High Levels Of Kinetic Energy Research Articles

Towards a safe system in low- and middle-income countries: vehicles that guide drivers on self-explaining roads

Road crashes cause a huge problem of public health in low- and middle-income countries (LMICs). The Safe System approach is generally considered as the leading concept on the way to road safety. Based on the fundamental premise that humans make mistakes, the overall traffic system should be ‘forgiving’. Sustainable safe road design is one of the key elements of the Safe System approach. Road design and speed control should help prevent crashes with a high level of kinetic energy. However, the road design principles behind the Safe System approach are certainly not leading in today’s infrastructure developments in most LMICs. Cities are getting larger with increasing motorization and expanding road networks. Existing through-roads in local communities are upgraded, resulting in heavy traffic loads and high speeds on places, that are absolutely not suited for this kind of traffic. Furthermore, a Safe System would require that functional design properties of vehicles and roads would be conceptually integrated, which is not the case at all. Although advanced driver assistance systems are on their way of development for quite a long period, their potential role in the Safe System concept is mostly unclear and at least strongly underexposed. The vision on future cars is dominated by the faraway concept of automation. This paper argues that the way to self-driving cars should take a route via the concept of guidance, i.e. vehicles that guide drivers, both on self-explaining roads and on more or less unsafe roads. Such an in-vehicle guidance system may help drivers to choose safe transport mode, a safe route and a safe speed, based on criteria related to safety and sustainability. It is suggested to develop driver assistance systems using relatively simple and cheap technologies, particularly for the purpose of use in LMICs. Such a guide may make roads self-explaining—not only by their physical design characteristics—but also by providing in-car guidance for drivers. In the future, the functional characteristics of both cars and roads may be conceptualized into one integrated Safe System, in which the user plays the central role. Such a guidance system may serve as the conceptual bridge between the roadway, the vehicle and the driver, and thus be considered as an indispensable component of the Safe System approach. It is argued that such a development is necessary to bring a breakthrough in road safety developments in LMICs and also give an acceleration towards zero fatalities in high-income countries.

An advanced aero-thermodynamic study of a heart-shaped dimpled pipe

The detailed flow field and local heat transfer enhancement in a pipe with heart-shaped dimples on the internal surface were experimentally studied. The flow structures were investigated at a flow regime of Re=20k in five different measurement planes around a dimple in the streamwise and spanwise directions using both planar PIV and stereo PIV. A ray tracing-based image correction method was utilized to overcome the important image distortions caused by the optically complex geometry of the dimple for the planar PIV measurements. Furthermore, the convective heat transfer coefficient on the wall of the dimple was investigated utilizing steady-state liquid crystal thermography (LCT) and infrared thermography within the flow regime range of Re=20k-60k. A comprehensive uncertainty analysis was conducted to account for the multiple measured quantities and corresponding error sources on such a complex geometry. The resulting heat transfer and flow fields revealed that maximum heat transfer enhancement is concentrated along the reattachment line downstream of the dimple where higher kinetic energy levels are observed. The enhancement factor, which is a measure of the heat transfer improvement relative to a smooth pipe, was evaluated on average at 1.7 across the dimpled surface, with local maxima reaching values up to 2.8. The dimpled pipe under examination had a relative skin friction coefficient of approximately 1.8 compared to a smooth pipe. This outperforms some of the roughness elements, such as ribs and spherical dimples, previously studied on similar circular channels in literature.

Method to Establish Sound and Acceleration Levels of High Pressure Reducing Valves

