Rectangular Source Research Articles

Numerical investigation of the melting process in a half horizontal cylinder with radial fins

In the present study, the melting phenomenon in a half horizontal cylinder cavity with rectangular heat sources is investigated using numerical lattice Boltzmann method. The cylinder is modeled two dimensionally and its boundaries are insulated. Also, the high temperature rectangular heat sources with constant area are located in radial position on cavity. The enthalpy-based lattice Boltzmann method is used for simulating the phase change problem in the cavity. Melting of lead with Stefan number of 0.86 and Prandtl number of 0.0236 is simulated in the cavity. The effects of pertinent parameters such as the aspect ratio of the fins 1,2.5,5,7.5, the Rayleigh number 103,104,105 and the angular position of the heat sources 0,15,45 are studied on the melting phenomenon. The results show that increasing the aspect ratio of the fin with constant area reduces the melting time and increases the liquid fraction at the same time. Also higher value of the Rayleigh number improves the natural convection effect and raises the rate of melting. Finally, it is observed that the highest rate of melting is obtained when two fins are positioned at 45 degrees with aspect ratio of 7.5 at Rayleigh number of 105.

Efficiency in Parallel Computing of FDS Model for Compartment Fire Simulation: Shared Memory System

This study evaluates the computational efficiency based on the parallel processing mode and domain decomposition method of the FDS model to enhance the computational performance of fire simulation. A single compartment of dimensions 12.0 m × 3.8 m × 3.0 m is considered along with a rectangular fire source (0.4 m × 0.4 m) fueled by n-Heptane. The computational domain was divided into 136,000 cells forming a grid size of 0.1 m, and the computational efficiency for each calculation was evaluated by the wall clock time for a simulation time of 300 s using a computational framework with 24 cores of a single CPU and a 256 GB shared memory system. The MPI and hybrid mode in FDS parallel offers a greater speed-up capability than the OpenMP mode, and the domain decomposition method used greatly affects the computational efficiency. The maximum speed-up with the OpenMP mode was less than 1.5 for a single computational domain, which indicates that there is an optimal condition for thread assignment and domain decomposition in the OpenMP mode. The present study is expected to contribute toward obtaining effective fire simulation results with limited computing power and time in fire protection engineering.

Impact of a closed space rectangular heat source on natural convective flow through triangular cavity

In the existing numerical analysis is developed to impact of a closed space rectangular heat source on natural convective flow-through triangular cavity. The present problem is expressed as non-linear governing equations extended mathematical model is solved by engaging a Galerkin weighted residual process of a finite element scheme. Some investigation is acted for several Rayleigh number (Ra) at Pr = 0.71 on flow pattern and heat variation inside an enclosure. The resulting numerical clarifications of the query are exhibited graphically in phases of streamlines, velocity profiles, isotherms, Rectangular bar effectiveness, mean Nusselt number, and average fluid temperature. The acquired outcomes verified that a rate of heat variation progress with the rise of a Rayleigh number within a triangular cavity. Results are verified relating to a published work.

Correction to: NaI cubic detector full‑energy peak efficiency, including coincidence and self‑absorption corrections for rectangular sources using analytical method

Correction to: NaI cubic detector full‑energy peak efficiency, including coincidence and self‑absorption corrections for rectangular sources using analytical method

Effects of burner aspect ratio on heat flux distributions beneath unconfined ceilings with different inclination angles

The present study experimentally investigated the heat flux distributions produced by rectangular fire sources under unconfined inclined ceilings, which have not been quantified in previous studies. The source–ceiling heights, heat release rates, inclination angles of the ceilings (from 0∘ to 20∘ ), and aspect ratios of the rectangular burners (from 1 to 10) were considered comprehensively for a total of 160 sets of test conditions. The results showed that the ceiling heat fluxes in the upstream and downstream areas decreased with an increase in the radial distance. However, with an increase in the ceiling's inclination angle, the attenuation rate of the upstream ceiling heat flux decreased, while the attenuation rate of the downstream ceiling heat flux increased. The upstream and downstream heat flux distributions beneath the ceiling under all the experimental conditions could be well described by a modified model. This study provided quantitative data and a basic understanding of the heat flux distributions under an inclined ceiling induced by different rectangular-source fire impingements, which were essentially different from other previously reported ceiling jets.

