Spatial Energy Distribution Research Articles

Turbulent Kinetic Energy in Bolt Fishway

The paper presents an analysis the spatial distribution of turbulent kinetic energy (TKE) for bolt fishways, including the impact of additional spillway slots and fixed channel development. The research was done for two models, each containing a different arrangement of slots. The presented results of research for bolt fishways were obtained as an effect of laboratory tests. The measurements were done for three components of instant flow velocity magnitude (speed). Analysis of the results was done for a 3D flow structure using Matlab software. In the case of bolt fishways, significant differences were noted for the method of velocity and TKE distribution, in reference to research comprising channels with biological development. It was stated that a reason for this is the flexible development of the channel. The occurrence of extreme TKE values in the chamber (pool) is strictly associated with the characteristics of interaction zones between various flow structures. It was also stated that the lower the parapet of the slot’s spillway shelf is in the fishway’s partition, the higher TKE could be expected just downstream of the section. These establishments may be important for the designing process in the case of fish passes of various types of construction.

Spatial Pattern Distribution of Wind and Solar Energy in USA

Renewable energy, compared to non-renewable energy, is cleaner for the environment. Previous studies on the United States of America (USA) renewable energy mainly focused on assessment of renewable emerging resource potential in some areas in USA. Spatial distribution patterns of renewable energy are valuable to have better management of renewable energy exploration. The objective of this study is to complete spatial pattern analyses of the USA renewable energy with focus on wind and solar energy. Several GIS tools, including High/Low Clustering, Grouping Analysis and Hotspot Analysis, are applied to analyze the energy spatial patterns. The analysis results show that solar energy is clustered at the southwest USA while wind is highly variable and dependent on the local geographic environment. The study results will be helpful to possible growth in this industry.

Single particle adhesion variability in additive manufacturing powders

ABSTRACT The adhesion properties of powder particles could profoundly influence the quality of parts made by Additive Manufacturing (AM) processes. Accurate experimental characterization of adhesion and the spatial surface adhesion distribution of a single microparticle has been a significant challenge, due mainly to difficulties associated with the micro-scale handling/manipulation in a controllable manner and uncertainty in the nature of micro/nano-scale contacts. In current work, an approach for determining the spatial energy/adhesion distribution on the surfaces of single microparticles used in AM is introduced and demonstrated using Molybdenum (Mo) metal particles as model particles. Both ultrasonic base and Surface Acoustic Wave (SAW)-based excitation techniques coupled with laser Doppler vibrometry are utilized to excite and acquire the vibrational rocking motion and to drive the rolling motion of single Mo particles on a Silicon (Si) substrate in a controllable manner and, thereby determining the spatial adhesion distribution on the particle surfaces. Spatial surface energy distribution data of microparticles could be utilized in Discrete Element Method (DEM) simulations as a statistical input for simulating local powder bed dynamics with increased accuracy, which would potentially lead to more predictable AM processes.

Effect of beam shape and spatial energy distribution on weld bead geometry in conduction welding

The size of a projected beam onto a workpiece and its intensity distribution profile defines the response of the material to the applied laser heat. This means that not only the processing parameters, but also the optical set-up and process tools define the process and the resulting weld profile. In high power laser delivery systems the beam propagation characteristics of the laser beam can vary during processing. A change of the focal distance, for instance, alters the spot size projected on the workpiece as well as its intensity distribution. Some dynamic optical systems can also change the shape of the projected beam. Galvo-scanners induce a small distortion to the projected beam from circular to elliptical when the mirrors deflect the beam across the working domain. This continuous change of the spatial energy distribution may affect the process stability and material response locally. This work examines the influence of changing the shape of the projected beam and its energy distribution on the weld bead profile in conduction laser welding, which is also relevant to laser cladding and additive manufacture. It has been found that for the same optical set-up and system parameters, different bead profiles can be obtained with different degree of distortion of the beam profile. In addition, different intensity distribution profiles led to different penetration depths for the same nominal beam diameter and energy density due to the difference in peak intensity.

Simulation and Experimental Study on Residual Stress Distribution in Titanium Alloy Treated by Laser Shock Peening with Flat-Top and Gaussian Laser Beams.

The residual stress introduced by laser shock peening (LSP) is one of the most important factors in improving metallic fatigue life. The shock wave pressure has considerable influence on residual stress distribution, which is affected by the distribution of laser energy. In this work, a titanium alloy is treated by LSP with flat-top and Gaussian laser beams, and the effects of spatial energy distribution on residual stress are investigated. Firstly, a 3D finite element model (FEM) is developed to predict residual stress with different spatial energy distribution, and the predicted residual stress is validated by experimental data. Secondly, three kinds of pulse energies, 3 J, 4 J and 5 J, are chosen to study the difference of residual stress introduced by flat-top and Gaussian laser beams. Lastly, the effect mechanism of spatial energy distribution on residual stress is revealed.