Abstract Severe service control valves or better, high-pressure reducing valves can see inlet pressures in excess of 4000 psi. Such valves are found in industries ranging from gas or petroleum wells, to chemical plants and steam-producing power plants (Goodwin, “Specifying Control Valves for Severe Service Conditions”, INTECH FOCUS, November (2022), p. 20). Such valves convert high levels of kinetic energy through a process of conversion of sound-producing turbulence to a reduced pressure level. Less desired by-products such as conversion are sound pressure levels that can exceed 120 decibels, a sound that is comparable to standing next to a jet plane taking off. Part of this energy conversion manifests itself as mechanical vibration which can cause undesirable high pipe acceleration which, over time, could severely damage piping (Almasi. “Flow Induced Vibrations in Piping Systems”. P.I. PROCESS INSTRUMENTATION, July, 2020; Blake, 1986, “Mechanics of Flow Induced Sound and Vibrato,” Vol. II, Complex Flow-Structure Interactions, Academic Press, Orlando, FL). Proposed here is an easy computer programmable method to check the sound and acceleration levels associated with noisy valves. It is believed such a paper harmonizing all aspects of aerodynamic valve noise, such as sound pressure, sound power, vibration, and acceleration can be of value. The purpose of this paper is to explain how such acceleration levels are estimated. There are four steps involved: (1) calculate the sound pressure level (SPL) from given process data, (2) convert sound pressure level into sound power level (Lwi), and (3) find the associated maximum pipe internal peak frequency (fp). (4) Based on the sound power level and the peak frequency of the sound, calculate the acceleration of the pipe (in m/second2).

Using Experimentally Validated Navier-Stokes CFD to Minimize Tidal Stream Turbine Power Losses Due to Wake/Turbine Interactions

Tidal stream turbines fixed on the seabed can harness the power of tides at locations where the bathymetry and/or coastal geography result in high kinetic energy levels of the flood and/or neap currents. In large turbine arrays, however, avoiding interactions between upstream turbine wakes and downstream turbine rotors may be hard or impossible, and, therefore, tidal array layouts have to be designed to minimize the power losses caused by these interactions. For the first time, using Navier-Stokes computational fluid dynamics simulations which model the turbines with generalized actuator disks, two sets of flume tank experiments of an isolated turbine and arrays of up to four turbines are analyzed in a thorough and comprehensive fashion to investigate these interactions and the power losses they induce. Very good agreement of simulations and experiments is found in most cases. The key novel finding of this study is the evidence that the flow acceleration between the wakes of two adjacent turbines can be exploited not only to increase the kinetic energy available to a turbine working further downstream in the accelerated flow corridor, but also to reduce the power losses of said turbine due to its rotor interaction with the wake produced by a fourth turbine further upstream. By making use of periodic array simulations, it is also found that there exists an optimal lateral spacing of the two adjacent turbines, which maximizes the power of the downstream turbine with respect to when the two adjacent turbines are absent or further apart. This is accomplished by trading off the amount of flow acceleration between the wakes of the lateral turbines, and the losses due to shear and mixing of the front turbine wake and the wakes of the two lateral turbines.

Simulation modelling of cold rolled metal strip by asymmetric technology

In the article provided the results of studies the optimization of energy-saving technologies in mechanical engineering using modern methods of simulation modeling is becoming an urgent area for the informatization of engineering production on the process of cold asymmetric rolling of metal sheets is accompanied by an inhomogeneous stress-strain state.The research considers the noncanonical areas of strain, an approach is proposed for determining the optimal technological parameters and studying the stress state of the cold rolling process using asymmetric rolling technology in the active zone of elastoplastic strains based on simulation using the application software LS-DYNA by LS-PrePost (R) version V4.6.1. To optimize energy-saving for rolling technologies, considered a stationary regime of symmetrical rolling, the kinetic energy does not change over time, and the potential energy in the active zone of elastic-plastic strains tends to increase. For the case of asymmetric rolling, a high level of kinetic energy is observed, and there is a fluctuation over time, explained by different coverage of asymmetric rollers in the zone of active elastic-plastic strains, as a result of which the stationary nature of the metal sheet rolling mode is violated.