Firefly Algorithm for Transient Electromagnetic Inversion

Transient electromagnetic (TEM) method is widely used in regional mineral resources surveys, environmental engineering geological surveys and shallow surface geophysical exploration, and so on. However, interpretation and inversion of TEM data is a complicated process. The traditional algorithm of TEM inversion employs the “smoke ring” fast imaging method, which can only reflect the approximate morphology of the stratigraphic model, and the inversion accuracy is low. Therefore, this method cannot meet the requirements of high-precision inversion. In this article, we present the firefly algorithm (FA) technology for TEM inversion. First of all, the response of the rectangular loop source TEM based on electric dipole integration was calculated and compared with the analytical solution results of the rectangular loop source and the accuracy of the algorithm was verified. Then, a layered medium model was established. The FA technology and “smoke ring” fast imaging method were used to perform inversion calculation, and the influence of random noise on the accuracy of the FA algorithm was analyzed. The results show that the FA has a high degree of fitting to the model, good anti-noise property, and fast search speed. Next, to illustrate the application effect of the FA algorithm in pseudo 2-D inversion, the 2-D model was established. The results show that the FA algorithm can reflect the distribution of the anomalous body more accurately, especially for the low-resistance anomalous body. Finally, we examined the effectiveness of the FA for TEM data processing by inverting survey data and comparing the results with those from the “smoke ring” fast imaging and particle swarm optimization (PSO) algorithms. The research works provide new methods and techniques for TEM data processing.

NaI cubic detector full-energy peak efficiency, including coincidence and self-absorption corrections for rectangular sources using analytical method

Low activities of radionuclides in environmental and occupational samples demand for the lower detection limits of the measuring system, which can be achieved by minimizing the source-to-detector distance. Analytical technique to calculate full-energy peak efficiency and total efficiency, self-absorption of sources and a coincidence factor of the NaI cubic scintillation detector with rectangular cavity for rectangular source have been derived. The photon path length of the volumetric sources calculated and determined source self-absorption. The photon attention by rectangular sources and detector cap materials is also calculated. In the experiments gamma aqueous source containing Eu-152 radionuclide covering range from 121 to 1408 keV was used. By comparison analytical method for calculating the full energy peak efficiency and the corrected experimental efficiency values are in good a agreement.

1Pb2-7 Investigation on Driving Signal of Sound Source Element in Reflection Point Search by Rectangular Sound Source

1Pb2-7 Investigation on Driving Signal of Sound Source Element in Reflection Point Search by Rectangular Sound Source

Understanding the effects of inclination angle and fuel bed width on concurrent flame spread over discrete fuel arrays

Concurrent flame spread over discrete fuel arrays is a dangerous flame configuration where flame spread has the same direction with induced airflow. However, inclined upward flame spread over discrete fuels is rarely concerned, especially for the varied fuel bed width. In this study, birch rods were mounted in the regular array spaced 9 mm apart. 36 groups of arrays by varying six inclination angles (θ, 15°–90° with an interval of 15°) and six kinds of column numbers (n, 1–11 with an interval of 2) were designed to study the combined effect of inclination angle and array fuel bed width on flame spread over discrete fuel arrays. Average flame spread rate was found to be independent on the fuel bed width for n>1, and mass loss rate per total mass is restricted by air entrainment when θ⩾75° or θ=60° and n>5. As the inclination angle increases, the heat transfer mechanism changed from radiant dominance to convective dominance. Moreover, in the cases of radiant dominance, average flame spread rate was proportional to the squared incident heat flux. By simplifying burning zone, a prediction model of mass loss rate was developed. Based on the aspect ratio, burning zone was further divided into line (λ⩾3) and rectangular (λ<3) fire sources, and then dimensionless correlations between the flame length and the heat release rate were proposed both for λ⩾3 and λ<3. In addition, during the upward flame spread process, flame length was found to be controlled by the competition between the accelerated upward buoyancy flow and the restriction of lateral air entrainment. This study provides a comprehensive insight for flame spread behavior of discrete fuels.

