Three-dimensional Pressure Distribution Research Articles

Experimental and numerical analysis of the fluid flow behavior of a tank corner impacting a water surface

The interaction of a tank impacting a water surface is an extremely complex nonlinear multiphase flow phenomenon. In this study, experiments and numerical simulations are used to systematically investigate the flow physics and load characteristics of a tank corner impacting a water surface. Free surface flow at different fall heights (200–800 mm) and inclination angles (0°–15°) was obtained through free fall experiments. The volume of fluids method and overset grid technology were used to simulate the water impact process of a three-dimensional structure accurately. For typical bubble flows, the numerical and experimental results agree well. On the basis of the three-dimensional flow characteristics and pressure distribution, flow behaviors, such as fluid climbing, corrugation disturbances, and air cavity effects, are analyzed. Bubble flow has a significant effect on the behavior mode of the impact load. In particular, the bubbles at the upper wall play a key role in the load characteristics at different locations. In addition, the influences of corrugations inside the tank's corner and the impact velocity on fluid flow were investigated. These results provide beneficial references for an in-depth understanding of the fluid flow and load characteristics between a tank and fluid.

Vortex evolution and merging mechanism across 180° sharp bend for laminar inflow

The present study deals with the fundamentals of vortex evolution and merging across a 180° sharp bend for laminar inflow (Re = 800). A three-dimensional flow and pressure distribution across the bend are analyzed by using particle image velocimetry measurements. The results show that the sudden flow redirection and adverse pressure gradient create a recirculation region in the vicinity of the divider wall. The vorticity and turbulent kinetic energy distribution highlight the presence of a shear layer between the recirculation and mainstream turning flow. A Rayleigh instability analysis shows the existence of centrifugal instabilities outside the shear layer in the mainstream turning flow. The imbalance of centrifugal and pressure forces act in unison to produce a net force that creates Dean instability across the mainstream turning flow. Consequently, two pairs of counter-rotating Dean vortices develop after the first turn, possibly merging into a single pair after the subsequent 90° turn. Finally, the evolution and merging of Dean vortices are explained with the help of a conceptual diagram illustrating the force interaction and the formation of counter-rotating currents.

A three-dimensional numerical pressure transient analysis model for fractured horizontal wells in shale gas reservoirs

Shale gas development has greatly contributed to the world's energy supply. Pressure transient analysis (PTA) has extremely helped the development of shale gas. In this paper, a three-dimensional numerical model for transient pressure analysis of multi-stage fractured horizontal wells (MFHWs) in shale gas reservoirs was proposed, which was based on the embedded discrete fracture model (EDFM). The adsorption effect of shale gas, stress sensitivity of shale reservoir, and high-velocity non-Darcy flow in fractures were considered in this model, and the model was solved by Matlab Reservoir Simulation Tool (MRST). The discrete process of governing equations is described in detail, the typical MFHW pressure transient response curve of a shale gas reservoir was obtained, different flow regimes were divided, and three-dimensional pressure distribution profile of different flow stages were drawn to clearly understand the flow states of shale gas in the reservoir. The effects of different flow mechanisms and fracture properties on the log–log curves of the MFHW pressure transient response were analyzed in detail. The numerical PTA model proposed in this paper not only considers a variety of complex flow mechanisms of shale gas, but also accurately describes the characteristics of complex fracture network of shale reservoirs in three-dimensional conditions through EDFM. In addition, the problems of the incomplete description of shale gas flow stages by conventional analytical methods and semi-analytical methods were avoided through the numerical solution. The pressure response behavior of fluid in shale gas reservoir can be better explained by using this model, which helps to reduce the uncertainty of shale reservoir development.

Subsonic and supersonic flow-induced vibration of sandwich cylindrical shells with FG-CNT reinforced composite face sheets and metal foam core

