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1
Ghimire, Anukul, Mads J. Andersen, Lindsay M. Burrowes, J. Christopher Bouwmeester, Andrew D. Grant, Israel Belenkie, Nowell M. Fine, Barry A. Borlaug, and John V. Tyberg. "The reservoir-wave approach to characterize pulmonary vascular-right ventricular interactions in humans." Journal of Applied Physiology 121, no. 6 (December 1, 2016): 1348–53. http://dx.doi.org/10.1152/japplphysiol.00697.2016.
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Using the reservoir-wave approach (RWA) we previously characterized pulmonary vasculature mechanics in a normal canine model. We found reflected backward-traveling waves that decrease pressure and increase flow in the proximal pulmonary artery (PA). These waves decrease right ventricular (RV) afterload and facilitate RV ejection. With pathological alterations to the pulmonary vasculature, these waves may change and impact RV performance. Our objective in this study was to characterize PA wave reflection and the alterations in RV performance in cardiac patients, using the RWA. PA pressure, Doppler-flow velocity, and pulmonary arterial wedge pressure were measured in 11 patients with exertional dyspnea. The RWA was employed to analyze PA pressure and flow; wave intensity analysis characterized PA waves. Wave-related pressure was partitioned into two components: pressures due to forward-traveling and to backward-traveling waves. RV performance was assessed by examining the work done in raising reservoir pressure and that associated with the wave components of systolic PA pressure. Wave-related work, the mostly nonrecoverable energy expended by the RV to eject blood, tended to vary directly with mean PA pressure. Where PA pressures were lower, there were pressure-decreasing/flow-increasing backward waves that aided RV ejection. Where PA pressures were higher, there were pressure-increasing/flow-decreasing backward waves that impeded RV ejection. Pressure-increasing/flow-decreasing backward waves were responsible for systolic notches in the Doppler flow velocity profiles in patients with the highest PA pressure. Pulmonary hypertension is characterized by reflected waves that impede RV ejection and an increase in wave-related work. The RWA may facilitate the development of therapeutic strategies.
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Li, Changfei, Fuping Gao, and Lijing Yang. "Breaking-Wave Induced Transient Pore Pressure in a Sandy Seabed: Flume Modeling and Observations." Journal of Marine Science and Engineering 9, no. 2 (February 5, 2021): 160. http://dx.doi.org/10.3390/jmse9020160.
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Previous studies on wave-induced pore pressure in a porous seabed mainly focused on non-breaking regular waves, e.g., Airy linear waves or Stokes non-linear waves. In this study, breaking-wave induced pore pressure response in a sandy seabed was physically simulated with a large wave flume. The breaking-wave was generated by superimposing a series of longer waves onto the foregoing shorter waves at a specified location. Water surface elevations and the corresponding pore pressure in the process of wave breaking were measured simultaneously at three typical locations, i.e., at the rear, just at, and in front of the wave breaking location. Based on test results, characterization parameters are proposed for the wave surface elevations and the corresponding pore-pressures. Flume observations indicate that the wave height was greatly diminished during wave breaking, which further affected the pore-pressure responses. Moreover, the measured values of the characteristic time parameters for the breaking-wave induced pore-pressure are larger than those for the free surface elevation of breaking-waves. Under the action of incipient-breaking or broken waves, the measured values of the amplitude of transient pore-pressures are generally smaller than the predicted results with the analytical solution by Yamamoto et al. (1978) for non-breaking regular waves with equivalent values of characteristic wave height and wave period.
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Chang, Chien-Kee, and Ching-Her Hwang. "STUDY OF STATISTICAL CHARACTERISTICS OF IRREGULAR WAVE PRESSURE ON A COMPOSITE BREAKWATER." Coastal Engineering Proceedings 1, no. 20 (January 29, 1986): 131. http://dx.doi.org/10.9753/icce.v20.131.
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Wave pressure is the most important external force for the design of breakwater. During recent years, there has been considerable development in the technology of vertical face breakwater; however, there is no reliable method to compute wave forces induced by irregular waves. The purpose of this study is to obtain statistical characteristics of irregular wave pressure distribution from the data of model tests. The results of this study shown that vertical face breakwater under the action of irregular waves, some waves are reflected, so that the next wave breaks a critical distance resulting in a rapidly rising shock pressure on the breakwater. On the average, the wave pressure increase with incoming wave height, but the maximum wave force does not necessarily occur for the largest wave height. It can be occurred for serval larger wave group in an appropiate phase composition. The irregular wave pressure distribution on the breakwater is quite uniform; the ratio of tested and calculated wave pressures decreases with the reduction of relative crest height of breakwater. Coda formula can predict the total horizontal force of the upper part of breakwater quite well except exetreme shock pressure occurred by non-breaking waves. Wave forces calculated by Miche-Rundgren and Nagai wave force formula are about 10% cummulated exceeding percentage of wave force obtained from model test.
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Meng, Yan Qiu, Guo Ping Chen, and Shi Chang Yan. "Wave-in-Deck Impulsive Pressure on Unsheltered Jetties Exposed to Waves and Current." Applied Mechanics and Materials 256-259 (December 2012): 1928–36. http://dx.doi.org/10.4028/www.scientific.net/amm.256-259.1928.
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Impulsive pressure induced by waves is an important factor to be considered in the design of offshore structures. This paper presents results from physical model tests on the impulsive pressure on deck of unsheltered jetties and similar structures exposed to directional waves in the presence of currents. The pressures were measured on a 1:50 scale model of a jetty head with down-standing beams and berthing members. Different incident wave angles, the current velocities and the angles between wave and current were considered to identify the effects of these factors on the impulsive pressures. Data collected from model tests were analyzed to gain insights on the mechanics of the impulsive pressure under different wave and current conditions. It is shown that the impulsive pressure is sensitive to the wave directionality and the current magnitude.
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Yan, Dong, Jinchang Zhao, and Shaoqing Niu. "Normal Reflection Characteristics of One-Dimensional Unsteady Flow Shock Waves on Rigid Walls from Pulse Discharge in Water." Shock and Vibration 2017 (2017): 1–12. http://dx.doi.org/10.1155/2017/6958085.
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Strong shock waves can be generated by pulse discharge in water, and the characteristics due to the shock wave normal reflection from rigid walls have important significance to many fields, such as industrial production and defense construction. This paper investigates the effects of hydrostatic pressures and perturbation of wave source (i.e., charging voltage) on normal reflection of one-dimensional unsteady flow shock waves. Basic properties of the incidence and reflection waves were analyzed theoretically and experimentally to identify the reflection mechanisms and hence the influencing factors and characteristics. The results indicated that increased perturbation (i.e., charging voltage) leads to increased peak pressure and velocity of the reflected shock wave, whereas increased hydrostatic pressure obviously inhibited superposition of the reflection waves close to the rigid wall. The perturbation of wave source influence on the reflected wave was much lower than that on the incident wave, while the hydrostatic pressure obviously affected both incident and reflection waves. The reflection wave from the rigid wall in water exhibited the characteristics of a weak shock wave, and with increased hydrostatic pressure, these weak shock wave characteristics became more obvious.
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Yan, Dong, Decun Bian, Jinchang Zhao, and Shaoqing Niu. "Study of the Electrical Characteristics, Shock-Wave Pressure Characteristics, and Attenuation Law Based on Pulse Discharge in Water." Shock and Vibration 2016 (2016): 1–11. http://dx.doi.org/10.1155/2016/6412309.