Experimental study on the characteristics of buoyancy-driven turbulent flame generated by rectangular fire sources with different length–width ratios in an open space

Fires caused by fuel leakage pose serious hazards to the city’s environment and safety. Different leakage conditions will lead to different shapes of fire sources and produce different hazards to the surrounding environment. To study the characteristics of rectangular fires, this paper conducted experimental studies on rectangular burners with different length–width ratios (n) in an open space. Propane was used as fuel. This study provides for the first time both primary data and new relationships for the temperature and velocity distribution of the flame on the horizontal section at different heights. When the heat release rate is constant, the plume mass flow rate on the horizontal section at the same height increases with the increase of the n. The expressions of temperature and velocity along the rectangular fire centerline are proposed. The empirical equations for calculating the Gaussian half-width of the square and rectangular fire plumes are presented. Finally, combining the expressions above, the correlations of flame mass flow rates in continuous and intermittent flame regions are derived and the calculated values are compared with the experimental data. It is found that the error range is less than 15%. This work can be used to predict the combustion characteristics of buoyancy-driven turbulent flames formed by gaseous fuel. It plays a guiding role in the risk assessment of the gaseous fuel transportation systems. Experimental data and related conclusions also provide important reference data and theoretical support for computational fluid dynamics (CFD) models.

A global model for flame pulsation frequency of buoyancy-controlled rectangular gas fuel fire with different boundaries

Pulsation frequency is an important characteristic parameter for buoyancy-controlled fuel diffusion flames. Fire experiments of a rectangular source with different aspect ratios were conducted in an open space and against sidewalls made from a calcium silicate board. Due to the blocking effect to restrict air entrainment to fire plumes, sidewall significantly reduced the flame pulsation frequency. Furthermore, the effect of the fuel exit velocity on the pulsation frequency became intense as the aspect ratio of the rectangle was increased to 7.45. Based on the modified hydraulic diameter for a rectangular fire source with a sidewall and corner, a global model was developed for predicting the flame pulsation frequency of the rectangular fire source with free, sidewall, and corner boundaries. The coefficient of determination of this improved model is 0.9991, and the local errors of this model are less than 15% considering all of the experimental data in the present work and available in the literature. This work provides a method for predicting flame pulsation frequency, accounting for sidewall effect and aspect ratio.

Wide‐viewing integral imaging display using rectangular light sources

AbstractWe propose a wide‐viewing integral imaging display. It consists of an organic light‐emitting diode, a barrier array, and a liquid crystal panel. The organic light‐emitting diode generates the rectangular light sources, and the liquid crystal panel displays the elemental images. The barriers are introduced to separate adjacent rectangular light sources and corresponding elemental images. Lights emitting from the rectangular light sources only illuminate the corresponding elemental images. The horizontal viewing angle and the luminance are both enhanced by increasing the horizontal width of the point light source. A prototype of the proposed integral imaging display is developed, and the experiment results agree well with the theory.

Experimental study and analysis of radiation heat fluxes received by a floor beneath an inclined ceiling

SummaryThis study experimentally investigates the radiation heat flux distribution received on the floor due to fire plume impinging upon an inclined ceiling, which has not been quantified previously. The radiation heat fluxes were measured on the floor for 160 experimental conditions, involving various fire source heat release rates, source‐ceiling heights, angles of ceiling inclination and dimensions (aspect ratios) of the rectangular sources. The main findings include that the declining rate of the radiation heat flux along with distance received by the downstream floor decreases, while that received by the upstream floor increases, with the increasing of ceiling inclination angle. The radiation heat flux received by the floor is higher as the ceiling inclination angle is smaller for the downstream side, while it is lower as the ceiling inclination angle is smaller for the upstream side. Both of these variations can be explained by change of the flow distribution as well as flame length due to combustion and heat released in the two directions beneath the inclined ceiling. Further, a model with various fire source heat release rates, source‐ceiling height, and ceiling inclination angles is proposed, to globally describe the radiation heat flux received by both the upstream and downstream floors.

