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• Impinging paper-thin sheets of liquids produces high energy dissipation rates. • The volume of energy dissipation is equal to the volume of the impingement zone. • A new expression for the energy dissipation rate was derived and compared with turbulence theory. • Large-eddy turnover time is approximately equal to liquid residence time in impingement zone. • Large-eddy kinetic energy decays exponentially in the impingement zone. The micromixing time of impinging thin liquid sheets depends upon the energy dissipation rate (∊). The kinetic energy released by the impingement has been previously studied and was found to be a function of the coefficient of restitution of the collision. In this work, the volume within which the released kinetic energy is dissipated was investigated. The volume of energy dissipation was determined by measuring the time required for the velocity of the liquid prior to the collision to be reduced to the velocity after the collision. High-speed video was used to measure the velocity of features, generated in the front single sheet, as they passed through the impingement zone and into the mixed sheet. The experimental results showed that the time required for the velocity change was approximately equal to the residence time of liquid in the impingement zone (t r). A new equation for ∊ was developed and compared with ∊ derived from turbulence energy-cascade theory. This comparison showed that the large-eddy turnover time (t Λ) was approximately equal to t r ; a result that is in accordance with the notion from turbulence energy-cascade theory that large, energy-containing eddies lose their energy within t Λ. Within the impingement zone, the large-eddy kinetic energy was found to decay exponentially with time. [ABSTRACT FROM AUTHOR]

In order to solve the blockage effect and energy dissipation phenomenon caused by cavitation in the low-pressure vortex core region, this paper analyzes the spatial evolution of vorticity intensity and turbulent kinetic energy intensity under different cavitation conditions based on the Wray–Agarwal (WA) model. First, the tip leakage flow characteristics are studied, the evolution of vorticity and vorticity intensity is analyzed, then the distribution of turbulent kinetic energy distribution in the blade tip region is studied, and finally, the vorticity transport characteristics of the tip region are analyzed. It is found that the tip leakage rate is less affected by the vortex cavitation of the tip leakage, and there is a strong interaction between the leakage flow at the tip leading edge and the trailing edge, and the separation vortices and low-speed regions formed in the end-wall region cause blockage of the flow passage. Low pressure causes cavitation to cover most regions of the suction surface, inhibiting the formation and development of the tip leakage vortices. The distribution range of high turbulent kinetic energy region is almost the same as that of high-vorticity region, and there is a positive correlation between the two intensities. Severe cavitation causes the high turbulent kinetic energy region at the outlet of the flow passage to develop in the radial and axial directions of the impeller, which increases the turbulent dissipation and energy loss. The change of vorticity transport intensity caused by cavitation is mainly reflected in the expansion contraction term, and the Coriolis force term plays a dominant role in the vorticity transport process. This paper provides a reference for further improving the performance of mixed-flow pumps. [ABSTRACT FROM AUTHOR]

Near-surface oceanic turbulence plays an important role in the exchange of mass, momentum, and energy between the atmosphere and the ocean. The climate modifying the air–sea CO 2 transfer rate varies linearly with the surface turbulent kinetic energy dissipation rate to the 1 / 4 power in a range of systems with different types of forcing, such as coastal oceans, river estuaries, large tidal freshwater rivers, and oceans. In the first part of this paper, we present a numerical study of the near-surface turbulent kinetic energy spectra deduced from a direct numerical simulation (DNS) compared to turbulent kinetic energy spectra deduced from idealized infrared (IR) images. The DNS temperature fields served as a surrogate for IR images from which we have calculated the underlying kinetic energy spectra. Despite the near-surface flow region being highly anisotropic, we demonstrated that modeled isotropic and homogeneous turbulence spectra can serve as an approximation to observed near-surface spectra within the inertial and dissipation ranges. The second part of this paper validates our numerical observations in a laboratory experiment. In this experiment, we compared the turbulent kinetic energy spectra near the surface, as measured using a submerged shear sensor with the spectra derived from infrared images collected from above the surface. The energy dissipation measured by the shear sensor was found to be within 20% of the dissipation value derived from the IR images. Numerically and experimentally, we have demonstrated that IR-based and remote measurement techniques of the aquatic near surface offer a potentially accurate and non-invasive way to measure near-surface turbulence, which is needed by the community to improve models of oceanic air–sea heat, momentum, and gas fluxes. [ABSTRACT FROM AUTHOR]

Dry coal separation is the key technology for coal separation in arid and water-scarce areas. The content of −6 + 1 mm coal gradually increases, and the weak gravity affect of this part of coal restricts the separation effect, causing serious resource waste and environmental pollution. In this paper, a process intensification method for compound dry separation based on high-frequency vibration was proposed to improve the separation effect of fine coal. The kinematic characteristics of the bed surface with high-frequency vibration was captured by the three-channels acceleration sensor, and the motion trajectories of different regions on bed surface were reconstructed. The separation area was located at the front end of the vibrating bed, and the elliptical trajectory promoted the material to roll. However, the tail of the bed showed a linear trajectory, the main team to the transport of the material. And then the force characteristics of various density particles were studied by using spherical inertial sensors. Compared with low-density particle swarm, the collision between high-density particles was more obvious, causing serious loss of kinetic energy, which increased the motion difference of particles with different densities. Furthermore, the significance of the effects of vibration frequency, bed inclination and air velocity on the separation effect of −6 + 1 mm coal and the interaction between the factors were investigated. Furthermore, the influence of vibration frequency, inclination, and air velocity on the separation effect and the interaction among various factors were explored. The influence of frequency and inclination was more obvious than that of gas velocity. And then a mathematical model was established to predict the calorific value of clean coal. The results illustrated that at a vibration frequency of 37.52 Hz, a bed inclination angle of 13.69°, and an air velocity of 2.26 m/s, the calorific of product was increased from 4306 kcal/kg to 5868 kcal/kg, and the heat efficiency reached 90.18%. The results provide a referable way to realize the large-scale and high-efficiency dry separation of fine coal. [ABSTRACT FROM AUTHOR]

During substructure formation in magnetized astrophysical plasma, dissipation of magnetic energy facilitated by magnetic reconnection affects the system dynamics by heating and accelerating the ejected plasmoids. Numerical simulations are a crucial tool for investigating such systems. In astrophysical simulations, the energy dissipation, reconnection rate, and substructure formation critically depend on the onset of reconnection of numerical or physical origin. In this paper, we hope to assess the reliability of the state-of-the-art numerical codes, pluto and koral by quantifying and discussing the impact of dimensionality, resolution, and code accuracy on magnetic energy dissipation, reconnection rate, and substructure formation. We quantitatively compare results obtained with relativistic and non-relativistic, resistive and non-resistive, as well as two- and three-dimensional set-ups performing the Orszag–Tang test problem. We find sufficient resolution in each model, for which numerical error is negligible and the resolution does not significantly affect the magnetic energy dissipation and reconnection rate. The non-relativistic simulations show that at sufficient resolution, magnetic and kinetic energies convert to internal energy and heat the plasma. In the relativistic system, energy components undergo mutual conversion during the simulation time, which leads to a substantial increase in magnetic energy at 20 per cent and 90 per cent of the total simulation time of 10 light-crossing times – the magnetic field is amplified by a factor of 5 due to relativistic shocks. We also show that the reconnection rate in all our simulations is higher than 0.1, indicating plasmoid-mediated regime. It is shown that in koral simulations more substructures are captured than in pluto simulations. [ABSTRACT FROM AUTHOR]

