Constant Velocity Phase Research Articles

Optimizing Electric Vehicle Performance, Range and Parameter Estimation through NEDC Urban and Suburban Analysis using MATLAB

This research paper focuses on electric vehicle (EV) driving range and parameter estimation, with an emphasis on analyzing the New European Driving Cycle (NEDC) urban and suburban drive cycles. By examining these drive cycles, we obtain critical data on the moments when an electric vehicle transitions between constant velocity, acceleration, and deceleration phases, which significantly affect power consumption and driving range. We investigate various techniques for parameter estimation, including battery capacity, energy consumption rates, and powertrain efficiency, essential for improving EV performance and providing realistic range expectations. Empirical experiments in diverse driving conditions contribute valuable data to refine our understanding of EV driving range and performance in different scenarios. The research underscores the role of predictive modeling, data analytics, and advanced technologies in real-time parameter estimation, offering precise and convenient range predictions to enhance user confidence.

Modeling and Analysis of the Drying Process of Lithium-Ion Battery Electrodes Based on Non-Steady-State Drying Kinetics

The drying process of lithium-ion battery electrodes is one of the key processes for manufacturing electrodes with high surface homogeneity and is one of the most energy-consuming stages. The choice of the drying parameters has a significant impact on the electrode properties and the production efficiency. In response to these issues, this study establishes the non-steady-state drying kinetic equation for the electrodes, revealing the comprehensive effects of various dominant factors on the drying process. The drying rate is closely related to the electrode surface temperature, thickness, and other factors. Furthermore, this study proposes a coupled model of hot air drying field and capillary porous electrode solvent evaporation. The results showed that approximately 90% of the solvent was removed in less than half of the drying time. Then, the mechanism and control factors of electrode solvent evaporation are analyzed. During the preheating phase, the drying rate is controlled by electrode heating and temperature rise. In the constant velocity phase, it is regulated by the heat transfer from the surface airflow, while in the deceleration phase, it is affected by the mass transfer from the electrodes. Additionally, the effects of different thicknesses, temperatures, and airflow speeds on the drying process were investigated. Finally, experimental verification demonstrated the optimal parameters within the scope of the study: a temperature of 363.15 K and airflow speeds of 2.3 m/s result in a higher drying rate, as well as favorable mechanical performance.

Effect of Repeated, On-Field Sprints on Kinematic Variables in Wheelchair Rugby Players.

The aim of the study was to evaluate the influence of repeated sprints on kinematic performance and propulsion variables during the acceleration and constant peak velocity phases in wheelchair rugby players classified as defensive (low point in defensive [LP-D]) or offensive players (high point in offensive [HP-O]). Twenty-two players (13 LP-D and 9 HP-O) performed 6 × 20-m repeated sprint field tests. We calculated peak wheelchair velocities, propulsion phase times, deceleration phase times, cycle times, and left-right velocity asymmetry of the best and last sprints during the acceleration and constant peak velocity phases, the rate of decline in performance variables between the best and the last sprint and a fatigue index. Peak velocities during the acceleration and constant peak velocity phases and mean velocity over the whole sprint were significantly higher during the best than last sprint. Peak velocities were higher during the acceleration and constant peak velocity phases for the best and last sprint for HP-O. The rate of decline in peak velocity during the constant peak velocity phase was higher for LP-D. Fatigue index and rate of decline in velocities and sprint time were higher for LP-D. Performance variables and the rate of decline in performance variables depended on functional capacity and wheelchair type.

On the dynamics of gravity current motion in a stratified ambient

This study presents LES results of lock-release propagating gravity current (GC) at the base of a linearly stratified ambient. The focus of the study is to investigate the effect of ambient stratification on GC motion for both subcritical and supercritical regimes. The effects of Reynolds number and the ratio of the fluid depth in the lock to the total ambient fluid depth on GC front velocity are also examined. Also, the effect of stratification strength on mixing is evaluated. It is found that both subcritical and supercritical GCs have a constant-velocity phase. This phase terminates due to the current interaction with the internal waves (IWs) for the former, while for the latter, it is due to the decay of the head buoyancy. The duration of the constant-velocity phase increases with increasing stratification strength when the current is supercritical. For weak stratification the turbulence is considerable, while it is suppressed with stronger stratification. Mixing is more intense for supercritical GCs; however, mixing efficiency is much higher for subcritical GCs.

