Variation Of Kinetic Energy Research Articles

Acoustic waves in functionally graded rods with periodic longitudinal inhomogeneity

Acoustic waves in periodic functionally graded (FG) 1 D rods are studied by applying the modified Cauchy formalism previously developed for analyzing dispersion of the surface acoustic waves (SAW) in stratified media. In case of harmonic waves traveling in a semi-infinite rod with harmonic periodicity of acoustic properties several phenomena were observed, including the non-periodic spatial variation of the phase velocity and wave magnitude, but spatially periodic variation of kinetic and strain energy.

Study on bubble penetrating solution/frother interface in the presence of ions

The drainage and rupture of solution/frother interface is a prerequisite to predict the adsorption of frother onto the bubble surface. Using a high-speed motion acquisition system, we investigated the dynamic penetration of bubble at the solution/frother interface under four factors that height, capillary inner diameter, ion concentration and ionic valence. Since the kinetic energy of bubble was proportional to the radius and rising velocity, the kinetic energy increased with increasing the height and capillary inner diameter while decreased with increasing the ion concentration and ionic valence. The variation of kinetic energy followed the order: capillary inner diameter > ion concentration > height > ionic valence. The drainage time of the bubble at the solution/frother interface was found to decrease as the kinetic energy increased independently of these factors, indicating that the rupture of the hydration film was significantly influenced by the kinetic energy. A solution column caused by the bubble penetrating the solution/frother interface was observed. The column height increased as the kinetic energy increased for the factors of height and capillary while an opposite trend was presented by the factors of ion concentration and ionic valence. IFT was discussed to be the essential reason for the difference in the penetration. IFT of the solution/air interface increased as the ion concentration increased independently of ion species, and the IFT of different interfaces followed the order: solution/air > frother/air > solution/frother. Our results can provide valuable insight into the development of technology for surfactant adsorption and mineral flotation.

Nonseasonal Variations in Near-Inertial Kinetic Energy Observed Far below the Surface Mixed Layer in the Southwestern East Sea (Japan Sea)

Near-inertial internal waves (NIWs) generated by surface wind forcing are intermittently enhanced below and within the surface mixed layer. The NIW kinetic energy below the surface mixed layer varies over intraseasonal, interannual, and decadal timescales; however, these variations remain unexplored, due to a lack of long-term, in situ observations. We present statistical results on the nonseasonal variability of the NIW kinetic energy 400 m below the surface mixed layer in the southwestern East Sea, using moored current measurements from 21 years. We used long time series of the near-inertial band (0.85–1.15 f) kinetic energy to define nine periods of relatively high (period high) and seven periods of relatively low (period low) NIW kinetic energy. The NIW kinetic energy average at period high was about 24 times higher than that at period low and those in specific years (2003, 2012–2013, 2016, and 2020) and decade (2010s) were significantly higher than those in other years and decade (2000s). Composite analysis revealed that negative relative vorticity and strong total strain significantly enhance NIW kinetic energy at 400 m. The relative vorticity was negative (total strain was positively enhanced) during seven (six) out of nine events of period high. NIW trapping in a region of negative relative vorticity and the wave capture process induce nonseasonal variations in NIW kinetic energy below the surface mixed layer. Our study reveals that, over intraseasonal, interannual, and decadal timescales, mesoscale flow fields significantly influence NIWs.

Wind Tunnel Test on Windblown Sand Two-Phase Flow Characteristics in Arid Desert Regions

Windblown sand two-phase flow characteristics become an essential factor in evaluating the windblown sand load on infrastructures and civil structures. Based on the measured wind characteristics in arid desert regions, windblown sand flow fields with three kinds of sand beds are simulated in the wind tunnel, respectively. The results indicate that the characteristic saltation height of sand particles increases with the wind speed and particle size in the windblown sand flow field. As the sand concentration increases, the wind speed decreases, and the turbulence intensity increases. The concentration, energy, and impact pressure of sand particles increase with increasing wind speed and decrease exponentially with increasing height. At the same wind speed, the concentration, energy, and impact pressure of the coarse sand, fine sand, and mixed sand increases, in turn. Moreover, the variation of kinetic energy with height is similar to that of total energy with height and the proportion of potential energy to total energy is quite small.