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Strong shock waves can be generated by pulse discharge in water. Study of the pressure characteristics and attenuation law of these waves is highly significant to industrial production and national defense construction. In this research, the shock-wave pressures at several sites were measured by experiment under different conditions of hydrostatic pressure, discharge energy, and propagation distance. Moreover, the shock-wave pressure characteristics were analyzed by combining them with the discharge characteristics in water. An attenuation equation for a shock wave as a function of discharge energy, hydrostatic pressure, and propagation distance was fitted. The experimental results indicated that (1) an increase in hydrostatic pressure had an inhibiting effect on discharge breakdown; (2) the shock-wave peak pressure increased with increasing discharge voltage at 0.5 m from the electrode; it increased rapidly at first and then decreased slowly with increasing hydrostatic pressure; and (3) shock-wave attenuation slowed down with increasing breakdown energy and hydrostatic pressure during shock-wave transfer. These experimental results were discussed based on the mechanism described.
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Prasad, Manika. "Acoustic measurements in unconsolidated sands at low effective pressure and overpressure detection." GEOPHYSICS 67, no. 2 (March 2002): 405–12. http://dx.doi.org/10.1190/1.1468600.
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Shallow water flows and over‐pressured zones are a major hazard in deepwater drilling projects. Their detection prior to drilling would save millions of dollars in lost drilling costs. I have investigated the sensitivity of seismic methods for this purpose. Using P‐wave information alone can be ambiguous, because a drop in P‐wave velocity (Vp) can be caused both by overpressure and by presence of gas. The ratio of P‐wave velocity to S‐wave velocity (Vp/Vs), which increases with overpressure and decreases with gas saturation, can help differentiate between the two cases. Since P‐wave velocity in a suspension is slightly below that of the suspending fluid and Vs=0, Vp/Vs and Poisson's ratio must increase exponentially as a load‐bearing sediment approaches a state of suspension. On the other hand, presence of gas will also decrease Vp but Vs will remain unaffected and Vp/Vs will decrease. Analyses of ultrasonic P‐ and S‐wave velocities in sands show that the Vp/Vs ratio, especially at low effective pressures, decreases rapidly with pressure. At very low pressures, Vp/Vs values can be as large as 100 and higher. Above pressures greater than 2 MPa, it plateaus and does not change much with pressure. There is significant change in signal amplitudes and frequency of shear waves below 1 MPa. The current ultrasonic data shows that Vp/Vs values can be invaluable indicators of low differential pressures.
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Menshikov, PV, VA Kutuev, and SN Zharikov. "Shock wave analysis: A case-study of Magnezitovaya Mine." IOP Conference Series: Earth and Environmental Science 991, no. 1 (February 1, 2022): 012045. http://dx.doi.org/10.1088/1755-1315/991/1/012045.
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Abstract The article presents the studies into the impact of shock waves induced by underground blasting. The instrumental measurement of actual pressures at the shock wave front in air in Magnezitovaya Mine during blasting is performed. Using the measurement data, the safe distances of shock wave impact out of possible personnel injury risk are determined. The excess pressure at the shock wave front in mine air is calculated with regard to local pressure losses. The calculated excess pressures are compared with the maximum allowable pressures for personnel, timber cofferdams, ventducts, appliances and power lines.
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Williamson, Derek C., and Kevin R. Hall. "Prediction of external wave pressures on a rubble mound breakwater." Canadian Journal of Civil Engineering 19, no. 4 (August 1, 1992): 639–48. http://dx.doi.org/10.1139/l92-073.
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The external pressures on the front face of a rubble mound breakwater resulting from wave attack are examined in this paper. This is done through extensive model tests employing regular waves up to 30 cm in height, on a conventionally designed breakwater with front slopes of 1:1.5, 1:2, and 1:3. The measured pressures are examined based on their relationship to a number of different parameters, including wave steepness, wave height, wave period, breakwater front slope, core permeability, and elevation on the breakwater relative to the still water level. The average differential pressure, the maximum recorded differential pressure, the average minimum pressure, and the pressure rise and fall times are investigated, producing a regression equation for each case based on a number of independent variables. The regression equations demonstrate the great effect of the elevation on the breakwater, and often wave steepness; the much lesser effect attributed to the breakwater front slope; and the minimal effect that the core permeability has on most of the components describing the external pressures measured on a breakwater under wave attack. Key words: breakwater, rubble, pressure, external, prediction.
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Ghosh, Sudip K., Patrick Janiak, Werner Schwizer, Geoffrey S. Hebbard, and James G. Brasseur. "Physiology of the esophageal pressure transition zone: separate contraction waves above and below." American Journal of Physiology-Gastrointestinal and Liver Physiology 290, no. 3 (March 2006): G568—G576. http://dx.doi.org/10.1152/ajpgi.00280.2005.
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Manometrically measured peristaltic pressure amplitude displays a well-defined trough in the upper esophagus. Whereas this manometric “transition zone” (TZ) has been associated with striated-to-smooth muscle fiber transition, the underlying physiology of the TZ and its role in bolus transport are unclear. A computer model study of bolus retention in the TZ showed discoordinated distinct contraction waves above and below. Our aim was to test the hypothesis that distinct upper/lower contraction waves above/below the manometric TZ are normal physiology and to quantify space-time coordination between tone and bolus transport through the TZ. Eighteen normal barium swallows were analyzed in 6 subjects with concurrent 21-channel high-resolution manometry and digital fluoroscopy. From manometry, the TZ center (nadir pressure amplitude) and the upper/lower margins of the pressure trough were objectively quantified. Using fluoroscopy, we quantified space-time trajectories of the bolus tail and bolus tail pressures and maximum intraluminal pressures proximal to the tail with their space-time trajectories. In every swallow, the bolus tail followed distinct trajectories above/below the TZ, separated by a well-defined spatial “jump” that terminated an upper contraction wave and initiated a lower contraction wave (3.32 ± 1.63 cm, P = 0.0004). An “indentation wave” always formed within the TZ distal to the upper wave, increasing in amplitude until the lower wave was initiated. As the upper contraction wave tail entered the TZ, it slowed and the tail pressure reduced rapidly, while indentation wave pressure increased to normal tail pressure values at the initiation of the lower wave. The TZ was a special zone of segmental contraction. The TZ is, physiologically, the transition from an upper contraction wave originating in the proximal striated esophagus to a lower contraction wave that moves into the distal smooth muscle esophagus. Complete bolus transport requires coordination of upper/lower waves and sufficient segmental squeeze to fully clear the bolus from the TZ during the transition period.
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Igra, O., G. Hu, J. Falcovitz, and W. Heilig. "Blast Wave Reflection From Wedges." Journal of Fluids Engineering 125, no. 3 (May 1, 2003): 510–19. http://dx.doi.org/10.1115/1.1567310.
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While a lot of attention was given to shock wave reflections from wedges during the past four decades, only little work was published regarding the similar case of blast wave reflection from wedges. In the present paper this subject is studied experimentally and theoretically/numerically. The obtained results show that the geometry of the reflected wave pattern is similar in the two cases when both incident waves have the same initial pressure jump across their fronts. However, different reflected pressure signatures (history) are observed in these two cases. The pressures obtained behind a reflected shock wave are always higher than those obtained behind the corresponding similar blast wave. In the present case differences as high as 17% were observed.
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Dunn, Charles. "Pressure wave transducing." Journal of the Acoustical Society of America 104, no. 6 (December 1998): 3153. http://dx.doi.org/10.1121/1.424234.
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Bose, Amar G., and William R. Short. "Pressure wave transducing." Journal of the Acoustical Society of America 82, no. 2 (August 1987): 727. http://dx.doi.org/10.1121/1.395366.
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Hsu, Hung-Chu, Yang-Yih Chen, Yi-Ru Chen, and Meng-Syue Li. "Experimental Study of Forces Influencing Vertical Breakwater under Extreme Waves." Water 14, no. 4 (February 20, 2022): 657. http://dx.doi.org/10.3390/w14040657.
