Omar M. Ramahi, Maged Aldhaeebi, Zhu Jin e Ming Zhu. "Numerical Modeling of the Radio Wave Over-the-Horizon Propagation in the Troposphere". Atmosphere 13, n. 8 (27 luglio 2022): 1184. http://dx.doi.org/10.3390/atmos13081184.
Testo completoAbstract (sommario):
Using atmospheric data, which include pressure, temperature, relative humidity and water vapor pressure, the actual refractive index of a specific segment of the atmosphere has been modeled. Based on the refractive index, a numerical method is presented to quickly estimate the propagation path of the radio wave in the troposphere. Utilizing the terrain and the surface medium model of the propagation area and the parabolic equation (PE) method, an image of the electric field distribution of radio waves in the troposphere is obtained. A comparison of propagation paths between the numerical method and the PE model is presented. Additionally, the effects of the antenna’s elevation angle have been studied. Physical measurements provide a reference for the accuracy of the simulation results obtained using the method presented in this work.
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Chen, Jiangping, Weijun Tao, Shi Huan e Chong Xu. "Data processing of wave propagation in viscoelastic split Hopkinson pressure bar". AIP Advances 12, n. 4 (1 aprile 2022): 045210. http://dx.doi.org/10.1063/5.0083888.
Testo completoAbstract (sommario):
In this study, the polymethyl methacrylate (PMMA) bar was taken as an example to study the data processing of the viscoelastic Split Hopkinson pressure bar (SHPB) during shock wave propagation. First, SHPB tests of the PMMA bar were conducted, and the strain data measured at the position of the strain gauges on the viscoelastic PMMA bar were processed by using the improved Lagrange analysis method (LAM) to obtain the full-field strain, particle velocity, and stress data. Then, the Zhu–Wang–Tang dynamic viscoelastic constitutive model was adopted, and the parameters were calibrated to determine the dynamic constitutive equation of the PMMA bar. By combining the characteristics method and the dynamic constitutive equation, numerical simulation was conducted to obtain the physical quantity data at each point on the PMMA bar, so as to realize the closed-loop test. By comparing the data obtained by the improved LAM with the data obtained by the characteristics method, it was found that the improved LAM can improve the calculation accuracy at the later loading stage and was more consistent with the actual situation, and the validity of data processing and the applicability of the dynamic constitutive equation at the early loading stage were verified as well. The improved LAM can be extended to the propagation calculation of the attenuation wave in SHPB tests of soft materials or low density materials.
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Zhu, X., W. B. Ye, T. Y. Li e C. Chen. "The elastic critical pressure prediction of submerged cylindrical shell using wave propagation method". Ocean Engineering 58 (gennaio 2013): 22–26. http://dx.doi.org/10.1016/j.oceaneng.2012.09.008.
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Qiu, Hua, Zheng Su e Cha Xiong. "Experimental investigation on multi-cycle two-phase spiral pulse detonation tube of two configurations". Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 233, n. 11 (4 dicembre 2018): 4166–75. http://dx.doi.org/10.1177/0954410018817455.
Testo completoAbstract (sommario):
The spiral tube structure is an effective method to shorten the axial length of the pulse detonation chamber. In this article, spiral pulsed detonation tube with two kinds of spiral configuration was experimentally investigated. Liquid gasoline and air were used as fuel and oxidant, respectively, and equivalence ratios were controlled to about 1.0. Based on the transient pressure along the tube, the propagation characteristics of the pressure waves in the multi-cycle spiral pulsed detonation tubes, such as pressure peaks, wave velocities and propagation process, were analyzed. Results showed that propagation of double compression waves was the common feature during the process of deflagration to detonation transition in the presented spiral tubes, and the onset of detonation was initiated by a local explosion in the second compression wave. The deflagration to detonation transition characteristics with detonation initiation and combustion characteristics without initiation in the spiral sections were both related to the dimensionless distance. Propagation characteristics of the pressure waves were influenced by the use of different spiral configuration. And some interesting phenomena were also found.
