Velocity Vector Research Articles

Research on relative reachable domain in target orbit for maneuvering spacecraft

Purpose Lots of successful space missions require that the maneuvering spacecraft can reach the target spacecraft. Therefore, research on relative reachable domain (RRD) in target orbit for maneuvering spacecraft is particularly important and is currently a hot-debated topic in the field of aerospace. This paper aims at analyzing and simulating the RRD in target orbit for maneuvering spacecrafts with a single fixed-magnitude impulse and continuous thrust, respectively, to provide a basis for analyzing the feasibility of spacecraft maneuvering missions and improving the design efficiency of spacecraft maneuvering missions. Design/methodology/approach Based on the kinematics model of relative motion, RRD in target orbit for maneuvering spacecraft with a single fixed-magnitude impulse can be calculated via analyzing the relationship between orbital elements, position vector and velocity vector of spacecrafts, and relevant studies are introduced to compare simulation results for the same case and validate the method proposed in the paper. With analysis of the dynamic model of relative motion, the calculation of RRD in target orbit for maneuvering spacecraft with continuous thrust can be transformed as the solution of the optimal control problem, and example emulations are carried out to validate the method. Findings For the case with a single fixed-magnitude impulse, simulation results show preliminarily that the method is in agreement with the method in Ref. (Wen et al., 2016), which treats the same case and thus is plausibly correct and feasible. For the case with continuous thrust, analysis and simulation results confirm the validity of the proposed method. The methods based on relative motion in this paper can efficiently determining the RRD in target orbit for maneuvering spacecraft. Originality/value Both theoretical analyses and simulation results indicate that the method proposed in this paper is comparatively simple but efficient for determine the RRD in target orbit for maneuvering spacecraft swiftly and precisely.

Three-Dimensional Visualization Of The Behavior Of Solid Particles Traveling In A Horizontal Gas Pipe Flow By Color PTV Using Discontinuously Changing Hue Illumination

In a gas pipe, a lot of solid particles remained during its construction. They are called dust and gas supply companies have tried to remove them using filters because they cause various problems. To optimize the maintenance period of dust removal filters, it is required to understand the behaviors of particles in the pipe. However, we do not fully understand yet because of their very complex behaviors caused by dune accumulated in the pipe. Furthermore, it is hard to investigate their behaviors with a traditional volumetric PTV using multiple cameras. Normally, its calibration is difficult because of the curvature of the pipe and the plural number of cameras. Therefore, we developed a new volumetric color PTV algorithm with discontinuously changing color illumination in the camera shooting direction, i.e. the depth direction. Color PTV can determine particle positions in three dimensions using a single camera but has low depth accuracy. Our new PTV measures particle positions and velocity vectors in the plane of picture using the same algorithm used in the normal planar PTV. On the other hand, particle positions and velocity vectors in the camera shooting direction are measured by a pattern of color changing on particle scattering light, which is our original method. To adopt the new volumetric PTV in the pipe flow, a volumetric light changing color discontinuously in the flow direction was irradiated and the particles were visualized using a camera installed at the outlet of the pipe. When a dune exists, the particles are thrown to the top of the pipe and their advection velocity is increased by the wakes generated by the dune. As a result, the dune makes more particles to be advected to a longer distance.

Kármán Street-Boundary Layer Interactions In Turbulent Flow

Understanding the intricate interplay between turbulent boundary layers and wake structures caused by obstacles in the flow is key to assessing the local shear stress fields as well as the drag. These types of flows can be relevant to natural phenomena including sediment and nutrient transport. While existing literature predominantly explores the flow downstream of cylinders mounted perpendicular to bounding surfaces or downstream of cylinders positioned outside the boundary layer region, this work experimentally studies the turbulent boundary layer passing over a cylindrical obstacle positioned near and parallel to the surface of an underlying solid wall. Planar particle image velocimetry (PIV) was performed in an open recirculating water channel for three test cases at a friction Reynolds number Reτ = 1320. Key parameters investigated include the cylinder diameter relative to the boundary layer thickness (D/δ = 0.09 and 0.01) and the gap between the cylinder and the wall (G/δ = 0.09), where the range of D/δ used is smaller than most examples found in the literature. Instantaneous and averaged velocity and vorticity fields are examined based on the PIV measurements. The results in Fig. 1 show how von Kármán vortex streets and turbulent boundary layer structures interact to form unique flow features. The larger cylinder generates a clear separation downstream of its axis as well as a wake that remains coherent over a distance δ downstream. The smaller cylinder with D/δ = 0.01 generates a much narrower and weaker wake, but still shows a clear influence on time-averaged velocity profile. Future experiments will evaluate flow conditions further downstream as well as additional values of G/δ for the same D/δ values.