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In order to understand the extreme wave acting on the vertical breakwater, a series of experiments were constructed in the wave tank to measure the variations of pressure on the front, rear faces, and below the caisson due to overtopping waves. The front and backward horizontal forces and the uplift forces were estimated by integrating the dynamic wave pressure distributions. The COBRAS numerical model was also used to calculate the wave loads under various overtopping waves. The measured wave pressures and wave forces were compared with the predictions of numerical results and showed good agreement. It was found that the forces acting on the backward side of the vertical structure induced by the wave overtopping should be considered. From the experimental data, new semi-empirical equations for calculating the maximum wave forces are proposed using a least squares approximation.
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Bonneton, P., and D. Lannes. "Recovering water wave elevation from pressure measurements." Journal of Fluid Mechanics 833 (November 6, 2017): 399–429. http://dx.doi.org/10.1017/jfm.2017.666.
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The reconstruction of water wave elevation from bottom pressure measurements is an important issue for coastal applications, but corresponds to a difficult mathematical problem. In this paper we present the derivation of a method which allows the elevation reconstruction of water waves in intermediate and shallow waters. From comparisons with numerical Euler solutions and wave-tank experiments we show that our nonlinear method provides much better results for the surface elevation reconstruction compared to the linear transfer function approach commonly used in coastal applications. More specifically, our method accurately reproduces the peaked and skewed shape of nonlinear wave fields. Therefore, it is particularly relevant for applications on extreme waves and wave-induced sediment transport.
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Mynard, Jonathan P., and Joseph J. Smolich. "Wave potential and the one-dimensional windkessel as a wave-based paradigm of diastolic arterial hemodynamics." American Journal of Physiology-Heart and Circulatory Physiology 307, no. 3 (August 1, 2014): H307—H318. http://dx.doi.org/10.1152/ajpheart.00293.2014.
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Controversy exists about whether one-dimensional wave theory can explain the “self-canceling” waves that accompany the diastolic pressure decay and discharge of the arterial reservoir. Although it has been proposed that reservoir and wave effects be treated as separate phenomena, thus avoiding the issue of self-canceling waves, we have argued that reservoir effects are a phenomenological and mathematical subset of wave effects. However, a complete wave-based explanation of self-canceling diastolic expansion (pressure-decreasing) waves has not yet been advanced. These waves are present in the forward and backward components of arterial pressure and flow (P±and Q±, respectively), which are calculated by integrating incremental pressure and flow changes (dP±and dQ±, respectively). While the integration constants for this calculation have previously been considered arbitrary, we showed that physiologically meaningful constants can be obtained by identifying “undisturbed pressure” as mean circulatory pressure. Using a series of numeric experiments, absolute P±and Q±values were shown to represent “wave potential,” gradients of which produce propagating wavefronts. With the aid of a “one-dimensional windkessel,” we showed how wave theory predicts discharge of the arterial reservoir. Simulated data, along with hemodynamic recordings in seven sheep, suggested that self-canceling diastolic waves arise from repeated and diffuse reflection of the late systolic forward expansion wave throughout the arterial system and at the closed aortic valve, along with progressive leakage of wave potential from the conduit arteries. The combination of wave and wave potential concepts leads to a comprehensive one-dimensional (i.e., wave-based) explanation of arterial hemodynamics, including the diastolic pressure decay.
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Kuo, Yi-Yu, and Yung-Fang Chiu. "Transfer function between wave height and wave pressure for progressive waves." Coastal Engineering 23, no. 1-2 (May 1994): 81–93. http://dx.doi.org/10.1016/0378-3839(94)90016-7.
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Wang, Pingyi, Lu Hua, Di Song, Meili Wang, and Ye Tian. "Experimental Study on Pressure Characteristics of Gravity Dam Surface under Impact of Landslide-Generated Impulse Waves." Sustainability 15, no. 2 (January 9, 2023): 1257. http://dx.doi.org/10.3390/su15021257.
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Landslide-generated impulse waves of a mountain-river reservoir will endanger the dam body’s stability and the dam structure’s safety and even pose a significant threat to the property safety of downstream residents. Timely prediction of dam surface pressure is essential for dam safety assessment. The pressure distribution characteristics and variation law of the gravity dam surface under the impact of landslide-generated impulse waves are studied through a three-dimensional physical model test. The results show that the landslide volume and angle are the key control factors of the first wave amplitude in front of the dam. The maximum and minimum pressures are near the water surface and at two-thirds of the water depth, respectively. The maximum pressure has a power function relationship with the maximum amplitude of the wave in front of the dam. Furthermore, the maximum amplitude of the first wave in front of the dam significantly influences the total pressure of the single-width wave on the dam surface. Based on the research results, the single-width wave total pressure prediction method is constructed under different first wave amplitudes in front of the dam, which can provide theoretical guidance and technical support for dam safety assessment and landslide-generated surge risk assessment.
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Banfi, Davide, Alison Raby, and David Simmonds. "CHARACTERISATION OF BREAKING WAVES ON THE EDDYSTONE LIGHTHOUSE: A LABORATORY INVESTIGATION ON WAVE PRESSURE." Coastal Engineering Proceedings, no. 35 (June 23, 2017): 15. http://dx.doi.org/10.9753/icce.v35.structures.15.
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Commonly, rock lighthouses are erected on the top of steep reefs and in limited water depths. The effect of these environmental conditions on wave loading requires deeper understanding. This paper investigates wave loading at small scale for a particular case study: the Eddystone lighthouse (UK). Load characteristics due to breaking waves are obtained by the use of pressure transducers and the test program is designed to generate a comprehensive data set covering a broader range of wave conditions. Although the magnitude of wave pressures is rather random from wave to wave of the same train of regular waves, the pressure impulsivity tends to decrease with increasing relative breaking distance. Four breaker types are described and particular attention is given to time histories of the line of action of horizontal force and vertical spatial distributions. Estimation of overall forces, obtained by pressure integration, indicates that the wave loading is strongly affected by the limited water depth condition. In fact, only small plunging waves are able to break at the structure; thus, they cause small forces despite the small breaking distances. Finally, the occurrence of the breakers is investigated on a dimensionless plane given by the combination of the Iribarren number and momentum flux of Hughes.
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Johnson, Jerome B. "Simple model of shock-wave attenuation in snow." Journal of Glaciology 37, no. 127 (1991): 303–12. http://dx.doi.org/10.1017/s0022143000005724.
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AbstractA simple momentum model, assuming that snow compacts along a prescribed pressure–density curve, is used to calculate the pressure attenuation of shock waves in snow. Four shock-loading situations are examined: instantaneously applied pressure impulses for one-dimensional, cylindrical and spherical shock-wave geometries, and a one-dimensional pressure impulse of finite duration. Calculations show that for an instantaneously applied impulse the pressure attenuation for one-dimensional, cylindrical and spherical shock waves is determined by the pressure density (P–ρ) compaction curve of snow. The maximum attenuation for a one-dimensional shock wave is proportional to (Xf–X0)−1.5for the multi-stage (P–ρ) curve and (Xf–X0)−2when compaction occurs in a single step (single-stage compaction), where (Xf–X0) is the shock-wave propagation distance. Cylindrical waves have a maximum attenutation that varies from (R–R0)−2for single-stage compaction and (R–R0)−1.5for multi-stage compaction, when (R–R0) ≪R0, whereRis the propagation radius andR0is the interior radius over which a pressure impulse is applied, toR−4when (R–R0) ≫R0Spherical waves have a maximum attenuation that varies from (R–R0)−2for single-stage compaction and (R–R0)−1.5for multi-stage compaction toR−6when 〈R–R0〉 ≫R0.The shock-wave pressure in snow for a finite-duration pressure impulse is determined by the pressure impulse versus time profile during the time interval of the impulse. After the pressure impulse ends, shock-wave pressure attenuation is the same as for an instantaneously applied pressure impulse containing the same total momentum. Pressure attenuation near a shock-wave source, where the duration of the shock wave is relatively short, is greater than for a shock wave farther from a source where the shock wave has a relatively long duration. Shock-wave attenuation in snow can be delayed or reduced by increasing the duration of a finite-duration pressure impulse. A sufficiently long-duration impulse may result in no shock-wave pressure attenuation in a shallow snow cover.
