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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 this paper, a heat generator with fluid agitation is developed and experimentally studied. This heat generator can convert kinetic energy from a wind turbine directly to thermal energy through the process of viscous dissipation—a process achieved through the agitation of the working fluid inside a container. In the experimental study, an electric motor (instead of a wind turbine) was used to provide the kinetic energy input to the heat generator. The torque, rotational speed, and temperature rise in the fluid were measured. Using the measured quantities, the efficiency of kinetic energy to sensible heat conversion was calculated. Experiments were conducted to investigate the effects of different impellers, rotational speeds, and working fluids, including distilled water, ethylene glycol (EG), and their respective nanofluids, with A l 2 O 3 nanoparticles at different concentrations. The study also found that the temperature rise in fluids due to viscous dissipation was influenced by the specific heat of the fluid, suggesting that the heat generator can be optimized for energy storage with high-specific-heat fluids, such as water, or for achieving a higher temperature rise with low-specific-heat fluids, such as ethylene glycol. The experimental results indicated that the heat generator was up to 90% efficient in converting kinetic energy to thermal energy. The study revealed that, for constant power input, the heat dissipation rate depends solely on the vessel's geometry, not the fluid properties. Optimizing the impeller design and baffles within the vessel is crucial for maximizing power input. For applications, a wind turbine can power this heat generator to provide heat to a house or a commercial building. [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]

The hydraulic engineering designers focus on shaping up the flow regime so that the greatest energy dissipation is ensured. On the other hand, the structural designers focus on load bearing capacity and durability of the structural components which may contradict the focus of the hydraulic experts. Such a case may occur when the spillway chute floor slab must be thin due to the limited spaces. Then, the dynamic load acting on the chute floor slab may compromise its long-term operation. The dynamic forces are created by the violent turbulences which may even coincide with the natural frequency of the reinforced concrete floor slab. Therefore, the objective of this paper is a complex approach to small-scale physical model testing which makes use of the latest rapid-prototyping techniques and the optical flow, and which in the end allows to estimate the magnitude of the dynamic hydraulic forces acting on the channel bed. The newly developed organic-shape energy dissipators play a key role in reducing the kinetic energy of water through its enhances aeration. The proposed method on a small scale can assist favorably the design process of real-scale hydraulic reinforced concrete structures. [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 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]

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]

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]

Triply Periodic Minimal Surface (TPMS)-based cellular structures are widely adopted due to their high surface-to-volume area, superior mechanical characteristics, and adaptive properties. This paper is dedicated to deriving a new semi-empirical equation for pressure drop in TPMS-based structures (specifically Schwarz-P, Schoen I-WP, Neovius). Both numerical and experimental tests were conducted to analyze the impact of TPMS parameters on pressure drop and velocity distribution. It was determined that flow through the Schwarz-P structure exhibits a tubular flow pattern, flow through the Neovius structure demonstrates active flow mixing, and flow through the Schoen I-WP structure does not have stagnant (dead) zones. A novel semi-empirical equation was formulated to calculate pressure drop as a function of flow parameters and TPMS-based structure parameters. This equation incorporates both viscous resistance (Δ p = f (v)) and kinetic energy loss (Δ p = f (v 2)) , enabling its application for predicting pressure drop across a wide range of practically interesting operational parameters. • Fluid flow through TMPS-based structures is numerically and experimentally investigated. • Schwarz-P, Schoen I-WP, and Neovius TPMS-based structures are tested. • Tubular flow pattern for Schwarz-P; active flow mixing for Neovius; no stagnant (dead) zones for Schoen I-WP. • A novel equation was formulated for the calculation of pressure drop through TMPS-based structure. [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]

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]

• 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]