In a seminal paper in the Philosophical Transactions of the Royal Society (A244, 87–112). Eshelby (Eshelby 1951 Phil. Trans. R. Soc. Lond. A 244, 87–112. (doi:10.1098/rsta.1951.0016)) introduced the concept of 'the force on an elastic singularity' and suggested that the extensions to dynamics include the application of the momentum flux. In this direction, it is shown that, in the non-uniformly motion of a dislocation there is a loss in quasi-momentum (or pseudo-momentum) across the scales ε to ε2, which induces an effective mass of the dislocation, and a loss in kinetic energy across the scales. It is shown through Noether's theorem that the rate of change of quasi-momentum in the volume enclosing the dislocation is equal to the flux of it through the surface minus a quasi-force, which is the dynamic J integral. The connection between the variation in the Hamiltonian and in the Lagrangian relates the quasi-force to the energy-release rate, yielding the same effective mass, while providing physical meaning both through momentum and energy. The effective mass of a dislocation is important in relating the energetics of defects from the micro to the macro scales, and the loss of quasi-momentum can have wider applications in continua. This article is part of the theme issue 'Foundational issues, analysis and geometry in continuum mechanics'. [ABSTRACT FROM AUTHOR]

In the impinging region of opposing jets, strong mixing and significant energy dissipation are observed, but the mixing parameters invariably change with the opposed impinging strength (OIS). In this paper, the ratio of the turbulent kinetic energy (TKE) intensity at the theoretical impinging point to the nozzle exit is defined as the opposed impinging strength. To examine the mixing properties of opposed impinging jets (OIJs) in a limited field under various OIS, a renormalization group k-ε turbulence model is employed to calculate three-dimensional OIJs under various OIS. The nozzle exit diameter is set to 0.6 m, and the inlet velocity is between 0.08 and 8 m/s, so the simulations are performed at Re between 4.8 × 104 and 4.8 × 106. This work focuses on the radial and vertical jets produced after impinging as well as the distribution of the TKE, flow field, and vortices. A thorough investigation reveals that although the OIS of the jets is primarily determined by the degree of jet development, it increases with the Reynolds number. A low OIS results in less mixing in the surrounding water and relatively unconstrained jet generation; however, it also results in limited energy extraction from the fluid. Once the OIS is high, there is more mixing in the surrounding water, and more energy is also lost during impinging. The distribution of vortices in the vortex field is not only influenced by the OIS but is also very closely related to the scale of the limited mixing field. [ABSTRACT FROM AUTHOR]

In this paper, large-eddy simulation of the interaction between a shock wave and the hypersonic turbulent boundary layer in a compression corner with a fixed 34° deflection angle at Ma = 6 for different Reynolds number cases is conducted. For investigating the effects of the Reynolds number for hypersonic cases, three cases where the free-stream Reynolds numbers are 14000, 20000, and 30000/mm are selected. The averaged statistics, such as the mean velocity, the skin friction, the heat flux, and the wall pressure, are used in this paper. The flow structures in the compression ramp including the shock wave and interaction region are discussed. The decomposition of the mean skin-friction drag for the flat flow is extended to be used in the compression corner. In addition, the turbulent kinetic energy is studied through the decomposition of the mean skin-friction drag for the flat-plate region and the corner region. It is found that higher Reynolds numbers would increase the turbulent kinetic energy by turbulent dissipation at the interaction region, while higher Reynolds numbers would decrease the turbulent kinetic energy by turbulent dissipation after reattachment. In addition, it is also found that the turbulent kinetic energy is larger with a higher Reynolds number and higher turbulent kinetic energy inhibits the movement from the separation point to the inflection point (x = 0 mm), which deduces larger separation bubbles. [ABSTRACT FROM AUTHOR]

This paper presents the results of a hydrodynamic experimental study of the hydraulic characteristics of flow in different vertical slot fishway (VSF) designs with L-shaped, polygonal, and semicircular baffles. A biological experiment was conducted using endemic fish to analyze the efficiency of the upstream passage of different VSF designs. Based on the results, a significant difference in water depth, slot velocity, turbulence kinetic energy, and efficiency of the upstream passage was observed. The L-shaped baffle had better energy dissipation; however, the fishway with a polygonal baffle had better efficiency of the upstream passage. The results indicated that the present VSFs are all fish-friendly for Chinese endemic fish, but VSFs with polygonal baffles may be a better choice. [ABSTRACT FROM AUTHOR]

The process of a submillimeter sphere eccentric impacting a single droplet under electric field is experimentally investigated by using high-speed micrographic techniques in this paper. The spheres are released at a fixed height to impact different positions of droplets. With the increase in electric field intensity, the impact behavior evolves from oscillation mode to submergence mode. The trajectory of the sphere deviates from the impact direction affected by the eccentric impact. Each mode can be divided into three stages: slamming, cavity developing, and reverting. In the slamming stage, the sphere is decelerated by hydrodynamic forces where the kinetic energy loss increases with the increase in Weber number We. Surface tension becomes the dominant force in the cavity developing stage due to the expanding cavity. The impact angle α and We show little influence on the expanding speed; thereinto We has a significant effect on the limit diameter of the cavity. The cavity with different α and We reaches a peak value near the critical state of the impact angle of 90 degrees. A scaling law is constructed to obtain the transitional boundary between the impact modes based on dimensional analysis and data rearrangement. The electric force is mainly used to accelerate the sphere in the gas phase and has little influence on the solid–liquid interaction behavior after contacting the droplet. [ABSTRACT FROM AUTHOR]

The current advanced aero-engine fan rotors are usually integrally-bladed rotor discs, and the root of the fan blade has irregular curved surface, which brings technical difficulties and challenges to achieve the blade releasing. In this paper, the dynamic response and energy dissipation process of the titanium alloy blade under shaped charge jet explosion were analyzed by numerical model, and the explosion damage mechanism of titanium alloy fan blades was clarified. Finally, a FBO test was conducted to verify the blade explosion release method in rotating state. Through the energy dissipation analysis of the whole explosion process, it can be seen that the overall residual kinetic energy of the blade is about 15.7 J, which is only 0.02 % of the initial kinetic energy of the releasing blade in rotating. It is indicated that the explosion separation method will not generate additional kinetic energy to the released blade. [ABSTRACT FROM AUTHOR]

Geometrical structures and operating performance of volutes used in centrifugal pumps are assessed in cross sections. By a volute, we mean the wetted part surrounding the impeller in a pump that converts the kinetic energy of water into potential energy. It is important to develop improved design principles and approaches for volutes to reduce hydraulic loss and increase the efficiency of pumps. However, when designing volutes, pump designers often neglect a key factor related to pump efficiency, namely, the energy loss due to the friction at the volute sidewall is directly proportional to the wetted perimeter of the cross section. In this paper, we show that the length of the wetted perimeter of the cross section is mathematically proportional to the friction loss in the volute. In addition, we present the design principles and calculation process to minimize the wetted perimeters of two kinds of cross section based on the velocity coefficient method using the same statistical data. The structures and shapes of the new cross sections are completely different from those of traditional volutes. Moreover, two different volutes with different cross sections are numerically investigated using a verified computational fluid dynamics technique. Both the head and the efficiency of the pump with the new volute are higher than those of a conventional pump under all working conditions. This paper provides a new design approach for the energy-saving volutes of centrifugal pumps. [ABSTRACT FROM AUTHOR]