Cavitation Onset In Counter-Rotating Vortices From Diverging Disks

Cavitation occurs when the local pressure, induced by high local velocities, drops below the vapor pressure, leading to the formation of vapor bubbles. The subsequent collapse of these bubbles can cause noise, erosion, and vibrations. Recent studies show that cavitation is sensitive to water quality, i.e., the nuclei populations, the chemical composition of water, and the presence of particles. Motivated by investigating the effects of water quality on cavitation, experiments are performed in a dedicated experimental facility. This consists in two co-axial disks that are initially at rest and mutually in contact, in a tank filled with water. The fast diverging movement of the top disk with respect to the bottom one produces a jet flow inside the gap between the disks, which leads to the formation of two counter-rotating vortices. The local pressure drop induced by high flow velocities leads to a phase change. To characterize the phenomenon, two optical techniques are applied, i.e., shadowgraphy and particle image velocimetry (PIV). In performing PIV reconstruction, the sum of correlation enhances the spatial resolution of the velocity vector fields. The pressure field in the region where the vortices occur is obtained from velocity data. The water quality effects on cavitation are investigated by adding salt and using water with an abundance of nuclei inside the tank.

Wing-to-Wall Distance Effect On The Large-Scale Turbulent Structures Interacting With A Wall

We experimentally investigate the effect of the wing-to-wall distance, also called ground clearance, on the three-dimensional flow generated by a wing at a 4° angle of attack and a chord Reynolds number of 1400. We perform 3D velocity measurements using Particle tracking velocimetry to characterize the wake downstream of the wing, evaluate the evolution of the intensity and the size of the wingtip and secondary counter-rotating vortices, and finally compute the aerodynamic coefficients using momentum balance equations. We extended the control volume method for drag and lift calculation to the case where the transverse plane downstream of the wing does not contain the whole wake. The secondary flow's vorticity isocontours and velocity vectors show a decrease in the downwash and vortex size with the ground clearance ratio (i.e., as we approach the ground). The computation of the circulation shows that this latter decays rapidly streamwise as we get closer to the wall, indicating a dissipation of the kinetic energy contained in the trailing vortices. The aerodynamic coefficients' results based on the control volume method show that the tested wing manifests a two-force regime evolution of the drag coefficient with the ground clearance ratio, as it first decreases when moving far from the ground before increasing as we move farther from the ground. A noteworthy high lift is generated when too close to the ground. Further application of the extended control volume method on DNS data is needed to validate the method.

Multiple-Exposure PTV With Variable Time Steps

Recording multiple exposures of the tracer particles onto a single digital image has the potential to simplify the hardware needed for 3D PTV measurements. A sequence with equal time intervals leads to the well-known directional ambiguity problem. Instead, a sequence with irregular time-intervals (two or more) allows resolving the ambiguity. Two fundamental criteria are introduced that determine whether a set of particle samples corresponds to a physical trace for a given neighborhood: the kinematic similarity criterion imposes similarity (i.e. proportionality) between the length travelled by the particle and time elapsed. Additionally, the trace regularity criterion favors sets with minimum fluctuations of the velocity vector. A numerical algorithm, based on combinatorial analysis is presented, whereby all possible sets are scrutinized and the set of particles yielding the minimum disparity from the above criteria corresponds to the physical trace. The algorithm is demonstrated using 3D experimental data and results are benchmarked against the state-of-the-art time-resolved analysis Shakethe-Box (single-frame, single-exposure).

