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Aperture plugging is a phenomenon that limits both the capacity and efficiency of pulp screens, which are critical components of the pulping, recycling, and papermaking processes. An understanding of when and how plugs begin to form can help avoid screen plugging, thus increasing papermaking and recycling efficiency. Small scale, fiber-optic pressure sensors were installed within screen cylinder apertures close to where plugging occurs to understand the mechanism of plug formation. Rotor pressure pulses within the aperture were measured during the plugging event. The pulse shape and magnitude during normal operation showed good agreement with past studies in which traditional pressure transducers were installed on the screen cylinder. However, prior to the onset of aperture plugging, the fiber-optic sensors showed that the variability of the pressure pulses increased and pulse magnitude within the slot decreased. The authors demonstrated that combining these variables by quantifying pulse variability using standard deviation and dividing that by pulse magnitude gave a result that was a strong predictor of aperture plugging. [ABSTRACT FROM AUTHOR]

Aperture plugging is a phenomenon that limits both the capacity and efficiency of pulp screens, which are critical components of the pulping, recycling, and papermaking processes. An understanding of when and how plugs begin to form can help avoid screen plugging, thus increasing papermaking and recycling efficiency. Small scale, fiber-optic pressure sensors were installed within screen cylinder apertures close to where plugging occurs to understand the mechanism of plug formation. Rotor pressure pulses within the aperture were measured during the plugging event. The pulse shape and magnitude during normal operation showed good agreement with past studies in which traditional pressure transducers were installed on the screen cylinder. However, prior to the onset of aperture plugging, the fiber-optic sensors showed that the variability of the pressure pulses increased and pulse magnitude within the slot decreased. The authors demonstrated that combining these variables by quantifying pulse variability using standard deviation and dividing that by pulse magnitude gave a result that was a strong predictor of aperture plugging.

Two- and three-dimensional analyses of transient flows considering the air–water interaction have been a challenge for researchers due to the complexity in the numerical resolution of the multiphase during emptying in pressurized water pipelines. The air–water dynamic interaction of emptying processes can be analyzed using thermodynamic and hydraulic laws. There is a lack in the current literature regarding the analysis of those phenomena using 3D models. In this research, several simulations were performed to study the complex details of two-phase flows. A 3D model was proposed to represent the emptying process in a single pipeline, considering a PVoF model and two-equation turbulence model. The model was numerically validated through 12 experimental tests and mesh sensitivity analysis. The pressure pulses of the air pockets were evaluated and compared with the experimental results and existing mathematical models, showing how the 3D models are useful for capturing more detailed information, such as pressure and velocity patterns of discrete air pockets, distribution of air and water velocity contours, and the exploration of temperature changes for an air pocket expansion. [ABSTRACT FROM AUTHOR]

Pigging technology is widely used in the oil and gas industry. During the course of pigging, after a water pressure test, the instability of the pig caused by terrain fluctuation can affect the stable operation of the pipeline and even cause burst accidents. This paper describes the four stages of pig movement in an inclined pipeline, with vapor-liquid eruption occuring in the last stage. A hydraulic transient model of the pigging operation after a water pressure test is established based on mass conservation and motion equations, the dynamic equation of the pig, and the vapor-liquid eruption model. The model can simulate the status of fluid flow in the pipeline, track the movement of the pig, and predict the pressure pulses. The simulation results are consistent with the data of two burst accidents, which verifies the correctness of the established model and the reliability of the calculated results. It can therefore provide a reliable and effective theoretical basis for developing a pigging plan on site.

This study was done in order to evaluate the effect of a novel pressure pulsation device (Pulsehaler™, Respinova Ltd., Israel) on the deposition pattern of inhaled aerosol in the lungs of COPD patients. Fifteen COPD patients were recruited to undergo spirometry and SPECT-CT lung scan following nebulization of radioactively labeled albuterol in saline solution with a jet nebulizer ("NEB") and with a combined Pulsehaler™/jet nebulizer ("PH + NEB") treatment. Central and peripheral segments of the coronal and transverse SPECT scans were evaluated for total counts and for the ratios between peripheral counts and central counts (penetration Index, "PI"). There was a significant improvement in FEV1 from before to after albuterol treatment in the PH + NEB group (151 ml ± 187, p < 0.008), but not in the NEB only group (66 ml ± 125, p = 0.06). FVC, FEF25–75, FEV1%, FVC%, FEF25, FEF50, and FEF75 also improved significantly in the PH + NEB group but not the NEB group. There were significant improvements seen between treatments for FEF25-75 (PH + NEB > NEB, p = 0.0176), FEF75 (PH + NEB > NEB, p = 0.0028), but not for the other spirometry measures. Borg scores also were improved significantly improved in PH + NEB vs NEB (p = 0.0006). Total lung deposition and total body deposition were lower in the PH + NEB treatments vs the NEB treatments. However, PI values were 3.08 ± 0.67 times greater on average with the PH + NEB (p = 0.026) as compared to NEB only. The magnitude of the increased penetration index observed in this study indicates that pressure pulsations should be further explored as means to improve drug delivery into the distal small airways of the bronchial tree. Effects of the pressure pulsations on small airway patency could be the mechanism by which the effect was achieved. [ABSTRACT FROM AUTHOR]