In mountainous areas, rock avalanches swarm downslope leading to large impact forces on structures. Baffle systems are usually set up in torrent channels to dissipate the flow energy and reduce the destructive effects. In this paper, a crown-like baffle system is proposed to better dissipate the flow energy. The energy dissipation mechanism of this system was investigated based on DEM. The results reveal more than 90% of the kinetic energy of the granular flow was dissipated by particle-particle interaction. Two effects, the impedance effect and the deflection effect, were identified. The influence of these effects leads to the formation and growth of cushions behind the baffles, and these cushions enhance the particle-particle interaction. Two crown-like baffle systems were compared with a conventional baffle system based on the typical avalanche model. The results reveal the cumulative residual kinetic energy of the crown-like baffle system with square baffles decreased by 18.75% with the same concrete consumption as the conventional baffle system. For the crown-like baffle system with triangular baffles, the cumulative residual kinetic energy decreased by 6.22% with 83.94% of the concrete consumption of the conventional baffle system. Hence, the proposed baffle system is more cost-effective compared with the conventional baffle system. [ABSTRACT FROM AUTHOR]

Proper EMA-balance (balance of kinetic energy, linear momentum and angular momentum), pressure-robustness and Re-semi-robustness (Re: Reynolds number) are three important properties of Navier–Stokes simulations with exactly divergence-free elements. This EMA-balance makes a method conserve kinetic energy, linear momentum and angular momentum in an appropriate sense; pressure-robustness means that the velocity errors are independent of the pressure; Re-semi-robustness means that the constants appearing in the error bounds of kinetic and dissipation energies do not explicitly depend on inverse powers of the viscosity. In this paper, based on the pressure-robust reconstruction framework and certain suggested reconstruction operators in Linke and Merdon [Comput. Methods Appl. Mech. Eng.311 (2016) 304–326], we propose a reconstruction method for a class of non-divergence-free simplicial elements which admits almost all the above properties. The only exception is the energy balance, where kinetic energy should be replaced by a suitably redefined discrete energy. The lowest order case is the Bernardi–Raugel element on general shape-regular meshes. Some numerical comparisons with exactly divergence-free methods, the original pressure-robust reconstruction methods and the EMAC method are provided to confirm our theoretical results. [ABSTRACT FROM AUTHOR]

This paper presents a numerical investigation of the liquefaction behavior of granular materials considering the initial static shear effects. Two typical cyclic failure modes were identified: cyclic liquefaction and residual deformation accumulation. During the simulation processes, the evolution of the applied work, strain energy, frictional dissipation, and kinetic energy was examined and interpreted by the law of thermodynamics. The relative magnitudes of the applied work and dissipation were found to be significantly different for the two distinct cyclic failure modes. For cyclic liquefaction, the applied work was smaller than the frictional dissipation, accompanied by continuous liberation of the strain energy. In contrast, for residual deformation accumulation, the applied work was nearly the same as dissipation, and the strain energy appeared to be stable and periodically varying in each cycle, indicating the attainment of a steady internal structure and thus a strong resistance to liquefaction. These observations can be interpreted by correlating the energy transfer and dissipation with the contact-normal-based fabric evolution of the granular system at microscale. [ABSTRACT FROM AUTHOR]

Rocking bodies can be found at all structural scales, from small museum exhibits to uplifting buildings. These structures, whose dynamic stability springs from the difficulty of mobilizing their rotational inertia, are ideal candidates for benefiting from the supplemental inertia provided by inerters. This benefit can be limited, however, if the inerter drives the structural response towards potentially undesirable motions by transferring back the kinetic energy accumulated within it at inconvenient times. To control this phenomenon, a clutching system can be employed to direct the interaction between the interter and the structure improving further its dynamic behaviour. To date, however, most of the studies dealing with clutching inerto-elastic or inerto-rocking systems under seismic excitation have adopted a rather simplistic idealisation of the clutch engagement-disengagement response. In this paper, we re-visit the impact effects on inerto-rocking structures and propose an improved mechanistic model of the clutching system. First, the effects of the inerter on the transition upon impact and the impact effects on the acceleration response of rocking blocks are analysed. Then, a set of original analytical expressions for rigid and flexible rocking structures equipped with a pair of clutched inerters are derived. The newly proposed models are used to examine the evolution of the energy dissipation in the device and the influence of key parameters like the clutch stiffness, gears play, viscous damping and dry friction on its response. We conclude by evaluating the behaviour of the detailed rocking model with clutched inerters to a set of realistic earthquake ground motions. Although important differences are observed in the evolution of energy dissipation and engagement response depending on the type and characteristics of the clutch model, largely comparable peak values of displacement are obtained. On the other hand, a more accurate representation of the clutch behaviour leads to potentially larger acceleration demands. Our analyses also show that, in general, the inclusion of the inerter results in higher coefficients of restitution, indicating lower energy dissipation during impact and that the infinite acceleration spikes predicted by Housner's model can be ignored if impact forces are sufficiently distributed over time as to cause continuous velocity transitions, but sharp enough not to appreciably affect the rotation response. [ABSTRACT FROM AUTHOR]

Fragmentation of blocks upon impact is commonly observed during rockfall events. Nevertheless, fragmentation is not properly taken into account in the design of protection structures because it is still poorly understood. This paper presents an extensive and rigorous experimental campaign that aims at bringing insights into the understanding of the complex phenomenon of rock fragmentation upon impact. A total of 114 drop tests were conducted with four diameters (50, 75, 100, and 200 mm) of rock-like spheres (made of mortar) of three different strengths (34, 23 and 13 MPa), falling on a horizontal concrete slab, with the objective to gather high-quality fragmentation data. The analysis focuses on the fragment size distribution, the energy dissipation mechanisms at impact and the distribution of energy amongst fragments after impact. The results show that the fragment size distributions obtained in this campaign are not linear on a logarithmic scale. The total normalised amount of energy loss during the impact increases with impact velocity, and consequently the total kinetic energy after impact decreases. It was also found that energy loss to create the fracture surfaces is a constant fraction of the kinetic energy before impact. The trajectories of fragments are related to the impact velocity. At low impact velocity, the fragments tend to bounce but, as the impact velocity increases, they tend to be ejected sideways. Although testing mortar spheres in normal impact is a simplification, the series of tests presented in this work has brought some valuable understanding into the fragmentation phenomenon of rockfalls. Highlights: Data of 114 controlled drop tests of mortar spheres are analysed. Fragment size distributions obtained in this campaign are not linear on a logarithmic scale. The total amount of energy loss during the impact increases with impact velocity, and consequently the total kinetic energy after impact decreases. Energy loss to create fracture surfaces is a constant fraction of the kinetic energy before impact. At low impact velocity, the fragments tend to bounce but, as the impact velocity increases, they tend to be ejected sideways. [ABSTRACT FROM AUTHOR]

Cohesion and rolling friction play key roles in governing the behavior of soil; however, only a limited number of studies have been able to assess the simultaneous contributions of these two microparameters on the macroproperties of soil. In this respect, the innovation of the current study includes an attempt to examine the interplay of these two primary parameters on the angle of repose (AoR) based on the discrete-element method (DEM). Lifting cylinder tests on cohesive wet sand have been carried out in DEM, while the cohesion and rolling friction are captured through proposed computational models. In this paper, macroparameters, such as the geometry and developmental stages of sand piles obtained in DEM simulation, are compared with experimental data, while their microevolution is quantified in detail. The results show that a large AoR can only be obtained when the cohesive and rotational frictional forces work in tandem. Increasing the cohesion and rolling friction results in smaller contact numbers, with increasing chain-like connections between particles and larger pore spaces to account for a larger AoR. For the first time, this study distinctly identifies three major stages that contribute to the AoR, based on the development of contact numbers and the transformation of energy. Accordingly, the linkage between macroscale AoR and the microstructural coordination number is formulated with varying levels of cohesion and rolling friction. The DEM results prove that the more cohesive the particles are, the greater the delay in the dissipation of kinetic energy. [ABSTRACT FROM AUTHOR]

