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Deciphering controls for debris-flow erosion derived from a LiDAR-recorded extreme event and a calibrated numerical model (Ro?bichelbach, Germany)
摘要： Debris flows are among the most destructive and hazardous mass movements on steep mountains. An understanding of debris-flow erosion, entrainment and resulting volumes is a key requirement for modelling debris-flow propagation and impact, as well as analysing the associated risks. As quantitative controls of erosion and entrainment are not well understood, total volume, runout and impact energies of debris flows are often significantly underestimated. Here, we present an analysis of geomorphic change induced by an erosive debris-flow event in the German Alps in June 2015. More than 50 terrestrial laser scans (TLS) of a 1.2 km long mountain torrent recorded geomorphic change in comparison to an airborne laser scan (ALS) performed in 2007. Errors were calculated using a spatial variable threshold based on the point density of ALS and TLS and the slope of the digital elevation models. Highest erosion rates approach 5.0 m3/m2 (mean 0.6 m3/m2). During the event 9,550 ± 1,550 m3 was eroded whereas only 650 ± 150 m3 was deposited in the channel. Velocity, flow pressure, momentum and shear stress were calculated using a carefully calibrated RAMMS Debris Flow model including material entrainment. Here we present a linear regression model relating debris-flow erosion rates to momentum and shear stress with an R2 up to 68 %. Channel transitions from bedrock to loose debris sections cause excessive erosion up to 1 m3/m2 due to previously unreleased random kinetic energy now available for erosion.
关键词： erosion,numerical modeling,debris flow,geomorphic change,RAMMS,LiDAR
更新于2025-09-23 15:22:29
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[IEEE 2018 VII. Lighting Conference of the Visegrad Countries (Lumen V4) - Trebic, Czech Republic (2018.9.18-2018.9.20)] 2018 VII. Lighting Conference of the Visegrad Countries (Lumen V4) - Bended Light-Guide Modeling Under Broken Cloud Arrays
摘要： Bended light-guides represent an effective way of transporting of daylight into interiors of buildings, which can not be illuminated by vertical or roof windows. The effectivity of using those kind of devices depends on their physical parameters (length, diameter, band orientation, inner reflectance). But dependence on exterior properties, such as position of Sun, turbidity of atmosphere and mainly the presence of broken cloud arrays, is prior. Experimental approach of describing behavior of a light-guide is practically impossible, because of rapid changes of exterior conditions and of unrepeatability of measurements. Therefore, there is a need of numerical modeling as accurate as possible, which takes into account a wide range of sky states and variable configuration of light-guide. So far, most of such modeling were based on using empirical models, while our approach includes local state of the atmosphere and also 3D light-guide. This contribution is focused on determining the efficiency of the bended light-guides with different bend angles and orientation of their upper part by various levels of cloud fractions and positions of Sun. As a modeling tool, a link between the programs Unisky Simulator and Holigilm was created. Unisky Simulator is designed to model sky luminance distributions for arbitrary meteorological conditions and Holigilm enables calculations of light transmittance through the bended light-guides.
关键词： bended light guide,numerical modeling,sky luminance distribution,cloud fraction
更新于2025-09-23 15:21:21
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Numerical modeling of coaxial powder stream in laser-powder-based Directed Energy Deposition process
摘要： Laser-powder-based Directed Energy Deposition (DED) process has been used extensively and becomes more and more popular in part manufacturing, repairing and prototype fabrication. It offers an effective way to deposit material via simultaneous delivery of the powders of desired material and laser beam. Complex physical events take place during the process and have great impacts on the success of the process, in which powder stream and its interaction with laser beam play a crucial role. In this paper, a new comprehensive numerical model for powder stream dynamics and heating process is developed to describe the coaxial powder stream and its interaction with laser beam. Reynolds Averaged Navier-stokes (RANS) approach is used for turbulent continuum gas flow while a discrete phase model (DPM) is applied to describe the dynamic behavior of the powder. Two-way coupling approach is adopted to account for the momentum transfer between gas and powder. A new thermal model is developed for powder stream, in which the interaction between powder stream and Gaussian laser beam is modelled through a novel numerical submodel. The obtained results of powder stream are compared with the experimental results from published literature and show good agreement.
关键词： Laser beam,Directed Energy Deposition,Coaxial powder stream,Numerical modeling
更新于2025-09-23 15:21:01
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Numerical model for small-signal modulation response in vertical-cavity surface-emitting lasers
摘要： We present a numerical model allowing for simulations of small-signal modulation (SSM) response of vertical-cavity surface-emitting lasers (VCSELs). The model of SSM response utilizes only the data provided by a static model of continuous-wave (CW) operation for a given bias voltage. Thus the fitting of dynamic measurement parameters is not needed nor used. The validity of this model has been verified by comparing experimental SSM characteristics of a VCSEL with the results of simulations. A good agreement between experiment and simulations has been observed. Based on the results obtained in the simulations of the existing laser, the impact of the number of quantum wells in the active region on the modulation properties has been calculated and analyzed.