An innovative sit-standing seat in urban buses: A new design to prevent falls and non-collision injuries.

Due to the rapid growth of metropolises and the insufficiency of public transportation, nowadays, many people travel on these vehicles in a standing position. This position leads to discomfort and the risk of falling or non-collision incidents for the passengers. The present study was conducted to analyze an innovative sit-standing seat to prevent falls and non-collision injuries in standing passengers. A total of sixteen participated in this study. EMG signal and Borg scale were used to assess muscle activity and discomfort, respectively. The mean Borg scale score for perceived discomfort was lower in the sit-standing position than the standing position in all body organs, except for the hips. Also, in the sit-standing position compared to the standing position, the muscle activity of the soleus and medial gastrocnemius muscles was significantly lower in the constant velocity and entire phases in both legs, lower in the right leg in the acceleration phase and lower in the left leg in the deceleration phase. So, this seat can be used as an innovative idea to improve the ergonomic condition of standing passengers to prevent falls and non-collision injuries on transit buses.

Influence of Wheelchair Type on Kinematic Parameters in Wheelchair Rugby

IntroductionIn wheelchair rugby, players use either an offensive or defensive wheelchair depending on their field position and level of impairment. Performance of wheelchair rugby players is related to several parameters, however it is currently unclear if differences in performance are related to wheelchair type or no: the effect of wheelchair type on performance variables has not been evaluated. The aim of this study was to compare offensive and defensive wheelchairs on performance variables during a straight-line sprint.MethodsThirteen able-bodied people performed two 20 m sprint trials: one with an offensive and one with a defensive wheelchair. Data were collected using inertial measurement units fixed on the wheelchair. Peak wheelchair velocities and left-right asymmetries in peak wheel velocities were measured during the acceleration and constant peak velocity phases. Sprint time, cycle frequency, and mean and maximum velocity were calculated over the entire sprint.ResultsThe peak velocities of the first 2 pushes (acceleration phase) were significantly higher with the defensive than the offensive wheelchair (p < 0.04 and p < 0.02). Mean and maximum sprint velocity were significantly higher (p < 0.03 and p < 0.04, respectively) with the defensive wheelchair. Cycle frequency and asymmetry did not differ between wheelchairs.ConclusionPerformance was higher with the defensive than the offensive wheelchair, suggesting that the frequent finding that the higher performance of offensive as compared to defensive players is not related to the use of an offensive wheelchair.

An investigation of bluff body flow structures in variable velocity flows

The present study explores three-dimensional vortex-dynamics past a wall-attached bluff body kept in a variable velocity field with numerical simulations. A trapezoidal pulse of mean velocity, consisting of acceleration phase from rest followed by constant velocity phase and deceleration phase to rest, is imposed at the inlet of the computational domain similar to the experimental study of Das et al. [“Unsteady separation and vortex shedding from a laminar separation bubble over a bluff body,” J. Fluids Struct. 40, 233–245 (2013)]. For a wide range of Reynolds numbers (96≤Reb≤2390), acceleration Reynolds numbers (196≤Rea≤978), and deceleration Reynolds numbers (310≤Red≤1522), different stages of flow evolution are systematically analyzed. The flow evolution starts with the formation of a primary vortex followed by a two-dimensional circular array of spanwise vortex tubes by inflectional shear-layer instability. At a sufficiently high Reynolds number, the shear layer vortices originated from two-dimensional fluctuations deformed by three-dimensional instabilities, giving fragmented streamwise vorticity. In addition, long-wavelength “tongue-like structures” and short-wavelength “rib-like structures” are evident near the top wall and the bluff body, respectively. The streamwise vorticity generation equation indicates that the spanwise vortex tubes initially tilt, resulting in streamwise vorticity, further amplified by the vortex stretching process. The distinct flow features, including mode shape, frequency, and growth rate associated with the shear-layer instability, are identified using the dynamic mode decomposition (DMD) algorithm. Using the maximum growth rate criteria, the DMD technique successfully separates the coherent shear layer modes associated with two-dimensional shear layer instability from the flow field.