29
Zhou, Changlong, Yingjun Li, Guicong Wang e Xue Yang. "Array model of shock pressure sensor for shooting point detection". MATEC Web of Conferences 355 (2022): 01027. http://dx.doi.org/10.1051/matecconf/202235501027.
Testo completoAbstract (sommario):
The array model of double-T shock pressure sensor is established. Shock wave is produced by a supersonic object in the air. Pressure is produced in the process of shock wave transmission. Different shock pressure sensors have different time to receive the pressure signal. In this paper, the shooting point calculation model and the finite element model of the double T-shaped array method are established. The simulation experiment is carried out. The law of shock wave propagation is verified. The model can be used to calculate the coordinates of shooting point quickly. This method is suitable for small angle oblique fire location problem, and improves the detection accuracy of shooting point.
30
Pan, Jiajia, e Hung Tao Shen. "Tsunami Intrusion and River Ice Movement". Water 11, n. 6 (20 giugno 2019): 1290. http://dx.doi.org/10.3390/w11061290.
Testo completoAbstract (sommario):
A two-dimensional wave model coupled with ice dynamics is developed to evaluate ice effects on shallow water wave propagation on a beach and in a channel. The nonlinear Boussinesq equations with ice effects are derived and solved by the hybrid technique of the Godunov-type finite volume method and finite difference method with the third-order Runge–Kutta method for time integration. The shock capturing method enables the model to simulate complex flows over irregular topography. The model is capable of simulating wave propagations accurately, including non-hydrostatic water pressure and wave dispersions. The ice dynamic module utilizes a Lagrangian discrete parcel method, based on smoothed particle hydrodynamics. The Boussinesq wave model is validated with an analytical solution of water surface oscillation in a parabolic container, an analytical solitary wave propagation in a flat channel, and experimental data on tsunami wave propagations. The validated model is then applied to investigate the interaction between ice and tsunami wave propagation, in terms of ice attenuation on tsunami wave propagations over a beach, ice deposition on the beach driven by the tsunami wave, and ice jam formation and release in a coastal channel with the intrusion of the tsunami wave. The simulated results demonstrated the interactions between tsunami waves and surface ice, including the maximum run up, ice movement along the beach, and ice jamming in a channel.
31
Liu, Xinying, e David F. Fletcher. "Verification of fluid-structure interaction modelling for wave propagation in fluid-filled elastic tubes". Journal of Algorithms & Computational Technology 17 (gennaio 2023): 174830262311597. http://dx.doi.org/10.1177/17483026231159793.
Testo completoAbstract (sommario):
This paper presents a verification study of wave propagation in fluid-filled elastic tubes using a coupled numerical simulation method by comparing the simulation results with analytical solutions. A three-dimensional fluid-structure interaction numerical model is built using Ansys software. Wave propagation is investigated by applying a pressure pulse at the inlet of a fluid-filled elastic tube. The speed of the pressure wave and the radial displacement of the tube are simulated and compared with theoretical values. Simulation results yield a high level of accuracy. Different structural elements are used to represent the tube, and their impact on the results is discussed. The effects of tube material, tube constraints and fluid properties are also investigated in this study.
32
Zheng, Zhixia, Limei Bai e Shaoquan Li. "Blood Pressure Model Based on Hybrid Feature Convolution Neural Network in Promoting Rehabilitation of Patients with Hypertensive Intracerebral Hemorrhage". Computational and Mathematical Methods in Medicine 2021 (7 dicembre 2021): 1–8. http://dx.doi.org/10.1155/2021/1980408.