Pigging technology is currently widely used in the oil and gas industry. The unstable movement of the pig in the pigging process after a water pressure test will not only affect the operation of pipes, but may even cause them to burst. In this paper, a transient hydraulic model of the pigging process after a water pressure test is established in a two-grid system. The model combines the mass and motion equations of the gas and liquid and then is solved by the method of characteristics. The combined method of computational fluid dynamics (CFD) software simulation and a semiempirical formula is used to study the gas-liquid flow pressure drop characteristics of T-abrupt and bend drain pipe. It is applied to the pig tracker and hydraulic pulse prediction to obtain the pig's position and speed. Finally, the field data and the simulation results are basically consistent after comparison, which verifies that the established model is correct and the calculation results are reliable. Hence, we can provide a reliable and effective theoretical basis for the on-site pigging scheme. [ABSTRACT FROM AUTHOR]

This paper investigates the impact of the propeller blade back cavitation on the induced pressure pulses. The study employs synchronous observation, wherein both cavitation and pressure pulses are measured concerning both time and space for a 4-bladed propeller in 5 different conditions. The correlation between the cavitation pattern and pressure pulses is presented to elucidate the mechanism behind the formation of the time history curve of pressure pulses. The results reveal that the pressure pulses induced by propeller cavitation exhibit a combination of consistency and discrepancy. It is demonstrated that the pressure pulses are directly proportional to the second derivative of the cavitation volume curve, allowing for the prediction of pressure pulses by the cavitation volume curve. The disturbances and cavitation evolution on each blade, superposition of adjacent blades, and fluctuations in cavitation collectively contribute to a distinctive curve of propeller cavitation-induced pressure pulses, ultimately determining its frequency spectrum. As the cavitation develops, the amplitudes and blade phase angles of 1st and 2nd blade frequency components of pressure pulses gradually increase. The higher-order components generally increase in amplitude, albeit with varying distributions and no regularity in phase angle variations. • Investigate cavitation and pressure pulses by synchronous observation experiment. • Verify the linear relationship between fluctuation pressure and second derivative of cavitation volume. • Investigate the influence of cavitation pattern on frequency spectrum of fluctuation pressure. [ABSTRACT FROM AUTHOR]

We study two events of structured Pc1 waves (pearls) observed by CARISMA magnetometers during a period of quiet magnetic (Kp ~1) and solar wind conditions on 1 August 2008. Bursts of proton precipitations and electromagnetic ion‐cyclotron waves were simultaneously observed by NOAA/POES and GOES satellites at dayside. Apparent correspondence was found between ground pearl pulsations and magnetospheric compressions observed by GOES and THEMIS satellites. We have found the Pc1 wave splitting into very close subfrequencies (within 0.1 Hz) that can be explained by weak magnetospheric compressions. The compressions are caused by pressure pulses originated from transient foreshock and interplanetary magnetic field discontinuities observed upstream of the bow shock by the THEMIS‐C probe. Thus, the observed pearls are compression‐related Pc1 waves generated under transient foreshock conditions. Key Points: Pc1 pearls at morning and EMIC waves on the dayside are found during quiet timePearls and EMIC waves are associated with weak and transient magnetospheric compressionsMagnetospheric compressions are produced by foreshock pressure pulses [ABSTRACT FROM AUTHOR]