The impact and aggregation of multiple alumina droplets on the inner wall of the solid rocket motor may generate a larger rebound aggregated droplet or adhere to the wall to form a liquid film. The rebound and adhesion characteristics of the aggregated droplet are of great significance for slag deposition and two-phase flow prediction in the motor. In this paper, the VOF (Volume of fluid) method is used to study the impact and aggregation process of multiple alumina droplets on the wall. Detailed numerical verifications are carried out, including the impact and aggregation of moving droplets, the aggregation and rebound of stationary droplets and the impact process of a single alumina droplet on the wall. It is found that the aggregated droplet will rotate when two droplets aggregate under small droplet diameter ratio, which is caused by the asymmetry aggregation process. The oscillation process intensifies when three droplets impact and aggregate on the wall, as a result, the aggregated droplet is easier to adhere to the wall. The viscous dissipation in the aggregation of droplets is huge, and the total viscous dissipation energy accounts for about 50% of the total energy when the aggregated droplets rebound. The influence of droplet diameter on the V ⁎ (rebound recovery coefficient) of the aggregated droplet and the rebound/adhesion results are dominated by the viscosity effect. While the influence of the parameters involving the initial spatial arrangement of droplets is dominated by the oscillation process, which will reduce the effective rebound kinetic energy, making a lower V ⁎ and the aggregated droplet easier to adhere. [ABSTRACT FROM AUTHOR]

This paper presents a novel method of labyrinth seals design. This method is based on CFD calculations and consists in the analysis of the phenomenon of gas kinetic energy carry-over in the seal chambers between clearances. The design method is presented in two variants. The first variant is designed for seals for which it is impossible to change their external dimensions (length and height). The second variant enables designing the seal geometry without changing the seal length and with a slight change of the seal height. Apart from the optimal distribution of teeth, this variant provides for adjusting chambers geometry to flow conditions. As the result of using both variants such design of the seal geometry with respect to leakage is obtained which enables achieving kinetic energy dissipation as uniform as possible in each chamber of the seal. The method was developed based on numerical calculations and the analysis of the flow phenomena. Calculation examples included in this paper show that the obtained reduction of leakage for the first variant ranges from 3.4% to 15.5%, when compared with the initial geometry. The relation between the number of seal teeth and the leakage rate is also analyzed here. The second variant allows for reduction of leakage rate by 15.4%, when compared with the geometry with the same number of teeth. It is shown that the newly designed geometry reveals almost stable relative reduction of leakage rate irrespective of the pressure ratio upstream and downstream the seal. The efficiency of the used method is proved for various heights of the seal clearance. [ABSTRACT FROM AUTHOR]

• The collision between a spar-type floating offshore wind turbine (FOWT) and ship is numerically investigated by the nonlinear finite element (FEM) method. • Model verification of finite element model is performed for both FOWT and ship. • The collision forces, displacements and accelerations of FOWT with different impact velocities are obtained. • The incurred structural damage of FOWT and ship with different impact velocities is evaluated. • The energy conversion ratio between FOWT and ship subjected to collision is obtained. This paper investigated the dynamic responses and the incurred structural damage of a 5 MW spar-type floating offshore wind turbine (FOWT) and a ship when they collide. Ansys/LS-DYNA was used to establish the finite element models (FEMs) of the FOWT and the ship and to subsequently conduct the collision analysis. The global dynamics of the FOWT are captured well by the FEM comparing with FAST code and a simplified 8-degree of freedom (8-DOF) model established in MATLAB. The validity of the ship FEM was guaranteed by the fact that the model outputs agree well with empirical formulas. A series of simulations were then carried out using the FEMs to analyze the impact forces, displacements, accelerations, damages and energy dissipation during the ship collision for various impact velocities. The results show that the peak collision force, peak spar platform displacement and peak tower top displacement increase almost linearly with the initial velocity of the ship. The maximum tower top acceleration during the collision consistently exceeds 0.2 g, severely affecting the normal operation of the FOWT. The collision causes dents on the spar platform rather than the collapse of the whole wind turbine. After the collision, the initial kinetic energy of the ship is mainly transformed into the plastic deformation energy of the FOWT and the energy dissipated in the water. In addition, assuming a rigid ship bow results in accurate FOWT dynamic responses but fails to provide a good evaluation of the spar platform deformation. [ABSTRACT FROM AUTHOR]