Optimizing strain energy extraction from multi-beam piezoelectric devices for heavy haul freight cars

Heavy haul trains used to transport commodities are generally very long and operated by a single individual. Owing to high noise levels from the rolling stock displacement, the driver cannot notice failures in the compartments. It is practically impossible to visually inspect the wagons located far from the locomotive. Sensors that can measure in-train forces may improve the train’s operation, indicating potential failures and preventing accidents and derailments. However, the freight cars employed in most of the railroads are not equipped with electric power sources, making inspections unlikely. Therefore, an energy harvesting system must be developed for the sensors to avoid the need for periodic battery charging or replacement. As a high level of kinetic energy is present in the rolling stock, a vibration energy harvester (VEH) system is an acceptable alternative. Among VEH devices, multi-beam piezoelectric materials used in planar zigzag (PZ) or orthogonal spiral outer fixed (OSo) configurations can be effective alternatives. These can be powered by low-frequency strains readily available in the freight cars. This study investigates the optimum geometries of PZ and OSo aiming to increase the generated power and minimize the structure mass with a focus on their application to ore wagons. Among the optimum solutions, the OSo geometry generates the maximum power, up to 20.93 mW, which is sufficient to feed some critical devices. Conversely, the PZ configurations present the highest energy density, up to 16.595 mW/kg(m s−2)2, which allows for a more suitable solution to be combined in serial and/or parallel pack configurations.

Rock Metamorphosis by Kinetic Energy

The objective of this work was to test the hypothesis that weathering-resistant surface layers found in intensively hammered petroglyphs at many sites worldwide and on other heavily battered metamorphosed rocks are the result of kinetic energy-induced tribological reactions. The methods of material testing included extensive fieldwork and in-situ studies at an Indian site that had been subjected to fluvial battery in the distant geological past; the removal of numerous surface and subsurface samples; and their analysis by several laboratory methods. These included binocular light microscopy, scanning electron microscopy, thin sectioning and elemental composition determination of crucial sites. It was confirmed that samples show evidence of crystallization by ductility of formerly amorphous silica cement in quartzite, yielding a tectonite of fully crystalline quartz. This finding confirms that the surficial application of very high levels of kinetic energy to certain rock types that are susceptible to metamorphosis can yield exceptionally weathering-resistant surface layers. This phenomenon has not been described before. Although it was first observed in rock art it is now thought to occur much more widely in numerous geological contexts, such as at fault mirrors, in the form of what has been regarded as glacial polish and on ventifacts.

Effect of recovery process on the efficiency of nano-diamond synthesis by shock compression

Shock-induced phase transitions of C60 fullerene crystal structure into amorphous nano-diamond is investigated through molecular dynamics simulations. For this purpose, the Hugoniostat scheme is employed to provide the material behavior in a wide range of shock strength. The shock pressure corresponding to the Hugoniot elastic limit and phase transition (PT) are extracted from the Hugoniot curves at 27 and 63 GPa, respectively, which are in close correlations with former experimental results. Increasing the shock strength beyond the PT, an incompressibility is observed in the material which accelerates the trend of temperature rise in the shocked structure followed by material melting. After the shock compression to a pressure above the PT, a quenching process is also imposed on the post-shock material to bring it into the ambient conditions. To this end, a range of cooling rates from 1013 K/s to infinity are examined. It is shown that although the increase in the cooling rate does not have any significant effect on the percentage of carbon atoms in sp3 hybridization, the stability of final product is enhanced to some extent by utilizing lower cooling rates. However, it should be noted that the cooling rate should be high enough to prevent the material from liquefying. Moreover, the simulation results emphasize on the importance of a quenching process within the shock compression. This scheme acts as a heat sink during the shock compression that discharge the high level of kinetic energy from the material and let the atoms to form a compact configuration. The simulation results are in agreement with some evidences in former experiments.

Impact of data assimilation on Eulerian versus Lagrangian estimates of upper ocean transport

AbstractUsing four‐dimensional variational analysis, we produce an estimate of the state of a coastal region in Northern Norway during the late winter and spring in 1984. We use satellite sea surface temperature and in situ observations from a series of intensive field campaigns, and obtain a more realistic distribution of water masses both in the horizontal and the vertical than a pure downscaling approach can achieve. Although the distribution of Eulerian surface current speeds are similar, we find that they are more variable and less dependent on model bathymetry in our reanalysis compared to a hindcast produced using the same modeling system. Lagrangian drift currents on the other hand are significantly changed, with overall higher kinetic energy levels in the reanalysis than in the hindcast, particularly in the superinertial frequency band.