Support vector regression method for predicting temperatures of heat sources cooled by forced convection in a horizontal channel

This paper presents the novel concept of Support Vector Regression method for predicting the temperatures of rectangular heat sources with dummy components cooled by forced convection in a horizontal channel. The substrate board considered for study is FR4 equipped with silicon heat sources resembles IC chips on printed circuit board. Six heat sources with three dummy components of four different sizes are considered for study. Three dimensional steady state numerical simulations have been performed using finite element method based commercially available software COMSOL Multiphysics 5.4. Laminar non-isothermal fluid flow with conjugate heat transfer module is used to study heat transfer in solids and fluid region. Air cooling of heat sources with dummy components is carried out to study heat transfer characteristics. Flowing air velocity of 2.5 m/s with uniform heat flux value of 5000 W/m2 is considered for study. Support Vector Regression programming is performed using Python programming language to predict temperatures of heat sources to explore optimal configuration. Random hundred different configurations were studied out of which 80% were used in training and 20% used for validation. Results show that the simulated and predicted temperature values are in agreements of ⩽10 %.

Experimental study on the radiant heat flux of wall-attached fire plume generated by rectangular sources

Radiant heat flux of fire plume is an essential parameter indicating the hazards of a fire. In this work, fire experiments of a wall-attached fire with different aspect ratios were conducted. In addition, the effect of the sidewall on mean flame height and radiant heat flux of the rectangular fire was investigated. The sidewall causes a decrease in air entrainment; therefore, the mean flame height is observed to increase. The radiant heat flux increased owing to the increase in flame height and thermal radiation from the heated sidewall. Experimental results of the mean flame height are consistent with those predicted by an existing model. This validated the reliability of the experimental setup for a rectangular wall-attached fire. Furthermore, a model based on the increase in flame height and thermal radiation from the heated sidewall was developed to estimate the radiant heat flux from a rectangular wall-attached fire. The error in prediction was less than 15% for this model.

Hollow rectangular multi-Gaussian Schell-model source.

We introduced a new class of a partially coherent source that can generate a field with a hollow rectangular profile, named the hollow rectangular multi-Gaussian Schell-mode source. The dependence of distribution of far-zone spectral density on the properties of the proposed source was analyzed. The results show that one can control the distribution properties of the far-zone intensity profile, including the thickness of the hollow edge, the shape of the hollow, the size of the hollow, and the orientation of the hollow, by adjusting the corresponding structural parameters of the source.

Characterizing Subsurface Rectangular Tilted Heat Sources Using Inductive Thermography

In this study, we characterize the lateral dimension, depth, and inclination of buried tilted rectangular heat sources from time domain temperature data measured at the surface. The heat sources are representative for planar defects that emit heat in thermographic tests with internal burst excitation. We present a semi-analytical expression for the evolution of the surface temperature distribution. The emitted flux, dimensions and inclination of the heat source are determined by fitting the model to two perpendicular surface temperature profiles and the temperature history at one point of the surface. We show that the sensitivity of the data to the geometrical parameters of the heat source decreases as the angle it makes with the surface increases. The study also shows that the optimum duration of the excitation corresponds to a thermal diffusion length covering the distance from the surface to the deepest end of the heat source. The accuracy and precision of the results for different noise levels and inclinations have been tested by fitting the model to synthetic data with added noise. Fittings of experimental induction thermography data on 3D printed photo-polymeric resin samples containing calibrated Cu slabs confirm that it is possible to characterize tilted rectangular heat sources from surface temperature data.