Performance, asymmetry and biomechanical parameters in wheelchair rugby players

ABSTRACT The practice of the wheelchair rugby is becoming more and more worldwide. However, few biomechanical studies have focused on this sport. The aim of this study was to compare kinematic parameters of wheelchair rugby players, classified as defensive players (LP-D) versus offensive players (HP-O). Twenty-nine wheelchair rugby players (17 LP-D and 12 HP-O) performed a 20-m sprint test. The peak velocities, temporal parameters (propulsion phase time, deceleration phase time, cycle time and cycle frequencies) and asymmetries (the difference in peak velocities between the right and the left wheels) were measured at the acceleration and constant peak velocity phases of the sprint by an inertial measurement unit which was placed on each rear wheel. At the acceleration and constant peak velocity phases, peak velocities and cycle frequencies were higher in HP-O players than LP-D players. The deceleration phase times and the cycle times were higher in LP-D players than HP-O players. However, no significant difference in asymmetry was found between LP-D players and HP-O players. The HP-O players showed superior performance than the LP-D players, but they could be more exposed at risk of injury at their upper limbs than LP-D players.

Hydrodynamics of weakly and strongly stratified two-layer lock-release gravity currents

A series of lock-release experiments are carried out to investigate the hydrodynamics of weakly and strongly stratified two-layer gravity currents (GC) on a flat bottom. A particle image velocimetry (PIV) system combined with an optical method is used to obtain the mixing process, front velocity, and velocity profiles of the two-layer GCs, focusing on the effect of the initial height ratio and lock aspect ratio. For a weakly stratified two-layer GC, the two layers mix thoroughly earlier with a higher initial height ratio and lock aspect ratio. A theoretical model is improved to predict the time that is necessary for the thorough mixing during the propagation of weakly stratified two-layer GCs. For a strongly stratified two-layer GC, a higher initial height ratio leads to a larger velocity of the upper layer because of the larger initial density difference, which results in a shorter time for the upper layer to outrun the lower layer. After the upper layer outruns the lower layer, the current has a constant-velocity phase and then a deceleration phase. The present investigation indicates that the maximum velocity in a vertical velocity profile of a strongly stratified two-layer GC is located at the position near to, or higher than the upper limit for single-layer GCs due to the smaller drag resistance at the upper boundary.

Two-dimensional simulations of coronal rain dynamics

Context. Coronal rain often comes about as the final product of evaporation and condensation cycles that occur in active regions. Observations show that the condensed plasma falls with an acceleration that is less than that of free fall. Aims. We aim to improve the understanding of the physical mechanisms behind the slower than free-fall motion and the two-stage evolution (an initial phase of acceleration followed by an almost constant velocity phase) detected in coronal rain events. Methods. Using the MANCHA3D code, we solve the 2D ideal magnetohydrodynamic equations. We represent the solar corona as an isothermal vertically stratified atmosphere with a uniform vertical magnetic field. We represent the plasma condensation as a density enhancement described by a 2D Gaussian profile. We analyse the temporal evolution of the descending plasma and study its dependence on such parameters as density and magnetic field strength. Results. We confirm previous findings that indicate that the pressure gradient is the main force that opposes the action of gravity and slows down the blob descent, and that larger densities require larger pressure gradients to reach the constant speed phase. We find that the shape of a condensation with a horizontal variation of density is distorted during its fall because the denser parts of the blob fall faster than the lighter ones. This is explained by the fact that the duration of the initial acceleration phase and, therefore, the maximum falling speed attained by the plasma, increases with the ratio of blob to coronal density. We also find that the magnetic field plays a fundamental role in the evolution of the descending condensations. A strong enough magnetic field (greater than 10 G in our simulations) forces each plasma element to follow the path given by a particular field line, which allows for the description of the evolution of each vertical slice of the blob in terms of 1D dynamics, without the influence of the adjacent slices. In addition, under the typical conditions of the coronal rain events, the magnetic field prevents the development of Kelvin-Helmholtz instability.