Baffles and check-dam systems are often used as granular flow (rock avalanches, debris flows, etc.) control structures in regions prone to dangerous geological hazards leading to massive landslides. This paper explores the use of numerical modelling to simulate large volume granular flow and the effect of the presence of baffles and check dam systems on granular flow. In particular, the paper offers a solution based on the smoothed particle hydrodynamics numerical method, combined with a modified Bingham model with Mohr–Coulomb yield stress for granular flows. This method is parallelised at a large scale to perform high-resolution simulations of sand flowing down an inclined flume, obstructed by rigid control structures. We found that to maximise the flow deceleration ability of baffle arrays, the design of baffle height ought to reach a minimum critical value, which can be quantified from the flow depth without baffles (e.g. 2.7 times for frictional flows with friction angle of 27.5°). Also, the check-dam system was found to minimise run-out distances more effectively but experiences substantially higher forces compared to baffles. Finally, flow-control structures that resulted in lower run-out distances were associated with lower total energy dissipation, but faster kinetic energy dissipation in the granular flows; as well as lower downstream peak flow rates. [ABSTRACT FROM AUTHOR]

This paper is concerned with limits on kinetic and magnetic energies and dissipation rates in forced flows that lead to dynamo action and a finite amplitude magnetic field. Rigorous results are presented giving upper and lower limits on the values of these quantities, in a simple cubic geometry with periodic boundary conditions, using standard inequalities. In addition to the general case, results in the special case of the Archontis dynamo are presented, in which fields and flows are closely similar in much of the domain. [ABSTRACT FROM AUTHOR]

This paper presents a quantitative analysis of system dynamic response, rockfall trajectory control, and kinetic energy evolution of the tests on the guiding flexible protection system (GFPS) based on 4D energy dissipation. The system achieves 4D protection against rockfall hazards on high and steep slopes, with 3D spatial motion and energy evolution control of rockfall trajectories in time history. After clarifying the structural principle of the system, analyzing the kinetic energy characteristics of the rockfall along the hill, and defining the multistage energy-dissipation control principle of the system, an evaluation method for rockfall energy evolution for quantitative back analysis was established for the whole course of system protection. Furthermore, the rockfall's energy decay characteristics in the guiding section were analyzed. Accordingly, a full-scale model of this system was constructed, and six in situ tests with and without the protection system were conducted. The system model was laid on a slope with a gradient of over 60°, a width of 130 m, and a height of 82 m, where the crushed rock developed. The maximum impacting energy was 2500 kJ. Quantitative back analysis of the experiment was carried out, and the results revealed that, compared with the unprotected tests, after the construction of the protection system, the motion duration of the falling block was extended by over 80%, the impact times increased by approximately five times, the bounce height reduced by roughly 80%, the transverse motion distance reduced by around 50%, and, for blocks that reached the bottom, the residual kinetic energy and the rolling distance away from the slope toe were both decreased by 70%. The combined energy-dissipation ratio was as high as 89%. [ABSTRACT FROM AUTHOR]

A slender footbridge can suffer from a large vibration under vertical human-induced excitation. To improve its serviceability, a tuned mass damper (TMD) has a wide application. However, considering the randomness and synchronization of crowd-induced excitation and the effect of crowd-structure interaction (CSI), the control robustness of a passive TMD needs to be improved. To achieve a better performance, a semi-active TMD (STMD) with variable mass and damping (VMD-STMD) is presented in this paper, which can not only adjust the own mass and frequency in real time to adapt to the dynamic characteristics of the footbridge through the water pump and electromagnetic valve, but also adjust its damping to improve the effect of energy dissipation through changing the eddy current damping. The proposed VMD-STMD can maximize the absorption of structural kinetic energy and dissipate. The working mechanism and control algorithm of VMD-STMD are introduced first, and then, a Euler-Bernoulli simply supported beam is studied. To highlight the best control effect and robustness of VMD-STMD, an optimized passive TMD, variable mass STMD (VM-STMD) and variable damping STMD (VD-STMD) are compared, 100 calculations of them based on crowd probabilistic models are proposed. The influence of CSI is investigated and different crowd density and synergy rate are discussed in detail. Through the maximum, mean and standard deviation of the three comfort evaluation indexes of the 100 groups of acceleration, the control effect and robustness of different TMDs are analyzed. Results show that structural dynamic responses and TMD's performance vary greatly due to the randomness of CSI. In general, VMD-STMD has the best control effect, and its standard deviation is also the smallest, indicating the best control robustness. ● A semi-active tuned mass damper (STMD) with variable mass and damping and its control algorithm are proposed. ● The randomness and synchronization of crowd and the crowd-structure interaction effect are investigated. ● STMDs with different control strategies are compared based on multiple calculations according to crowd probabilistic models. ● Combined variable mass and damping STMD has the best control effect and robustness. [ABSTRACT FROM AUTHOR]

[Display omitted] • Flow characteristics of high shear mixer was studied by Particle Image Velocimetry. • Strain rate was studied under different structures. • Turbulence kinetic energy dissipation rate was studied under different structures. • Two dimensionless correlations were established to predict hydrodynamics performance. The in-line teethed high shear mixers (HSMs) have been widely used in the chemical industry. However, there is still a lack of comprehensive understanding of the hydrodynamics characteristics about the attractive process equipment. In this paper, the effects of rotor and stator structures and rotor speed on flow characteristics of in-line teethed HSM are systematically studied by the particle image velocimetry experiment for the first time. The results show that increasing the rotor speed can significantly increase the strain rate (S xy) and turbulence kinetic energy dissipation rate (ε). Especially, when the shear gap width is reduced from 1.5 mm to 0.5 mm, the mean ε increases by 96.8 %. Furthermore, two dimensionless correlations are established between the maximum value of the S xy , ε and rotor and stator geometrical parameters to provide a valuable guidance for the geometrical design and optimization of in-line teethed HSM. [ABSTRACT FROM AUTHOR]

Finescale strain parameterization (FSP) of turbulent kinetic energy dissipation rate has become a widely used method for observing ocean mixing, solving a coverage problem where direct turbulence measurements are absent but CTD profiles are available. This method can offer significant value, but there are limitations in its broad application to the global ocean. FSP often fails to produce reliable results in frontal zones where temperature–salinity (T/S) intrusive features contaminate the CTD strain spectrum, as well as where the aspect ratio of the internal wave spectrum is known to vary greatly with depth, as frequently occurs in the Southern Ocean. In this study we use direct turbulence measurements from Diapycnal and Isopycnal Mixing Experiment in the Southern Ocean (DIMES) and glider microstructure measurements from Autonomous Sampling of Southern Ocean Mixing (AUSSOM) to show that FSP can have large biases (compared to direct turbulence measurement) below the mixed layer when physics associated with T/S fronts are meaningfully present. We propose that the FSP methodology be modified to 1) include a density ratio (Rρ)-based data exclusion rule to avoid contamination by double diffusive instabilities in frontal zones such as the Antarctic Circumpolar Current, the Gulf Stream, and the Kuroshio, and 2) conduct (or leverage available) microstructure measurements of the depth-varying shear-to-strain ratio Rω(z) prior to performing FSP in each dynamically unique region of the global ocean. Significance Statement: Internal waves travel through the ocean and collide, turbulently mixing the interior ocean and homogenizing its waters. In the absence of actual turbulence measurements, oceanographers count the ripples associated with these internal waves and use them estimate the amount of turbulence that will transpire from their collisions. In this paper we show that the ripples in temperature and salinity that naturally occur at sharp fronts masquerade as internal waves and trick oceanographers into thinking there is up to 100 000 000 times more turbulence than there actually is in these frontal regions. [ABSTRACT FROM AUTHOR]