Testo completoAbstract (sommario):
Objective. Accurate prediction of the rise of blood pressure is essential for the hypertensive intracerebral hemorrhage. This study uses the hybrid feature convolution neural network to establish the blood pressure model instead of the traditional method of pulse waves. Methods. The pulse waves of 100 patients were collected, and the pulse wave was decomposed into three bell wave compound forms to obtain the accurate pulse wave propagation time. Then, the mixed feature convolution neural network model ABP-net was proposed, which combined the pulse wave propagation time characteristics with the pulse wave waveform characteristics automatically extracted by one-dimensional convolution to predict the arterial blood pressure. Finally, according to the prediction results, 20 patients were treated before the high blood pressure appeared (model group), and another 20 patients with a daily fixed treatment scheme were selected as the control group. Results. In 80 training sets, compared with linear regression and the random forest method, the hybrid feature convolution neural network has higher accuracy in predicting blood pressure. In 20 test sets, the blood pressure error was eliminated within 5 mmHg. The total effective rate in the model group and the control group was 95.0% and 85.0%, respectively ( P = 0.035 ). After treatment, the scores of self-care ability of daily life and limb motor function in the model group were higher than those in the control group ( P < 0.05 ). There were 8 cases (13.6%) in the model group and 17 cases (28.3%) in the control group due to the recurrence of cerebrovascular accident ( P = 0.043 ). Conclusion. Drug treatment guided by a blood pressure model based on a hybrid feature convolution neural network for patients with hypertensive cerebral hemorrhage can significantly and smoothly reduce blood pressure, promote the health recovery, and reduce the occurrence of cerebrovascular accidents.
33
Zhao, Yang, Zhenghan Peng, Shuyuan Kong, Pinghua Yang e Xiao Wang. "Simulation of ultrasonic characterization for the microstructure of titanium alloy". Journal of Physics: Conference Series 2775, n. 1 (1 giugno 2024): 012003. http://dx.doi.org/10.1088/1742-6596/2775/1/012003.
Testo completoAbstract (sommario):
Abstract This paper describes a method of simulating the ultrasonic longitudinal wave (P-wave) propagation in titanium alloy. The two-dimensional geometric model of polycrystalline titanium alloy is established using the Voronoi algorithm. Then, the model was imported into COMSOL software for grid division and parameter setting. The continuous observation of P-wave propagation was realized after adding the physical field of sound pressure and the boundary condition. Further, the first and second transmitted P-wave obtained the ultrasonic attenuation spectrum (UAS). The inverse method determines the average grain size (AGS) by fitting the UAS. It was found that the AGS D ¯ = 47.5 μm of the titanium alloy was obtained by the least square fitting method, and the relative error between the inverse value of AGS and the set value in the model approached 5%.
34
Liang, Shin-Jye, Chih-Chieh Young, Chi Dai, Nan-Jing Wu e Tai-Wen Hsu. "Simulation of Ocean Circulation of Dongsha Water Using Non-Hydrostatic Shallow-Water Model". Water 12, n. 10 (12 ottobre 2020): 2832. http://dx.doi.org/10.3390/w12102832.
Testo completoAbstract (sommario):
A two-dimensional non-hydrostatic shallow-water model for weakly dispersive waves is developed using the least-squares finite-element method. The model is based on the depth-averaged, nonlinear and non-hydrostatic shallow-water equations. The non-hydrostatic shallow-water equations are solved with the semi-implicit (predictor-corrector) method and least-squares finite-element method. In the predictor step, hydrostatic pressure at the previous step is used as an initial guess and an intermediate velocity field is calculated. In the corrector step, a Poisson equation for the non-hydrostatic pressure is solved and the final velocity and free-surface elevation is corrected for the new time step. The non-hydrostatic shallow-water model is verified and applied to both wave and flow driven fluid flows, including solitary wave propagation in a channel, progressive sinusoidal waves propagation over a submerged bar, von Karmann vortex street, and ocean circulations of Dongsha Atolls. It is found hydrostatic shallow-water model is efficient and accurate for shallow water flows. Non-hydrostatic shallow-water model requires 1.5 to 3.0 more cpu time than hydrostatic shallow-water model for the same simulation. Model simulations reveal that non-hydrostatic pressure gradients could affect the velocity field and free-surface significantly in case where nonlinearity and dispersion are important during the course of wave propagation.