Flow dynamics and turbulent coherent structures around sediment reduction plates of a sewer system

In the management of urban drainage networks, great interest has been generated in the removal of sediments from sewer systems. The unsteady three-dimensional (3D) flow and turbulent coherent structures surrounding sediment reduction plates in a sewer system are investigated by means of the detached-eddy simulation (DES). Particular emphasis is given to detailing the instantaneous velocity and vorticity fields within the grooves, along with an examination of the three-dimensional, long-term, average flow structure at a Reynolds number of approximately 105. Velocity vectors demonstrate continuous flapping of the flow on the groove wall, periodically interacting with ejections of positive and negative vorticity originating from the grooves. The interaction between the three-dimensional groove flow and the shear flow leads to the downstream transport of patches of positive and negative vorticity, which significantly influence sediment transport. The high-velocity shear flows and strong vortices generated in undulating topography, as identified by the Q-criteria, are the key factors contributing to the efficient sediment reduction capabilities of the sediment reduction plates. The sediment reduction plates with partially enclosed structures exhibit low sedimentation rates in grooves on the plate, a broader acceleration region, and a lesser impact on the flow capacity. The results improve the understanding of the hydrodynamics and turbulent coherent structures surrounding the sediment reduction plates while elucidating the driving factors behind the enhancement of sediment scouring and suspension capacities. These results indicate that the redesign of the plates as partially enclosed structures contributes to further improving their sediment reduction performance.

Effect of impeller rotational phase on the FDA blood pump velocity fields.

The Food and Drug Administration (FDA) blood pump is an open-source benchmark cardiovascular device introduced for validating computational and experimental performance analysis tools. The time-resolved velocity field for the whole impeller has not been established, as is undertaken in this particle image velocimetry (PIV) study. The level of instantaneous velocity fluctuations is important, to assess the flow-induced rotor vibrations which may contribute to the total blood damage. To document these factors, time-resolved two-dimensional PIV experiments were performed that were precisely phase-locked with the impeller rotation angle. The velocity fields in the impeller and in the volute conformed with the previous single blade passage experiments of literature. Depending on the impeller orientation, present experiments showed that volute outlet nozzle flow can fluctuate up to 34% during impeller rotation, with a maximum standard experimental uncertainty of 2.2%. Likewise, the flow fields in each impeller passage also altered in average 33.5%. Considerably different vortex patterns were observed for different blade passages, with the largest vortical structures reaching an average core radii of 7 mm. The constant volute area employed in the FDA pump design contributes to the observed velocity imbalance, as illustrated in our velocity measurements. By introducing the impeller orientation parameter for the nozzle flow, this study considers the possible uncertainties influencing pump flow. Expanding the available literature data, analysis of inter-blade relative velocity fields is provided here for the first-time to the best of our knowledge. Consequently, our research fills a critical knowledge gap in the understanding of the flow dynamics of an important benchmark cardiovascular device. This study prompts the need for improved hydrodynamic designs and optimized devices to be used as benchmark test devices, to build more confidence and safety in future ventricular assist device performance assessment studies.

Interplay of chemotactic force, Péclet number, and dimensionality dictates the dynamics of auto-chemotactic chiral active droplets.