Study of Energy Dissipation of Pooled Stepped Spillways

Water transferring to the dam downstream creates high levels of kinetic energy. Stepped spillways are amongst the most effective spillways in reducing the kinetic energy of the flow moving towards the downstream. The geometry of the steps in stepped spillways can affect the reduction of kinetic energy of the flow transferring to the downstream. Therefore, in this study the effect of different number of steps and discharge on flow pattern especially energy dissipation were investigated. The VOF method was used to simulate the flow surface and the k-ε (RNG) turbulence model was used for flow turbulence simulation. Comparing the results obtained from the numerical simulation with the experimental data indicated an acceptable level of consistency. Comparing the obtained results showed that decreasing the number of the steps of pooled stepped spillways reduced flow velocity and increased the relative energy dissipation at the end of the spillway. Decreasing the number of steps increased the turbulent kinetic energy value. Also, the maximum turbulent kinetic energy was obtained near the step’s pool. Moreover the results indicated that the value of turbulent kinetic energy increased along the spillway.

Spatial distribution and sources of organic carbon in the surface sediment of Bosten Lake, China

Abstract. Lake sediment is an important carbon reservoir. However, little is known on the dynamics and sources of sediment organic carbon in Bosten Lake. We collected 13 surface (0–2 cm) sediment samples in Bosten Lake and analyzed total organic carbon (TOC), total nitrogen (TN), stable carbon isotopic composition in TOC (δ13Corg), and grain size. We found a large spatial variability in TOC content (1.8–4.4 %) and δ 13Corg value (−26.77 to −23.98 ‰). Using a three-end-member mixing model with measured TOC : TN ratio and δ13Corg, we estimated that 54–90 % of TOC was from autochthonous sources. Higher TOC content (> 3.7 %) was found in the east and central-north sections and near the mouth of the Kaidu River, which was attributable to allochthonous, autochthonous plus allochthonous, and autochthonous sources, respectively. The lowest TOC content was found in the mid-west section, which might be a result of high kinetic energy levels. Our study indicated that the spatial distribution of sediment TOC in the Bosten Lake was influenced by multiple and complex processes.

Mechanical Design and Control Method for SEA and VSA-based Exoskeleton Devices for Elbow Joint Rehabilitation

Robot-aided rehabilitation training allows patients to receive a more effective and stable rehabilitation process. Exoskeleton devices are superior to the endpoint manipulators and cable suspension devices on the aspect that they can train and measure the angle and torque on each joint of impaired limbs. For robotic devices, physical safety should be guaranteed since the robot-assisted training relies on high human-robot interaction especially for exoskeletons. Traditional robotic devices mainly introduce the stiffness actuator, while the high levels of kinetic energy of robots will induce unsafe. For guaranteeing the safety of patients, compliant actuator such as the series elastic actuator (SEA) and variable stiffness actuator (VSA) design has been involved into these devices. The added compliance can make robots intrinsically safe and realize the energy-efficient actuation. The VSA used a variable stiffness elastic component instead of a constant stiffness elastic component, and VSAs is deemed to a kind of SEAs. A closed-loop interaction control method was used for SEAs to generate low impedance. By comparison, the VSA realizes adaptable compliance properties with inherent mechanical design. Thus, for SEAs, an additional mechanism is needed to adjust the output stiffness. In this paper, two kinds of compliant exoskeleton devices designed with the SEA and VSA respectively are introduced. The mechanical design and control method for each device are introduced; especially the design for guaranteeing patients’ safety.

Ultra-Precision Polishing of N-Bk7 Using an Innovative Self-Propelled Abrasive Fluid Multi-Jet Polishing Tool