Dynamic Modeling and Analysis of a Mine Hoisting System with Constant Length and Variable Length

A coal mine hoisting system includes two parts, one is a constant-length cable system, and the other is a variable-length cable system. In this paper, the nonlinear dynamic modeling of a coal mine hoisting system is established through Hamilton’s principle. The nonlinear partial differential equations of the coal mine hoisting system are discretized into ordinary differential equations by the fourth-order Galerkin truncation. The nonlinear dynamic responses and four key kinematic and structural parameter analysis of the coal mine hoisting system in the acceleration phases, constant velocity phases, and deceleration phases are given. The results show that the axial vibration displacements of the constant-length cable are an order of magnitude smaller than that of the variable-length cable. The load has the greatest effect on the axial vibration displacement of the hoisting cable. Adversely, the speed has the least effect on the axial vibration displacement of the hoisting cable.

Research on Load Estimation for a PMLM Actuated Vibration Stage

This paper puts forward a new load estimation method in time domain for PMLM servo loop tuning. This method takes advantage of the symmetry of cogging force distribution and identifies the friction force in constant velocity phase. Experiments have been carried out on a PMLM actuated vibration stage to validate the method. It’s discovered that it’s better to take an average of two estimations as the true value with movement range by 0.25 pitch’s difference so that cogging effect could be eliminated. Moreover, movement range is better to be greater than 1 pitch. Motor force constant should be calibrated according to its actual output.

Comparison Between the FLUIDICS Experiment and Direct Numerical Simulations of Fluid Sloshing in Spherical Tanks Under Microgravity Conditions

The fluids behaviour within a spherical tank under microgravity conditions is investigated through a comparison between the original data from the FLUIDICS experiment carried out in the ISS and Direct Numerical Simulations for two-phase flows. The study case consists in the rotation of a spherical tank around a fixed axis. The tank is filled with a liquid with physical properties similar to those of liquid propellants and gases used in the space industry. Two tanks with different filling ratios have been tested in space. Cameras and sensors allow extracting the fluids dynamics and the temporal evolution of the force and torque exerted by the fluids on the tank wall. Several manoeuvres corresponding to different angular velocities and angular accelerations are submitted on both tanks. The velocity profile is divided into four phases: from zero, the angular velocity around the vertical axis increases linearly until it reaches the required constant value for which the fluids stabilise in the second phase, then the angular velocity decreases until it recovers zero. Numerical simulations are computed with the home-made code DIVA which is based on the Level Set method coupled with the Ghost Fluid Method. The force in the radial direction gives the value of the centrifugal force during the constant angular velocity phase. The average centrifugal force is well predicted by the simulations, the comparison with the experimental data exhibits errors lower than 3% for the half-filled tank. Considering the vertical torque, the effect of the Euler acceleration is clearly visible through the important peaks of opposite sign observed during the acceleration and the deceleration phases. Moreover, the oscillations of the gas bubble during the second phase can be observed from the torque evolution. Their magnitude decreases throughout time until the steady state is reached. The measured and predicted temporal evolutions match together until the magnitude of the oscillations reaches the noise level of the data. The bubble oscillations are much more damped for the tank containing a larger amount of liquid (75%). The frequency of these oscillations are investigated applying the Fourier transform of the torque signals and by looking at the videos taken during the experiment. Similar oscillation frequencies are observed with the experimental setup and the numerical simulations, even for the manoeuvre with the lower Bond numbers. We verify that the oscillation frequency increases with the angular velocity. Finally, the comparison exhibits that the numerical simulations provide an accurate prediction of the fluids behaviours in microgravity conditions for this range of Bond numbers.