35
GROBY, JEAN-PHILIPPE, e CHRYSOULA TSOGKA. "A TIME DOMAIN METHOD FOR MODELING VISCOACOUSTIC WAVE PROPAGATION". Journal of Computational Acoustics 14, n. 02 (giugno 2006): 201–36. http://dx.doi.org/10.1142/s0218396x06003001.
Testo completoAbstract (sommario):
In many applications, and in particular in seismology, realistic propagation media disperse and attenuate waves. This dissipative behavior can be taken into account by using a viscoacoustic propagation model, which incorporates a complex and frequency-dependent viscoacoustic modulus in the constitutive relation. The main difficulty then lies in finding an efficient way to discretize the constitutive equation as it becomes a convolution integral in the time domain. To overcome this difficulty the usual approach consists in approximating the viscoacoustic modulus by a low-order rational function of frequency. We use here such an approximation and show how it can be incorporated in the velocity-pressure formulation for viscoacoustic waves. This formulation is coupled with the fictitious domain method which permits us to model efficiently diffraction by objects of complicated geometry and with the Perfectly Matched Layer Model which allows us to model wave propagation in unbounded domains. The space discretization of the problem is based on a mixed finite element method and for the discretization in time a 2nd order centered finite difference scheme is employed. Several numerical examples illustrate the efficiency of the method.
36
Calvo, Lucas, Diana De Padova, Michele Mossa e Paulo Rosman. "Non-Hydrostatic Discontinuous/Continuous Galerkin Model for Wave Propagation, Breaking and Runup". Computation 9, n. 4 (14 aprile 2021): 47. http://dx.doi.org/10.3390/computation9040047.
Testo completoAbstract (sommario):
This paper presents a new depth-integrated non-hydrostatic finite element model for simulating wave propagation, breaking and runup using a combination of discontinuous and continuous Galerkin methods. The formulation decomposes the depth-integrated non-hydrostatic equations into hydrostatic and non-hydrostatic parts. The hydrostatic part is solved with a discontinuous Galerkin finite element method to allow the simulation of discontinuous flows, wave breaking and runup. The non-hydrostatic part led to a Poisson type equation, where the non-hydrostatic pressure is solved using a continuous Galerkin method to allow the modeling of wave propagation and transformation. The model uses linear quadrilateral finite elements for horizontal velocities, water surface elevations and non-hydrostatic pressures approximations. A new slope limiter for quadrilateral elements is developed. The model is verified and validated by a series of analytical solutions and laboratory experiments.
37
Xie, Biting, Xiuli Zhang, Hao Wang, Yuyong Jiao e Fei Zheng. "Investigations into the Rock Dynamic Response under Blasting Load by an Improved DDA Approach". Advances in Civil Engineering 2021 (8 febbraio 2021): 1–10. http://dx.doi.org/10.1155/2021/8827022.
Testo completoAbstract (sommario):
Evaluation of blasting-induced rock damage and fragmentation is very important for safety control of construction in the jointed rock mass. The discontinuous numerical models are commonly applied due to the advantages in modeling fragmentation and treating discontinuities. In this paper, the rock fracturing algorithm and rate dependent strength law are incorporated into the discontinuous deformation analysis (DDA) to study the wave propagation and rock fragmentation phenomena in dynamic problems. By reproducing Hopkinson pressure bar tests under different loading rates, the improved method is validated to be capable of solving dynamic failure problem. Finally, taking the Xiucun tunnel as an example, its failure process under the action of the explosive wave is simulated, and some failure features are captured. In addition, the explosion wave propagation and its induced particle vibration in surrounding rock are studied. The reasonable simulation results indicate that the modified DDA method can effectively model the stress wave propagation and joint growth process in the jointed rock under blasting load.