Differences of turbulence modulation by heavy particles on solid wall and erodible bed surface

In this paper, wall-resolved large-eddy simulation of turbulence, Lagrangian point-force model of particle tracking, and two-way coupling approach are used to simulate the particle-laden flow over a rigid wall. The flow is a turbulent open channel flow with the particle-free friction Reynolds number of Reτ=4200. Together with the simulated results over an erodible bed from Zheng et al. [J. Fluid Mech. 918, 1–27 (2021)], the influence of the lower boundary condition of particle motion with the wall-normal gravity on turbulence modulation is thoroughly compared. It is found that high-inertia (St+=244.5) particles studied in this work moving over a rigid wall increase the mean fluid velocity and the scales of turbulence structures away from the wall, suppress turbulence fluctuations and Reynolds stress, and reduce the scales of turbulence structures near the wall as compared with the particle-free flow. Gravitational settling of particles accounts for most of the changes, and the crossing trajectory caused by particles bouncing near the rigid wall is responsible for the reduction of the scales of the near-wall turbulence structures. On the contrary, the splashing process of particles over the erodible bed leads to the decrease in the mean fluid velocity, the anisotropic variation of turbulent kinetic energy, the shrink of the outer turbulence structure, and the enlargement of the near-wall streaks. The results reveal the significance of the near-wall particle motion (rebound or splashing) on turbulence modulation.

Design and development of mechanically operated blood collection and monitoring device

A blood collection monitor is a device used during the blood collection process to provide a shaking moment to the blood being received from the donor thereby mixing the blood homogeneous with the anticoagulants in the blood bag. The shaking moment and anticoagulants prevent blood coagulation. The amount of blood to be collected varies from donor to donor which ranges from 350 ml to 450 ml. The existing electronic blood collection monitors being used in hospitals and laboratories include not only mechanical but also an electric mechanism that provides oscillations to a blood bag, quantify the blood amount and measure the flow of blood. However, the dependency of these devices on external electric power sources limits its application in rural areas as well as large-scale donation camps. The present study offers a mechanical blood collection monitor which does not require any external power for its functioning and thereby overcomes the drawbacks of the conventional device. The present paper offers the design considerations and systematic study of the proposed mechanical blood collection monitor. Additionally, the linkage mechanism and associated gear train were analysed using ANSYS and ADAMS which further opens up the ways to study the variations in kinetic energy and torquing moment.

Relativistic mechanics and thermodynamics. III. Rotation

A covariant four-tensor rotation equation—for bi-dimensional composite body—, by generalising cross product to four-vectors, is obtained. From it, a relativistic angular impulse-angular momentum variation equation (Poinsot–Euler rotation equation) and its pseudo-work-rotational kinetic energy variation equation (Poinsot–Euler pseudo-work equation), are obtained for a body spinning—with constant angular momentum direction—by external torques. Two rotational processes are analysed by using this four-tensor formalism—completed by a four-vector fundamental equation (Newton’s second law and thermodynamics first law)—: a rotating body subjected to conservative and friction forces torque—a mechanical energy dissipation process—, and a device spinning by torque produced by chemical reactions—a mechanical energy production process.

On the incipient sediment suspension downstream of three-dimensional wall-mounted obstacles

The incipient sediment suspension downstream of a thin square tab with various inclination angles was fundamentally described using experiments and theoretical arguments. Volumetric particle tracking velocimetry and particle image velocimetry were applied to measure the sediment particle distributions and wake flows under various incoming velocities and obstacle inclination angles. Results show that suspension of sediments occurred downstream of the obstacles due to the enhanced local turbulence intensities. Although the sediment volumetric fraction was mostly determined by the variation of wake turbulence kinetic energy under low inclination angles (i.e., obstacles nearly parallel to incoming flow), this was not the case under high inclination angle counterparts where distinct downward velocities dominated the wake region and suppressed the sediment suspension. This led to the decrease of sediment volumetric fraction with the growth of tab inclination at high inclination angles. Supported by flow measurements, a revised Rouse number was introduced which allows to quantitatively integrate the coupled influence of turbulence mixing load and vertical flows across various incoming velocities and inclination angles.