Based on the linear fluid-solid interaction (FSI) model and classical shell theories, vibration behavior of sandwich cylindrical shells subjected to external incompressible or compressible fluid flow is investigated. The sandwich shell includes the same outer and inner face sheets made of carbon nanotube (CNT) reinforced composites and a metal foam core. The effective mechanical properties of CNT reinforced composites are obtained using the extended rule of mixture. Also, the porosity distribution through the foam thickness is assumed to be in the form of a trigonometric function. Equations of motion and corresponding boundary conditions are derived according to the Donnell's, Love's and Sanders’ theories. For the first time, a closed-form expression of three-dimensional pressure distribution in both subsonic and supersonic regimes of compressible flow passing along the length of shell is presented by studying conservation of mass, generalized Bernoulli equation and linear fluid-solid interaction. The governing equations are exactly and analytically solved to develop natural frequencies and mode shapes of fluid-loaded sandwich shells with various boundary conditions using the state-space and Galerkin's methods. So the validity and accuracy of the Galerkin's method in conjunction with beam modal functions for different boundary conditions are investigated. In addition, a closed-form expression is obtained for critical upstream speed of water flow at which the dynamic instability of sandwich shells occurs. Findings indicate the frequency ratio (fWet/fDry) of air-loaded sandwich shells decreases slightly with upstream speed in the subsonic regime, while a significant increase is seen in the supersonic regime (more than 20%). Also, the effect of flow specifications on the natural frequency and critical speed are much more pronounced for larger values of aspect (L/R) and wall slenderness (R/h) ratios. It is shown that Love's shell theory is accurate enough for vibration analysis of flow-induced sandwich cylindrical shells with different geometric ratios and boundary conditions and the sanders’ terms can be neglected.

Effects of journal static eccentricity on dynamic responses of a rotor system under base motions using FDM inertia model

When an oil-lubricated rotor-bearing system is subjected to base motions, it will inevitably be affected by oil-film forces, base excitations, and inertial forces. The alignment state cannot be guaranteed over time, resulting in a static eccentricity. An inertia model for open-ended SFD incorporated three-dimensional fluid velocities and pressure distribution represented by the Reynolds number. In addition to viscous pressure, the inertial pressure distribution was also solved by finite difference method (FDM), and the oil-film forces were determined by numerical integration. Using transient modal integration method, dynamic responses of a rotor-SFD-support system considering oil-film inertia were simulated. The effects of oil-film inertia, static eccentricity, and base motions on transient responses and bifurcation behavior were discussed. The results indicate that for large eccentricity ratio, the oil-film inertia increases the reaction forces. For medium and large static eccentricity, the journal performs quasi-periodic motions. Under base harmonic translation, a series of sub- and super-harmonic frequencies kΩ±Ωz are stimulated along with the multiples of rotational frequency kΩ and base harmonic frequency Ωz. The bifurcation motion of journal with static eccentricity fluctuates seriously in resonance. Overall, nonlinear dynamic responses of rotor-damping-support systems subjected to base motions can be evaluated during dynamics design and vibration suppression.

Numerical investigation of flow around a square cylinder in accelerated flow

To investigate the flow field evolution and resultant aerodynamic characteristics of a square cylinder during flow acceleration, large-eddy simulations were undertaken to simulate flow with a dimensionless acceleration rate ap of 0.0048. The adopted ap resembles that is likely to be experienced during a severe downburst wind storm. The tested incidence angle α ranges from 0° to 45° and the time-dependent Reynolds number Re [Re = U(t)D/v, where U(t) is the time-dependent inflow velocity and D and v are the cylinder length and the kinematic viscosity, respectively] varies from 0 to 5 × 104 throughout the simulation. Results revealed that the flow around a square cylinder in accelerated flow evolves through three distinct temporal flow phases: namely, Phase I (Ia and Ib) where no vortex shedding (the instantaneous lift force through this period is zero) is observed, Phase II, where periodic vortex shedding and associated lift force oscillations are initiated and enhanced, and Phase III where stable vortex shedding occurs. Phase I can be further broken down into Phase Ia, which is characterized by laminar shear layer separation and the existence of steady recirculation vortices in the near wake region, and Phase Ib (only present at α = 0° and 45°) which is distinguished by the presence of quasi-steady recirculation vortices behind the cylinder. Aside from the variation of flow patterns, the transient lift and drag coefficients and the wind pressure distributions, as well as the spatial evolution of three-dimensional flow structures and pressure distributions, are also elucidated in detail.

Three-Dimensional Urethral Profilometry-A Global Urethral Pressure Assessment Method.

Background: To present a new method of urethral pressure examination, and to evaluate diagnostic capabilities of three-dimensional profilometry, as an alternative to classical urethral profile (UPP). Using five channel catheters and dedicated software, a global urethral pressure image is obtained. The method eliminates the main limitation of classical urethral profilometry, where the catheter orientation determines the pressure picture limited to only one point in the urethral circumference; we observed up to 50% differences in pressure measures depending on the point of urethral circumference where the measurement was taken. Methods: This is a preliminary study containing a method presentation and analysis of the use in varied clinical cases of either healthy patients or patients with lower urinary tract symptoms (LUTS). The article includes a technique and equipment description and a full evaluation of selected cases, including three-dimensional urethral pressure distribution graphics. Results and Conclusions: Three-dimensional profilometry compared to the classical technique is comparable regarding the time, cost, technical difficulty and patient discomfort. At the same time, we obtained much more data on the urethral pressure and its distribution. The results are easy to interpret due to the 3D movable graphics created automatically by the dedicated software.