Experimental investigation of combustion characteristics and NOx formation of coal particles using laser induced breakdown spectroscopy

To study the mechanism of coal combustion and NOx formation, the combustion of coal particles in different atmospheres (O2/N2, O2/CO2) with different O2 concentrations was investigated using the CO2 laser as a heat source. The spatial distribution of atoms and groups (e.g., H at 656.2 nm, O at 777.3 nm, CN at 388.3 nm) relating to the combustion flame were measured simultaneously using laser induced breakdown spectroscopy (LIBS). The residual energy was measured during the collection of LIBS spectra in the combustion process, which could be characterized the temperature profiles of combustion flame due to the positive correlation with temperature. The combustion stage could be clearly discriminated by the emission of H and CN, along with the flame temperature. The residual energy obtained in different atmospheres indicated that the impact of combustion atmosphere on flame temperature is greater in the char combustion stage rather than volatile combustion stage. It was determined from the temporal and spatial distribution of residual energy and CN intensity that a higher flame temperature leads to a higher concentration of CN. The correlation between the generation of CN and the NOx formation was also investigated to show that the formation approaches of NOx are similar in the O2/CO2 and O2/N2 atmospheres, while the fuel-N conversion paths are different between volatile combustion and char combustion stages. The measurement of temporal and spatial distributions of LIBS spectra with varying flame temperatures is significant in revealing the mechanism of coal-particle combustion and NOx formation.

Thermal transport in C3N nanotube: a comparative study with carbon nanotube

One-dimensional nanotubes, such as carbon nanotube (CNT) and C3N nanotube (C3NNT), are attracting growing research interest due to their excellent electrical and thermal properties. In this work, the thermal transport of a single-walled C3NNT is investigated in comparison with a single-walled CNT using classical molecular dynamic simulations. We firstly observe that the thermal conductivity (k) of C3NNT is lower than that of CNT. Due to the phonon scattering in the N atoms of C3NNT, the energy is localized around the N atoms. Monotonic decreasing trends of k with increasing temperature are shown in CNT and C3NNT, indicating strong Umklapp phonon scattering. Afterwards, uniaxial strains from −10% to 14% are applied to the nanotubes, and the thermal conductivity initially increases and then decreases. Phonon density of states, phonon dispersions, participation ratios, and spatial distribution of energy are used to analyze the phonon behaviors in nanotubes. This work provides fundamental thermo-physical knowledge to the thermal management of CNT and C3NNT based nanoelectronics.

Polymeric materials for photon management in photovoltaics

In the field of photovoltaics, achieving high efficiency in both light absorption and light trapping simultaneously remains challenging. Photon management, which refers to the engineering of materials and device architectures to control the spatial or spectral distribution of optical energy, offers a number of promising approaches for the optimization of this tradeoff. Among these are antireflective structures with pronounced surface patterned profiles that reduce surface reflectivity, light trapping approaches but also spectral conversion concepts. With the continuous development of photovoltaic device architectures and designs, the engineering of novel photon management strategies and the availability of suitably tailored polymeric materials for such applications will contribute to enhanced device efficiencies as well as sustained long-term performance. In this review, we summarize the recent progress in the development and implementation of photon management strategies for different photovoltaic technologies specifically based on the use of polymeric materials, and we discuss their contribution to the field.

Spatial and temporal distributions of turbulence under bichromatic breaking waves

The present study aims to extend insights of surf zone turbulence dynamics to wave groups. In a large-scale wave flume, bichromatic wave groups were produced with 31.5 s group period, 4.2 s mean wave period, and a 0.58 m maximum wave height near the paddle. This condition resulted in plunging-type wave breaking over a fixed, gravel-bed, barred profile. Optic, acoustic and electromagnetic instruments were used to measure the flow and the spatial and temporal distributions of turbulent kinetic energy (TKE). The measurements showed that turbulence in the shoaling region is primarily bed-generated and decays almost fully within one wave cycle, leading to TKE variations at the short wave frequency. The wave breaking-generated turbulence, in contrast, decays over multiple wave cycles, leading to a gradual increase and decay of TKE during a wave group cycle. In the wave breaking region, TKE dynamics are driven by the production and subsequent downward transport of turbulence under the successive breaking waves in the group. Consequently, the maximum near-bed TKE in the breaking region can lag the highest breaking wave by up to 2.5 wave cycles. The net cross-shore transport of TKE is in the shoaling region primarily driven by short-wave velocities and is shoreward-directed; in the wave breaking region, the TKE transport is seaward-directed by the undertow and the long-wave velocities. Downward transport of TKE is driven by the vertical component of the time-averaged flow. The cross-shore and vertical diffusive transport rates are small relative to the advective transport rates.