As the demand for optical glasses has increased, precision requirements for specific shapes, forms, surface textures, and sizes (miniaturization) have also increased. The standards and surface finishes applied to the reference mirrors used in measuring appliances are crucial. Hence, enhancements in figuring and surface finishing are indispensable to manufacturing industries. In this article, a novel self-propelled multi-jet abrasive fluid polishing technique is proposed for an ultra-precision polishing process in which a blade-less Tesla turbine was used as a prime mover. The turbine was characterized by high swirling velocity at the outlet; therefore, high levels of kinetic energy moving away from the turbine were used as polishing energy. Computational fluid dynamics (CFD) was also used to simulate the flow on the turbine blades. With a newly designed and manufactured polishing tool, the optimal polishing parameters for improving the surface roughness of crown optical glasses (N-BK7) were investigated. Taguchi's experimental approach, an L18 orthogonal array, was employed to obtain the optimal process parameters. An analysis of variance (ANOVA) was also conducted to determine the significant factors. The surface roughness has been improved by approximately 94.44% from (Ra) 0.36 μm to (Ra) 0.02 μm. This study also presents a discussion on the influence of significant factors on improving surface roughness.

Stabilizing action of pressure in homogeneous compressible shear flows: effect of Mach number and perturbation obliqueness

AbstractCompressibility exerts a stabilizing influence on a variety of high-speed shear flows such as turbulent mixing layers, transitioning boundary layers and homogeneously sheared turbulence. An important stabilizing feature that is common amongst all shear flows is the velocity–pressure interaction dynamics. In this study, velocity–pressure interactions of individual perturbation or fluctuation modes are investigated using direct numerical simulations and linear analysis in high-Mach-number homogeneous shear flow. For a given perturbation wave mode, the action of pressure is shown to depend on two important factors: the orientation of the perturbation wavevector with respect to the shear plane and the Mach number. It is shown that the streamwise perturbation wave mode rapidly develops a high level of kinetic energy but is self-limiting owing to the action of pressure. On the other hand, the energy of spanwise perturbation wave modes grows unaffected by pressure or Mach number. Oblique modes combine spanwise and streamwise characteristics and are shown to be chiefly responsible for stabilizing effects seen in shear flows. Three regimes of obliqueness of different linear stability characteristics are identified. The critical role of perturbation obliqueness on stabilization is established.

Comparative Numerical Analysis of Sheet Formed into a V-Shaped Die Using Conventional and Electromagnetic Forming Processes

A comparative and numerical study on the formability of a sheet formed into a V-shaped die using a conventional stamping operation and an electromagnetic forming (EMF) process was performed. To evaluate the damage evolution and failure prediction using a finite-element method (FEM), the Gurson-Tvergaard-Needleman plasticity material model was employed in the numerical simulation. The impact of the sheet with the die generates a complex stress state during the EMF process. Damage suppression due to the tool-sheet interaction may be one of the main factors contributing to the increased formability in the EMF process compared to the conventional forming operation. In addition, a high level of kinetic energy produces high strain-rate constitutive and inertial effects, which delay the onset of necking and may also be responsible for the increased formability using EMF.

Numerical and experimental investigation of dynamic deformation and destruction of a plate subjected to local loading

The numerical simulation and experimental results and their analysis are presented for the dynamic elastic-plastic deformation of a disk subjected to penetrating loading produced by a short cylindrical steel pin. The pin keeps the high level of kinetic energy due to the heavy joined mass. The computer model has been verified by the comparison of the numerical and experimental dynamic forces, and the residual displacements and deformations of the plate. The careful analysis of the deformation and failure of the plate is presented in the paper.

Trailing vortices around a 45° pitched‐blade impeller

AbstractThe trailing vortex system near impeller blades has been identified as the major flow mechanism responsible for mixing and dispersion in stirred vessels, and high turbulence levels in the vortices have an important impact on such phenomena as drop breakup and cell damage in bioreactors. Numerical computations of the flows require more detailed information on the velocity characteristics generated by different impeller designs than is available in the literature. Our study on the mean flow and turbulence structure generated by a pitched‐blade turbine with four 45° inclined blades found that single trailing vortex is formed around each turbine blade. The vortex axis spread out radially by less than 0.0015 T and was inclined at 20° to the horizontal plane. The vortices merged into the bulk flow structure at around 135° behind each blade. Periodicity of the mean flow due to the crossing of the individual blades and high levels of kinetic energy of turbulence (k) are contained within a radial distance of around r/T = 0.23 from the axis and a vertical distance of z/T = 0.07–0.46 from the bottom of the vessel. The k levels decay to nearly‐uniform and low values outside this region. The results are compared with earlier investigations, and their implications for mixing processes and CFD predictions of the flows are discussed. The data identify flow regions accurately where intense turbulence is present and thus give useful indications for the optimization of mixing processes.