Standing ultralow frequency waves redistribute energy and momentum around the Earth's magnetosphere. The eigenfrequencies of these standing waves can be measured by applying the cross‐phase technique to ground magnetometer data. To make a detection, the flux tubes in the vicinity of the magnetometers must all be driven at their local eigenfrequencies by a source with a sufficient frequency width. Therefore, successful measurement of the local eigenfrequencies indicates that a broadband source is exciting the flux tubes. We have analyzed 10 years of magnetometer data with an automated cross‐phase algorithm and used correlations with the OMNI data set to understand under what conditions broadband excitation occurs and how the conditions affect the eigenfrequency values. This is the largest such survey of its kind to date. We found that lower eigenfrequencies at higher latitudes (L>5) and higher eigenfrequencies at lower latitudes (L<4) were excited under different conditions. It was also possible to directly compare the first and third harmonics at midlatitudes. The lower eigenfrequencies were excited during more disturbed conditions, and we suggest that these harmonics are driven by solar wind pressure pulses or the Kelvin‐Helmholtz instability at the magnetopause. The higher eigenfrequencies were excited when the magnetosphere was relatively quiet, and we suggest that the cause was waves generated upstream of the Earth's bow shock. The eigenfrequencies were observed to decrease in the middle magnetosphere during disturbed intervals. This is because the intensification of the ring current weakens the magnetic field. Variations in magnetic local time and latitude were also investigated. Key Points: Pressure pulses and Kelvin‐Helmholtz instabilities excite Pc5 eigenfrequencies at L>5Upstream waves generated in the foreshock are a source of Pc4 eigenfrequencies at L<4Enhancements in the ring current act to decrease eigenfrequencies in the inner magnetosphere [ABSTRACT FROM AUTHOR]

Pigging techniques are widely used in the oil and gas industry. The unsteady motion of the PIG in an undulating pipe section during the pigging process after a water pressure test affects the stable operation of the pipeline and also causes a pipe rupture accident in serious cases. First, an experimental study was conducted to investigate the pigging process of air–water two phase pipe flows, and the PIG reverse movement and hydraulic pulse phenomenon were observed. Subsequently, a hydraulic transient model of the pigging process after a water pressure test was established in a dual-grid system. The model combined mass and motion equations of gas and liquid and PIG dynamic equations, considered three types of PIG motion states, namely positive movement, reverse movement and still, and used the method of characteristics to solve the equations. The model exhibits the ability for PIG tracing and hydraulic pulse prediction. It can be used to obtain the position and speed of the PIG. Finally, the field data and simulation results were compared, and the results indicated that they are essentially identical. This verified the accuracy of the model that is established in this study and the reliability of computed results and provided a reliable and effective theoretical basis for the development of field pigging plans. [ABSTRACT FROM AUTHOR]

The problem on oil filtration in the reservoir model with the preset differential pressure harmonically varying in time on its faces is solved. Hysteresis effects of capillary pressure under change in the direction of fluid expulsion are considered. The influence exerted by liquid fluctuations on cleaning the near-well zone from possible capillary blocking of aqueous phase is estimated. The action of alternating pressure pulses on the oil-saturated reservoir model is investigated. It is shown that harmonic change in liquid pressure promotes removal of immobile capillary-blocked water from the near-well zone. The results of in-situ experiments on wave action on the wellbottom zone and oil production stimulation are presented. [ABSTRACT FROM AUTHOR]

Stress and water injection induce deformations and changes in pore pressure in the soil. The interaction between the mechanical deformations and the flow of water induces a change in porosity and permeability, which results in nonlinearity. To investigate this interaction and the impact of mechanical vibrations and pressure pulses on the flow rate through the pores of a porous medium under a pressure gradient, a poroelastic model is proposed. In this paper, a Galerkin finite element method is applied for solving the quasi-static Biot’s consolidation problem for poroelasticity, considering nonlinear permeability. Space discretisation using Taylor-Hood elements is considered, and the implicit Euler scheme for time stepping is used. Furthermore, Monte Carlo simulations are performed to quantify the impact of variation in the parameters on the model output. Numerical results show that pressure pulses and soil vibrations in the direction of the flow increase the amount of water that can be injected into a deformable fluid-saturated porous medium. [ABSTRACT FROM AUTHOR]