Delayed fission energy effect on LWR normal operation and transients

In reactor core analysis, equilibrium delayed fission energy is often assumed except for estimating the decay heat during reactor shutdown or post-accident scenarios. In this paper, we investigated a few slow and fast transient operational conditions in which the assumption of equilibrium delayed energy could be questionable. A model of lumping the delayed heat source into groups has been adopted in this study to calculate the time-dependent delayed power in the CASL neutronics code MPACT. For the normal operational depletion, the time-integrated effect of the delayed heat shows a small impact in calculating the flux normalization factor, and thus eigenvalue and depletion isotopics. The effect of delayed energy for the reactivity-initiated accident (RIA) problems is more interesting. For a PWR 3-D full core simulation of rod ejection, the peak core power is reduced by about 3% and the decay heat is significantly higher after SCRAM, with an overall energy release increased by 7%. Therefore, the time-dependent delayed model is more beneficial for fast transient analysis. In addition to the temporal effect, the spatial distribution of energy deposited from delayed gamma rays are compared with that from prompt gamma rays for a few typical LWR mini-lattices, and the results affirm that using the scaling approach for spatial energy deposition of delayed gamma rays has good accuracy.

Uni-Antenna Spatial Energy Compression Based on Unsteady Coherent Interference

In this work, the unique spatial energy compression phenomenon of uni-antenna frequency diverse system based on the unsteady coherent interference is explored comprehensively. By compressing the element spacing of linear frequency diverse array (FDA) to near-zero, the decoupling of angle dimension is significantly achieved from the conventional range-angle-dependent beampattern. Inspired by the ever-shrinking element spacing, the concept of uni-antenna frequency diverse system is firstly proposed. The relations between a series of parameters (i.e. the number of diversity, frequency offset values) and spatial energy distributions is investigated in-depth. The uni-antenna frequency diverse synthesizing method allows the focusing intensity and focusing period of transmitted energy to be flexibly adjustable. The electric intensity of the proposed uni-antenna frequency diverse system has at least 4dB more compared with that in conventional phased array at each special focusing ribbon, which brings a great improvement of SNR in radar detection. This system provides a very promising and potential research and development direction on collaborative detection scheme while integrating phased array technology. With energy compression and focusing in both angle and range dimensions achieved, illustrating that such interference fringes phenomenon of frequency diverse antenna system is more promising and suitable for high performance detection and ranging applications.

Application of Ultrasonic Anemometer Array to Field Measurements of the Downwash Flow of an Agricultural Unmanned Helicopter

Abstract. Unmanned helicopters are widely used in agricultural spray applications; however, there is a lack of high-accuracy field data on the complex downwash flows caused by such helicopters to support efficient spraying. Therefore, we aimed to collect high-accuracy reference data by developing an ultrasonic anemometer array and related software to measure the downwash flow velocity field of a common agricultural unmanned helicopter (Copterworks AF-25B) during outdoor hovering and forward flight. Differential GPS and image scaling were used to determine the exact position and velocity of the helicopter to ensure repeatability of the tests. When the hovering height of the rotor above the ground plane was y/R = 2.5 (where y is the height above ground level and R is the radius of the rotor), the maximum downwash velocity reached 7 m s-1 at x/R = 0.5 (where x is the radial distance from the axis of the rotor). In addition, we obtained the spatial distribution of the turbulence kinetic energy. The attached flow velocity in the near-ground boundary layer increased radially and reached a maximum of 3 m s-1 at x = 3.6 m, after which it decreased. Comparatively, the maximum downwash velocity during forward flight occurred between x/R = 0.5 and 1.5 and was only about 3 m s-1, which was less than half the maximum downwash velocity while hovering. In addition, the circulation flow below the rotor tips had a velocity of 1.5 m s-1. The downwash flow lasted more than 1 s as the helicopter passed over a given point on the ground, the downwash velocity decreased from 3 m s-1 to 1.5 to 2.5 m s-1, and the symmetry of the flow field was not maintained. This study is the first application of an ultrasonic anemometer array to measure the airflow around an unmanned helicopter and provides high-accuracy field data that can be used as a reference for future indoor and simulation studies. Keywords: Agricultural unmanned helicopter, Downwash flow velocity field, Forward flight, Hovering, Ultrasonic anemometer.