Variation of turbulent kinetic energy due to dimples in intake manifold for diesel engine

This work compares the application of spherical dimples in a modified intake manifold for the diesel engine to a normal intake manifold in terms of turbulent kinetic energy. In this work spherical dimples having an h/d ratio of 0.5 are used. These dimples had been designed by using designing tools in the design modeler module of ANSYS. Same bend angle condition 60° degree from the axis of manifold had been taken for both modified and normal intake system. The main purpose of this work is to observe the variation in turbulent kinetic energy due to the incorporation of spherical dimples in a intake model with a 20 mm diameter, 200 mm length and with a bend around 160 mm length. In this flow dynamics parameters other than turbulent kinetic energy like velocity and pressure were also observed. All numerical analyses were carried out on the FLUENT module of ANSYS and significant improvements of 25.45% and 35.41% for partial and full dimpled surface were reported in turbulent kinetic energy with respect to normal intake manifold, which were obtained due to modifications in the intake system. This work provides path to develop new techniques for enhancing mixing in the diesel engine.

Time Dependent Effect of flow properties on addition of heat to the air flow at Compressible Subsonic Speeds

Heat addition process is a governing phenomenon in turbojet and ramjet burners, where heat is added to the flow during the fuel-air combustion process. In the present work, an analytical study has been performed to investigate the effect of heat addition on the basic flow properties based on compressible Rayleigh flow model between the subsonic and sonic flow regime. The unsteady nature of flow properties in these regimes have been evaluated analytically by adding heat through the walls of a constant area, frictionless duct in which air flow occurs over different periods of time. Sudden variation of temperature, pressure, velocity and kinetic energy of the flow were found at flow Mach number M = 0.94. Flow velocity and kinetic energy increases until the flow approaches M = 0.94, afterwards there is a rapid increase in the flow velocity and kinetic energy until it reaches sonic conditions. Conversely, pressure decreased till the flow reaches M = 0.94, there after a sudden drop was observed. Flow enthalpy increased initially, reached maximum at flow M = 0.845 and then reduced till sonic conditions. Based on the observations, it has been concluded that the heat energy contributed to increase the kinetic energy thereby reducing the temperature of the flow.

Variability and upward trend in the kinetic energy of western boundary currents over the last century: impacts from barystatic and dynamic sea level change

Global sea level reconstruction (RecSL) for 1900–2015 was used to estimate the variations in oceanic kinetic energy (OKE) and compare OKE with changes in wind patterns and wind kinetic energy (WKE); the comparison was done for each latitude and for 5 western boundary currents (WBCs). Two contributors to variability in sea level were analyzed: gravitational, rotational and deformational effects (GRD) related to changes in water masses (barystatic sea level change), and changes in the sterodynamic sea level (SDSL), associated with changes in wind, steric sea level and ocean circulation. GRD changes were responsible for latitudinal multidecadal variations with time scale of ~ 60 to 80 years, while SDSL changes were responsible for interannual and decadal variability, and together with the Greenland ice melt, to sea level acceleration since the 1960s. Regional changes near WBCs show a coherent upward trend in OKE (+ 24% ± 3 increase per century), while trends in WKE over the same regions changed widely from -11% (decrease) over the Gulf Stream region to + 28% (increase) over the Brazil Current region. Low frequency oscillations of wind and oceanic kinetic energy are correlated in some WBCs (e.g., R = 0.5 in the Kuroshio region) but not in others (e.g., R = -0.05 in the Gulf Stream region). The study suggests that several forcing mechanisms contribute to the increased OKE, they include an increased wind-stress curl over subtropical gyres, local changes in wind patterns that impact some WBCs, and large uneven warming near WBCs that increased sea level gradients and thus intensified OKE.