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Johnson, Jerome B. "Simple model of shock-wave attenuation in snow." Journal of Glaciology 37, no. 127 (1991): 303–12. http://dx.doi.org/10.3189/s0022143000005724.
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AbstractA simple momentum model, assuming that snow compacts along a prescribed pressure–density curve, is used to calculate the pressure attenuation of shock waves in snow. Four shock-loading situations are examined: instantaneously applied pressure impulses for one-dimensional, cylindrical and spherical shock-wave geometries, and a one-dimensional pressure impulse of finite duration. Calculations show that for an instantaneously applied impulse the pressure attenuation for one-dimensional, cylindrical and spherical shock waves is determined by the pressure density (P–ρ) compaction curve of snow. The maximum attenuation for a one-dimensional shock wave is proportional to (Xf–X0)−1.5 for the multi-stage (P–ρ) curve and (Xf–X0)−2 when compaction occurs in a single step (single-stage compaction), where (Xf–X0) is the shock-wave propagation distance. Cylindrical waves have a maximum attenutation that varies from (R–R0)−2 for single-stage compaction and (R–R0)−1.5 for multi-stage compaction, when (R – R0) ≪ R0, where R is the propagation radius and R0 is the interior radius over which a pressure impulse is applied, to R−4 when (R – R0) ≫ R0 Spherical waves have a maximum attenuation that varies from (R – R0)−2 for single-stage compaction and (R – R0)−1.5 for multi-stage compaction to R−6 when 〈R – R0〉 ≫ R0.The shock-wave pressure in snow for a finite-duration pressure impulse is determined by the pressure impulse versus time profile during the time interval of the impulse. After the pressure impulse ends, shock-wave pressure attenuation is the same as for an instantaneously applied pressure impulse containing the same total momentum. Pressure attenuation near a shock-wave source, where the duration of the shock wave is relatively short, is greater than for a shock wave farther from a source where the shock wave has a relatively long duration. Shock-wave attenuation in snow can be delayed or reduced by increasing the duration of a finite-duration pressure impulse. A sufficiently long-duration impulse may result in no shock-wave pressure attenuation in a shallow snow cover.
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Asharchuk, Nika, and Evgenii Mareev. "Dynamics of Laser-Induced Shock Waves in Supercritical CO2." Fluids 7, no. 11 (November 10, 2022): 350. http://dx.doi.org/10.3390/fluids7110350.
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We studied the dynamics of laser-induced shock waves in supercritical CO2 (scCO2) for different pressures and temperatures under nanosecond optical breakdown. We estimated the shock wave pressure and energy, including their evolution during shock wave propagation. The maximal shock wave pressure ~0.5 GPa was obtained in liquid-like scCO2 (155 bar 55 °C), where the fluid density is greater. However, the maximal shock wave energy ~25 mJ was achieved in sub-critical conditions (67 bar, 55 °C) due to a more homogeneous microstructure of fluid in comparison with supercritical fluid. The minimal pressure and energy of the shock wave are observed in the Widom delta (a delta-like region in the vicinity of the critical point) due to the clusterization of scCO2, which strongly affects the energy transfer from the nanosecond laser pulse to the shock wave.
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Wang, Sheng Hung, Lee Long Han, and Tsing Tshih Tsung. "Dynamic Pressure Calibration of Pressure Sensors Using Liquid Step Pressure Generator." Key Engineering Materials 437 (May 2010): 8–12. http://dx.doi.org/10.4028/www.scientific.net/kem.437.8.
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. This study presents the dynamic calibration of pressure sensors using a developed liquid step wave generator. This approach is sufficient to display the transient response of pressure sensors in the time and frequency domains and it depends on the performance of pressure generators. In this study, the liquid step wave generator was developed via a reformed spool valve generating a liquid step wave with a short rise time that current generators have not achieved so far. A small sensing cavity, where maintains the liquid step wave, and a contact seal were adopted herein to limit the pressure transient of the fluid in the generator, such that the rise time and the bandwidth of the liquid step wave can reach 30.0 µs and 10.4 kHz. The experimental results not only display the performance of the liquid step wave generator, but also reveal the dynamic characteristics of three different test pressure sensors using the developed liquid step wave generator.
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Na, Byoungjoon, and Haeng Sik Ko. "Experimental Study on Impact Pressure at the Crown Wall of Rubble Mound Seawall and Velocity Fields using Bubble Image Velocimetry." Journal of Korean Society of Coastal and Ocean Engineers 34, no. 4 (August 31, 2022): 119–27. http://dx.doi.org/10.9765/kscoe.2022.34.4.119.
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To investigate varying wave impact pressure exerting at the crest wall of rubble mound seawall, depending on breaking wave properties, regular waves with different wave periods were generated. Wave velocity fields and void fraction were measured using bubble image velocimetry and simple combined wave gauge system (Na and Son, 2021). For the waves with shorter wave period, maximum horizontal velocity was less reduced compared to incident wave speed while breaking-induced air entrainment was occurred intensely, leading to a significant reduction of wave impact pressure at the crest wall. For the waves with longer wave periods, less air wave entrained and the wave structure followed a flip-through mode (Cooker and Peregrine, 1991), resulting in an abrupt increase of the impact pressure.
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Lu, Xi, Shu Shan Wang, Feng Ma, and Yun Peng Hao. "Numerical Simulation on Pressure Field Characteristics of Underwater Explosion with Double Explosive Sources." Applied Mechanics and Materials 713-715 (January 2015): 1794–99. http://dx.doi.org/10.4028/www.scientific.net/amm.713-715.1794.
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By using the AUTODYN, the study of numerical simulation on pressure field characteristics of underwater explosion detonated by the double explosive sources at the same time shows that a coupled zone with increased pressure appears after the two initial shock waves transmit through each other and at the intersection of the two initial shock waves, the mach wave appears. The transmitted waves diffract around bubbles with a reflected rarefaction wave. The peak pressure in the central area between the two explosive sources is caused by transmitted wave and has dishing isosurface. And the peak pressure outside the two explosive sources is caused by initial shock wave and has spherical isosurface. Coupled peak pressure in the plane of symmetry is two times more than incident peak pressure and with the propagation of shock wave, the ratio of coupled peak pressure and incident peak pressure gradually increases.
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Wan, Yu, Wenjie Li, Hongbo Du, and Xiao Yang. "Investigation of Shock Wave Pressure Transmission Patterns and Influencing Factors Caused by Underwater Drilling Blasting." Water 14, no. 18 (September 12, 2022): 2837. http://dx.doi.org/10.3390/w14182837.
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Underwater blasting technology has been widely used in inland waterway improvement projects. However, due to the particularity and complexity of underwater blasting, it is difficult to predict the transmission patterns of underwater blasting shock waves. Therefore, based on the Guoyuan Port Phase II project in Chongqing, the transmission patterns and influencing factors of underwater drilling blast shock wave pressure were investigated by field monitoring and numerical simulation. In this study, a total of 45 groups of shock wave pressures were measured, and the underwater shock wave pressure transmission formula obtained through data fitting was P = 27.39 × (Q1/3/R)1.25. Furthermore, the shock wave pressure transmission process in water was numerically simulated, and the simulation results were verified using field monitoring data. The results showed that the simulation and measured results were consistent. Finally, the influence of water depth, flow rate, and flow direction on the transmission pattern of shock wave pressure was analyzed, based on a numerical simulation method. The results showed that the more blastholes there are, the smaller the peak pressure of the shock wave. The lower the depth of blasting, the faster the decay of shock wave pressure. The flow rate has less effect on the shock wave pressure. At flow rates of 1, 2, 3, and 4 m/s in the range of 0 to 50 m, the shock wave pressure in the upstream flow decreased by 5.7%, 7.4%, 9.1%, and 10.2%, respectively, compared with that in the downstream flow. This study provides a theoretical basis for safety control of underwater drilling blasting engineering in inland waterways.