Towards a wearable monitoring tool for in-field ice hockey skating performance analysis

The capturing of movements by means of wearable sensors has become increasingly popular in order to obtain sport performance measures during training or competition. The purpose of the current study was to investigate the feasibility of using body worn accelerometers to identify previous highlighted performance related biomechanical changes in terms of substantial differences across skill levels and skating phases. Twenty-two ice hockey players of different caliber were equipped with two 3D accelerometers, located on the skate and the waist, as they performed 30 m forward skating sprints on an ice rink. Two measures of the temporal stride characteristics (contact time and stride time) and one measure of the propulsive power (stride propulsion) of a skating stride were calculated and checked for discriminating effects across (i) skill levels and (ii) sprint phases as well as for their (iii) strength of association with the sprint performance (total sprint time). High caliber players showed an increased stride propulsion (+22%, P < 0.05) and shorter contact time (−5%, P < 0.05). All three analysed variables highlighted substantial biomechanical differences between the accelerative and constant velocity phases (P < 0.05). Stride propulsion of acceleration strides primarily correlated to total sprint time (r = −0.57, P < 0.05). The results demonstrate the potential of accelerometers to assess skating technique elements such as contact time or elements characterizing the propulsive power such as center of mass acceleration, to gauge skating performance. Thus, the findings of this study might contribute to establishing wearable sensors for in-field ice hockey skating performance analysis.

Isolator Dynamics During Unstart of a Dual-Mode Scramjet

The phenomenology of unstart in a dual-mode ethylene-fueled scramjet is studied in the presence of inflow distortion using carefully calibrated unsteady Reynolds-averaged Navier–Stokes computations with an emphasis on understanding the large-scale transients over the length scale of the flowpath. The computational approach is validated with experimental data for two combustor operating states that bound the dual-mode and unstart conditions. Unstart is induced via an imposed fuel-staging transient that emulates the experiments. Inlet distortion introduces three-dimensional effects in the isolator, which primarily manifest in the nature of side wall separation and flow curvature; however, localized regions of heat release are shown to contribute to unstart-inducing side wall separation. A wall-pressure-based metric used to track shock-train motion in experiments is adapted to identify a period of constant shock-train speed and an incipient unstart condition. During the constant-velocity phase, separation on the upper wall modulates the supersonic core, resulting in a change from an oblique to a normal-like shock-train configuration. The incipient unstart state precedes the ejection of the shock train from the isolator, which is suggestive of a precursor to unstart. This metric highlights the importance of the side wall corner region during the unstart process and complements other studies of three-dimensional effects in similar isolator geometries.

Electric field of a point charge in truncated hyperbolic motion

We find the electric field of a point charge in ‘truncated hyperbolic motion’, in which the charge moves at a constant velocity followed by motion with a constant acceleration in its instantaneous rest frame. The same Lienard–Wiechert formula holds for the acceleration phase and the constant velocity phase of the charge’s motion. The only modification is that the formula giving the retarded time is different for the constant velocity motion than it was for the accelerated motion. The electric field lines are continuous as the retarded time increases through the transition time between constant velocity and accelerated motion. As the transition time approaches negative infinity the electric field develops a delta function contribution that has been introduced by others as necessary to preserve Gauss’s law for the electric field.

Towards a quantitative understanding of pyroclastic flows: Effects of expansion on the dynamics of laboratory fluidized granular flows

We conducted laboratory dam-break experiments on initially fluidized granular flows using two different fine-grained powders (mean grain sizes 47 and 67μm) down a smooth, horizontal channel with an impermeable base. The powders were first fluidized and expanded to a known degree in the flume reservoir, then released down the channel by opening a sliding gate. The mixture formed rapidly moving flows that defluidized and deposited progressively as they propagated. The experiments were similar to those carried out previously using volcanic ash by Girolami et al. (2008, 2010) but explored a much larger range of initial aspect ratios (height-to-length ratio, a=0.25 to 4). They were designed to investigate the effects of initial expansion (up to 50vol.% above loose packing) and aspect ratio on the dynamics of flow propagation and deposition, and to explore different scalings in order to determine the physical parameters governing these processes. The flows exhibit a similar behaviour to other types of transient granular flows, including three well defined propagation phases (acceleration, constant velocity, and stopping phases) and the progressive aggradation of a basal static layer during emplacement. The deposit aggradation velocity depends only on the initial powder expansion and is similar to that of a collapsing bed of the same powder, expanded by the same amount, under quasi-static, non-shearing conditions. At a given initial expansion, the maximum runout distance scales with the initial bed height h0, the runout duration with (h0/g)1/2 and the maximum velocity with (gh0)1/2. However, runout distance and duration both increase with increasing initial expansion. This is attributed to the effect of hindered settling in delaying defluidization of the dense, but slightly expanded, suspension. The data enable us to identify an additive scaling law providing a smooth transition from non-expanded to expanded flows.