Investigating the effect of mixing layer rheology on granular flow over entrainable beds using SPH method

This paper numerically studies the interaction of a flowing granular material with an entrainable granular bed, while materials are mixed at the interface of two materials. The rheological behavior of this granular mixture is characterized by a generalized viscoplastic model that includes local volume fraction of materials as well as their physical properties, i.e. size, density, and friction angle. Additionally, the effect of the dynamics of entrained bed-type particles on the rheology of the granular mixture is considered. The governing equations of the flow are discretized using the Incompressible Smoothed Particle Hydrodynamics (SPH) method in which mixing of particles can be conveniently simulated. Two benchmark problems, with and without entrainment, are solved to assess the accuracy of the underlying computational procedure in the absence of mixing. Some other test cases are also solved by including the mixing effect, and the effect of various model parameters is studied. Variations in momentum, maximum velocity, and total kinetic energy of flow with time are reported, and some physical interpretations are presented.

Seasonal variations of inertia gravity waves over Hyderabad (17.4 °N, 78.5 °E), a tropical station using radiosonde measurements

Gravity waves play an important role not only in transferring the momentum and energy to the upper atmosphere but also significantly contribute in different global atmospheric phenomenon like Brewer-Dobson circulation along with planetary waves. Larger differences in the gravity wave model parameters with the real observations has recommended more observational studies for better predictions. In this paper, we have launched 80 GPS-radiosondes in different seasons (20 per each season) to parameterize the inertia gravity wave (IGW) characteristics over a tropical station Hyderabad (17.4° N, 78.5 °E). FFT analysis of zonal, meridional winds and temperature fluctuations shows the generation of IGW over this latitude irrespective of the presence of strong tides and Quasi Two Day Wave (QTDW). Monsoon and winter amplitudes are maximized in both tropospheric and stratospheric regions. Hodograph analysis is used to estimate the IGW parameters. No significant seasonal changes are observed in vertical and horizontal wavelengths and are ranged between 2 – 4 km and 100–1700 km respectively. Horizontal group velocities are found to be lesser in tropospheric region than stratospheric one, while the vertical group velocities showed the opposite nature in all the seasons. About 80–90% hodographs show the upward propagation of IGW in stratospheric region and the direction of horizontal wave propagation is not very clear. Vertical wavenumber spectra reveal the isotropic nature of the waves and agreed well with the universal spectrum of power law. The slopes reached canonical values (−3) in both the height regions for all the seasons. Kinetic energy variations in all the seasons show interesting facts about source regions in different seasons. Strong convection and wind shear along with tropical easterly jets are responsible for the generation of these waves in monsoon, whereas, sudden enhancement in meridional wind shear is the source mechanism during winter.

Effect of Rear Wing on Time-Averaged Ground Vehicle Wake With Variable Slant Angle

Abstract The slant angle plays a crucial role in the flow property of hatchback ground vehicles. An optimum slant angle is obligatory for better handling the ground vehicles when fitted with a rear wing. In this regard, the variation of time-averaged flow properties around a wing-attached hatchback ground vehicle (Ahmed body) due to a variable slant angle is accessed by this paper. The design includes a scaled Ahmed body as a reference ground vehicle and a rear wing with NACA 0018 profile. The computational studies are executed with Reynolds-averaged Navier–Stokes based k-epsilon turbulence model with nonequilibrium wall function. The vehicle's model is scaled to 75% of the actual model, and analyses are conducted with Reynolds number 2.7 × 106. After the study, it is observed that a 15 deg slant angle is the critical angle for the wing attached state in which the drag coefficient is maximum. After this angle, a sudden reduction of coefficients is observed, where 25 deg is critical for without wing condition. Besides this, the two counter-rotating horseshoe vortices in the separation bubble and side edge c-pillar vortices also behave differently due to the wing's presence. The turbulent kinetic energy variation and the variation in coefficients of surface pressure are also affected by the rear wing attachment. This paper will assist in finding the optimum slant angle for hatchback ground vehicles in the presence of a rear wing. Thus the study will help in increasing stability and control for hatchback ground vehicles.