In living and synthetic active matter systems, the constituents can self-propel and interact with each other and with the environment through various physicochemical mechanisms. Among these mechanisms, chemotactic and auto-chemotactic effects are widely observed. The impact of (auto-)chemotactic effects on achiral active matter has been a recent research focus. However, the influence of these effects on chiral active matter remains elusive. Here, we develop a Brownian dynamics model coupled with a diffusion equation to examine the dynamics of auto-chemotactic chiral active droplets in both quasi-two-dimensional (2D) and three-dimensional (3D) systems. By quantifying the droplet trajectory as a function of the dimensionless Péclet number and chemotactic strength, our simulations well reproduce the curling and helical trajectories of nematic droplets in a surfactant-rich solution reported by Krüger et al. [Phys. Rev. Lett. 117, 048003 (2016)]. The modeled curling trajectory in 2D exhibits an emergent chirality, also consistent with the experiment. We further show that the geometry of the chiral droplet trajectories, characterized by the pitch and diameter, can be used to infer the velocities of the droplet. Interestingly, we find that, unlike the achiral case, the velocities of chiral active droplets show dimensionality dependence: its mean instantaneous velocity is higher in 3D than in 2D, whereas its mean migration velocity is lower in 3D than in 2D. Taken together, our particle-based simulations provide new insights into the dynamics of auto-chemotactic chiral active droplets, reveal the effects of dimensionality, and pave the way toward their applications, such as drug delivery, sensors, and micro-reactors.

3D reconstruction of an inertial-confinement fusion implosion with neural networks using multiple heterogeneous data sources.

3D asymmetries are major degradation mechanisms in inertial-confinement fusion implosions at the National Ignition Facility (NIF). These asymmetries can be diagnosed and reconstructed with the neutron imaging system (NIS) on three lines of sight around the NIF target chamber. Conventional tomographic reconstructions are used to reconstruct the 3D morphology of the implosion using NIS [Volegov et al., J. Appl. Phys. 127, 083301 (2020)], but the problem is ill-posed with only three imaging lines of sight. Asymmetries can also be diagnosed with the real-time neutron activation diagnostics (RTNAD) and the neutron time-of-flight (nToF) suite. Since the NIS, RTNAD, and nToF each sample a different part of the implosion using different physical principles, we propose that it is possible to overcome the limitations of too few imaging lines of sight by performing 3D reconstructions that combine information from all three heterogeneous data sources. This work presents a new machine learning-based reconstruction technique to do just this. By using a simple physics model and group of neural networks to map 3D morphologies to data, this technique can easily account for data of multiple different types. A simple proof-of-principle is presented, demonstrating that this technique can accurately reconstruct a hot-spot shape using synthetic primary neutron images and a hot-spot velocity vector. In particular, the hot-spot's asymmetry, quantified as spherical harmonic coefficients, is reconstructed to within ±4% of the radius in 90% of test cases. In the future, this technique will be applied to actual NIS, RTNAD, and nToF data to better understand 3D asymmetries at the NIF.

Steadiness of technical variables as a determinant factor of performance in a virtual simulated regatta

ABSTRACT The aim of this investigation is to explore the relationship between Optimist sailing performance with boat steadiness as well as the steadiness of cyclic variables related to sailors’ technique, in the upwind leg of a regatta. Thirty-two sailors from the optimist class (16 bottom level and 16 top level) performed a regatta in a semi-immersive simulator which measures the instantaneous velocity, heading, boom, heel, and rudder angle and hiking effort. It was calculated the mean values as well as the short-term steadiness and long-term steadiness throughout the test. Top level and bottom level sailors were compared and the correlation between these variables and mean velocity were analysed. Significant differences were found between groups on mean values, STS values and LTS values as well as significant correlations ranging r values between 0.385 and 0.768. If the steadiness of sailing variables is considered, they appear as determinants of performance in Optimist class while this is not observed when analysing mean values.

On the Method for Solving the Problem of Ice Cover Deformation under an Arbitrary Moving Load

