Rectangular Source Research Articles

Experimental study on determination of flame height and lift-off distance of rectangular source fuel jet fires

Flame height and lift-off distance of vertically oriented rectangular source natural gas jet fires with buoyancy-momentum flame Froude number up to 3.06 are investigated by a series of experiments. The jet fires are produced by rectangular equal-area nozzles (314 mm2) with 6 aspect ratios (length to width of the nozzle exit) ranging from 5:1 to 50:1. It is found the flame height (excluding lift-off) gradually decreases as the aspect ratio increases for a given heat release rate due to an improvement of buoyant entrainment. With refinement values of the entrainment strength constant C1 for different source aspect ratios being obtained, the application of the classic correlation of Quintiere & Grove can be extended to characterize the flame height of jet fire in transition regime from buoyancy-controlled to momentum-controlled. The value of C1 can be considered as constant (0.216) due to varying slightly with increasing aspect ratios. Moreover, it is revealed that increased aspect ratio reduces the lift-off distance as a result of an improvement of mixing and entrainment in the orifice near field. A unified dimensionless correlation based on the Mixedness-Reactedness Flamelet Theory to predict lift-off distances is developed, which gives encouraging results comparing to the measured values for different source aspect ratios and different equivalent diameters.

The boundary value problem of a three-dimensional generalized thermoelastic half-space subjected to moving rectangular heat source

This paper deals with a new mathematical model of three-dimensional generalized thermoelasticity which has been improved using Lord–Shulman theory. The governing equations on non-dimensional forms have been applied to a three-dimensional half-space subjected to a rectangular moving heat source and traction-free surface by using the Laplace and double Fourier transform techniques. The inverses of the double Fourier and Laplace transforms have been calculated numerically by applying the complex formula of inversion of the transform by of the Fourier expansion method. The numerical results of the temperature increment, strain, stress, and displacement distributions have been represented in graphs for various values of the heat source speed parameter to show its effect on the thermo-mechanical waves. The heat source speed parameter leads to significant effects on both the thermal and mechanical waves.

Toward the temperature distribution on ball bearing inner rings during single-grit grinding

The paper studies the post-grinding temperature distribution on the inner ring of ball bearing 7008C. A grinding model was proposed to calculate the temperature distribution using the finite element method. The grinding process was simplified based on abrasive grain grinding motion. Our calculation takes account of the non-linear variation in physical properties of the bearing material as the temperature changes and the effects of convective heat transfer in the surrounding environment. A rectangular heat source and cyclic loading method were used to simulate the energy input during grinding, and the grinding temperature fields under different processing parameters were obtained. The calculated temperature fields are in good agreement with experimental results. The proposed model was then utilized to analyze the influence of different processing parameters on the temperature distribution, providing a basis for predicting the phase change and analyzing the post-grinding residual stress. Through processing parameter adjustments, the optimal parameter combinations that do not lead to material phase changes were identified. We hope this analysis will shed some light on the optimization of the bearing grinding process.

1P2-4 Investigation on Arrangement of Sound Source Elements to Improve Results of Reflection Point Search by Rectangular Sound Source

1P2-4 Investigation on Arrangement of Sound Source Elements to Improve Results of Reflection Point Search by Rectangular Sound Source

Синтез структуры решателя системы математического моделирования OpenFOAM для анализа теплового режима светодиодного светильника

Today LED lamps are used more and more widely in various fields of human activity. The operation of LEDs substantially depends on the thermal dissipation power and temperature. In this regard, one of the mandatory stages in the process of creating such lamps is the analysis of their thermal mode, which is necessary for the development of a heat sink. In order to analyze the thermal mode and design the heat sink for powerful LED lamps, the authors synthesized the structure of the problem solver. The new structure was based on the structure of the basic laplacianFoam solver and the application of the swak4foam library functions, which is a part of the OpenFOAM computational fluid dynamics toolbox. The results of the thermal mode simulation of the LED thermal model (a plate with a rectangular heat source) obtained using a modified solver were compared with those obtained by the proprietary solver of the CAD/CAE SolidWorks system and those obtained by analytical computation. The data adequacy of the modified solver was estimated and its practical application verified. The thermal mode of the Samsung LC009D LED, which is placed on the flat-plate finned heat sink, was analyzed. The Kaufer 5204 glue ability to be used in such design with natural convection cooling of the heat sink was tested. The glue thickness was 0.1 mm and its thermal conductivity was 1,5 W/(m•К). The heat sink’s heat transfer coefficient was 10 W/(м2•К). The paper presents corresponding temperature distributions and shows that the new technique can be used for solving problems that arise when designing LED lamps