Design and analysis of energy-efficient solar panel cooling system using computational fluid dynamics

This paper highlights the design of an effective liquid cooling system that utilizes the heat generated from the solar panel as a cooling medium to maintain the optimal desired temperature of the solar panel. The coolant for this finned cooling system is selected based on its vaporizing temperature range and thermal cycle characteristics. For analysis purposes, a CAD model is generated in Solidworks CAD package, and further meshing and numerical simulations are performed using Ansys Fluent software. Flow and heat transfer characteristics of the cooling system are investigated by plotting stream functions, velocity, and temperature distributions inside the system. Probing of variations in temperature, pressure and turbulent kinetic energy along vertical as well as longitudinal direction is graphically analysed. Thus, elucidating characteristic of parametric conditions under observation. This study’s results can be the potential background for designing an efficient solar panel cooling system with superior thermal performance.

Meso-scale signatures of inertial transitions in granular materials

Granular materials have a complex collective behavior based on simple interactions between grains. The global behavior stems from dynamic rearrangements in the micro-structure. The local increase (resp. decrease) of the density generates jamming (resp. unjamming). In this paper, instabilities in the form of localized bursts of kinetic energy are studied at both the micro-scale (i.e. grain scale) and meso-scale (i.e. cluster scale). The bursts are defined from the variation of kinetic energy. The meso-domains (grain loops in 2D) are built from the tessellation of the medium. We analyze the gain and loss of meso-structures during a localized burst. Surprisingly, micro-structural reorganizations are able to keep the overall statistical equilibrium constant. The introduction of strain-like and stress-like quantities at the mesoscopic scale makes it possible to propose an expression that can be assimilated to mesoscopic second-order work. At this intermediate scale, the negative values of the second-order work are correlated to the appearance of bursts of kinetic energy, which stands for a meso-scale counterpart of Hill’s macroscopic criterion of mechanical instability.

C-Legged Hexapod Robot Design Guidelines Based on Energy Analysis

C-legged hexapod robots offer a balanced trade-off between the robust stability of wheeled robots and the increased-motion capabilities of legged robots, and therefore, are currently of great interest. This article investigates the impact of mass, leg radius, and angular velocity on the energy consumption of C-legged hexapod robots, in order to develop a set of design guidelines that maximize the robot’s performance. The kinematic model of a single C-leg system is obtained and used to determine the system’s energy consumption associated with gravitational potential energy (GPE) and kinetic energy (KE) variations. Both the kinematic model and energy model are validated in a custom-made test bench. Our results show that the kinematic model very accurately predicts the trajectory of the system in space, but due to the varying load experienced by the motor, the system lags compared to the model predictions. Furthermore, the energy model has been also validated experimentally and successfully predicts the motor consumption periods. Using the energy model, it has been concluded that the angular velocity of the leg and the leg radius have an exponential relationship with motor peak power demand—directly affecting the motor selection. On the other hand, the mass is inversely proportional to the robot efficiency, and therefore, must be kept as low as possible.

Simulation of flow pattern around series of groynes with different orientations in meandering channels

The mechanism of flow and turbulence around groynes in a meandering channel is very complex phenomena. To simulate the flow pattern around groynes in meanders a 3D numerical model was built with groynes of different inclinations by using ANSYS Fluent. The developed model was verified by the results of experimental study in meanders. Pressure, velocity, stream lines and turbulent kinetic energy for different groyne angles such as 15°, 30°, 45°, 90°, 120° and 150° were compared and analyzed to find the ideal angle configuration for different functions. Streamlines profiles were studied to understand more about the formation of scours and vortices around the groyne. The study of streamline profiles helped in the study of vortex and scours. The most dynamic variation in pressure and turbulent kinetic energy within the contours were found for groynes with 90° orientation. Large numbers of vortices between the groynes were observed for groynes with 15° and 90° orientation and these vortices were observed between the second and third groynes. For groynes in the meandering, the ideal angle for controlling the velocity was found out to be 45°, as it showed very small number of vortices in the groyne field. The results of the study showed that numerical modelling could be used efficiently for the study of flow and turbulence around groynes in meanders.