Introduction. The development of the polar areas of the World Ocean and the need to solve various problems associated with a large number of freezing inland water bodies issue new challenges for science. These challenges include the problem of studying the behavior of ice cover when exposed to various types of loads. Of great interest is the consideration of problems about the action of a moving load on the ice cover. A moving load simulates the effect of moving vehicles on ice. However, in papers devoted to the above problems, cases of load movement along a straight-line trajectory are considered. The objective of this research is to develop a method for studying the behavior of ice cover under the action of a load moving arbitrarily.Materials and Methods. The article proposes a method for solving the problem of the action of a force moving along an arbitrary trajectory on the ice cover of a reservoir of finite depth. The problem amounts to solving a system of two differential equations. The first of them models the behavior of the ice cover, and it is the equation of vibrations of a viscoelastic plate. The second equation simulates the behavior of fluid in a state of potential flow, and it is Laplace's equation. To solve the system of differential equations, integral transformations in time, space and variables were used. The resulting solution was expressed through an iterated integral, which was calculated using numerical methods.Results. The development and implementation of the method resulted in solving the problem of the movement of a concentrated force along an ice cover according to an arbitrary law. At the same time, studies were carried out on the behavior of displacements and stresses in the ice cover depending on the speed and acceleration of the movement of the vertical load, on the depth of the reservoir, and on the viscoelastic properties of ice. In addition, the distribution of the velocity vector of fluid particles along the depth of the reservoir was calculated.Discussion and Conclusion. The proposed method is very effective for solving problems of moving loads acting on the ice cover of a reservoir of finite depth. It provides solving problems about the action of a load moving along an ice cover along a complex trajectory. The results obtained can be used to calculate the stress and displacement of the ice cover during the laying of ice roads or the construction of airfields on the ice.

Substantiating the rational shape of a drum-type working tool for surface soil treatment

The working bodies of agricultural implements should minimize resistance to movement. The shape of a curved tooth, which is fixed between two cylindrical disks, has been considered in this paper. Several such sections on the shaft form a drum similar to a harrow roller or a needle harrow. When rolling, the tooth sinks into the soil, followed by its loosening. The task was to find such a shape of the tooth, which at the first stage of immersion in the soil would slide over it as much as possible with minimal deformation, and at the second stage would balance it and turn it over. The object of the study is a drum-type working body. The work of a straight tooth with its transformation into a curved tooth was analyzed. As a result of such an analysis and subsequent search, a rational shape of a drum-type tillage working body was obtained for the purpose of reducing resistance when it is buried in the soil. The involute of a circle turned out to be such a curve. A tooth in the form of an involute of a circle has a peculiarity: at the moment of contact of the tooth with the ground, the absolute velocity vector is directed perpendicular to it. The result is explained by the fact that as the disks roll, the tooth sinks into the soil, and the point of entry remains unchanged, and the tooth itself slides practically along itself, especially in the upper layers of the soil. In known working bodies, their curvilinear form was selected experimentally. The proposed shape of the working body was obtained analytically. To reduce the resistance of the teeth entering the soil, the ratio of the tillage depth to the radius of the drum is important. The immersion of the blade to the full depth should correspond to a 30° rotation of the drum. After diving to the maximum depth, it begins to weigh the soil to the surface or loosen it. The field of application of such a tooth shape can be the improvement of the working bodies of tillage implements

Neutron emission from a source moving in a gravitational field

This work is devoted to the problem of neutron field formation near elliptical orbits of space objects equipped with nuclear power plants. The high-energy part of the fission spectrum is not affected by the gravitational field. Radiation safety is ensured by the triad fair for a point source: activity-distance-time. The connection between space object orbit parameters and neutron flux density occurs for the thermal (near-thermal) part of the spectrum. The possibility of formation of a stable neutron trace in the volume of a «torus» around the orbit of a space object is considered. The paper presents theoretical and numerical evidence of the validity of the hypothesis put forward. The introduction considers the separation effect of Galileo's relativity principle in the case of rectilinear uniform motion of a point isotropic neutron source on a plane. The occurrence of angular asymmetry of the neutron distribution in a stationary coordinate system when their relative velocity is close to the transport velocity of the source is illustrated. Under these conditions, a significant velocity dispersion of initially monochromatic neutrons is also recorded. This expected fundamental kinematic effect determines the characteristic distribution of neutrons in the gravitational field when the source moves along the Kepler orbit. The solution of the problem is carried out in the velocity space. It is argued that if the distribution of neutrons in the velocity space is such that their velocities are collinear to the orbital velocity of the source, this indicates the existence of a neutron flux near the orbit. The problem is analysed on the example of one revolution of a hypothetical space station by simulation modelling. For this purpose, thermal neutron packets with isotropic angular distribution were generated at eight points of an elliptical orbit. The neutron and source velocity fluxes at the selected points of the orbit were compared in a coordinate system related to the earth. The obtained data made it possible to calculate the densities of neutron velocity fluxes to the front and rear hemispheres relative to the source orbital motion as a function of the polar angle, while the value of the determinant of the correlation matrix – an indicator of collinearity of neutron velocity vectors in the flux - was fixed. The results of the studies confirm the hypothesis put forward about the possibility of formation of a «trace» in the orbit of a thermal neutron source, which determines the need to take it into account as a significant component of radiation risk.