In this paper, experimental and numerical methods are presented to describe the hydrodynamic process of the vibration-induced detachment of a droplet from a superhydrophobic surface. We conduct the investigation of the droplet dynamics under various vibration and impact parameters, from an energy conversion perspective. In particular, the energy dissipation that occurs following the droplet impact is analyzed quantitatively. We identify three viewpoints on vibration-induced droplets. Firstly, the phase angle is the dominant factor in characterizing the droplet morphology evolution and energy dissipation on a vibrating surface. The law governing the initial phase angle is affected by the vibration frequency, while the intensity is affected by the vibration amplitude. Secondly, the energy dissipation is positively correlated with the maximum spreading diameter and impact velocity. A larger initial diameter tends to produce a longer contact time. Finally, the central jet formation depends heavily on the upward velocity of the concave liquid, under the peculiar morphology of a vibration-induced droplet. For all these effects, up to 60% of the total energy is squandered during impact, while the surface energy remains almost constant. Much of the droplet's kinetic energy is lost in resisting the viscous force of the substrate. • The droplet dynamics under various vibration and impact parameters are examined. • The phase angle is dominant in characterizing morphology and energy dissipation. • The central jet phenomenon depends on the upward velocity of the concave liquid. • Much of the kinetic energy is lost in resisting the viscous force of the substrate. [ABSTRACT FROM AUTHOR]

A large-scale landslide in a deep valley often travels a long distance. The moving landslide debris impacts into the valley and interacts with the river and the opposite side of the valley. In the landslide movement process, energy, mass and momentum transfers inevitably take place. An in-depth study of energy and mass transfer mechanisms in various types of flow-like landslides will provide a scientific basis for developing energy criteria for evaluating landslide hazard chains and mitigation measures. In this study, a coupled DEM-ALE method is used to systematically evaluate the energy transfer mechanisms in landslides of various solid concentrations. The landslide dynamics involving river damming can be divided into three stages: the travel stage, the interaction stage, and the deposition stage. Kinetic energy is dominant in the travel stage but the frictional energy dissipation increases rapidly in the interaction stage. In the deposition stage, the kinetic energy changes to other energy components. The energy transfer mechanisms differ in different types of landslides. The kinetic energy of the fluid phase is mainly dissipated by viscosity shearing and turbulence, which is less efficient than internal and boundary frictional dissipations in the solid phase. The fraction of friction-dissipated energy increases with the solid concentration of the landslide mixture. Most of the remaining energy is dissipated by turbulence. Kinetic energy is the main energy transfer component during the landslide-river interaction. Flows of lower solid concentrations, e.g., debris flows, impact larger areas but are less likely to block a river. • This paper reveals energy-transfer mechanisms in flow-like landslides using a coupled DEM-ALE method. • The fraction of landslide kinetic energy reaches its peak at the early travel stage. • The fraction of frictional dissipated energy increases with the solid concentration. • Kinetic energy is the main energy transfer component during landslide-river interactions. • Energy dissipates rapidly via friction when the landslide impacts into the opposite bank. [ABSTRACT FROM AUTHOR]