Experimental Study on Flame‒Flame Interaction and Its Merging Features Induced by Double Rectangular Propane Diffusion Burners With Various Aspect Ratios

ABSTRACTAn experimental study is conducted to reveal the flame‒flame interaction (including completely continuous merging phenomenon, intermittent merging phenomenon, and non-merging phenomenon) of and the merging flame length of double propane diffusion flame with various aspect ratios, and its influence is measured in terms of the fire heat release rates, separate spaces between rectangular sources and different pool aspect ratios (1:1, 1:2, 1:4, and 1:8). The flames merging behaviors are recorded by a charge-coupled device (CCD) camera. The merging probability of double propane diffusion flame is found to increase with the increasing of the heat release rate and the pool aspect ratio. A correlation has been developed to estimate the merging probability of the double propane diffusion flame under different aspect ratios and separate spaces. The correlation is proposed to describe the merging flame length of two rectangular diffusion flames with various aspect ratios, which is an inverse proportional function of dimensionless heat release rate.

Subthreshold characteristics analysis and modeling of fully depleted silicon-on-insulator MOSFETs with high-k SiO2 stacked gate structure

In this paper, a high-k stacked and SiO2 gate structure is proposed for the fully depleted silicon-on-insulator (FDSOI) MOSFET. We constructed a two-dimensional (2D) model to compute its subthreshold surface potential, threshold voltage, drain-induced barrier lowering (DIBL) effect and fringing-induced barrier lowering (FIBL) effect. Given the structure and wide range of dielectric permittivities of a FDSOI MOSFET, the device in the subthreshold mode is separated into four distinct rectangular equivalent sources, 2D boundary value problems of the Poisson and Laplace equation are built on the polygon region. We used the eigenfunction expansion to solve the 2D boundary value problems and obtain their semianalytical solutions. The computational outcomes demonstrate that the high-k and SiO2 stacked gate structure can suppress the degradation of the FDSOI MOSFET threshold voltage and the aggravation of the DIBL effect. The computational cost of this model is much lesser than traditional models; thus, it can be used for circuit simulators and modeling of FDSOI MOSFETs.

Sustained Uplift at a Continental Rift Caldera

AbstractCaldera systems are often restless and experience pulses of uplift and subsidence, with a weak, but significant link to eruption. Characterizing the spatial and temporal patterns of deformation episodes provides insight into the processes responsible for unrest and the architecture of magmatic and hydrothermal systems. Here we combine interferometric synthetic aperture radar images with data from Global Positioning System and a network of seismometers at a continental rift caldera Corbetti, Ethiopia. We document inflation that started mid‐2009 and is ongoing as of 2017, with associated seismicity. We investigate the temporal evolution of the deformation source using a Hastings‐Metropolis algorithm to estimate posterior probability density functions for source model parameters and use the Akaike information criterion to inform model selection. Testing rectangular dislocation and point sources, we find a point source at a depth of 6.6 km (95% confidence: 6.3 − 6.8 km) provides the statistically justified fit. The location of this source is coincident with a conductive anomaly derived from magnetotelluric measurements. We use a joint inversion of two geodetic data sets to produce a time series, which shows a volume input of 1.0 × 107 m3/year. This is the first observation of a prolonged period of magma reservoir growth in the Main Ethiopian Rift and has implications for hazard assessment and monitoring. Corbetti is < 20 km from two major population centers and has estimated return periods of ∼500 and ∼900 years for lava flows and Plinian eruptions, respectively. Our results highlight the need for long‐term geodetic monitoring and the application of statistically robust methods to characterize deformation sources.