38
Antsiperov, V. E., A. S. Bugaev, M. V. Danilychev e G. K. Mansurov. "Method for estimation of the pulse wave propagation velocity by a manual pneumatic arterial pressure sensor". CARDIOMETRY, n. 18 (18 maggio 2021): 38–43. http://dx.doi.org/10.18137/cardiometry.2020.18.3843.
Testo completoAbstract (sommario):
The paper discusses a new method for diagnosing atherosclerosis using a pneumatic arterial blood pressure sensor previously developed by the authors hereof. The possibility of applying a pneumatic sensor to measure the pulse wave transit time referring to a synchronous ECG is treated herein. The specification of the method consisting in the selection of the characteristic moment of the pulse wave as the timestamp, when measuring the signal transit time in relation to the R-peak of the synchronous ECG, is justified hereby. The averaged values of the wave transit time at different points of the artery, taking into account the variability of the front delay values, are used to directly determine the pulse wave propagation velocity in the area between the measurement points.
39
Lin, Shu-Chao, Qing-Zhao Hou, Anna Derlatka, Shan Gao, Jin-Jun Kang e Xiao-Lei Dong. "The Study on the Shock Wave Propagation Rule of a Gas Explosion in a Gas Compartment". Shock and Vibration 2022 (6 gennaio 2022): 1–17. http://dx.doi.org/10.1155/2022/5938950.
Testo completoAbstract (sommario):
Combined with the k-ε turbulence model of general application, a refined finite element model of a utility tunnel’s gas compartment filled with the methane/air mixture is developed. A series of analyses are made by using the powerful industry-leading computational fluid dynamics (CFD) software flame acceleration simulator (FLACS) to study the shock wave propagation rule in the gas compartment. The longitudinal and transversal distribution laws of the explosion shock wave are gained taking into consideration the spatial characteristics of the gas compartment. The influences of a few parameters, such as initial conditions and section size of the gas compartment, on the shock wave propagation rule are further discussed. The basic procedure for predicting the peak pressure of the blast wave is provided by considering the initial conditions and the gas compartment, and the corresponding injury effect of the explosion wave on the living beings is assessed. The investigation demonstrates that the peak pressure by the coupled effect between the initial conditions is significantly influenced, especially at the upper and lower gas explosion limits. The peak pressure increases gradually as the width or height increases, and both basically meet the linear relation. The proposed method can forecast the peak pressure of the explosion shock wave in the gas compartment accurately. According to the peak pressure longitudinal and transversal distributions of the blast wave, the peak pressure is far greater than the killing pressure threshold in the underground and closed space; consequently, it is not safe for the living beings in the gas compartment.
40
Qaisar, Hayat, Li Yun Fan, En Zhe Song, Xiu Zhen Ma, Bing Qi Tian e Naeim Farouk. "Study of Effect of Diesel Fuel Properties on Pressure Wave Profile". Applied Mechanics and Materials 681 (ottobre 2014): 19–22. http://dx.doi.org/10.4028/www.scientific.net/amm.681.19.
Testo completoAbstract (sommario):
High pressure (HP) fuel pipeline is one of the vital components of Combination Electronic Unit Pump (CEUP) fuel injection system besides pump and injector. Effect of four key fuel properties including density, viscosity, acoustic wave speed and bulk modulus on pressure wave profile has been investigated using a 1D viscous damped mathematical model. Wave equation (WE) based mathematical model has been developed in MATLAB using finite difference method. Dynamic variations of these fuel properties during fuel injection cycles have also been incorporated in mathematical model by utilizing empirical formulas. The results show that these four key fuel properties not only vary with the pressure during fuel injection process but also define the trend of pressure wave propagation inside HP fuel pipeline.
41
Le, Thi Thanh Giang, Kyeong Sik Jang, Kwan-Sup Lee e Jaiyoung Ryu. "Numerical Investigation of Aerodynamic Drag and Pressure Waves in Hyperloop Systems". Mathematics 8, n. 11 (6 novembre 2020): 1973. http://dx.doi.org/10.3390/math8111973.