• We propose the novel planar and cylindrical metamaterials for energy dissipation and shock isolation. • Mechanical responses of unit cells are affected by geometric parameters and boundary conditions. • Increasing the number of layers and tailored geometric parameters are beneficial for energy dissipation and shock isolation. • Shock isolation performance improves due to the snap-through behaviors. Dissipating kinetic energy from shock and vibration is an urgent requirement for various applications in aerospace to mechanical engineering. This paper proposes a series of innovative metamaterials with planar and cylindrical patterns for elastic energy dissipation and shock isolation. The planar unit cell with two axes of reflectional symmetry mainly consists of two V-shaped regions, four identical right triangle regions, and narrow regions. The stereometric and cylindrical unit cells are obtained through rotating and convolving methods. The mechanics of energy dissipation and shock isolation are systematically investigated with finite element analysis (FEA), and experiments. Results show that various mechanical responses of unit cells are obtained through tailoring combined geometric parameters and additional boundary conditions, and the planar unit cell has stronger bistability than the cylindrical one. Then, the designed multilayers metamaterials exhibit considerable energy dissipation via the snap-through induced hysteric force-displacement behaviors, whose performances are influenced by geometric parameters and the number of layers. Lastly, the designed metamaterials could effectively suppress the acceleration responses via the snap-through behaviors induced by elastic instability. The shock response process and corresponding deformation mechanics are investigated experimentally and numerically. The designed metamaterials have potential in shock and vibration engineering. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Particle-laden bubbles interacting with an air-liquid interface were investigated. • Bubble kinetic energy is dissipated via shape change and motion of attached particles. • A damped oscillation model was used to represent the bubble collision dynamics. • Particle influence on bubble collision dynamics quantified by damping coefficient. • A higher damping effect is experienced by bubbles with a higher particle coverage. The collision, bouncing and potential bursting of air bubbles with air-liquid interfaces are key processes involved in the initial stage of foam formation. While fundamental studies of these processes, especially for gas-liquid-solid froth systems, are very valuable for a better understanding of various chemical engineering separation systems, these are scarce. This paper investigates the dynamics of rising bubbles, without particles attached and with various particle coverages, as they collide with an air-liquid interface. For uncoated bubbles, an increase in distance from the bubble releasing point to the air-liquid interface resulted in higher bubble approach velocities, although with minor changes in the velocity fluctuation frequency. This increase in approach velocity was not observed for bubbles with relatively high particle coverage. For particle-laden bubbles, the collision with the interface is associated with movement of the particles over the surface of the decelerating bubble. This particle motion on the bubble surface, combined with bubble shape pulsation, contributes to the kinetic energy dissipation of the approaching bubble. A damped oscillation model was derived to represent the velocity of the bubble interacting with the interface, which shows that the amplitude of the velocity decreases gradually with the increase in particle coverage. The damping coefficient in the model, introduced to quantify the influence of attached particles, is shown to increase with particle coverage, confirming the key role that particles play in bubble collision dynamics at an air-liquid interface and allowing, for the first time, the prediction of their behavior. [ABSTRACT FROM AUTHOR]

[Display omitted] • Modeling of rubberized concrete-filled steel tubular columns under cyclic bending. • Dynamic explicit analyses with kinetic energy control of short columns using ABAQUS. • Influence of rubberized concrete (RuC) on columns' energy dissipation capacity (ΔE) • Lower brittleness of RuC is offset by its lower strength, reducing (ΔE) of columns. • RuC with increased strength is shown to potentially increase ΔE of columns. In this paper, the mechanical behaviour of short rubberized concrete-filled steel tubular (RuCFST) columns with square cross-section under combined cyclic bending and (monotonic) compression is studied numerically. For this purpose, dynamic explicit analyses with kinetic energy control (for the quasi-static behavior to be obtained) using the commercial finite element modelling package ABAQUS were performed. Firstly, a brief introduction and literature review on the topic is made. Then, the numerical models are described in detail with emphasis on the modelling of the materials (natural aggregate concrete (NAC), rubberized concrete (RuC) and steel) under cyclic loading. An in-depth presentation of the numerical results is made afterwards. It includes firstly a verification of the models by comparison of the numerical results with their experimental counterparts, the latter previously obtained by the authors. Secondly, a numerical study on the effectiveness of RuC on the energy dissipation capacity of CFST columns under lateral cyclic loading is performed. It is concluded that the models yield similar results regarding stiffness, maximum loads, load–displacement curves and failure modes as those obtained experimentally, with RuC leading to a moderate reduction (of up to 2%) of the strength of the columns. Regarding the energy dissipation capacity of the columns, it is concluded that RuC generally leads to a reduction of this property (of circa 2.5% per each 5% of rubber aggregates replacement). The lower strength and stiffness of the RuC mixes designed for this study compared to NAC are found to generally offset the benefit of their lower brittleness in increasing the energy dissipation capacity of the columns. [ABSTRACT FROM AUTHOR]

• A double row line vortex is formed behind the mandrel, the turbulent kinetic energy and dissipation rate of the windward side of the mandrel sheath are the largest. • The shed structure of composite insulator results in the uneven pressure distribution between the sheds. • The high-speed flow in the horizontal direction directly impacts the lower surface of the V-string composite insulator shed WIAD, which will form a vortex, and induce the pressure fluctuation of sheds. In order to investigate the internal causes of fatigue failure of composite insulators under extreme wind loads. In this paper, the numerical model of FXBW-500/300 composite insulator(CI) is constructed firstly. Based on RNG k-ε turbulence model, the flow field of single side of V-string, flow field between large and small sheds of suspension string composite insulation and near flow field of whole insulator were carried out. The results show that the change of circumferential pressure and turbulent kinetic energy at the junction of shed and mandrel of CI is the largest, and the stress concentration is easy to occur at the junction of shed and core rod. Meanwhile, the suspension CI is better than the V-string CI in the variation amplitude of wind pressure and turbulence of flow field near the shed. [ABSTRACT FROM AUTHOR]