There is increasing interest in optimizing ships for the actual operating condition rather than just for calm water. In order to optimize the propeller designs for operations in waves, it is essential to study how the propeller performance is affected by operation in waves. The effect of various factors that influence the propeller is quantified in this paper using a 8000 dwt chemical tanker equipped with twin-podded propulsion as a case vessel. Propeller performance in waves in terms of cavitation, pressure pulses, and efficiency is compared with the performance in calm water. The influence of wake variation, ship motions, RPM fluctuations and speed loss is studied. Substantial increase in cavitation and pressure pulses due to wake variation in the presence of waves is found. It is found that the effect of other factors is relatively small and easier to take into account as compared to wake variation. Therefore, considering the wake variation at least in the critical wave condition (where the wavelength is close to ship length) in addition to calm water wake is recommended in order to ensure that the optimized propeller performs well both in calm water and in waves. [ABSTRACT FROM AUTHOR]

The present paper deals with the side effects of propellers cavitation, i.e. pressure pulses and radiated noise. These effects are gaining more and more importance for commercial ships for different reasons. Pressure pulses significantly affect comfort onboard, thus their reduction is of utmost importance for all ships carrying passengers. As regards the underwater radiated noise, in the last decade interest has shifted from navy applications to commercial ships, due to the concern for the rising background noise in the oceans. The propellers, generating noise directly in water, represent one of the main contributions to the overall underwater noise emitted from ships. Due to the complexity of the mechanisms of propeller noise generation, different complementary strategies have to be followed to properly analyze the problem, ranging from induced pressure pulses to broadband noise and cavitation. In the present work, part of the activities carried out in the framework of the collaborative EU FP7 project AQUO (Achieve QUieter Oceans by shipping noise footprint reduction, www.aquo.eu) are reported. The paper presents the investigations carried out on a specific test case represented by a single screw research vessel, which is analyzed with three different strategies: numerical calculations, model scale investigations and fullscale measurements.

The present paper is focused on an experimental investigation of pressure pulses and radiated noise for two alternative designs of a propeller of a high-speed craft. The propellers have been designed in the context of a research project starting from two different rake distributions (forward rake to increase thrust and efficiency, backward rake to reduce cavitation), using different techniques (traditional lifting line / lifting surface and optimization algorithm coupled with a panel code), leading thus to rather different geometries. Propellers have been tested through cavitation tunnel experiments. The activity represents an interesting case study for this kind of measurement in presence of rather large cavitation extensions. The effects of cavitation on different components of pressure pulses and noise are investigated for the different rake distributions adopted. Results clearly shows the effects of this geometrical characteristic on cavitation and pressure pulses pointing out that, in some cases, propeller hydrodynamic performances may determine pressure pulses intensity more than cavitation extensions. A simplified numerical approach, adopting stationary RANS calculations, for the evaluation of the effects of propeller geometry, has been proposed. Results show a good correlation with measurements allowing to have an insight into the phenomenon and confirming the effect of the rake. [ABSTRACT FROM AUTHOR]

In view of environmental concerns, there is increasing demand to optimize the ships for the actual operating condition rather than for calm water. Now, in order to apply this for propeller design, a first step would be to study the effects of waves on propeller operation. Therefore, the aim of this paper is to identify and quantify the effect of various factors affecting the propeller in waves. The performance of KVLCC2 propeller in the presence of three different waves has been compared with calm water performance. Changes in performance in terms of cavitation, pressure pulses, and efficiency have been studied. Significant increase in pressure pulses has been observed due to wake change in waves even though cavitation did not show any significant change. An analysis using cavitation bucket diagram in different wave conditions indicates that a propeller optimized for calm water wake may perform much worse in the presence of waves. Therefore, having wake variation at least in critical wave conditions (where the wavelength is close to ship length) in addition to calm water wake could be very useful to ensure that the propeller performs equally well in the presence of waves. [ABSTRACT FROM AUTHOR]

Pressure and proximity measurements made in a tunnel indicate that a typical vehicle passage produced on the tunnel roof an initial pressure increase of small magnitude, followed by a sharp and more substantial drop in pressure below atmospheric. The magnitude of the pressure drop was found to increase with smaller clearances between the vehicle top and the tunnel roof, consistent with the Bernoulli relation and the vehicle speed. The dynamic pressures potentially may have significant effects on the vibration and noise environments on the lower floors of "air rights construction" buildings that span highways. [ABSTRACT FROM AUTHOR]