Testo completoAbstract (sommario):
Hyperloop is a new, alternative, very high-speed mode of transport wherein Hyperloop pods (or capsules) transport cargo and passengers at very high speeds in a near-vacuum tube. Such high-speed operations, however, cause a large aerodynamic drag. This study investigates the effects of pod speed, blockage ratio (BR), tube pressure, and pod length on the drag and drag coefficient of a Hyperloop. To study the compressibility of air when the pod is operating in a tube, the effect of pressure waves in terms of propagation speed and magnitude are investigated based on normal shockwave theories. To represent the pod motion and propagation of pressure waves, unsteady simulation using the moving-mesh method was applied under the sheer stress transport k–ω turbulence model. Numerical simulations were performed for different pod speeds from 100 to 350 m/s. The results indicate that the drag coefficient increases with increase in BR, pod speed, and pod length. In the Hyperloop system, the compression wave propagation speed is much higher than the speed of sound and the expansion wave propagation speed that experiences values around the speed of sound.
42
Kim, Young Kook, Kazuyuki Hokamoto e Shigeru Itoh. "A Study on the Consolidation of Cu, Ni / Graphite Powder Using Shock Compaction Method". Materials Science Forum 566 (novembre 2007): 345–50. http://dx.doi.org/10.4028/www.scientific.net/msf.566.345.
Testo completoAbstract (sommario):
A shock compaction method using an underwater shockwave is used to consolidate the Cu/graphite and Ni/graphite composites. The copper powder (particle size < 45 m) and nickel powder (particle size < 150 m) were respectively mixed with the graphite powder (particle size < 45 m, purity 99.9%). The propagation phenomenon of underwater shock wave is studied by means of numerical analysis (LS-DYNA 3D) in terms of the magnitude and distribution of shock pressure impinged on the powder surface. The shock pressure of underwater shock wave obtained from shock compaction device is approximately 16 GPa. To make a big size material (ø30mm), we changed the inner size of powder container from ø10 mm to ø30 mm. We confirmed that the consolidation possibility of the big size composite materials (Cu/graphite, Ni/graphite) by the shock compaction method using underwater shock wave.
43
Yang, Fan, Liugang Li, Zhimin Li e Pengbo Wang. "Numerical Simulation of Acoustic Wave Generated by DC Corona Discharge Based on the Shock Wave Theory". Applied Sciences 13, n. 16 (15 agosto 2023): 9251. http://dx.doi.org/10.3390/app13169251.
Testo completoAbstract (sommario):
The audible noise generated by corona discharge has the N-type characteristic at the initial generation stage, and it is a typical shock wave. This shock wave usually only exists around the corona source with a tiny range, making it difficult to obtain its characteristics through experimental measurements. An electrosound-combined simulation of the corona discharge based on the shock wave theory was conducted, and the development process involving the corona discharge, shock wave, and sound wave was simulated. First, the corona was numerically simulated based on the 2D pin–plate axisymmetric hydrodynamic model. It was found that the plasma was mainly distributed near the axis of the corona field where the electric field changed violently, and the maximum value of the electric field appeared at the head of the discharge channel. Then, the plasma energy was equivalent to the explosive energy, and a plasma explosion shock model was established. It was found that the shock wave pressure had obvious positive and negative pressure zones, and the propagation velocity decays to the sound velocity gradually. Finally, the shock wave pressure derived by the explosion model was used as the acoustic source, and the acoustic wave propagation process was simulated. The simulated sound pressure waveform had the same characteristics as the relevant experimental measurement results, proving that the developed method possessed strong applicability and gave rise to a new angle for the simulation of corona-generated audible noise.
44
KIMURA, Yuki, e Eijiro INAMURA. "A Method for Estimating the Direction of Shock Wave Propagation Using a Pressure Transducer". Proceedings of Conference of Kanto Branch 2024.30 (2024): 14I05. http://dx.doi.org/10.1299/jsmekanto.2024.30.14i05.