Methodology for the systematic design of conical plain bearings for use as main bearings in wind turbines

With the possibility to replace sliding segments on the tower without disassembling the drivetrain, the use of segmented plain bearings with conical sliding surfaces as main bearing in wind turbines has a great potential to reduce the maintenance costs and thus the levelized cost of energy (LCOE). Furthermore, the short axial design leads to lower investment costs. Since this design is totally new and no design guidelines are available so far, the objective of this paper is to investigate the influence of the geometric parameters on the hydrodynamic pressure distribution of the bearing. In this context a parameter screening is performed using a suitable test field according to Plackett and Burman in order to determine the most relevant parameters. With the help of the simulations carried out after this test field, correlations between the geometric parameters and the hydrodynamic pressure distribution are evaluated. To be able to quantitatively analyze the three-dimensional pressure distribution, several key values are defined in this paper that describe the pressure distribution. The content of this paper is part of a methodology with the goal of developing a design guideline for conical plain bearings.

Evaluation of Loosening and Soil Compaction with a Working Tool of Tillage Machines Using a Hydrodynamic Model

The article presents a methodology for the theoretical assessment of the processes of loosening and compaction of the soil with a working tool based on pressure distribution patterns in the soil stratum obtained using the computational fluid dynamic model (CFD model). A computational fluid dynamics model is developed to assess the stress-strain state of the soil and soil particles' movement, implemented in the FlowVision computer program. As a model, the FlowVision Free Surface model is adopted, in which the Navier-Stokes equations, the transfer equations of turbulent functions, and the transfer equation for the filling function are solved. The implementation of this model made it possible to establish three-dimensional pressure distribution patterns, based on which zones of deformation, loosening, and compaction in the soil were determined in interaction with a vertical working tool. The implementation of this methodology will theoretically justify the geometric parameters of tillage tools and machines, taking into account the conditions for forming the required quality of tillage by loosening and compaction.

Estimation of angle-dependent absorption coefficients from spatially distributed in situ measurements.

A method is proposed for measuring the angle-dependent absorption coefficient of a boundary material in situ. The method relies on decomposing a non-uniform three-dimensional pressure distribution, measured in the vicinity of a boundary, into plane-wave components (i.e., via estimation of its wavenumber transform). The incident and reflected plane-wave components at the boundary are separated in the wavenumber domain, from which it is possible to deduce an absorption coefficient for each angle of incidence simultaneously. The technique is used to verify theoretical predictions of the angle-dependent absorption coefficient of an absorbing ceiling, based on in situ measurements in a conventional room.

Revisiting the mechanical properties of the nucleon

We discuss in detail the distributions of energy, radial pressure and tangential pressure inside the nucleon. In particular, this discussion is carried on in both the instant form and the front form of dynamics. Moreover we show for the first time how these mechanical concepts can be defined when the average nucleon momentum does not vanish. We express the conditions of hydrostatic equilibrium and stability in terms of these two and three-dimensional energy and pressure distributions. We briefly discuss the phenomenological relevance of our findings with a simple yet realistic model. In the light of this exhaustive mechanical description of the nucleon, we also present several possible connections between hadronic physics and compact stars, like e.g. the study of the equation of state for matter under extreme conditions and stability constraints.

Instant tsunami bore pressure and force on a cylindrical structure

This study investigates tsunami bore impact on a cylindrical structure. A physical study was carried out in a large wave flume with a horizontal floor. Experiments covered a range of bore heights (140–210 mm) and bore velocities (1.98–2.45 m/s). The vertical and angular distributions of the applied pressure were measured using a vertical array of pressure sensors. The cylindrical structure was rotated so that the sensors were orientated at several angles between 0° and 135°, giving in effect a three-dimensional pressure distribution around the structure. The total stream-wise force was computed as a summation of the hydrostatic and hydrodynamic forces. A hydrodynamic coefficient of 0.65 was found to be appropriate for this study. The height of the centre of effort of the force on the cylinder surface was estimated by dividing the measured moment by the measured force, and was found to be proportional to the actual water height at the front face of the cylinder.