Studying the redistribution of kinetic energy between the morphologically distinct parts of the fragments cloud formed from high-velocity impact fragmentation of an aluminum sphere on a steel mesh

Numerical simulations of experiments (Shumikhin et al., 2014) on the fragmentation of aluminum spheres with diameter of 6.35 mm on single steel-mesh bumpers of different specific mass are carried out in the present work. Specific mass of the mesh bumpers in these experiments was varied by changing the diameter of the wire from which was woven the mesh. The spatial distribution of fragments, their mass and kinetic energy (KE) are determined. The results of the numerical simulations are in good agreement with the experimental data showing that the cloud of fragments composes of two morphologically distinct groups of fragments, which differ greatly in mass: the central group, consisting mainly of four large fragments, and four groups of linearly-distributed chains of smaller fragments. The numerical simulations in agreement with the experiments show that KE of the central group of fragments decreases relative to the total KE of the fragments cloud with increasing the specific mass of the mesh, while the relative KE of other smaller fragments increases.

Flow structure and fish passage performance of a brush-type fish way: a field study in the İyidere River, Turkey

The fish passage performance and flow structure of a brush fish pass were investigated at the İncirli Small Hydropower Plant on the İyidere River, located in the East Black Sea region of Turkey. The spatial distributions of velocity vectors, power velocity, Froude number and turbulent kinetic energy are presented. The flow is quasi-uniform and subcritical, which provides different migration corridors with favourable hydraulic conditions; importantly for the fish, these corridors continue through the complete fish pass. The flow–bristle interaction creates a reduced velocity and low-turbulence resting zones. In addition, the passage efficiency of the brush fish pass was assessed using passive integrated transponder telemetry. The results clearly showed that upstream passage efficiency differs between fish species: Salmo coruhensis performed better than Alburnoides fasciatus on the same fish passage. The passage efficiency for the target fish species S. coruhensis was calculated to be 82.4%. The data revealed that the brush fish passage provides passage for small-bodied fish (total body length <15cm) in a high-gradient channel with a slope of 10%. The monitoring data revealed that bristles as flexible hydraulic elements are beneficial for migrating fish.

Small nuclear power plants for power supply in arctic regions: assessment of spent nuclear fuel radioactivity

The purpose of the present study is the investigation of mass composition of long-lived radionuclides accumulated in the fuel cycle of small nuclear power plants (SNPP) as well as long-lived radioactivity of spent fuel of such reactors. Analysis was performed of the published data on the projects of SNPP with pressurized water-cooled reactors (LWR) and reactors cooled with Pb-Bi eutectics (SVBR). Information was obtained on the parameters of fuel cycle, design and materials of reactor cores, thermodynamic characteristics of coolants of the primary cooling circuit for reactor facilities of different types. Mathematical models of fuel cycles of the cores of reactors of ABV, KLT-40S, RITM-200M, UNITERM, SVBR-10 and SVBR-100 types were developed. The KRATER software was applied for mathematical modeling of the fuel cycles where spatial-energy distribution of neutron flux density is determined within multi-group diffusion approximation and heterogeneity of reactor cores is taken into account using albedo method within the reactor cell model. Calculation studies of kinetics of burnup of isotopes in the initial fuel load (235U, 238U) and accumulation of long-lived fission products (85Kr, 90Sr, 137Cs, 151Sm) and actinoids (238,239,240,241,242Pu, 236U, 237Np, 241Am, 244Cm) in the cores of the examined SNPP reactor facilities were performed. The obtained information allowed estimating radiation characteristics of irradiated nuclear fuel and implementing comparison of long-lived radioactivity of spent reactor fuel of the SNPPs under study and of their prototypes (nuclear propulsion reactors). The comparison performed allowed formulating the conclusion on the possibility in principle (from the viewpoint of radiation safety) of application of SNF handling technology used in prototype reactors in the transportation and technological process layouts of handling SNF of SNPP reactors.

Temperature decoupled viscosity-density product measurement in liquid by utilizing a dual-mode AlN-based acoustic wave resonator

In this letter, we report a two-in-one acoustic wave resonator with Rayleigh and Lamb modes for temperature decoupled viscosity-density product sensing. The Lamb mode of the resonator is sensitive to both the viscosity-density product and the ambient temperature, while the Rayleigh mode only responds to the ambient temperature and is not affected by liquid properties. These unique characteristics of the two modes are due to the different spatial distributions of the acoustic energy. Taking advantage of the aforementioned features, a beat frequency strategy is proposed to decouple the temperature influence from the viscosity-density product measurement, thus realizing temperature independent viscosity-density product sensing in a single acoustic wave resonator chip. Experimental results show that the accurate measurement of the viscosity-density product can be achieved in Newtonian liquids with a sensitivity of −0.36 MHz/kg m−2 s−0.5 within a wide temperature range from 20 °C to 80 °C. Our work holds great promise for liquid property measurement occasions with large fluctuations in ambient temperature, such as oil and gas exploration, automobile, and aeronautic applications.