In porous media, non-wetting phase droplets snapping off in a constricted microchannel are one of the most common phenomena in two-phase flow processes. In this paper, the application range of the classic quasi-static criterion in rectangular cross section microchannels is obtained. For three different droplet breakup phenomena—total breakup, partial breakup, and non-breakup—observed in experiments when a non-wetting phase droplet passes through a microchannel constriction, the breakup is caused by the droplet neck snapping off in a channel constriction. A critical criterion for the dynamic snap-off event in a two-phase flow is proposed considering the effect of viscous dissipation by mechanical analysis, energy dissipation analysis, and many microfluidic experiments. When the droplet front flows out of the constriction, snap-off will occur if the surface energy release exceeds the required energy for viscous dissipation and kinetic energy conversion. The unique partial breakup phenomenon is affected by droplet surfactant distribution and the acceleration effect in the constriction center. This partial breakup phenomenon in experiments is an essential evidence for the non-uniform distribution of surfactants in the droplet surface. The results of this study contribute to understanding pore-scale mass transfer and flow pattern changes within porous media. [ABSTRACT FROM AUTHOR]

In this paper, the energy losses in big band saw machines are investigated. These losses are caused by the geometric and angular inaccuracies with which the leading wheels are made. Expressions for calculating the kinetic energy of the mechanical system in the ideal and the real cases are obtained. For this purpose, expressions for calculating the velocities of the centers of the masses in two mutually perpendicular planes are obtained. A dependence for calculation of the kinetic energy losses of the mechanical system in final form is received. Optimization procedure is used to determine the values of the parameters at which these losses have minimum values. The proposed study can be used to minimize energy losses in other classes ofwoodworking machines. [ABSTRACT FROM AUTHOR]

In this paper, we consider a simplified model of turbulence for large Reynolds numbers driven by a constant power energy input on large scales. In the statistical stationary regime, the behaviour of the kinetic energy is characterized by two well-defined phases: a laminar phase where the kinetic energy grows linearly for a (random) time tw followed by abrupt avalanche-like energy drops of sizes S due to strong intermittent fluctuations of energy dissipation. We study the probability distribution P[tw] and P[S] which both exhibit a quite well-defined scaling behaviour. Although tw and S are not statistically correlated, we suggest and numerically checked that their scaling properties are related based on a simple, but non-trivial, scaling argument. We propose that the same approach can be used for other systems showing avalanche-like behaviour such as amorphous solids and seismic events. This article is part of the theme issue 'Scaling the turbulence edifice (part 1)'. [ABSTRACT FROM AUTHOR]

In a series of papers, we investigate the effect of collisions between turbulent molecular clouds on their structure, evolution, and star formation activity. In this paper, we look into the role of the clouds' initial virial ratios. Three different scenarios were examined: both clouds initially bound, one cloud bound and one unbound, and both clouds initially unbound. Models in which one or both clouds are bound generate filamentary structures aligned along the collision axis and discernible in position–position and position–velocity space. If neither cloud is bound, no filaments result. Unlike in previous simulations of collisions between smooth clouds, owing to the substructure created in the clouds by turbulence before the collisions, dissipation of kinetic energy by the collision is very inefficient and in none of our simulations is sufficient bulk kinetic energy lost to render the clouds bound. Simulations where both clouds are bound created twice as much stellar mass than the bound–unbound model, and both these scenarios produced much more stellar mass than the simulation in which both clouds are unbound. Each simulation was also compared with a control run in which the clouds do not collide. We find the bound–bound collision increases the overall star formation efficiency by a factor of approximately two relative to the control, but that the bound–unbound collision produces a much smaller increase, and the collision has very little effect on the unbound–unbound cloud collision. [ABSTRACT FROM AUTHOR]

In order to further enrich the theory of rotational stall, this paper explored the mechanism of internal energy loss in the mixed-flow pump under stall condition based on the shear stress transport (SST) k-ω turbulence model, identified the vortices in the impeller by the Q -criterion method, and characterized the turbulence intensity by the turbulent kinetic energy (TKE). The results show that the SST turbulence model can well predict the positive slope characteristics of the energy performance curve of a mixed-flow pump, and there are obvious characteristics of rotating stall in impeller. The numerical results of the energy performance curve and internal flow field are in good agreement with the experimental results. Under stall conditions, there exist swirls and vortices at impeller inlet, which makes the flow inception angle increase by 38°. Meanwhile, the tip leakage flow causes certain energy loss in the rim region, but the high loss area caused by the leakage vortex does not coincide with the core region of the leakage vortex. The interaction between stall vortex and the main flow in the flow passage results in the large-scale blockage area, which is the most fatal effect on the head drop of the mixed-flow pump. The backflow appears on the suction surface of the blade outlet, which has a great impact on the main flow and leads to a large hydraulic loss. The typical characteristics of critical stall and deep stall are found. Under the critical stall condition, part of the leakage flow overflows the leading edge of the lower blade and affects the flow of the next passage. While under deep stall condition, the streamlines of the leading edge of stall vortex reaches the inlet of the next stage blade and overflows, causing a lot of energy loss. And the interference effect between tip leakage flow and stall vortex is strengthened. In general, under the deep stall condition, the average turbulent kinetic energy value in the passages is the highest, and the uniformity of flow rate distribution in the four passages is the worst, resulting in the largest energy loss, which is at the lowest head in the saddle area. • Mechanism of internal energy loss in mixed-flow pump under stall condition is explored. • Swirls and vortices at impeller inlet results in more energy loss and continuous weakening the work capacity of blades. • The high loss area caused by tip leakage vortex does not coincide with tip leakage vortex core region. • The interaction between stall vortex and main flow in flow passage results in large-scale blockage area. • Average turbulent kinetic energy value in flow passages is the highest under deep stall condition. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to calculate the Hugoniot relations of polyurea; also to investigate the atomic-scale energy change, the related chain conformation evolution and the hydrogen bond dissociation of polyurea under high-speed shock. Design/methodology/approach: The atomic-scale simulations are achieved by molecular dynamics (MD). Both non-equilibrium MD and multi-scale shock technique are used to simulate the high-speed shock. The energy dissipation is theoretically derived by the thermodynamic and the Hugoniot relations. The distributions of bond length, angle and dihedral angle are used to characterize the chain conformation evolution. The hydrogen bonds are determined by a geometrical criterion. Findings: The Hugoniot relations calculated are in good agreement with the experimental data. It is found that under the same impact pressure, polyurea with lower hard segment content has higher energy dissipation during the shock-release process. The primary energy dissipation way is the heat dissipation caused by the increase of kinetic energy. Unlike tensile simulation, the molecular potential increment is mainly divided into the increments of the bond energy, angle energy and dihedral angle energy under shock loading and is mostly stored in the soft segments. The hydrogen bond potential increment only accounts for about 1% of the internal energy increment under high-speed shock. Originality/value: The simulation results are meaningful for understanding and evaluating the energy dissipation mechanism of polyurea under shock loading, and could provide a reference for material design. [ABSTRACT FROM AUTHOR]