Three-dimensional kinematics and limb kinetic energy of running cockroaches.

We tested the hypothesis that fast-running hexapeds must generate high levels of kinetic energy to cycle their limbs rapidly compared with bipeds and quadrupeds. We used high-speed video analysis to determine the three-dimensional movements of the limbs and bodies of cockroaches (Blaberus discoidalis) running on a motorized treadmill at 21 cm s-1 using an alternating tripod gait. We combined these kinematic data with morphological data to calculate the mechanical energy produced to move the limbs relative to the overall center of mass and the mechanical energy generated to rotate the body (head + thorax + abdomen) about the overall center of mass. The kinetic energy involved in moving the limbs was 8 microJ stride-1 (a power output of 21 mW kg-1, which was only approximately 13% of the external mechanical energy generated to lift and accelerate the overall center of mass at this speed. Pitch, yaw and roll rotational movements of the body were modest (less than +/- 7 degrees), and the mechanical energy required for these rotations was surprisingly small (1.7 microJ stride-1 for pitch, 0.5 microJ stride-1 for yaw and 0.4 microJ stride-1 for roll) as was the power (4.2, 1.2 and 1.1 mW kg-1, respectively). Compared at the same absolute forward speed, the mass-specific kinetic energy generated by the trotting hexaped to swing its limbs was approximately half of that predicted from data on much larger two- and four-legged animals. Compared at an equivalent speed (mid-trotting speed), limb kinetic energy was a smaller fraction of total mechanical energy for cockroaches than for large bipedal runners and hoppers and for quadrupedal trotters. Cockroaches operate at relatively high stride frequencies, but distribute ground reaction forces over a greater number of relatively small legs. The relatively small leg mass and inertia of hexapeds may allow relatively high leg cycling frequencies without exceptionally high internal mechanical energy generation.

Interaction between a spatially growing turbulent boundary layer and embedded streamwise vortices

The interaction between a zero-pressure-gradient turbulent boundary layer and a pair of strong, common-flow-down, streamwise vortices with a sizeable velocity deficit is studied by large-eddy simulation. The subgrid-scale stresses are modelled by a localized dynamic eddy-viscosity model. The results agree well with experimental data. The vortices drastically distort the boundary layer, and produce large spanwise variations of the skin friction. The Reynolds stresses are highly three-dimensional. High levels of kinetic energy are found both in the upwash region and in the vortex core. The two secondary shear stresses are significant in the vortex region, with magnitudes comparable to the primary one. Turbulent transport from the immediate upwash region is partly responsible for the high levels of turbulent kinetic energy in the vortex core; its effect on the primary stress 〈u′v′〉 is less significant. The mean velocity gradients play an important role in the generation of 〈u′v′〉 in all regions, while they are negligible in the generation of turbulent kinetic energy in the vortex core. The pressure-strain correlations are generally of opposite sign to the production terms except in the vortex core, where they have the same sign as the production term in the budget of 〈u′v′〉. The results highlight the limitations of the eddy-viscosity assumption (in a Reynolds-averaged context) for flows of this type, as well as the excessive diffusion predicted by typical turbulence models.

Detailed Stress Tensor Measurements in a Centrifugal Compressor Vaneless Diffuser

Detailed flow measurements have been made in the vaneless diffuser of a large low-speed centrifugal compressor using hot-wire anemometry. The three time mean velocity components and full stress tensor distributions have been determined on eight measurement planes within the diffuser. High levels of Reynolds stress result in the rapid mixing out of the blade wake. Although high levels of turbulent kinetic energy are found in the passage wake, they are not associated with strong Reynolds stresses and hence the passage wake mixes out only slowly. Low-frequency meandering of the wake position is therefore likely to be responsible for the high kinetic energy levels. The anisotropic nature of the turbulence suggests that Reynolds stress turbulence models are required for CFD modeling of diffuser flows.