Measurement and prediction of the detachment of Aspergillus niger spores in turbulent flows

Aspergillus niger (A. niger) spores can induce numerous health problems. Once the airflow-imposed drag force on an A. niger spore exceeds its binding force with the colony, the spore is detached. Turbulent flow may considerably increase the spore detachment. No method is currently available for prediction of the drag force on a spore and its detachment in turbulent flows. This investigation measured the turbulent velocities and detachment of A. niger colonies in a wind tunnel. Computational fluid dynamics (CFD) was employed to model an A. niger unit subjected to turbulent flow blowing. The top 1 % quantile instantaneous velocity of the turbulent flow was specified as the steady entry flow boundary condition for solving the peak velocity distribution and the peak drag forces onto spores. The predicted spore detachment ratios were compared with the measurement data for model validation. The results revealed that the spore detachment ratios with a turbulence intensity of 17 % to 20 % can be twice to triple the ratio with a turbulence intensity of approximately 1 %, when the average velocity for blowing remains the same. The proposed CFD model can accurately predict the detachment ratios of the A. niger spores. Environmental ImplicationSome people are sensitive to the Aspergillus niger (A. niger) spores, and excessive exposure can cause nasal congestion, skin tingling, coughing, and even asthma. Turbulent flow can considerably increase the spore detachment, due to the increased airflow-imposed drag force on the spores during turbulence. This investigation developed a numerical model to solve for the peak velocity distribution and the peak drag forces onto spores in turbulent flows to predict the spore detachment. With the numerical tool, the airborne fungal spore concentrations would be predictable, which paves a way for intelligent and precise control of fungal aerosol pollution.

Two-dimensional flow vector measurement based on all-fiber laser feedback frequency-shifted multiplexing technology

The decomposition and identification of signals are crucial for flow vector acquisition in a multi-dimensional measurement. Here, we proposed a two-dimensional (2D) flow vector measurement system based on all-fiber laser feedback frequency-shifted multiplexing technology. The reliable performance of the system is characterized by experimental verification and numerical simulation. An orthogonal dual-beam structure is employed to eliminate the impact of an unknown incident angle in the practical application. Meanwhile, the vector velocity signals in 2D can be decomposed into one-dimensional (1D) scalar signals by adopting the frequency-shifted multiplexing, which makes it easy to obtain the vector information and velocity distribution of fluid motion through the self-mixing interference frequency spectrum. Moreover, the measured flow rates present a high linearity with syringe pump speeds ranging from 200 to 2000 μL/min, and the velocity information of the different incidence angles is easily obtained with high precision. This work may pave the way for the acquisition and processing of multi-dimensional flow vector signals, with potential applications in biomedical monitoring and microflow velocity sensing.

Uncertainty quantification for velocity measurement with 2D2C PIV

Abstract In this paper, A theoretical model of dimensionless instantaneous and average velocity measurement uncertainty quantification with 2D2C PIV is established under the framework of generally adopted international uncertainty quantification standards. The effectiveness of the model is verified using uniform flow field testing data. Combined with the semi-quantitative analysis of the theoretical model, uncertainty control suggestions of PIV measurement are given. The major source affecting the uncertainty of instantaneous velocity measurement is reference velocity, particle instantaneous pixel displacement, and their correlation term. For average velocity measurement uncertainty quantification, the uncertainty of particle average pixel displacement is effectively controlled by taking a large number of particle images. Thus three single-component terms: calibration factor, particle average pixel displacement, reference velocity and two correlation terms: particle average pixel displacement-calibration factor, particle average pixel displacement-reference velocity all made an important contribution to average velocity measurement uncertainty. To reduce uncertainty of PIV velocity measurement, one can reduce the reference velocity measurement uncertainty, optimize PIV algorithm and improve the calibration factor by applying high spatial resolution imaging system in experiment. And reducing reference velocity measurement uncertainty and improve space resolution are the key and feasible way.