Wave energy along the Romanian Southern Black Sea coast

Wave energy is among the resources to provide the most significant contribution to the European energy system in the future. Detailed wave climate analysis is needed for the selection of accurate types of wave energy generation structure and feasibility of wave energy sites. There are current studies on spatial distribution of Black Sea wave energy, that use measured or modeled data. In this study we used measured data (significant wave height and period and wind speed) recorded in 4 locations on the Romanian Southern coast during 5 years (2013-2018) in order to estimate the available wave energy potential.

Numerical simulations of magnetically confined plasmas

Since 2012, the INFN ion source group has been undertaking an intense activity on numerical modelling of magnetically confined plasmas, presently carried out in the framework of the PANDORA project. The aim is the development of a predictive tool for the design of Electron Cyclotron Resonance (ECR) Ion Sources or Traps and ECR-based Charge Breeders, able to determine spatial density and energy distributions for both electrons and ions. The work mainly concerns the study of two aspects: on one hand, the interaction of an ion beam with a magnetized plasma; on the other hand, the microwave-to-plasma coupling, including the 3D plasma electrons dynamics in the confinement magnetic field and intra-particles collisions. This contribution describes the state-of-the-art of the work on both fronts: an overview of the beam-plasma interaction, the latest results about the ECR-plasma density fine structure, as well as electrons spatial temperature distribution will be shown.

Response of the Meltwater Erosion to Runoff Energy Consumption on Loessal Slopes

Soil properties are influenced by freeze-thaw, which in turn influences soil erosion. Despite this, only a few studies have investigated the impacts on soil hydrodynamic processes. The objective of this study was to evaluate the impact of soil freezing conditions on runoff, its energy consumption, and soil erosion. A total of 27 laboratory-concentrated meltwater flow experiments were performed to investigate the soil erosion rate, the runoff energy consumption, and the relationship between the soil erosion rate and runoff energy consumption by concentrated flow under combinations of three flow rates (1, 2, and 4 L/min) and three soil conditions (unfrozen, shallow-thawed, and frozen). The individual and combined effects of soil condition, flow rate, and runoff energy consumption on the soil erosion rate were analyzed. For the same flow rate, the shallow-thawed and frozen slope produced mean values of 3.08 and 4.53 times the average soil erosion rates compared to the unfrozen slope, respectively. The number of rills in the unfrozen soil slope were 4, 3, and 2 under the flow rate of 1, 2, and 4 L/min, respectively. The number of rills in the thawed-shallow and frozen soil slope were all 1 under the flow rate of 1, 2, and 4 L/min. The rill displayed disconnected distribution patterns on the unfrozen slope, but a connected rill occurred on the shallow-thawed and frozen slopes. The average rill width on unfrozen, thawed-shallow, and frozen soil slopes increased by 1.87 cm, 4.38 cm, and 1.68 cm as the flow rate increased from 1 L/min to 4 L/min. There was no significant difference in the rill length on the frozen slope under different flow rates (p > 0.05). The runoff energy consumption ranged from unfrozen > shallow-thawed > frozen slopes at the same flow rate. The soil erosion rate had a linear relationship with runoff energy consumption. The spatial distribution of the runoff energy implied that soil erosion was mainly sourced from the unfrozen down slope, shallow-thawed upper slope, and frozen full slope.

Scratch hardness of glass

Since Mohs devised his prominent scale for mineral classification, the scratching behavior of inorganic solids has been intuitively related to material hardness. However, lateral deformation testing by instrumented indentation reveals a large variability in the resistance to scratch deformation relative to hardness, caused by the extent to which scratching requires higher work of deformation at given hardness due to material pileup and friction. Across a broad variety of glassy materials (with covalent, ionic, and metallic bonding), there is a strong correlation between scratch hardness and bulk modulus. Other than in crystalline materials, however, the spatial distribution of bond energy is heterogeneous on a molecular scale, so that no simple correlation exists with the mean-field average of bond energy density. Instead, inherent heterogeneity in the spatial distribution of bond energy and associated fluctuations in rigidity on a superstructural scale suggest an analogy between glasses and granular media.