Investigation of three-dimensional active earth pressure and load transfer according to aspect ratio

ABSTRACTAlthough there is a noticeable difference between two-dimensional and three-dimensional earth pressures, most researchers have suggested various earth pressure theories under the two-dimensional condition. Only a few studies have been conducted on the three-dimensional load transfer to the adjacent ground, whereas most studies in literature on the three-dimensional active earth pressure have been conducted by focusing on the stability of active wall. For accurate prediction of the three-dimensional active earth pressure, it is required to study not only the three-dimensional earth pressure distribution but also the three-dimensional load transfer to the adjacent ground. In this paper, size and distribution of the three-dimensional active earth pressure as well as the load transfer according to aspect ratio of retaining wall are investigated through a series of model tests. As a results, the three-dimensional active earth pressure distribution showed the highest value at the wall height of 0.5–0.55h when the aspect ratio of equal to 1.2 or higher. The load transfer showed higher values in vertical direction than horizontal direction. The load transfer distribution can be evaluated by applying the size and effect range of the loads transferred to the adjacent soil of the retaining wall.

Numerical Investigation of the Three-Dimensional Pressure Distribution in Taylor Couette Flow

An investigation is conducted on the flow in a moderately wide gap between an inner rotating shaft and an outer coaxial fixed tube, with stationary end-walls, by three-dimensional Reynolds-averaged Navier–Stokes (RANS) computational fluid dynamics (CFD), using the realizable k−ε model. This approach provides three-dimensional spatial distributions of static and dynamic pressures that are not directly measurable in experiment by conventional nonintrusive optics-based techniques. The nonuniform pressure main features on the axial and meridional planes appear to be driven by the radial momentum equilibrium of the flow, which is characterized by axisymmetric Taylor vortices over the Taylor number range 2.35×106≤Ta≤6.47×106. Regularly spaced static and dynamic pressure maxima on the stationary cylinder wall follow the axial stacking of the Taylor vortices and line up with the vortex-induced radial outflow documented in previous work. This new detailed understanding has potential for application to the design of a vertical turbine pump head. Aligning the location where the gauge static pressure (GSP) maximum occurs with the central axis of the delivery pipe could improve the head delivery, the pump mechanical efficiency, the system operation, and control costs.

Characterization of free field radiation in brass instrument horns under swept sine excitation using a linear microphone array

A linear array with 23 microphones is used to scan a planar section of the sound field radiated into an anechoic environment by a range of brass instruments excited by a sinusoidal sine sweep. The planar section contains the symmetry axis of the bell and covers a rectangular area of 0.9 by 0.6 metres, starting at the plane of the bell and extending away from it along the longest side. The linear microphone array is perpendicular to the symmetry axis and is stepped along the axis. The resulting matrix of signals is processed to separate the linear and non-linear parts of the response; the three-dimensional pressure distribution in the sound field is deduced on the assumption that the field is cylindrically symmetric. This data then allows the visualization and further analysis of the frequency dependence of radiated wave fronts in brass instrument bells. Comparison is drawn between the observations and the predictions of several popular radiation models.

A THREE-DIMENSIONAL INVERSE METHOD FOR THE DESIGN OF SAILS

This paper investigates an inverse process for the design of yacht sails. The method is described and then applied to the design of optimal sails for a specific yacht. The proposed inverse method generates the three-dimensional shapes of a headsail and mainsail from prescribed loading (i.e. differential pressure) distributions, accounts for the effect of the sea surface, and also simulates the twist and shear of the incoming flow. The uncoupled iterative routine solves a sequence of analysis steps so that the sail shapes are deformed in such a way that their updated loading distributions converge to the specified target distributions. During each iteration equations derived from two-dimensional Thin Aerofoil Theory, calculate a geometry correction from the difference between the current and target loading distributions. This correction is applied to the sail geometry, and a vortex lattice method code calculates the updated three-dimensional differential pressure distributions, which are again compared to the target distributions. Usually only five iterations are required to converge to sail shapes that have the target loading distributions. The inverse method has been validated by inverting the traditional way of analysing sails, i.e. a set of sails with known geometry has been analysed and the loading distributions on the headsail and mainsail were calculated. These distributions were then used as an input for the inverse code. It was found that the difference in camber between the original sails and the calculated geometry is less than 0.01% of camber at the mid-span of the sails. The second part of the paper presents two methods for the design of optimal sails for a yacht. One of the methods uses the more traditional analysis approach, while the other employs the inverse method described in this paper. The optimisation is performed for a Transpac 52 yacht in 12 knots (6.5 m/s) of true wind speed to obtain the best velocity made good. Results from both methods are presented and discussed and it is found that the results in terms of boat speed are similar although the trims differ slightly. However, the new inverse method is approximately nine times faster than the traditional analysis approach.