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Nian, Ting Kai, Bo Liu, and Ping Yin. "Seafloor Slope Stability under Adverse Conditions Using Energy Approach." Applied Mechanics and Materials 405-408 (September 2013): 1445–48. http://dx.doi.org/10.4028/www.scientific.net/amm.405-408.1445.
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The effects of ocean waves on the stability of seafloor slopes are of great importance in marine environment. The stability of a seafloor slope considering wave-induced pressure is analyzed using the kinematic approach of limit analysis combined with a strength reduction technique. A seafloor slope without waves is considered first. Furthermore, waved-induced pressure is considered to act on the surface of slope as an external load to analyze the effects on the stability of slope by waves. The results show that the adverse effect of waves on slope stability increases with an increase of the wave height as well as a decrease of the water depth.
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Umeyama, Motohiko. "Dynamic-pressure distributions under Stokes waves with and without a current." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 376, no. 2111 (December 11, 2017): 20170103. http://dx.doi.org/10.1098/rsta.2017.0103.
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To investigate changes in the instability of Stokes waves prior to wave breaking in shallow water, pressure data were recorded vertically over the entire water depth, except in the near-surface layer (from 0 cm to −3 cm), in a recirculating channel. In addition, we checked the pressure asymmetry under several conditions. The phase-averaged dynamic-pressure values for the wave–current motion appear to increase compared with those for the wave-alone motion; however, they scatter in the experimental range. The measured vertical distributions of the dynamic pressure were plotted over one wave cycle and compared to the corresponding predictions on the basis of third-order Stokes wave theory. The dynamic-pressure pattern was not the same during the acceleration and deceleration periods. Spatially, the dynamic pressure varies according to the faces of the wave, i.e. the pressure on the front face is lower than that on the rear face. The direction of wave propagation with respect to the current directly influences the essential features of the resulting dynamic pressure. The results demonstrate that interactions between travelling waves and a current lead more quickly to asymmetry. This article is part of the theme issue ‘Nonlinear water waves’.
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Papadimitrakis, Yiannis Alex, En Yun Hsu, and Robert L. Street. "The role of wave-induced pressure fluctuations in the transfer processes across an air–water interface." Journal of Fluid Mechanics 170 (September 1986): 113–37. http://dx.doi.org/10.1017/s0022112086000824.
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The structure of the pressure and velocity fields in the air above mechanically generated water waves was investigated in order to evaluate their contribution to the transfer of momentum and energy from wind to water waves. The measurements were taken in a transformed Eulerian wave-following frame of reference, in a wind-wave research facility at Stanford University.The organized component of the fluctuating static pressure at the channel roof was found to contain contributions from both the sound field and the reflected water wave. The acoustic contributions were accounted for by appropriately correcting the pressure amplitude and phase (relative to the wave) and its contribution to the momentum and energy exchange. The wave-induced pressure coefficient at the fundamental mode shows in general an exponential decay behaviour with height, but the rate of decay is different from that predicted by potential-flow theory. The wave-induced pressure phase relative to the wave remains fairly constant throughout the boundary layer, except when the ratio of the wave speed to the freestream velocity, c/Uδ0 = 0.78 and 0.68. This phase difference was found to be about 130° during active wave generation, with the pressure lagging the wave. The momentum and energy transfer rates supported by the waves were found to be dominated by the wave-induced pressure, but the transfer of the corresponding total quantities to both waves and currents may or may not be so dominated, depending on the ratio c/Uδ0. The direct contribution of the wave-induced Reynolds stresses to the transfer processes is negligible.
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ZHAO, W., Z. L. JIANG, H. R. YU, T. SAITO, and K. TAKAYAMA. "WAVE PROPAGATION ANALYSIS IN A PRESSURE-WAVE-REFRIGERATOR." Modern Physics Letters B 19, no. 28n29 (December 20, 2005): 1747–50. http://dx.doi.org/10.1142/s0217984905010372.
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Pressure wave refrigerators (PWR) refrigerate the gas through periodical expansion waves. Due to its simple structure and robustness, PWR may have many potential applications if the efficiency becomes competitive with existing alternative devices. In order to improve the efficiency, the characteristics of wave propagation in a PWR are studied by experiment, numerical simulation and theoretical analysis. Based on the experimental results and numerical simulation, a simplified model is suggested, which includes the assumptions of flux-equilibrium and conservation of the free energy. This allows the independent analysis of the operation parameters and design specifics. Furthermore, the optimum operation condition can be deduced. Some considerations to improve the PWR efficiency are also given.
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Li, Yiqiao, Shengqiang Shen, Chao Niu, Yali Guo, and Liuyang Zhang. "The Effect of Different Pressure Conditions on Shock Waves in a Supersonic Steam Ejector." Energies 15, no. 8 (April 15, 2022): 2903. http://dx.doi.org/10.3390/en15082903.
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The complex flow phenomena in a three-dimensional supersonic steam ejector were simulated with a non-equilibrium condensation model including real physical properties in different pressure conditions. The different working conditions include discharge pressure, motive pressure, and suction pressure. The influence of different pressures on shock waves in the steam ejector was investigated comprehensively. The intrinsic causes of shock wave variation with pressure conditions were explained in detail. The results show that the width of the primary shock train region expand with an increase in the motive pressure or a decrease in suction pressure. The diamond shock waves move downstream with an increase in motive pressure or a decrease in suction pressure. The shocking position in the diffuser moves upstream until it reaches the diffuser entrance with an increase in discharge pressure or a decrease in motive pressure or suction pressure. The intensity and number of oblique shock waves in the diffuser increase with an increase in motive pressure and suction pressure or a decrease in discharge pressure. The existence of only one shock wave in the diffuser is a necessary and insufficient condition for the ejector to enter a double choking mode.
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Prokash Chandra Roy, Arafater Rahman, and Mihir Ranjan Halder. "Numerical Investigation of Aerodynamic Characteristics of Hyperloop System Using Optimized Capsule Design." International Journal of Automotive and Mechanical Engineering 19, no. 4 (January 3, 2023): 10132–43. http://dx.doi.org/10.15282/ijame.19.4.2022.10.0784.
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As a consequence of research on developing a speedy transportation system, Hyperloop is one of the best solutions now as smaller resistant forces are developed on the capsule body compared to conventional ground transportation systems due to movement in a vacuum and no contact with the ground. In this study, a capsule of an elliptical-shaped head and semicircular-shaped rear was chosen for analysis. Aerodynamic drags were calculated at different evacuated tunnel pressures. The computational regime was a 360 meters long tunnel. The inlet and outlet were pressure far-field boundaries while the wall was moving, with a Blockage Ratio (BR) of 0.36. Characteristics of different regions were identified in choked conditions. The drag was found to be lesser than the capsule of semicircular ends at different speeds. The pressure drag and friction drag were increased with the increase in velocity in the same tunnel pressure. By investigating different flow regions, it was found that a series of rhomboidal-shaped shock waves appear at high speeds. The formation and nature of this shock wave were also investigated, and found that it is caused due to shock wave and expansion wave interaction that results in the fall of pressure and temperature in the wake region.