关键词： optical data transfer,numerical modeling,semiconductor lasers,small-signal modulation response
更新于2025-09-23 15:21:01
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A forward approach for the validation of soot sizing??models using laser-induced incandescence (LII)
摘要： While validating the numerical modeling of the primary particle size distribution (PPSD) in sooting flames, a common practice is to compare the numerical results to the corresponding experimental data obtained with the Time-Resolved Laser-Induced Incandescence (TiRe-LII) technique. Since the PPSD is not directly measured by TiRe-LII, but derived with a post-processing procedure, various uncertainties and errors can potentially affect the consistency of such comparison requiring the estimation of many input parameters. On the contrary, nowadays, detailed numerical simulations provide access to a more complete set of data, which can be used to reconstruct the incandescence signal. In this work, a forward approach for the generic validation of numerical models for the PPSD is performed. It is based on the numerical reconstruction of the temporal evolution of the incandescence from the numerical results and its comparison with the measured signal. First, two indexes are proposed to quantify the agreement between the numerically synthesized and the measured signals. Then, the effectiveness of the proposed approach is demonstrated a priori by quantifying the potential errors that can be avoided with this new strategy compared to the classical approach. Finally, the feasibility of the proposed procedure is proven by comparing synthesized signals to the experimental ones available in the literature for a laminar premixed flame. It is shown that the proposed approach can be used for strengthening the analysis on numerical model performances in addition to the classical approach.
关键词： validation,soot sizing models,numerical modeling,primary particle size distribution,laser-induced incandescence
更新于2025-09-23 15:21:01
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The Thermal Behavior of a Dual-Function Solar Collector Integrated with Building: An Experimental and Numerical Study on the Air Heating Mode
摘要： This paper presented a novel solar collector that can work in air or water heating mode depending on the seasonal requirement. The dual-function solar collector (DFSC) integrated with a building as well as a reference building without the DFSC were built to test thermal behavior in passive air heating mode during winter. The buildings were equipped with an apparatus to control the room temperature. During the testing procedure, experimental study on the DFSC system was carried out under two conditions, where the indoor temperature was controlled and non-controlled. The results showed that the average temperature of the test room was about 3.43 ?C higher than that of the reference room under the non-controlled condition. When the room temperature was controlled at 18 ?C, the power consumptions of the test room and reference room were 4.322 kWh and 7.796 kWh, respectively. Consequently, the corresponding daily power consumption saved could reach up to around 3.5 kWh. Moreover, a dynamic numerical model on the DFSC along with the building was developed taking the ?n effect of the Cu-tubes into account. The numerical results are found to be well consistent with the measured data. A parametric study on with/without Cu-tubes and depth of the air channel was carried out. It is found that the existing Cu-tubes functioning as water heating can enhance the air heating ef?ciency when the depth of air channel is of a suitable size.
关键词： ?at plate solar collector,dual-function,passive air heating,numerical modeling
更新于2025-09-23 15:21:01
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Modeling of Injection-dependent Non-radiative Recombination via Point and Extended Defects in mc-Si
摘要： Non-radiative (NR) carrier recombination limits the efficiency of photovoltaic energy conversion. Minority carrier lifetimes in Si exhibit a variety of dependences on optical injection levels, depending on the types of defects present. To date, models of non-radiative recombination in silicon were proposed for point defects (e.g., Fe interstitials) and extended defects (e.g., dislocations). Direct measurement of local carrier concentration near recombination centers is technically difficult, therefore, computational modeling may be helpful to understand various carrier recombination pathways in materials such as mc-Si. In this paper, modeling is used to compare intensity-dependent NR recombination lifetimes in Si. The usefulness of the model goes beyond mc-Si photovoltaics.
关键词： interstitials,numerical modeling,non-radiative recombination,silicon,Dislocations
更新于2025-09-23 15:19:57
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Electromagnetic Physical Numerical Modeling of a GaN Distributed Transferred Electron Devicea??Based Planar Waveguide THz Oscillator
摘要： The radio frequency (RF) operation of a planar waveguide THz oscillator based on the distributed transferred electron device (DTED) is theoretically investigated by means of 2-D time-domain numerical physical modeling based on the self-consistent solution of the Maxwell and free electron energy-momentum macroscopic transport equations.
关键词： circuit design analysis,distributed transferred electron device (DTED),2-D time-domain electromagnetic physical numerical modeling,planar waveguide THz oscillator
更新于2025-09-23 15:19:57
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Dynamics of dual-pulse laser energy deposition in a supersonic flow
摘要： Dynamics of plasma generated by the dual-pulse laser in a supersonic flow was studied numerically. The mathematical model includes species, momentum, electronic, vibrational and translational energy equations for the multicomponent ionized air. The model examines temporal dynamics of the formed air plasma and how it affects the drag, pressure signature and vorticity generation in a supersonic flow around a wedge. We observed that nonequilibrium plasmas is more effective in the drag reduction compared with the simultaneous thermal energy addition. The maximum drag reduction of around 50% and the maximum drag coefficient reduction of 30% was attained through the dual-pulse laser energy deposition. Variation of the plasma spot orientation did not significantly influence the drag reduction. We suggested that the surface pressure changes were not controlled by the vorticity generation but occurred due to the density changes and the formation of the low–density plasma spot.
关键词： supersonic flow control,energy deposition,laser,numerical modeling
更新于2025-09-23 15:19:57
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Elliptic cavity filled with hybrid nanomaterial under consideration of magnetic field
摘要： CVFEM usage for modeling of nanomaterial flow style in a permeable elliptical tank including Lorentz effect was scrutinized in current research. Hybrid material with use of homogeneous model was applied and radiation term has been involved in governing equations. Outputs have been depicted in contours and plots. In addition, new formula for Nu was reported. Augment of Nu with considering greater permeability can be explained by stronger temperature gradient in cases with higher Da. Nanomaterial flow become suppress with augment of Ha which results lower Nu. As Ha augment from 0 to 20, 18% reduction has been reported in Nu. Permeability has favor influence on nanomaterial flow and the impact of Ha is opposite of permeability.
关键词： Numerical modeling,Radiation,Hybrid nanomaterial,Lorentz
更新于2025-09-23 15:19:57