BEARING BOUNDARY ELEMENT METHOD BASED ON GEOMETRICALLY SIMILAR ROLLER CONDITIONS

To solve the three-dimensional pressure and load distribution of roller bearings, a new boundary element method (BEM) is presented in this report. First, a discrete model of the initial location roller was established, and the other rollers' discrete data could be obtained using geometrically similar conditions of this model. Based on the three-dimensional elastic contact BEM, all of the bearing rollers could be described as one object; therefore, the roller bearing problem of a multi-object contact system could be simplified as the problem of a three-object contact system. Bearing boundary elements were used to realize the discontinuous traction on the contact area, and the Hertz contact theory was used to revise the contact widths between the rollers and the bearing races, including the inner and outer races. A coupling matrix equation was established, and the boundary matrix equation's condensation process was illustrated. A bearing-BEM program was compiled based on geometrically similar roller conditions, in which a four-row tapered roller bearing in a rolling mill was simulated. The bearing contact pressure and load, roller contact widths and number of contact rollers were obtained. Lastly, the simulation result was compared with that of the traditional bearing-BEM (T-BBEM) and the experimental data, which proved the validity and effectiveness of the developed method.

Finite element analysis and experimental study on contact pressure of hydraulic support bud-shaped composite sealing ring

By the fluid dynamics theory analysis of the sealing interface, the importance of sealing contact pressure research for sealing performance is discussed. By experiments and data analysis for nitrile rubber buna and polyurethane, Mooney–Rivlin model parameters of two materials are obtained. By the finite element analysis of bud-shaped composite sealing ring under different pressures and secondary analysis, sealing contact pressure distribution curve of finite element analysis has been obtained. Sealing experimental apparatus is designed and assembled. The contact pressure distribution curve and three-dimensional pressure distribution field are obtained using the pressure-sensitive film. The results from finite element analysis and experiment are consistent with the conclusion of fluid dynamics theory analysis. The research content and design have great significance for sealing mechanism study.

Holograms for acoustics.

Holographic techniques are fundamental to applications such as volumetric displays, high-density data storage and optical tweezers that require spatial control of intricate optical or acoustic fields within a three-dimensional volume. The basis of holography is spatial storage of the phase and/or amplitude profile of the desired wavefront in a manner that allows that wavefront to be reconstructed by interference when the hologram is illuminated with a suitable coherent source. Modern computer-generated holography skips the process of recording a hologram from a physical scene, and instead calculates the required phase profile before rendering it for reconstruction. In ultrasound applications, the phase profile is typically generated by discrete and independently driven ultrasound sources; however, these can only be used in small numbers, which limits the complexity or degrees of freedom that can be attained in the wavefront. Here we introduce monolithic acoustic holograms, which can reconstruct diffraction-limited acoustic pressure fields and thus arbitrary ultrasound beams. We use rapid fabrication to craft the holograms and achieve reconstruction degrees of freedom two orders of magnitude higher than commercial phased array sources. The technique is inexpensive, appropriate for both transmission and reflection elements, and scales well to higher information content, larger aperture size and higher power. The complex three-dimensional pressure and phase distributions produced by these acoustic holograms allow us to demonstrate new approaches to controlled ultrasonic manipulation of solids in water, and of liquids and solids in air. We expect that acoustic holograms will enable new capabilities in beam-steering and the contactless transfer of power, improve medical imaging, and drive new applications of ultrasound.

Three-Dimensional Modeling of the Thermal Behavior of a Lithium-Ion Battery Module for Hybrid Electric Vehicle Applications

This paper reports a modeling methodology to predict the effects of operating conditions on the thermal behavior of a lithium-ion battery (LIB) module. The potential and current density distributions on the electrodes of an LIB cell are predicted as a function of discharge time based on the principle of charge conservation. By using the modeling results of the potential and current density distributions of the LIB cell, the non-uniform distribution of the heat generation rate in a single LIB cell within the module is calculated. Based on the heat generation rate in the single LIB cell determined as a function of the position on the electrode and time, a three-dimensional thermal modeling of an LIB module is performed to calculate the three-dimensional velocity, pressure, and temperature distributions within the LIB module as a function of time at various operating conditions. Thermal modeling of an LIB module is validated by the comparison between the experimental measurements and the modeling results. The effect of the cooling condition of the LIB module on the temperature rise of the LIB cells within the module and the uniformity of the distribution of the cell temperatures are analyzed quantitatively based on the modeling results.