Testo completo
45
Yu, Jin, Zehan Liu, Ze He, Xianqi Zhou e Jinbi Ye. "Fluctuation Characteristic Test of Oblique Stress Waves in Infilled Jointed Rock and Study of the Analytic Method". Advances in Civil Engineering 2020 (11 gennaio 2020): 1–12. http://dx.doi.org/10.1155/2020/7924742.
Testo completoAbstract (sommario):
The propagation of stress waves in filled jointed rocks involves two important influencing factors: transmission-reflection phenomena and energy attenuation. In this paper, the split Hopkinson pressure bar (SHPB) test is used to shock the filled rock with joint angles of 0, 30, and 45° and the thickness of 4 mm and 10 mm, respectively, in three different velocities. The wave curves of the incident wave, reflected wave, and transmission are obtained. The effects of the filling angle and joint thickness on wave propagation are analyzed. Based on the propagation characteristics of stress waves in joints, the stress expression of oblique incident stress waves propagating in filling joints is derived, and the energy coefficient of transmission and reflection is calculated. The results show that the propagation of stress wave in filling joints is related to the impact rate. The larger the impact rate is, the larger the maximum voltage amplitude of the three waves is. And the increasing amplitude of the incident and reflected waves is larger than the transmitted wave; the greater the impact velocity is, the smaller the stress-strain curve gap of the three dip joints is, and the fracture strength of the specimen decreases with the increase of the joint dip angle. The larger the joint dip angle is, the smaller the deformation of the rock-like specimen is. The change of the transmission coefficient is related to the joint angle, and the larger joint angle weakens the influence of the joint width on the transmission of the transmitted wave; under each impact velocity, the theoretical and experimental stress peaks are approximately the same, and the transmission coefficient maintains a good consistency with the oblique incident angle.
46
Leconte, Roman, Jean-Camille Chassaing, François Coulouvrat e Régis Marchiano. "Propagation of classical and low booms through kinematic turbulence with uncertain parameters". Journal of the Acoustical Society of America 151, n. 6 (giugno 2022): 4207–27. http://dx.doi.org/10.1121/10.0011771.
Testo completoAbstract (sommario):
The propagation of sonic boom through kinematic turbulence is known to have an important impact on the noise perceived at the ground. In this work, a recent numerical method called FLHOWARD3D based on a one-way approach is used to simulate the propagation of classical and low-boom waveforms. Kinematic turbulence is synthesized following a von Kármán energy spectrum. Two- and three-dimensional (2D and 3D) simulations are compared to experimental measurements, and 2D simulations are found to be slightly less accurate than 3D ones but still consistent with experimental levels around 98% of the time. A stochastic study is carried out on the 2D simulation using the generalized polynomial chaos method with parameters of the von Kármán spectrum as uncertain parameters. Differences between the propagation of a classical N-wave and low booms are observed: the classical N-wave shows higher peak pressure and variations than low-boom signatures. The standard deviation for the peak pressure, the D-weighted sound exposure level (D-SEL), and the perceived level in dB (PLdB) metrics all show a linear increase with the distance, with a faster increase for the classical N-wave for the peak pressure and D-SEL and a similar increase between the different booms for PLdB. In general, it is found that low-boom waveforms show less sensitivity to turbulence.
47
Yan, Chenglong, Chen Shu, Jiafeng Zhao, Lingyu Su, Yiheng Tong, Qiaofeng Xie e Wei Lin. "Influences of thermal physical property parameters on operating characteristics of simulated rotating detonation ramjet fueled by C12H23". AIP Advances 12, n. 11 (1 novembre 2022): 115309. http://dx.doi.org/10.1063/5.0101939.