Enhanced solar energy utilization of thermal energy storage tanks with phase change material and baffle incorporating holes

In response to the pressing need for more efficient thermal energy storage solutions, this study investigates the strategic implementation of baffles in phase change material (PCM) tanks to enhance thermal performance. PCM offers a promising solution for efficient thermal energy storage (TES); however, ensuring uniform temperature distribution inside the tanks remains challenging. Horizontal baffles with holes of varying diameters were introduced in Tanks 02, 03, and 04, while an inclined baffle with holes was used in Tank 05. The Tank 06 benefitted from an inclined baffle with holes of different diameters. A comprehensive analysis of all Tanks was evaluated by assessing PCM and water heat flux, PCM and water static enthalpy, Richardson number, velocity vectors, temperature, and liquid fraction contours. The results demonstrated that significant improvements were achieved with the addition of baffles. Tank 01, without a baffle, exhibited a melting time of 2860 s. However, the introduction of baffles resulted in reduced melting times for Tanks 02 to 06: 2360 s (17.48 %), 2350 s (17.83 %), 2400 s (16.08 %), 2320 s (18.88 %), and 2240 s (21.67 %), respectively; which led to enhance TES efficiency, and a quicker energy storage process. The study also includes a comprehensive economic analysis, evaluating the total cost (Ctotal) and performance-economic ratio (Pc). Tank 06 shows superior economic performance, with a Pc value of 0.26 despite a slightly higher cost than Tank 01 by $2 USD. These findings highlight the baffle design’s effectiveness in achieving better heat transfer and uniform temperature distribution within PCM tanks, making them more efficient for TES applications.

Modeling and analysis of plastic abrasive jet flow characteristics

In this study, the particle velocity and spatial distribution of a plastic abrasive jet were modeled for the removal of surface coatings from a new generation of ship hulls by plastic abrasive jet machining. The particle velocity in the jet has been accurately tested through high-speed photography. It was found that the particle velocity of plastic abrasives with the same particle size was larger than conventional abrasives. Downstream from the nozzle exit axis, the divergence profile of the abrasive jet is approximately linear at distances up to 6.2dN; at distances higher than 6.2dN, the divergence profile line of the abrasive jet is approximately “flared”. The particle velocity of the plastic abrasive increased with increasing jet pressure, and no significant decrease of particle velocity was found in the limited measurement range. The instantaneous velocity distribution of the particles has been discussed in terms of axial and radial directions along the jet. For the radial velocity distribution of the abrasive jet, a relatively steady state is observed in the cross-section of the jet near the nozzle outlet. The results of the model calculations are in accordance with the experimental test data in terms of both tendency and margin of change.

An Exact Solution to the Inverse Problem of Steady Free-Surface Flow over Topography

AbstractA simple exact solution is presented to the inverse problem in steady, two-dimensional idealised flow over topography that seeks the bottom profile given knowledge of the free-surface data. Attention is focused on the case when a uniform stream flows over a localised obstacle, although the solution is not restricted to this case. The inverse problem is formulated as a Stieltjes integral equation which is solved exactly using a Fourier transform. The solution requires the analytic continuation of two real functions representing the surface speed and the angle between the surface velocity vector and the horizontal. Some example surface profiles and their corresponding bottom topographies are discussed. Although the solution requires the prescription of the surface as a function of the velocity potential, it is shown to closely resemble the corresponding profile in physical space, even for quite large surface displacements, while significant discrepancy occurs at the bottom. Inference of the bottom profile from discrete surface data is accomplished by way of polynomial interpolation and rational approximation in the complex plane for the sample case of a hydraulic fall.