Distribution Of Energy Input Research Articles

Nanosecond volume discharge in the non-stationary high-speed profiled channel flow

The aim of the work is an experimental and numerical investigation of the interaction between the pulse volume discharge with a high-speed flow in the rectangular profiled channel (obstacle on the bottom wall). The special type of combined discharge—pulse volume discharge with preionization by an ultraviolet radiation from plasma sheets—is used. The flow around the obstacle influences the pulse discharge plasma distribution. The short-pulse initiation of a high power discharge leads to the effects observable in the time range up to millisecond. Ultrafast local heating of the medium with the formation of blast (shock) waves is carried out during the creation of a high nonequilibrium sub microsecond pulsed plasma. The duration of the shock-wave effect of the pulsed discharge is from 20 to 120 μs in supersonic and transonic flow. The spatially inhomogeneous distribution of energy input in a supersonic flow associates with the density lowest areas, which occur in a gas flow regime in a channel with an obstacle on the bottom. Discharge localization regions are sources of more intense wall surface local heating observed in the infrared range. A numerical calculation is carried out in order to match the calculated and experimental gas dynamical configurations.

A Visualization Method of Quantifying Carbon Combustion Energy in the Sintering Packed Bed

Carbon combustion provides energy to reach essential temperatures in the sintering packed bed. A visual and quantitative evaluation on the energy input distribution inside the bed is urgently demanded to learn energy-saving potential of sintering process and subsequently to suppress greenhouse gas emission. Herein, after a two-dimensional simplified model of sintering packed bed is established and validated against the temperature measurements on the sintering pot experiment, this work highlights a mesh-based visualization method of quantifying carbon combustion energy in the packed bed. To be more specific, local transient temperature distributions in all meshed grids are first extracted from numerical simulation results. Then each grid is colorized according to the specific criteria on five pre-defined energy input (EI) states. As a result, the effects of carbon segregation and cross-sectional shape on the energy efficiency of sintering packed bed are quantitatively compared and optimized. These two case studies not only demonstrate the principle, process, and application of the proposed visualization method, but also stimulate its future potential in various areas.

Impact of laser beam oscillation strategies on surface treatment of microalloyed steel

The depth homogeneity of laser-treated zones is one possible factor to define the quality and efficacy of altered mechanical properties in materials. For instance, half-rounded cross-sectional shapes of laser hardened zones using Gaussian beams provide dissimilar hardened depth in the edges and center of the treated area. This means that the in-depth distribution of compressive residual stress varies between the edges and the center of the hardened area. Nonhomogeneity of compressive residual stress distributions can inhibit fatigue properties and can lead to product failure. The utilization of oscillated laser beams has been proven to improve the welding efficiency and energy input distribution to the material, which promises achieving a homogeneous depth of laser-treated zones in hardening applications. Therefore, this work examines the influence of triangular, square, and circular beam oscillation strategies on the energy input distribution during the process and the geometry of the laser-treated zones on microalloyed steel. Laser beam pathways were assembled using a vector graphic editor to visualize the energy distribution from each oscillation strategy. Cross section images of the hardened tracks were taken and related to the thermal energy input profiles. It was revealed that each oscillation strategy demonstrates characteristic temporal and spatial thermal energy input distribution, influencing the geometry of the hardened zone. The circular oscillation strategy produced a widely constant depth in contrary to the triangular and square beam oscillation due to its characteristic energy distribution that allows homogeneous heat dissemination in the material. This confirms that the laser beam oscillation strategy can tailor the energy input distribution to optimize the processing outcome.

Research on track overlapping during Selective Laser Melting of powders

The Selective Laser Melting (SLM) process fabricates components from powders by adding material and its processing principle is based on track overlapping regime, which has been studied in this paper. The inter-layer stagger scanning strategy was employed to avoid nonuniform distribution of energy input. By theoretical deduction and experimental observation, three types of overlapping regime were revealed: intra-layer overlapping regime, inter-layer overlapping regime and mixed overlapping regime with coexistence of the first two types. The overlapping patterns and the corresponding microstructures were then discussed. Experimental result showed that specimens fabricated by inter-layer overlapping regime had high relative density when track space was not larger than 0.2mm. A cooling insert with relative density of about 93% was also obtained at track space of 0.12mm.

Explosive Compaction of Sand Foundation: Laboratory Test

The charge weight, charge placement (in profile) and depth of charges are important factors in design of Explosive Compaction for saturated loose sand. Six laboratory tests have been conducted to investigate the potential of charge weight, charge placement (in profile) and depth of charge in blast densification, Concentrated Charge has adopted in two of them, the others are Decked or Tiered Charges. Variation of cone penetration tests and ground profile changes were measured. The results of laboratory tests prove the decked and tiered charges are more effective for ground treatment in explosive compaction, more specifically, the more uniform distribution of energy input, the more effective for ground treatment. However, the effective limits of these relationships have not been well defined in qualitative guidance.