The Vertical City Weather Generator (VCWG v1.3.2)

Abstract. The Vertical City Weather Generator (VCWG) is a computationally efficient urban microclimate model developed to predict temporal and vertical variation of potential temperature, wind speed, specific humidity, and turbulent kinetic energy. It is composed of various sub-models: a rural model, an urban vertical diffusion model, a radiation model, and a building energy model. Forced with weather data from a nearby rural site, the rural model is used to solve for the vertical profiles of potential temperature, specific humidity, and friction velocity at 10 m a.g.l. The rural model also calculates a horizontal pressure gradient. The rural model outputs are applied to a vertical diffusion urban microclimate model that solves vertical transport equations for potential temperature, momentum, specific humidity, and turbulent kinetic energy. The urban vertical diffusion model is also coupled to the radiation and building energy models using two-way interaction. The aerodynamic and thermal effects of urban elements, surface vegetation, and trees are considered. The predictions of the VCWG model are compared to observations of the Basel UrBan Boundary Layer Experiment (BUBBLE) microclimate field campaign for 8 months from December 2001 to July 2002. The model evaluation indicates that the VCWG predicts vertical profiles of meteorological variables in reasonable agreement with the field measurements. The average bias, root mean square error (RMSE), and R2 for potential temperature are 0.25 K, 1.41 K, and 0.82, respectively. The average bias, RMSE, and R2 for wind speed are 0.67 m s−1, 1.06 m s−1, and 0.41, respectively. The average bias, RMSE, and R2 for specific humidity are 0.00057 kg kg−1, 0.0010 kg kg−1, and 0.85, respectively. In addition, the average bias, RMSE, and R2 for the urban heat island (UHI) are 0.36 K, 1.2 K, and 0.35, respectively. Based on the evaluation, the model performance is comparable to the performance of similar models. The performance of the model is further explored to investigate the effects of urban configurations such as plan and frontal area densities, varying levels of vegetation, building energy configuration, radiation configuration, seasonal variations, and different climate zones on the model predictions. The results obtained from the explorations are reasonably consistent with previous studies in the literature, justifying the reliability and computational efficiency of VCWG for operational urban development projects.

Impact of tibetan plateau snow cover on tropical cyclogenesis via the Madden–Julian oscillation during the following boreal summer

This study investigates the role of the interannual variation of boreal winter (December–February) snow cover over the Tibetan Plateau (TPSC) in modulating the relationship between the Madden Julian Oscillation (MJO) and tropical cyclogenesis over the western North Pacific (WNP) during the following boreal summer (June–October). During the boreal summer following a high snow cover anomaly (SCA), MJO-associated convection tends to be confined to the west of 140 °E, coinciding with more frequent tropical cyclone (TC) activity in this region. By contrast, there tends to be stronger MJO-associated convection extending farther east during years following low SCA. The MJO-associated convection extends to ~ 160 °E over the WNP basin with a peak around 140 °E. Thus, more TCs form farther east in the WNP in these years. We use composite analyses of large-scale environmental factors to demonstrate that low-level relative vorticity is one of the most important factors in controlling TCs in response to the change of MJO-associated convection between years with high SCA and low SCA. Meanwhile, eddy kinetic energy variations associated with the MJO are consistent with changes in tropical cyclogenesis over the WNP basin between years with high and low SCA. The Asian summer monsoon plays an important role in linking prior winter TPSC to MJO activity in the following summer. During high-SCA years, increased snow cover results in positive soil moisture anomalies and cooling over the Tibetan Plateau, thus weakening the following summer Asian monsoon and weakening associated water vapor advection, while the opposite chain of events occurs in low-SCA years. These changes in high-SCA years are favorable for MJO propagation and are unfavorable for MJO propagation in low-SCA years. Meanwhile, the interannual variation of SCA exerts a significant impact on the upper-tropospheric circulation and thus changes in vertical wind shear. During high-SCA years, there are anomalous upper-level easterlies in the Indian Ocean and upper-level westerlies in the Pacific Ocean, which result in anomalous easterly wind shear in the Indian Ocean and anomalous westerly shear in the Pacific Ocean. The opposite shear pattern arises in low-SCA years. In addition to changes in wind shear, the background vertical motion associated with changes in TPSC may also be partly responsible for changes in MJO activity.