Trajectory planning for overhead crane by trolley acceleration shaping

This paper proposes a novel off-line trolley trajectory planning method for underactuated overhead cranes. The proposed technique is feasible and efficient for overhead crane operation. Dynamic coupling between trolley motion and payload swing was successfully exploited using a staircase form of trolley acceleration. The payload swings in the constant velocity phase were efficiently suppressed and the trolley reached the desired position using this technique. The reasonable number of stairs can be determined by evaluating the residual oscillation amplitude according to the number of stairs and variation in the natural frequency of the pendulum. The proposed approach was first simulated from the kinematics viewpoint to verify the validity of the trolley trajectory and the swing angle of the payload. The proposed approach was then combined with the dynamics of the overall crane, wherein the robust sliding mode controller was applied to ensure that the trolley tracks the designed trajectory. The numerical simulation results demonstrated superior performance and robustness against parameter uncertainties of the proposed method. The proposed method exhibited potential for application in the control of underactuated systems, such as overhead cranes, single-link flexible-joint manipulators, and flexible Cartesian manipulators.

DYNAMICS OF CORONAL RAIN AND DESCENDING PLASMA BLOBS IN SOLAR PROMINENCES. I. FULLY IONIZED CASE

Observations of active regions and limb prominences often show cold, dense blobs descending with an acceleration smaller than that of free fall. The dynamics of these condensations falling in the solar corona is investigated in this paper using a simple fully ionised plasma model. We find that the presence of a heavy condensation gives rise to a dynamical rearrangement of the coronal pressure that results in the formation of a large pressure gradient that opposes gravity. Eventually this pressure gradient becomes so large that the blob acceleration vanishes or even points upwards. Then, the blob descent is characterised by an initial acceleration phase followed by an essentially constant velocity phase. These two stages can be identified in published time-distance diagrams of coronal rain events. Both the duration of the first stage and the velocity attained by the blob increase for larger values of the ratio of blob to coronal density, for larger blob mass, and for smaller coronal temperature. Dense blobs are characterised by a detectable density growth (up to 60% in our calculations) and by a steepening of the density in their lower part, that could lead to the formation of a shock. They also emit sound waves that could be detected as small intensity changes with periods of the order of 100 s and lasting between a few and about ten periods. Finally, the curvature of the falling path is only relevant when a very dense blob falls along inclined magnetic field lines.

A near‐inertial mode observed within a Gulf Stream warm‐core ring

Layering of ocean velocity “fine structure” has been coherently observed across the entire extent of a Gulf Stream warm‐core ring using a shipboard acoustic Doppler current profiler system in September 2009 and independently sampled as the ring transited a moored array. Lines of constant velocity phase generally followed isopycnals as they deepened within the ring center. We also observed a clear separation of the vertical structure of the flows associated with the ring (of order 0.5 m/s) with the shorter (200 m) and less energetic (~0.2 m/s) flows of the velocity fine structure, which was further observed to rotate clockwise with increasing depth, consistent with downward propagating near‐inertial waves (NIWs). Observations are consistent with a ring‐scale NIW packet, probably wind forced, that shows enhanced NIW energy within the sloping pycnocline at depths of 300–700 m. Evidence of wind‐forced NIWs within anticylonic eddies in a numerical simulation shows some similar features to our observations, which we try to understand physically with basic WKB‐type wave/current dynamics along the lines of previously published work and a new calculation of NIW trapping within an isolated, baroclinic vortex.