In turbulent premixed flames, the fractal dimension of flame iso-surface is argued to be D = 7 / 3 for Damköhler's large-scale limit (D a > > 1) and D = 8 / 3 for Damköhler's small-scale limit (D a ∼ O (1)) based on heuristic scaling arguments. However, such scaling arguments do not consider the effect of the intermittent nature of turbulent kinetic energy dissipation on the flame surface. In this paper, we account for the effects of intermittent dissipation on the fractal dimension of low D a turbulent premixed flames. Intermittent dissipation leads to variability in the inner cut-off, which then affects the scalar flux and total interface area. We account for these variabilities through two approaches: coarse-grained approach based on the moments of the dissipation and fine-scale analysis by adopting the multifractal formalism. We derive two corrections to the upper-limit of fractal dimension – D = 8 / 3 + 3 / 4 (1 − D 1 / 4) and D = 8 / 3 + 2 / 3 (3 − D 1 / 3). We further show that the second correction leads to an explicit dependence of the fractal dimension (D) on the scaling exponent (ξ) of the velocity structure function through the relation: D = 7 / 3 + ξ. Thus, we explicitly quantify the effect of the intermittent nature of turbulence upon low D a premixed combustion. [ABSTRACT FROM AUTHOR]

• The paper focus on the effects of non-uniform inflow on a small modular reactor coolant pump (SMRCP). • This paper delves into the vortex structure inside the SMRCP to evaluate the impact of non-uniform inflow on its performance. • Using the Q -criterion to identify complex vortex structures and analyzing the mechanism of non-uniform inflow. • The internal flow state of key hydraulic components of the SMRCP during one rotation cycle is analyzed. In small modular reactors, the extremely short distance between the steam generator (SG) and the reactor coolant pump (RCP) results in a non-uniform inflow at the pump inlet. Therefore, in order to investigate the effect of non-uniform inflow on the small modular reactors coolant pump (SMRCP), the internal vortex structure of the SMRCP was investigated in this study. Firstly, the uniform and non-uniform inflow models were constructed for the comparison of the study, and the CFD method was used to obtain the hydraulic characteristic curve and internal flow field information of the pump, and the CFD results were verified by experiments. The results show that the efficiency and head of the uniform inflow model is both higher than that of the non-uniform inflow model, and the non-uniform inflow has an effect on the performance of the pump. Secondly, by analyzing the velocity streamline distribution and vortex distribution under the pump steady calculation results, it is found that the non-uniform inflow will greatly change the flow state in the pump, and a large-scale reflux vortex is formed at the outlet of the casing under the non-uniform inflow, and the vortex structure changes the flow distribution in the casing. Finally, the vortex distribution of the impeller channel under transient calculation of the pump under different models for one week of impeller rotation, the turbulent kinetic energy distribution of the diffuser inlet and outlet and three-dimensional vortex distribution are extracted for comparison, and the analysis shows that the vortex structure of the SMRCP is slow to dissipate due to the influence of the non-uniform inflow, and the turbulence kinetic energy dissipation is serious, which influences the performance of the pump. This study provides new directions for optimizing the performance of the SMRCP under non-uniform inflow. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study on the effects of the Reynolds number (Resj = 300, 600, and 900) and porosity (ϕ = 20%–85%) on synthetic jet vortex rings impinging onto a porous wall. Laser-induced fluorescence and particle image velocimetry are used to acquire flow information qualitatively and quantitatively. When Resj is low (Resj = 300), ϕ plays a key role in determining the formation of transmitted vortex rings downstream. For the first time, a row of individual small-scale vortex rings that form at the lowest porosity (ϕ = 20%) have been observed in the synthetic jet/porous wall interaction. As Resj increases to 900, the triggered Kelvin–Helmholtz instability promotes the vorticity cancellation at a low porosity (ϕ = 30%), and thus contributes to the formation of a transmitted vortex ring. It is concluded that the vorticity cancellation is the dominant factor affecting the generation of a transmitted vortex ring. Time-averaged characteristics indicate that for a low Resj, the incoherence of the vortex ring is mainly due to the viscous effects. However, for a high Resj, it is the transition that leads to a significant enhancement in the turbulent kinetic energy. Measurements of flow macroscopic parameters show that the loss of the momentum flux exhibits a linear relationship with ϕ for all Resj, while the loss of the kinetic energy transport is nonlinearly dependent on ϕ. Incorporating ϕ, this study presents a more comprehensive similarity parameter, ϕln(Resj2 d h * 3 ), to characterize the synthetic jet/porous wall interaction. [ABSTRACT FROM AUTHOR]

This paper studies the turbulent kinetic energy ( k ⊥ ) in 2D isothermal electrostatic interchange-dominated E × B drift turbulence in the scrape-off layer and its relation to particle transport. An evolution equation for the former is analytically derived from the underlying turbulence equations. Evaluating this equation shows that the dominant source for the turbulent kinetic energy is due to interchange drive, while the parallel current loss to the sheath constitutes the main sink. Perpendicular transport of the turbulent kinetic energy seems to play a minor role in the balance equation. Reynolds stress energy transfer also seems to be negligible, presumably because no significant shear flow develops under the given assumptions of isothermal sheath-limited conditions in the open field line region. The interchange source of the turbulence is analytically related to the average turbulent E × B energy flux, while a regression analysis of TOKAM2D data suggests a model that is linear in the turbulent kinetic energy for the sheath loss. A similar regression analysis yields a diffusive model for the average radial particle flux, in which the anomalous diffusion coefficient scales with the square root of the turbulent kinetic energy. Combining these three components, a closed set of equations for the mean-field particle transport is obtained, in which the source of the turbulence depends on mean flow gradients and k ⊥ through the particle flux, while the turbulence is saturated by parallel losses to the sheath. Implementation of this new model in a 1D mean-field code shows good agreement with the original TOKAM2D data over a range of model parameters. [ABSTRACT FROM AUTHOR]

• The dynamic mechanical properties and fracture energy of the NSCB samples is presented. • All fracture modes of concrete exhibit the mode Ⅰ failure in NSCB tests. • The dynamic fracture energy shows a significant dependence on loading rate, increasing with the loading rate. • The repaired specimens consume more energy than the notched specimens and have a lower kinetic energy of flying fragments. Concrete constructions commonly contain cracks or defects during forming and service, repair operations are necessary in many situations. However, limited investigations conducted on the dynamic fracture toughness (DFT) of repaired concrete structures. This paper investigates the cracking behavior of concrete structures through notched dynamic semi-circular bend (NSCB) tests performed using a split Hopkinson pressure bar (SHPB) apparatus with two measurement techniques, namely digital image correlation (DIC) and crack propagation gauge (CPG), to capture the flying half angular velocity and crack propagation speed of NSCB concrete specimens under various loads. The results demonstrate a linear increase in both DFT and crack propagation speed of concrete with the loading rate. Additionally, a threshold value exists beyond which the crack speed stabilizes, and the DFT is not evidently influenced by the notch depths. The cracks propagate along the aggregates and remain mostly intact under a relatively low loading rate. With an increased loading rate, the damage pattern of some otherwise deflected aggregates changes resulting in crack penetration and significantly reducing the fracture surface roughness. Repaired specimens exhibit greater energy dissipation at the same loading rate, thereby producing flying fragments with lower kinetic energy, which can prevent secondary damage to internal personnel and structures. [ABSTRACT FROM AUTHOR]