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Zuckerman, B. D., E. C. Orton, L. P. Latham, C. C. Barbiere, K. R. Stenmark, and J. T. Reeves. "Pulmonary vascular impedance and wave reflections in the hypoxic calf." Journal of Applied Physiology 72, no. 6 (June 1, 1992): 2118–27. http://dx.doi.org/10.1152/jappl.1992.72.6.2118.
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The alterations in pulsatile hemodynamics that occur during hypoxic pulmonary vasoconstriction have not been well characterized. Changes in oscillatory hemodynamics, however, may affect right ventricular-pulmonary vascular coupling and the dissipation of energy within the lung vasculature. To better define hypoxic pulsatile hemodynamics, we measured main pulmonary artery proximal and distal micromanometric pressures and ultrasonic flow in four open-chest calves during progressive hypoxia. Main pulmonary artery impedance and pressure transmission spectra were calculated using spectral analysis methods. Measured pressure and flow signals were separated in the time domain into forward and backward components. Hypoxia increased pulmonary blood pressure and resistance and produced multiple modifications in the impedance and pressure transmission spectra that indicated increased wave reflections and elasticity. The impedance and apparent phase velocity first-harmonic values were increased in amplitude, and the pressure transmission modulus plot showed an increased peak value. In addition, the impedance modulus plot demonstrated a rightward shift and increased oscillation in the mid- to high-frequency range. The time domain analysis also confirmed increased wave reflections and elasticity. Hypoxia produced large backward-traveling (reflected) pressure and flow waves. The initial portions of these waves arrived at the heart during systole, producing characteristic changes in the measured pressure and flow waveforms. With prolonged hypoxia, main pulmonary artery pulse wave velocity increased by 30%. Thus, hypoxia is associated with complex alterations in pulmonary artery elasticity and wave reflections that act to increase the oscillatory afterload of the right ventricle.
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Tsung, Tsing Tshih, Lee Long Han, Liang Chia Chen, and Ho Chang. "Performance Characterization of Pressure Sensors Using an Improved Pressure Square Wave Generator." Key Engineering Materials 295-296 (October 2005): 533–38. http://dx.doi.org/10.4028/www.scientific.net/kem.295-296.533.
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The purpose of this paper is to analyze and compare the dynamic characteristics of various structure pressure sensors using the Improved Pressure Square Wave Generator (IPSWG). The developed IPSWG is a signal generator that creates pressure square waves as an excitation source. The dynamic characteristics of pressure sensor in hydraulic systems can be measured and evaluated effectively due to the high excitation energy. The method is also useful for dynamic testing and characterization for a high frequency range, which cannot be performed by the traditional methods, such as the hammer kit excitation, sweeping frequency pressure wave, and random frequency wave. Result shows that piezoelectric sensors (quartz) have a largest gain margin and overshoot. The strain gauge sensor has a smaller gain margin and overshoot. The piezoelectric sensor is more suitable for measuring dynamic pressure.
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Veic, Duje, and Wojciech Sulisz. "Impact Pressure Distribution on a Monopile Structure Excited by Irregular Breaking Wave." Polish Maritime Research 25, s1 (May 1, 2018): 29–35. http://dx.doi.org/10.2478/pomr-2018-0019.
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Abstract The problem of impact pressure distribution on a monopole structure excited by irregular breaking waves is investigated. The analysis is performed by applying a numerical model that combines potential flow model with a Navier-Stokes/VOF solution. The temporal pressure distribution is analysed for two breaking wave cases characterized by the significant difference in the steepness of the wave front. The peak impact pressures are observed in the region below the overturning wave jet where the pressure increases rapidly resulting in a peak value of the slamming coefficient equal to Cs=2π. The vertical load distribution provided by the derived model is more realistic than a rectangular shape distribution applied in engineering practice. This is because the vertical load distribution strongly depends on breaking wave shape and it is difficult to uniquely approximate such a load distribution by a rectangle.
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Zhang, Sheng, Xiang Hao Yang, and Xin Wen Li. "Numerical Simulation Analysis of the Effect on the One-Dimension Assumption in Different Diameter SHPB Pressure Bar by Two Kinds of Loading Waveform." Advanced Materials Research 787 (September 2013): 759–64. http://dx.doi.org/10.4028/www.scientific.net/amr.787.759.
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t is one of precondition of determining rock material dynamic parameters for one-dimension assumption of the elastic pressure bar. In order to analyze its effect by loading wave type, the dynamic stress was simulated with Ls-dynamic finite element software, when SHPB(Split Hopkinson Pressure Bar) pressure bar with diameter of 50 mm, 75 mm and 100 mm were impacted respectively by a cycle rectangular loading wave and half sine loading wave. The stress waves of cross section in different diameter pressure bar and the different distance with pressure bar end were compared and analyzed. The results indicated that the dispersion of stress waves was very serious and the matching ability of stress wave at different distances in pressure bar was poor when the rectangular wave was loaded. However, the dispersion of stress wave was not obvious with the increase of the diameter of pressure bar and the change of pressure bar when the half sine wave was loaded. The half sine loading wave which can strictly meet the one-dimension assumption is one of the ideal loading waveforms of the rocky heterogeneous materials.
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Christensen, N. I., and H. F. Wang. "The Influence of pore pressure and confining pressure on dynamic elastic properties of Berea sandstone." GEOPHYSICS 50, no. 2 (February 1985): 207–13. http://dx.doi.org/10.1190/1.1441910.
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Compressional‐ and shear‐wave velocities of watersaturated Berea sandstone have been measured as functions of confining and pore pressures to 2 kbar. The velocities, measured by the pulse transmission technique, were obtained at selected pressures for the purpose of evaluating the relative importance of confining pressure and pore pressure on elastic wave velocities and derived dynamic elastic constants. Changes in Berea sandstone velocities resulting from changes in confining pressure are not exactly canceled by equivalent changes in pore pressure. For properties that involve significant bulk compression (compressional‐wave velocities and bulk modulus) an incremental change in pore pressure does not entirely cancel a similar change in confining pressure. On the other hand, it is shown that a pore pressure increment more than cancels an equivalent change in confining pressure for properties that depend significantly on rigidity (shear‐wave velocity and Poisson’s ratio). This behavior (as well as observed wave amplitudes) is related to the presence of high‐compressibility clay that lines grains and pores within the quartz framework of the Berea sandstone.
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Czosnyka, Zofia, Marek Czosnyka, and John D. Pickard. "CSF Pulse Pressure and B Waves." Journal of Neurosurgery 103, no. 4 (October 2005): 767–68. http://dx.doi.org/10.3171/jns.2005.103.4.0767.
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Abstract Object. The appearance of numerous B waves during intracranial pressure (ICP) registration in patients with idiopathic adult hydrocephalus syndrome (IAHS) is considered to predict good outcome after shunt surgery. The aim of this study was to describe which physical parameters of the cerebrospinal fluid (CSF) system B-waves reflect and to find a method that could replace long-term B-wave analysis. Methods. Ten patients with IAHS were subjected to long-term registration of ICP and a lumbar constant-pressure infusion test. The B-wave presence, CSF outflow resistance (Rout), and relative pulse pressure coefficient (RPPC) were assessed using computerized analysis. The RPPC was introduced as a parameter reflecting the joint effect of elastance and pulsatory volume changes on ICP and was determined by relating ICP pulse amplitudes to mean ICP. Conclusions. The B-wave presence on ICP registration correlates strongly with RPPC (r = 0.91, p < 0.001, 10 patients) but not with CSF Rout. This correlation indicates that B waves—like RPPC—primarily reflect the ability of the CSF system to reallocate and store liquid rather than absorb it. The RPPC-assessing lumbar short-term CSF pulse pressure method could replace the intracranial long-term B-wave analysis.