Comparison of analytical and numerical welding temperature field calculation

Analytical and numerical methods are used to estimate the temperature field due to the heat effects of welding. Numerical techniques are more adapted for industrial complex applications where analytical solutions do not exist yet. However, computational time is much lower with analytical models and a combination of both methods is investigated. Therefore, the two approaches are introduced and confronted in this paper. The finite-element software Ansys has been used for numerical simulations and Scilab for analytical simulations. In order to get a similar result quality, both methods have to be analysed and compared with respect to boundary conditions. These configurations are presented in this paper. Before starting any analysis, the analytical and numerical models have to be comparable. For the numerical simulation, every in- or output is given in discrete form and, for the analytical simulation, in continuous form. Thus, an analysis of the energy input distribution in both models is compulsory to ensure that the same amount of energy is applied. After this first study, a comparison of the analytical and numerical temperature field simulation is done from a fix point source in an infinite volume in steady state to a moving point source in a finite dimension in a transient state. A good agreement between the analytical and the numerical simulation results is found. However, some techniques, like a consideration of an image heat source for the analytical model or the selection of boundary conditions for the numerical model, need to be taken into consideration when the degree of complexity of the study (finite dimension or cooling time) increases. The limit of the comparison is reached when the geometry becomes too complex and when the effect of variable thermal properties with temperature cannot be neglected.

Gasdynamic effects of periodic energy input into a divergent channel

The influence of the space-time characteristics of a pulsed energy source on a supersonic flow through a divergent channel is considered. It is found that low-frequency energy sources used for generating the thrust may provide a considerably higher specific force than continuous energy input. The influence of the duration of periodically applied energy pulses on the specific force is shown to be nonmonotonic. Short pulses provide a much higher specific force compared with steady energy input. The nonuniformity of the energy input distribution along the channel is found to have a noticeable effect on the specific force.

AGN effect on cooling flow dynamics

We analyzed the feedback of AGN jets on cooling flow clusters using three-dimensional AMR hydrodynamic simulations. We studied the interaction of the jet with the intracluster medium and creation of low X-ray emission cavities (Bubbles) in cluster plasma. The distribution of energy input by the jet into the system was quantified in its different forms, i.e. internal, kinetic and potential. We find that the energy associated with the bubbles, (pV+γ pV/(γ−1)), accounts for less than 10 percent of the jet energy.

The microarcsecond sky and cosmic turbulence

Radio waves are imprinted with propagation effects from ionized media through which they pass. Owing to electron density fluctuations, compact sources (pulsars, masers, and compact extragalactic sources) can display a wide variety of scattering effects. These scattering effects, particularly interstellar scintillation, can be exploited to provide superresolution, with achievable angular resolutions (≲1 μas) far in excess of what can be obtained by very long baseline interferometry on terrestrial baselines. Scattering effects also provide a powerful sub-AU probe of the microphysics of the interstellar medium, potentially to spatial scales smaller than 100 km, as well as a tracer of the Galactic distribution of energy input into the interstellar medium through a variety of integrated measures. Coupled with future γ-ray observations, SKA observations also may provide a means of detecting fainter compact γ-ray sources. Though it is not yet clear that propagation effects due to the intergalactic medium are significant, the SKA will either detect or place stringent constraints on intergalactic scattering.

Effect of Vacuum on Mixing Behavior in a Ladle. A Watermodel Study.

Rising inert gas bubbles in a vacuum ladle experience phenomenal expansion in the top portion of the bath due to the steep variation of absolute pressure. This makes the top layers of the melt substantially more agitated than the bottom regions. The present study is an attempt to characterize the mixing process in such a vacuum ladle by a watermodel, simulating the effect of extra stirring in the top layers of the bath. The simulation is done through a two-level blowing, in which an additional gas stream is injected into the main bubble plume at 75 % of the bath height. It was found that mixing under such a simulated condition is worse than that in a bottom purged ladle, for identical total energy inputs to the bath. The study reveals that the energy imparted in the top layers of the liquid in the vacuum ladle is less effective in promoting mixing. The pattern of stirring energy input distribution along the height of the bath is an important parameter in determining the mixing behavior in a ladle, apart from the total energy input.

Modeling the F layer during specific geomagnetic storms

Important progress has been made recently in developing an understanding of the effects of geomagnetic storms in the thermosphere and ionosphere. Numerical simulations of theoretical storms with the coupled thermosphere ionosphere model (CTIM) have provided a better understanding of the dynamics of the upper atmosphere and have also permitted the identification of the processes responsible for global storm effects at highlatitude and midlatitude. The theory developed based on the model simulations can explain most of the apparent coherence of local time and seasonal dependencies and the apparent randomness in the longitudinal response of the global ionosphere, uncovered through statistical analysis of storm observations. A true test of the model and the theory is their ability to predict the large‐scale distribution of storm effects for specific storms. In this paper, CTIM simulation results for the December 7–9, 1982, period are presented. We compare model results with DE 2 temperature and plasma density data. We also compare modeled electron densities with ionosonde data from several sectors in both hemispheres. The global characteristics of the response are reproduced by the model, and we are able to explain the pronounced longitude differences in the summer hemisphere. The Australian sector passes through midnight during the main driven phase of the storm and experiences the largest energy input and the largest neutral composition changes. The deepest ionospheric negative phase seen in ionosonde data is over Australia and is consistent with this interpretation. Given the large uncertainties in our knowledge of the magnitude and spatial distribution of energy input during a particular storm, predicting local changes is still a challenge.

Ionospheric heating in the F -region

Measurements of electron temperature made in Ariel I have been analyzed to calculate the ionospheric energy input required to maintain the electron temperature above the ion temperature. The results are found to be consistent with the energy input due to photo-ionization in the daytime, provided that allowance is made for the effects of the escaping flux of photoelectrons spiralling upwards along the geomagnetic field lines which impartenergy to the ionosphere by electron-electron interaction. However, it is found that during the night an energy input of particle origin is observed, a close agreement being found between the distribution of energy input and that of the fluxes of low-energy particles observed by Savenko, Shavrin & Pisavenko 1963. The particle flux contributes less than 30% to the heat input in the daytime and its diurnal variation is small.