Testo completoAbstract (sommario):
Two-phase rotating detonation ramjets are considered to be suitable for aerospace applications due to their high thermodynamic cycle efficiency. These engines have an extremely complex internal flow field, in which the liquid fuel undergoes physical and chemical processes such as fragmentation, evaporation, mixing, and combustion; these processes also interact with detonation waves that have significant gradients. This makes it difficult to simulate a three-dimensional (3D) full-process rotating detonation combustion chamber. Here, based on the Euler–Lagrangian simulation method, a 3D numerical combustion chamber was simulated using kinetic theory and the constant thermal physical property parameter (TPPP) calculation method. The accuracy of these methods was then compared with the existing experimental results and theoretical values. Calculating the TPPPs using kinetic theory brought about a relatively high-pressure peak and detonation wave temperature; the detonation wave profile was also finer and more precise. The detonation wave propagation velocity of the two-phase detonation is estimated to be about 60% of the theoretical gas-phase CJ velocity. The calculation method of physical parameters has relatively little influence on the engine’s operating frequency and the detonation wave's propagation velocity but has a more significant influence on the peak pressure. Constant TPPPs can be used when the Kelvin–Helmholtz–Rayleigh–Taylor model with insufficient precision is used to consider the breakup of droplets and leads to the acceleration of the propagation speed of two-phase detonation waves.
48
Zdeshchyts, A. V., e V. M. Zdeshchyts. "Propagation of elastic waves in cross-sectionally heterogeneous rods". IOP Conference Series: Earth and Environmental Science 1415, n. 1 (1 dicembre 2024): 012081. https://doi.org/10.1088/1755-1315/1415/1/012081.
Testo completoAbstract (sommario):
Abstract The article is devoted to measuring the propagation speed of elastic waves in metal rods of variable cross-section. The paper examines the dependence of the speed measure of propagation of elastic waves on the geometric and physical characteristics of the rods. The research methods are based on the use of known statements of the impact theory during the collision of a ball with the end of a metal rod. Solid rods, stepped rods, and rods with axisymmetric holes of different depths were experimentally studied. A piezo sensor connected to a digital oscilloscope was used to record pressure fluctuations at the end of the rod. The method of least squares was used for processing and further analysis of experimental data. Theoretical and experimental studies proved that there are two characteristic areas in which the speed of propagation of an elastic wave in a non-homogeneous cross-sectional rod differs from the value of the wave speed in a one-dimensional rod. A sinusoidal functional dependence of the propagation speed of the elastic wave on the caliber of the rod was obtained.
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Jia, Fan, Hongyang Cheng, Sihong Liu e Vanessa Magnanimo. "Elastic wave velocity and attenuation in granular material". EPJ Web of Conferences 249 (2021): 11001. http://dx.doi.org/10.1051/epjconf/202124911001.
Testo completoAbstract (sommario):
Discrete Elements Method simulations are carried out to investigate waves propagation in isotropic, frictional granular media. The focus is on the effects of confining pressure, microstructure and input frequency on both wave velocity and attenuation. The latter is described via the seismic quality factor Q and three different measurement approaches are compared, in time and frequency domain. The simulation data validate previous findings on the scaling of wave velocity with confining pressure and coordination number. The quality factor Q shows a non-monotonic behavior with input frequency.
50
Chukkol, Y. B., I. Bello e M. Abdullahi. "Non-linear wave propagation in a weakly compressible Kelvin-Voigt liquid containing bubbly clusters". Vestnik Udmurtskogo Universiteta. Matematika. Mekhanika. Komp'yuternye Nauki 33, n. 1 (marzo 2023): 171–94. http://dx.doi.org/10.35634/vm230112.
Testo completoAbstract (sommario):
The effect of bubble-bubble interaction on wave propagation in homogeneous weakly compressible viscoelastic bubbly flow is investigated using the reductive perturbation method. The bubble dynamics equation is derived using the kinetic energy conservation approach. The bubble dynamics and mixture equations are coupled with the equation of state for gas to investigate the shock wave propagation phenomenon in the mixture. A two-dimensional Korteweg-de VriesBurger (KdVB) equation in terms of a pressure profile is derived. It is found that the bubble-bubble interaction has no effect when using the parameters under our consideration.