This paper combines two strains in the literature on subgrid-scale parameterizations for eddying ocean models to develop six new parameterizations and test them in an idealized quasigeostrophic model. The first strain develops nonlinear, Smagorinsky-like Leith scalings for the viscous coefficient based on reasoning about the turbulent forward enstrophy cascade of geophysical turbulence. The second introduces backscatter whose amplitude is scaled to re-inject a portion of the energy dissipated by other parameterizations. In the new parameterizations developed here the backscatter and viscous coefficients depend on each other and are set to simultaneously absorb the forward enstrophy (or potential enstrophy) cascade and backscatter a portion of the dissipated energy. The addition of backscatter to Leith-scaled nonlinear viscosity improves the simulations at resolutions from 4 km to 24 km by increasing the total kinetic energy and by reducing the fraction of the total energy dissipation rate associated with the net effect of viscosity and backscatter. Versions that use biharmonic viscosity to absorb the enstrophy cascade perform better than versions using a harmonic viscosity, and purely viscous closures perform better than closures that dissipate both kinetic and potential energy. Stochastic and deterministic backscatter schemes are developed, and though similar, the deterministic schemes perform slightly better. • Developed backscattering Leith parameterizations. • Compared old and new parameterizations across resolutions. • Backscattering 2D Leith parameterizations perform well. [ABSTRACT FROM AUTHOR]

• Flow-induced vibration of bluff body has positive effect on laminar mixing. • Laminar mixer can achieve excellent performance when blocking ratio is 1/4. • High reduced velocity leads to low MI which is not conducive to solution mixing. • MI reaches 0.55 at X / D = 20 when U *=4 and β =1/4, and energy loss of fluid is small. Solution mixing in microfluidic devices is very common in chemical, biological, medical and other fields, and it is challenging to achieve rapid mixing in laminar flow. In this paper, flow-induced vibration is introduced to promote laminar mixing and the influence of two-degree-of-freedom vibration of bluff body on the mixing performance of solutions are studied numerically. The vibration response of body, mixing concentration, vorticity, and mixing index under different blocking ratios are analyzed, and the motion trajectory under the optimal blocking ratio is presented. It is found that the blocking ratio directly affects the vibration of cylinder, and then has a significant impact on the mixing performance. When the blocking ratio β =1/4, although the mixing index is not the maximum of all the blocking ratios considered, the kinetic energy loss of the fluid is lower than that at larger blocking ratio, resulting in excellent comprehensive mixing performance. When the reduced velocity U *=4 for β =1/4, the best mixing performance is achieved with a mixing index of 0.55, and the pressure drop of the fluid during the mixing process is very small. Besides, the motion trajectory of the cylinder presents a typical shape of "8″. The strong vibration in the y direction and the shedding vortex at the downstream position of the cylinder can effectively promote fluid mixing. [ABSTRACT FROM AUTHOR]

Vortex-induced vibration (VIV) is a prevalent phenomenon observed in marine submersible buoys subjected to ocean currents, significantly compromising the structural fatigue life and sensor stability. Meanwhile, the provision of in-situ energy supply and long-term sustainability pose significant challenges for marine submersible buoys. To tackle these issues, this paper presents a novel approach that entails the simultaneous utilization of VIV energy and suppression of VIV through the implementation of a rolling-structured, freestanding triboelectric-layer-based nano-generator (RF-TENG). An experimental investigation has been conducted to explore the power generation mechanism of RF-TENG when subjected to VIV excitation, as well as the vibration suppression effect of RF-TENG on VIV. The following conclusions have been drawn: (1) The maximum power generation is observed within the filling rate range of 50%–60%, where the conversion of kinetic energy to electrical energy resulting from particle friction prevails. Correspondingly, the maximum vibration suppression rate is achieved within the filling rate range of 60%–90%, primarily attributed to energy dissipation due to particle collisions. Notably, at approximately 60%–70% filling rate, RF-TENG exhibits a relatively efficient and balanced performance in terms of both energy utilization and vibration suppression. (2) Particle motion irregularity is a prominent factor that greatly influences the power conversion efficiency, which is manifested as the presence of the third harmonic component in the output voltage and current. The power conversion efficiency of RF-TENG attains its peak value at a filling rate of 50%. (3) Within a certain range, an increase in particle diameter contributes to enhancing the robustness and VIV suppression efficiency of RF-TENG. However, it comes at the cost of reduced power generation capacity. In this study, under the excitation of VIV experienced by a cylinder with an effective amplitude of approximately 1.56 cm and a frequency of approximately 1.62 Hz, RF-TENG achieves a power generation density of 80 mW/m3 and a VIV amplitude suppression rate of 24%. These results suggest that RF-TENG is an effective method for synchronously collecting energy and suppressing VIV in marine structures. • The RF-TENG demonstrated a power density of 80 mW/m3 and reduced VIV amplitude by 24%. • The energy conversion mechanisms of the RF-TENG for power generation and VIV suppression are distinct. • Larger particle diameter improved system robustness and vibration suppression but decreased optimal power generation. • Irregular particle motion significantly reduces power conversion efficiency through third harmonic excitation. [ABSTRACT FROM AUTHOR]

Unsignalized mid-block crosswalks are adopted to regulate unauthorized crossings by promoting drivers' yielding to pedestrians. Although pedestrian–vehicle interactions at crosswalks have been widely studied, the effects of such facilities regarding traffic flow and emissions have been overlooked. This paper presents a vehicle–pedestrian cellular automata model to analyze the effects of two types of crosswalk systems: raised and zebra, on traffic characteristics. The model allows microscopically studying the impact of the induced speed heterogeneity in terms of traffic flow, CO 2 emissions, and kinetic energy dissipation. Simulation results show that traffic flow experiences four phases in both systems: maximum current, congestion, jamming, and blocking; with second-order transitions among them. The maximum current phase is the only one with free-flow conditions shrinking faster in the system with a raised crosswalk than in the one with zebra. Both systems reach the blocking phase when the pedestrian entrance rate surpasses a critical value. However, raised crosswalk has lesser repercussions in CO 2 emission and energy dissipation by eliciting traffic calm. This study enhances the comprehension of the impacts of mid-block crosswalks, depending on the manner in which they are deployed. • Pedestrian–vehicle interactions at unsignalized mid-block zebra and raised crosswalks. • Characterization of the alterations promoted by raised and zebra crosswalks in terms of traffic flow, CO 2 emissions, and kinetic energy dissipation. • Cellular automata model for analyzing pedestrian–vehicle interactions at mid-block crosswalks. [ABSTRACT FROM AUTHOR]

The paper presents the results of the numerical calculation of the flow around hybrid unmanned aircraft with X-tail stabilizers. This aircraft design is an innovative combination of a gyroplane and a multirotor. The aerodynamic properties of the two-part X-tail stabilizer were analysed. The aerodynamic forces and moments on this element of the aircraft were specified from the CFD simulation calculations for the defined values of the angle of attack and the slip angle, and particular attention was paid to the differences between the upper and lower parts of the stabilizer. In addition, the turbulence kinetic energy on the surface of the vortex core region were analysed to conduct a qualitative and quantitative analysis of energy losses in flow, resulting from local separation and vortices. The obtained results allow for conducting further aerodynamic comparative analyses on other types of stabilizers. [ABSTRACT FROM AUTHOR]