This paper provides an overview to all the published computational work in the Journal of Wind Engineering and Industrial Aerodynamics in the field of train aerodynamics since 1992. It has been found that in early nineties the computational power was limited and thus simplified potential flow solves and 1D codes were the main tools for train aerodynamics. Solution of the fully viscus and turbulent flow for train aerodynamics was limited to 2D cases using the steady RANS solvers on coarse meshes. In later nineties, the increase in computational power allowed for the solution of the fully turbulent flow around 3D models of high-speed trains using RANS models. Recently and due to the significant increase in computational power, the high fidelity Detached Eddy Simulations (DES) and Large Eddy Simulations became the computational methods for the different issues in train aerodynamics. It has been found that although computational wind engineering (CWE) contributed significantly in the development of new high-speed trains in the past thirty years, there are still number of emerging issues in the aerodynamics of high-speed trains that require considerable investigations by the CWE community. • The paper reviews all the computational paper for train aerodynamics published in the JWEIA from 1992 to 2022. • New trends in the investigations of traditional issues of train aerodynamics are presented. • Emerging issues in train aerodynamics are presented. [ABSTRACT FROM AUTHOR]

The attenuation of mud pressure pulses in the drilling fluid inside drill string has restricted the application of mud pulse telemetry systems in directional drilling operations. This paper aims to investigate the effects of suspended solid particles on the propagation and attenuation characteristics of pressure pulses. In this work, an analytical model estimating the wave speed and attenuation factor of pressure pulses has been proposed based on the solid–liquid two-fluid model by performing linear perturbation theory, with the interactions of the solid–liquid two phases being considered. The model calculations are compared with the results of the experiments, showing good agreement. Based on the model, the propagation behavior of pressure pulses has been analyzed to ascertain the important parameters affecting the wave speed and attenuation factor. The results indicate that the angular frequency of the pressure pulses, the volume fraction, size and density of the solid particles all exert significant influence on the pressure pulses propagation and attenuation. Lower angular frequency, solid particle size and density tend to reduce the attenuation of pressure pulses. The pressure pulses have maximum attenuation when the volume fraction falls within the range of 20%–30%. For different angular frequencies, the general effects of the volume fraction, size and density of the solid particles on the wave speed and attenuation factor are the same, although they differ in degree. [ABSTRACT FROM AUTHOR]

Tunnel ventilation fans are subjected to pressure pulses as a consequence of trains passing the ventilation shafts within which they are installed. These pressure pulses alter the volume flow rate through a ventilation fan, and consequently the static pressure field around fan blades. Today’s trains typically travel through railway tunnels faster than has been the historic norm. Additionally, platform screen doors are now a standard feature of metro systems. Both result in the trains involved inducing larger pressure pulses than industrial fan designers have traditionally assumed. Although tunnel ventilation fan in-service failures are rare, engineers increasingly associate those failures with new or renovated tunnel systems with larger pressure pulses. Consequently, we require insight into the aerodynamic and mechanical consequences that occur with subjecting a tunnel ventilation fan to a pressure pulse. In the research reported in this paper, the authors model the pressure pulse induced by a train in a tunnel system as a rapidly changing fan volume flow rate. The authors computed the fan operating point by means of a large eddy simulation with a one-equation sub-grid scale turbulence model. The authors undertook the computation using the open source computational fluid dynamic code OpenFOAM. An analysis of the computational results provides an insight into the effects of turbulent structures that develop within the fan blade passage. The analysis indicates that a pressure pulse too brief to drive a tunnel ventilation fan into stall still results a doubling of the unsteady aerodynamic and mechanical forces to which the blade is subjected. A doubling of unsteady mechanical forces as a consequence of a pressure pulse constitutes an increase significant enough to contribute to the tunnel ventilation fan’s in-service mechanical failure. [ABSTRACT FROM PUBLISHER]

The methods of adaptive medial filtration are used to select components of the initial electrochemical signal that can be identified as pressure pulses under the conditions of cavitation in the tests carried out in a vibration-testing machine. We determine the time dependences of the pressure pulses and selected electrochemical signals under the conditions of cavitation for a given potential. [ABSTRACT FROM AUTHOR]

In situ observations of the flanks of the magnetospheric boundary (magnetopause and boundary layer) sometimes show periodic surface waves to be present. We propose a straightforward but powerful technique for analyzing such periodic boundary waves. The result of this analysis is a two-dimensional picture of the structure of the wave in a reference frame that travels tailward with the wave. We give a few examples of wave patterns that can be recovered from AMPTE/IRM data. We demonstrate that the proposed method is a valuable tool that can shed a new light on issues such as the value of the wave speed, the location of flow vortices in the boundary layer, the identification of the unstable surface in the case of a Kelvin–Helmholtz instability, and the non-sinusoidal form of surface waves. [Copyright &y& Elsevier]