The usage of a large number of civil unmanned aerial vehicles (UAVs) has caused potential hazards to the safe operation of manned aircraft. In this paper, a full-size commercial aircraft nose and a typical UAV with the whole level were selected for collision test, by which the verified finite element (FE) models were applied to four representative regions of the nose for collision simulation. A 1,360 g UAV and a 1,800 g bird have collided with the nose respectively under the same conditions and the former caused more serious damage. The kinetic energy of UAV as well as the hardness of its major components plays a critical role in evaluating damage of the nose, and the greater the kinetic energy loss, the more serious the damage of the nose is in general. It was very possible that the battery of UAV would penetrate the skin to enter the inside of nose with high speed and cause explosion and fire. The flying posture of UAV has an effect on the nose damage and no penetration happened to the lower panel of the main windshield under various possible impact postures of UAV with a velocity of 152 m/s. The existing anti-bird strike airworthiness clauses concerning the aircraft nose as CCAR 25.571 are not suitable for the design of nose against UAV strike and are suggested to be improved with extensive research findings in the future, including the operational requirements of UAVs and the design guidelines for a UAV collision mitigation. [ABSTRACT FROM AUTHOR]

• Multi-barrel system under transverse impact. • Analytical and numerical performance evaluation of the system. • Fluid addition provides support and additional energy absorbing mechanism. • Fluid transport and viscous dissipation provide additional energy absorption. • Decreased deformation and increased structural lifetime with fluid addition. Guardrail end terminals and roadside crash cushions are common technologies deployed to absorb and redirect the energy of a colliding vehicle. The purpose of these devices is to reduce damage to structures and vehicles while limiting the effects these collisions have on motorists. The primary mode of energy absorption of these structures is through physical deformation. This physical deformation can often create hazardous scenarios for vehicle occupants. This paper shows the study of a new (patent pending) crash attenuator composed of a multi-chambered, fluid-filled barrier. Kinetic energy of the colliding vehicle is transferred to the fluid and through the internal structure. As fluid moves through the structure, energy is dissipated through viscous friction; therefore, reducing the peak forces experienced by the vehicle and its occupants and reducing damage to the structure and the vehicle. Experiments were conducted using a mechanical ram to impact a dual-chambered cylindrical plastic container partially filled with water. The impact event was recorded using a high-speed camera and the acceleration impulse was measured using an accelerometer attached to the ram. The results of this study show that the addition of interior chambers and fluid decreased the reaction forces by nearly 50% and a two-fold increase in energy absorbing efficiency as compared to an empty structure. Analytical and numerical approaches were used to assess the energy dissipation due to plastic deformation of the structure. The addition of fluid and internal chamber reduced the plastic deformation of the sample by 9.1% as compared to the empty structure. This confirms the ability of the present structure to maintain low reaction forces while reducing damage to the structure and in turn increasing barrier lifetime. The present barrier technology can potentially replace existing guardrail end terminal and crash cushion systems and due to its small footprint, can be utilized in areas where traditional systems cannot be deployed due to space constraints. [ABSTRACT FROM AUTHOR]

We present a new approach based on the notion of inertance for the simultaneous collisions without friction of a rigid solid. The calculations are performed using the screw (plückerian) coordinates, while the results are obtained in matrix form, and they may be easily implemented for different practical situations. One calculates the velocities after collision, the energy of lost velocities, and the loss of the kinetic energy. The general algorithm of calculation is described in the paper. The main assumption is that the normal velocities at the contact points vanish simultaneously. The coefficients of restitution at the contact points may be equal or not. Some completely solved applications are also presented, and the numerical results are discussed. The numerical values depend on which coefficient of restitution is used. [ABSTRACT FROM AUTHOR]