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Kakinuma, Taro. "Tsunamis Generated and Amplified by Atmospheric Pressure Waves Due to an Eruption over Seabed Topography." Geosciences 12, no. 6 (May 31, 2022): 232. http://dx.doi.org/10.3390/geosciences12060232.
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Numerical simulations were generated using a nonlinear shallow-water model of velocity potential to study the fundamental processes of tsunami generation and amplification by atmospheric pressure waves. When an atmospheric pressure wave catches up with an existing tsunami that is propagating as a free wave over an abrupt change in water depth, the amplified tsunami propagates in the shallower water. An existing tsunami propagating as a free wave over a sloping seabed is also amplified by being passed by atmospheric pressure waves. When atmospheric pressure waves travel over an abrupt change in water depth, the water surface profile of tsunamis in the shallower water depends on both the interval of the atmospheric pressure waves and the phase of the tsunami-generation process over the change in water depth. Moreover, when atmospheric pressure waves travel over an abrupt change in water depth, the tsunami amplitude in the shallower water increases, as the water depth of the shallower area is decreased and the Proudman resonance is further reduced. When an atmospheric pressure wave train with positive pressure travels over a sloping seabed, the amplification of tsunami crests propagating as free waves is controlled by leaving the forced water waves following the atmospheric pressure waves. Conversely, the amplitudes of tsunami troughs propagating as free waves increase.
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Banner, Michael L. "The influence of wave breaking on the surface pressure distribution in wind—wave interactions." Journal of Fluid Mechanics 211 (February 1990): 463–95. http://dx.doi.org/10.1017/s0022112090001653.
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In reviewing the current status of our understanding of the mechanisms underlying wind-wave generation, it is apparent that existing theories and models are not applicable to situations where the sea surface is disturbed by breaking waves, and that the available experimental data on this question are sparse. In this context, this paper presents the results of a detailed study of the effects of wave breaking on the aerodynamic surface pressure distribution and consequent wave-coherent momentum flux, as well as its influence on the total wind stress.Two complementary experimental configurations were used to focus on the details and consequences of the pressure distribution over breaking waves under wind forcing. The first utilized a stationary breaking wave configuration and confirmed the presence of significant phase shifting, due to air flow separation effects, between the surface pressure and surface elevation (and slope) distributions over a range of wind speeds. The second configuration examined the pressure distribution, recorded at a fixed height above the mean water surface just above the crest level, over short mechanically triggered waves which were induced to break almost continuously under wind forcing. This allowed a very detailed comparison of the form drag for actively breaking waves and for waves of comparable steepness just prior to breaking (‘incipiently’ breaking waves). For these propagating steep-wave experiments, the pressure phase shifts and distributions closely paralleled the stationary configuration findings. Moreover, a large increase (typically 100%) in the total windstress was observed for the breaking waves, with the increase corresponding closely to the comparably enhanced form drag associated with the actively breaking waves.In addition to further elucidating some fundamental features of wind-wave interactions for very steep wind waves, this paper provides a useful data set for future model calculations of wind flow over breaking waves. The results also provide the basis for a parameterization of the wind input source function applicable for a wave field undergoing active breaking, an important result for numerical modelling of short wind waves.
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Yu, Shuisheng, Leilei Niu, and Jin Chen. "Experimental and Numerical Studies on Bond Quality of Fully Grouted Rockbolt under Confining Pressure and Pull-Out Load." Shock and Vibration 2022 (August 25, 2022): 1–12. http://dx.doi.org/10.1155/2022/7012510.
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In mining engineering, the in situ stress changes with the stress induced by the surrounding mining activities. It positively or negatively affects the propagation of ultrasonic guided waves in rockbolts. Therefore, the effect of in situ stress in rockbolt support was determined by applying confining pressure and pull-out load in a laboratory test and using ultrasonic guided waves to test the rockbolt. Furthermore, the propagation law of ultrasonic guided waves and bond quality of the rockbolt under the interaction of the pull-out load and confining pressure were studied. Numerical simulations were performed to deduce the guided wave propagation process in grouted systems, and the influencing mechanism of the pull-out load and confining pressure on the guided wave propagation was discussed. The laboratory test and numerical simulation results show that the confining pressure weakens the guided wave propagation without pull-out load. Under the same pull-out load, the guided wave propagation gradually strengthens with increasing confining pressure. A larger confining pressure weakens the weakening effect of the pull-out load and suppresses the discreteness of the guided wave propagation. Under the same confining pressure, the guided waves did not diffract well into the cement mortar and concrete with increasing pull-out load, the confining pressure restricted the radial vibration of the guided waves, and the guided wave propagation law weakened. Thus, the pull-out load plays a weakening role in the propagation law of ultrasonic guided waves.
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Wang, Bo, Jialin Hao, Shengdong Liu, Fubao Zhou, Zhendong Zhang, Heng Zhang, and Huachao Sun. "Experimental Study on the Effect of Gas Pressure on Ultrasonic Velocity and Anisotropy of Anthracite." Geofluids 2019 (August 19, 2019): 1–10. http://dx.doi.org/10.1155/2019/3183816.
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To research the elasticity of gas-bearing coal fluid-solid two-phase medium with seismic exploration method is critical to the prevention of gas disasters. To investigate the elasticity, the ultrasonic elastic test of anthracite samples under different gas pressures was carried out and the ultrasonic velocity and anisotropy of the samples were analyzed in this study. The results show that the velocities (P- and S-waves) decrease in turn in the strike, dip, and vertical directions. However, a negative linear correlation is proved to exist between ultrasonic velocity and gas pressure. With the increase of gas pressure, the anisotropy degree of both the P-wave and the S-wave of the samples decreases but the declining degree of the P-wave is greater than that of the S-wave. In addition, the decrease in velocity and the anisotropy degree of the P-wave is greater than that of the S-wave, indicating that the P-wave is more sensitive to gas pressure changes in terms of velocity and its anisotropy degree.
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Dunst, Paul, Tobias Hemsel, Peter Bornmann, Walter Littmann, and Walter Sextro. "Optimization of Ultrasonic Acoustic Standing Wave Systems." Actuators 9, no. 1 (February 14, 2020): 9. http://dx.doi.org/10.3390/act9010009.
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Ultrasonic acoustic standing wave systems find use in many industrial applications, such as sonochemical reactions, atomization of liquids, ultrasonic cleaning, and spray dry. In most applications, highest possible sound pressure levels are needed to achieve optimum results. Until now, the atomization of liquids is limited to fluids with low viscosity, as systems generating sufficient sound pressure for atomizing fluids with higher viscosities are often not marketable due to their low throughput or high costs. For the production of polymer or metal powders or the dispensing of adhesives, highest sound pressures should be achieved with systems in suitable size, with good efficiency and at low cost but without contamination of sonotrodes and reflectors by the dispersed media. An alternative to the use of more powerful transducers is increasing the intensity of the acoustic standing wave field by optimizing the boundary conditions of the acoustic field. In most existing standing wave systems a part of the radiating sound waves does not contribute to the process, as the waves spread into the wrong direction or wipe themselves out due to interference. In order to obtain maximum sound pressure amplitudes in the standing wave field, all waves should be trapped between the sonotrode and the reflector. In addition, the resonance condition should be met for all radiated waves. These conditions can be fulfilled by optimizing the shapes of sonotrode and resonator as well as the distance between them. This contribution reports on a model, which is able to simulate the sound field between a transducer surface and a reflector. Using a linear finite-element model, the boundary conditions of the standing wave system are optimized. Sound pressure levels of the standing wave field are calculated for different shapes of reflectors and boundary conditions like the distance between the transducer and the reflector. The simulation results are validated by sound-field measurements via refracto-vibrometry and a microphone. Finally, optimization guidelines for the generation of high-intensity acoustic standing wave fields are shown and verified by measurements.