Purpose It is significant to know the real-time indexes about the turbulence flow of the ocean system, which has a deep influence on ocean productivity, distribution of the ocean populations and transmission of the ocean energy, especially the measurement of turbulence flow velocity. So, it is particularly urgent to provide a high-sensitivity, low-cost and reliable fluid flow sensor for industry and consumer product application. This paper aims to design a micro fluid flow sensor with a cross beam membrane structure. The designed sensor can detect the fluid flow velocity and has a low kinetic energy dissipation rate.Design/methodology/approach In this paper, a micro fluid flow sensor with a cross beam membrane structure is designed to measure the ocean turbulence flow velocity. The design, simulation, fabrication and measurement of the designed sensor are discussed. By testing the simply packaged sensor in the fluid flow and analyzing the experiments data, the results show that the designed sensor has favorable performance.Findings The paper describes the tests of the designed sensor, and the experimental results show that the designed sensor can measure the fluid flow velocity and has a sensitivity of 11.12 mV/V/(m/s)2 and a low kinetic energy dissipation rate in the range of 10-6-10-4 W/kg.Originality/value This paper provides a micro-electro-mechanical systems fluid flow sensor used to measure ocean turbulence flow velocity. [ABSTRACT FROM AUTHOR]

This paper presents an analytical investigation on the free vibration, static buckling and dynamic instability of channel-section beams when subjected to periodic loading. The analysis is carried out by using Bolotin's method. By assuming the instability modes, the kinetic energy and strain energy of the beam and the loss of the potential of the applied load are evaluated, from which the mass, stiffness and geometric stiffness matrices of the system are derived. These matrices are then used to carry out the analyses of free vibration, static buckling and dynamic instability of the beams. Theoretical formulae are derived for the free vibration frequency, critical buckling moment, and excitation frequency of the beam. The effects of the lateral restraint applied to the flange, the section size of the beam and the static part of the applied load on the variation of dynamic instability zones are also discussed. [ABSTRACT FROM AUTHOR]

The Galilean invariant thermodynamically compatible conservation laws that admit a class of generalized solutions is analyzed. The main feature of the generalized solutions considered in this paper is that they describe smooth solutions with the kinetic energy and total pressure loss, which accompany the dynamic process of heat supply. The principal properties of the generalized solutions analyzed in Godunov's works are the Galilean invariance and thermodynamic compatibilty of the original conservation laws under the closed mathematical formulation of the thermal gas-dynamic process. [ABSTRACT FROM AUTHOR]

• The liquid bridge force causes a completely different kinetic response. • The equilibrium position is affected by both particle properties and liquid bridge. • As the excitation velocity increases, the periods show a linear relation. • The wave propagation process can be divided into two stages. • A U-shaped trend appears throughout the dissipation process. Wet granular materials exhibit unique physical and mechanical properties, especially in relation to wave propagation, which is quite different from dry granular materials. In this paper, by introducing the capillary bridge force into the discrete element method, the stress wave in mono-sized bead string with various water content has been studied. First the vibration of two particles with liquid bridge has been analyzed. The presence of the liquid bridge force causes the kinetic response of the particles to exhibit completely different properties than that of the dry particles. The equilibrium position is affected by both the physical properties of the particles and the liquid bridge properties. Then the wave propagation behaviors in a mono-sized bead string have been analyzed. According to whether the liquid bridge volume has an effect on granular motion, the whole process can be divided into two stages. Stage I, particles are physically contacted with each other directly. The influence of liquid bridge force is independent of the bridge volume. Stage II, particles start to oscillate back and forth at their equilibrium positions, the influence of the liquid bridge force becomes related to the bridge volume. The kinetic energy dissipation first decreases and then increases. A U-shaped trend appears throughout the dissipation process. In our work, the mechanical properties of wet granular materials are studied from two levels: particle vibration and wave propagation, which will provide theoretical guidance for the application of granular materials in aqueous environment. [ABSTRACT FROM AUTHOR]

Urban landslides always occur where development has taken place on pre-existing unstable land. Due to rapid urbanization, human activities expand onto sloping terrain and disturb the geological environment, increasing the urban landslide risk. When a rapid flow-like landslide occurs, the landslide mobility can be affected by the presence of buildings located along its flow path. In this paper, the effect of building blockage on landslide mobility and the associated energy dissipation mechanisms are evaluated based on a well-documented landslide, which happened on 20 December 2015 in Shenzhen, China. The landslide flow process is reproduced by three-dimensional terrain analyses using LS-DYNA, considering three scenarios; namely, green field, movable buildings, and fixed buildings. Simulations show that the presence of densely located buildings significantly affects flow pattern, travel distance, deposition, and energy transfer mechanism. A fully developed debris fan in the flat area is observed in the green field case. The buildings in the runout path decelerate the flow process, leading to lower landslide mobility and less volume deposited in the accumulation zone. The shortest runout distance and widest and thickest deposits are observed in the fixed buildings case. The debris fan in the movable buildings case is closer to reality. Fixed buildings pose more constraint on surface moving material, leading to the largest deformation, largest internal energy, and smallest kinetic energy of the soil mass. The dissipation of the largest frictional energy occurs in the movable buildings case due to the long sliding distance of the damaged buildings. The internal energy of the landslide mass dominates the energy transfer mechanism. The results presented here indicate the need to consider building clusters when conducting urban landslide hazard mapping and risk assessment. [ABSTRACT FROM AUTHOR]

Dipolarization fronts (DFs) are important for energy conversion, particle acceleration, and flux transport in the magnetotail. The partition of energy conversion between ions and electrons and the energy dissipation at DFs are not well understood. In this paper, we present a statistical study of energy conversion and dissipation of 122 DFs observed by Magnetospheric Multiscale mission in the magnetotail. Statistically, electromagnetic energy transfers to plasma at DF. The released energy is mainly transferred to ions rather than electrons. On average, ions gain energy across the whole DF, while electrons gain energy at the leading part but lose energy at the trailing part of DFs. Joule dissipation J · (E+ve × B) can be either positive or negative at DFs, and its average value is very small. The kinetic energy dissipation parameter Pi − D does not exhibit clear signatures at the DFs; hence, it is not suitable for quantifying the energy dissipation at DF. Key Points: Statistical study of the energy conversion and dissipation at DFs observed by MMSElectromagnetic energy released at DF mainly goes to heat and accelerate ionsAverage Joule dissipation across DF is very small, and the parameter Pi − D is not suitable for quantifying the energy dissipation at DF [ABSTRACT FROM AUTHOR]

In this paper, the possibility of utilizing a wind turbine to recapture a portion of the kinetic energy losses of a car, irrespective of being a traditional car that is propelled by an internal combustion engine or an electric vehicle (EV) that is propelled by an electric motor, is appraised. To investigate the topic, a small wind turbine has been inserted at the back of the condenser of a car to recover a portion of the kinetic energy of wind passing through the condenser's crisscrossed bars. A portion of this wind is caused by wind existing outside the car, and the main portion is caused by the kinetic energy originating from the car movement. In the absence of the wind turbine, the wind passing through the condenser's crisscrossed bars hits the middle part of the car's chassis and loses its energy. Thus, not only the wind turbine uses a portion of the kinetic energy losses of the car to produce electricity but also, since it has been embedded at the back of the condenser, it has no impact on the aerodynamic coefficient of the car, i.e., it does not produce any extra resistive force. When the car is parked, and there is no kinetic energy resulting from the car movement, a small flow of wind available outside the car is converted into electricity stored in the car's battery. To realize the proposed scheme, a 100-W wind turbine, a permanent-magnet synchronous generator coupled to the turbine, and a novel built hybrid power generation system combining the wind-driven generator's output power with that of the car's battery have been embedded in an EV having a total weight of 1855 kg. Experimental measurements conducted under realistic operation of the EV are given that prove the traveling range of the EV and the power efficiency of the EV's power supply are enhanced by, 6.4 km and 0.2% respectively, by recovering only a portion of the kinetic energy losses of the EV. These two benefits also prove the novelty and contributions of this work in successfully recovering a portion of the kinetic energy losses of a car by using a small wind turbine embedded in the car. [ABSTRACT FROM AUTHOR]