Static Ground Displacement for an Induced Earthquake Recorded on Broadband Seismometers

ABSTRACTUsing geodetic methods, significant static ground deformation has been observed for many large natural earthquakes. Some of the largest earthquakes induced by hydraulic-fracturing operations have been observed in the Western Canada Sedimentary Basin; however, because of the size and depths of these events, the associated static ground deformations have not yet been observed using traditional geodetic techniques. A seismic processing technique, developed for small volcano-seismic events, has the potential to resolve micrometer-scale static displacements using broadband seismic data. In this study, we test this processing method using vertical component broadband recordings of an Mw 4.1 event acquired at four nearby broadband seismometers. Estimated static displacements at the four stations are compared with the theoretical surface displacement field for a dislocation on a finite rectangular source within a homogeneous, elastic half-space. The theoretical displacements have the same polarities as the measured displacements across the seismic network and have similar amplitudes for three of the four stations. However, one station yielded unstable results, which shows that care must be taken when using this method. These results suggest that this processing method has potential for obtaining surface deformation for small to moderate-sized earthquakes using broadband data.

Verification of the welding heat source models in arc welding and hybrid plasma-MAG welding processes based on temperature field tests

Hybrid welding processes belong to a new group of welding varieties that most often combine two classic welding methods, such as laser welding with MIG/MAG welding or plasma welding with MAG welding. Modeling of welding stresses in this type of welding requires the definition of a new type of heat source model that combines a concentrated stream of energy with a classic heat source, which occurs in an electric arc. The paper presents the results of temperature field modeling in conventional MAG welding and hybrid plasma-MAG welding. In the first case, the heat source model described by Goldak was used, and in the second case, the Goldak model was combined with the developed rectangular heat source model with a homogeneous distribution. The temperature distributions obtained from the simulations were verified by spot temperature measurements during welding with thermocouples. A fairly good agreement of the numerical analysis results with the temperature measurements for MAG welding was obtained, while in the case of hybrid welding the discrepancies between the modeling and temperature measurements were greater. The results were discussed, indicating potential causes and factors influencing the obtained test results.

Sensitivity of InSAR and teleseismic observations to earthquake rupture segmentation

SUMMARYEarthquakes often rupture across more than one fault segment. If such rupture segmentation occurs on a significant scale, a simple point-source or one-fault model may not represent the rupture process well. As a consequence earthquake characteristics inferred, based on one-source assumptions, may become systematically wrong. This might have effects on follow-up analyses, for example regional stress field inversions and seismic hazard assessments. While rupture segmentation is evident for most Mw &amp;gt; 7 earthquakes, also smaller ones with 5.5 &amp;lt; Mw &amp;lt; 7 can be segmented. We investigate the sensitivity of globally available data sets to rupture segmentation and their resolution to reliably estimate the mechanisms in presence of segmentation. We focus on the sensitivity of InSAR (Interferometric Synthetic Aperture Radar) data in the static near-field and seismic waveforms in the far-field of the rupture and carry out non-linear and Bayesian optimizations of single-source and two-sources kinematic models (double-couple point sources and finite, rectangular sources) using InSAR and teleseismic waveforms separately. Our case studies comprises of four Mw 6–7 earthquakes: the 2009 L’Aquila and 2016 Amatrice (Italy) and the 2005 and 2008 Zhongba (Tibet) earthquakes. We contrast the data misfits of different source complexity by using the Akaike informational criterion (AIC). We find that the AIC method is well suited for data-driven inferences on significant rupture segmentation for the given data sets. This is based on our observation that an AIC-stated significant improvement of data fit for two-segment models over one-segment models correlates with significantly different mechanisms of the two source segments and their average compared to the single-segment mechanism. We attribute these modelled differences to a sufficient sensitivity of the data to resolve rupture segmentation. Our results show that near-field data are generally more sensitive to rupture segmentation of shallow earthquakes than far-field data but that also teleseismic data can resolve rupture segmentation in the studied magnitude range. We further conclude that a significant difference in the modelled source mechanisms for different segmentations shows that an appropriate choice of model segmentation matters for a robust estimation of source mechanisms. It reduces systematic biases and trade-off and thereby improves the knowledge on the rupture. Our study presents a strategy and method to detect significant rupture segmentation such that an appropriate model complexity can be used in the source mechanism inference. A similar, systematic investigation of earthquakes in the range of Mw 5.5–7 could provide important hazard-relevant statistics on rupture segmentation. In these cases single-source models introduce a systematic bias. Consideration of rupture segmentation therefore matters for a robust estimation of source mechanisms of the studied earthquakes.