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Jeong, Youn Ju, Young Jun You, and Yoon Koog Hwang. "Wave Induced Hydraulic Pressure by Wave Conditions of Pontoon Typed Floating Structures." Advanced Materials Research 250-253 (May 2011): 1444–47. http://dx.doi.org/10.4028/www.scientific.net/amr.250-253.1444.
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In this study, in order to verify wave induced buoyancy effects by wave conditions of wave height and period, experimental studies were conducted to the floating structures of pontoon type. A series of small-scale tests with various wave cases were performed to the pontoon models. Two small-scale pontoon models having different bottom details were fabricated and tested under the five different wave cases. Six hydraulic pressure gauges were attached on the bottom of pontoon models and wave induced hydraulic pressure was measured during the tests. Finally, hydraulic pressure subjected to the bottom of pontoon models were compared with each other. As the results of this study, it was found that wave induced hydraulic pressures at bottom were dependent on the wave period as well as wave height, and waffled bottom shape hardly influenced on wave induced hydraulic pressure.
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Nagasawa, Takumi, Kaito Iuchi, Ryo Takahashi, Mari Tsunomura, Raquel Pantojo de Souza, Keiko Ogawa-Ochiai, Norimichi Tsumura, and George C. Cardoso. "Blood Pressure Estimation by Photoplethysmogram Decomposition into Hyperbolic Secant Waves." Applied Sciences 12, no. 4 (February 9, 2022): 1798. http://dx.doi.org/10.3390/app12041798.
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Photoplethysmographic (PPG) pulses contain information about cardiovascular parameters. In particular, blood pressure can be estimated using PPG pulse decomposition analysis, which assumes that a PPG pulse is composed of the original heart ejection blood wave and its reflections in arterial branchings. Among pulse decomposition wave functions that have been studied in the literature, Gaussian waves are the most successful ones. However, a more adequate pulse decomposition function could be found to improve blood pressure estimates. In this paper, we propose pulse decomposition analysis using hyperbolic secant (sech) waves and compare results with corresponding Gaussian wave decomposition. We analyze how the parameters of each of the two types of decomposition waves correlate with blood pressure. For this analysis, continuous blood pressure data and PPG data were acquired from ten healthy volunteers. The blood pressure of volunteers was varied by asking them to hold their breath for up to 60 s. The results suggested sech wave decomposition had higher accuracy in estimating blood pressure than the Gaussian function. Thus, sech wave decomposition should be considered as a more robust alternative to Gaussian wave pulse decomposition for blood pressure estimation models.
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Shi, He, Jinzhe Gong, Aaron C. Zecchin, Martin F. Lambert, and Angus R. Simpson. "Hydraulic transient wave separation algorithm using a dual-sensor with applications to pipeline condition assessment." Journal of Hydroinformatics 19, no. 5 (July 18, 2017): 752–65. http://dx.doi.org/10.2166/hydro.2017.146.
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Over the past two decades, techniques have been developed for pipeline leak detection and condition assessment using hydraulic transient waves (i.e. water hammer waves). A common measurement strategy for applications involves analysis of signals from a single pressure sensor located at each measurement site. The measured pressure trace from a single sensor is a superposition of reflections coming from upstream, and downstream, of the sensor. This superposition brings complexities for signal processing applications for fault detection analysis. This paper presents a wave separation algorithm, accounting for transmission dynamics, which enables the extraction of directional travelling waves by using two closely placed pressure sensors at one measurement site (referred to as a dual-sensor). Two typical transient incident pressure waves, a pulse wave and a step wave, are investigated in numerical simulations and laboratory experiments. Comparison of the wave separation results with their predicted counterparts shows the wave separation algorithm is successful. The results also show that the proposed wave separation technique facilitates transient-based pipeline condition assessment.
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D’Asaro, Eric. "Surface Wave Measurements from Subsurface Floats." Journal of Atmospheric and Oceanic Technology 32, no. 4 (April 2015): 816–27. http://dx.doi.org/10.1175/jtech-d-14-00180.1.
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AbstractPressure gradient measurements on a subsurface Lagrangian float are used to measure the spectrum of surface waves for 100 days of measurements at Ocean Weather Station Papa. Along Lagrangian trajectories of surface waves, the pressure is constant and the vertical pressure gradient fluctuations equal the Eulerian fluctuations at the mean float depth to second order in wave height. Measurement of the pressure difference between the top and the bottom of the float can thus be used to measure the waves. Corrections for the wave decay with depth, for the vertical motion of the float, for the finite sampling interval, and for the sampling noise (among others) are necessary to obtain accurate results. With these corrections, scalar spectra accurately match those from a nearby Waverider buoy for significant wave heights greater than about 3 m. For smaller wave heights, noise in the pressure measurements biases the float spectral measurements. Significant wave height is measured with an rms error of 0.37 m over the measured range of 1–9 m. This demonstrates that Lagrangian floats accurately follow the Lagrangian trajectories of surface waves. More detailed and quieter measurements of float motion could likely measure directional wave spectra from below the surface. Similar methods could be used to infer surface wave properties from other subsurface vehicles.
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Teles, Alisson Roberto, Paulo Roberto Franceschini, and Jorge Luiz Kraemer. "Intracranial Pressure vs Intracranial Pressure-Wave Amplitude." Neurosurgery 71, no. 2 (August 2012): E523—E524. http://dx.doi.org/10.1227/neu.0b013e31825a562a.
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Hao, Ming Sheng, and Hong Lei Liu. "Study on the Characteristics of Shock Wave Pressure Caused by Underwater Blasting." Applied Mechanics and Materials 405-408 (September 2013): 692–95. http://dx.doi.org/10.4028/www.scientific.net/amm.405-408.692.
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By analyzing the characteristics of shock waves in underwater blasting of two bridge piers and monitoring their pressures, this paper found the rule that shock wave pressure varies with different distances from the explosion source. The method of comparison was applied in this study. Based on the characteristic parameters such as pressure amplitude and positive action time, the attenuation formula of shock wave in shallow water was proposed. The results of this paper are of great importance to the engineering design and construction as well as environmental safety assessment.
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Kimura, Tatsuto, Masahiro Masuko, Naoki Fujii, Hideki Kaida, and Naoto Kihara. "NUMERICAL AND HYDRAULIC EXPERIMENTS ON BORE PRESSURE DUE TO TSUNAMI." Coastal Engineering Proceedings, no. 36 (December 30, 2018): 18. http://dx.doi.org/10.9753/icce.v36.currents.18.
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The 2011 Tohoku earthquake tsunami struck a wide area of the northeastern coast of Japan, and many coastal structures and buildings were damaged by the tsunami. Most of the buildings were damaged by the tsunami wave pressure. After the tsunami, characteristics of tsunami waive pressures have been investigated by many researcher, and are being clarified. As shown in previous studies, there are three regimes charactering the vertical pressure profiles. The first one is the impulsive pressure, which is observed just after the tsunami-bore impacted structures. In this regime, strong hydrodynamic pressures are generated by the fluid-solid impact process. After that, the bore pressure is observed, and both the hydrodynamic and hydrostatic pressures contribute the pressure profile. After that, the flow near the structures reaches a quasi-steady state, and the pressure profile becomes hydrostatic. Most of the evaluation equations of tsunami wave pressure proposed by the previous studies can be used against the impulsive pressures and the pressures in the quasi-steady-state regime. On the other hand, the characteristics and quantitative evaluations of the bore pressure remain immature. In this study, in order to clarify the characteristics of the bore pressure, experiments on the bore pressure are carried out, and furthermore, three-dimensional numerical simulations are also carried out.