A study on the maximum temperature of ceiling jet induced by rectangular-source fires in a tunnel using ceiling smoke extraction

This study analyzes the physics characteristics of the flame plume temperature, induced by a ceiling jet and their coupling with an extraction flow. As it is knows, the maximum increase in the temperature of a ceiling jet is a key parameter for tunnel fire safety. The ceiling maximum temperature has been analyzed and its evolution model has also been correlated in the past. However, those previous suggested correlations had considered the fire source shape is square or circular. Actually the van shape is rectangular, the corresponding fire source may be rectangular, which is necessary to extend it to other conditions of rectangular fire sources. It has also been noted that the smoke transport characteristics changed by the ceiling smoke extraction. The aim of this experimental work is to study the maximum increase in the temperature of a ceiling jet induced by rectangular-source fires with different burner aspect ratios (ranging from 1 to 8.2) in a tunnel, using a ceiling smoke extraction. The effects of different burner aspect ratios on the ceiling maximum smoke temperature increase were studied with and without a ceiling smoke extraction. The change of the burner aspect ratios, the ceiling mechanical extraction rate, and the heat release rate were also analyzed. The evolution characteristics of the ceiling maximum plume temperature rise, considering the different burner aspect ratios, with the change in the aspect ratios of burners without the ceiling extraction were firstly obtained. A new normalized equation of the ceiling maximum plume temperature, through the addition of an impact factor for the ceiling smoke extraction rate, of a ceiling jet induced by rectangular-source fires was established. The results indicated that the new global model can effectively predict experimental data.

Angular and Spectral Distributions of the Broadband Radiation of a Photoemission Source

Angular dependence of the electric field of electromagnetic wave generated by a rectangular photoemission source with the given surface density of dipole moment is determined. The dipole emission is initiated by the wave that propagates along the surface at a superluminal phase velocity. The spectral distribution of the radiation is determined, and the angular distribution of the radiation energy is calculated.

Radiant Heat Flux Profile of Horizontally Oriented Rectangular Source Fuel Jet Fires

A series of numerical simulations were performed to investigate the flame radiant heat flux of horizontally oriented jet fires by rectangular source fuel with the same orifice area (400 mm2) but different aspect ratios (1, 2, 4). The natural gas was carried out as fuel, of which the jet velocity varied from 27.5 to 205.8 m/s. The nondimensional radiant heat flux was defined to reveal the effect of fuel jet velocity and orifice aspect ratio on radiant heat flux. Results show that the flame size increases with the increasing fuel jet velocity and the larger orifice aspect ratio results in shorter flame length. The radiant heat flux is affected by the orifice aspect ratio as the different soot particle distribution. The predicted model to characterize the radiant heat flux is proposed by taking the orifice aspect ratio into account. The prediction results of proposed model agree well with the simulated data and previous experimental results.

A Method for Generating Rectangle Area Light Source Using Water Surface Lighting

Light reconstruction refers to the calculation of light source information based on the actual lighting. In order to ensure the consistency of light illumination, the method based on light source modeling has been widely applied in real scenes, but the research on generating virtual light sources using real lighting results under virtual scenes is relatively scarce. In this paper, a method for generating a rectangle surface light for a virtual scene using water surface light images is proposed. Firstly, light shadow in water surface is extracted by the seed superpixel propagation method after superpixel segmentaion. Secondly, the boundary of each light shadow region is extracted using the superpixel label. Finally, important sampling, based on the physical rendering of the BRDF model, is used on the points in the light shadow boundary, and a rectangular area surface light source corresponding to each light shadow is calculated by a ray-traced rectangular area surface light source generation algorithm. It is proven that rectangular surface light source can be generated precisely in a virtual scene by comparing with the actual rectangular area light source.

The Temperature Profile of Rectangular Fuel Source Jet Fire with Different Aspect Ratio

Abstract With more and more natural gas has been transported by pipelines, the possibility of natural gas jet fire caused by inner or outer factors is increased gradually. That will result in casualties and domino effect to make further disaster and serious loss of property. It is imperative to study jet fire and prevent jet fire happening. This paper investigates the temperature profile for square and rectangular fuel nozzle (long side sets along transverse) horizontal jet fires. The numerical simulation code was carried out to simulate jet fires with different jet velocity varied from 27.5 m/s to 205.8 m/s. The fuel leak area for square and rectangular was same (400 mm 2 ), but the aspect ratio (width / length, W/L) were 1:1 and 1:4, respectively. Results show that the temperature increase with the jet velocity, and the relationship between maximum temperature along centreline and jet velocity is closed to line which slope is 1.82. The simple function for this connection was established. The maximum temperature of vertical direction locates at 1m from centreline, and the maximum temperature increase with jet velocity. The temperature along centreline for rectangular flame is less than square flame at same point and the high temperature area along horizontal direction is less. It is deduced the rectangular nozzle results in flame shorter and more width due to larger relative surface area and air entrainment. The high temperature area in transverse direction for rectangular nozzle is greater than square.

Coatings for FEL optics: preparation and characterization of B4C and Pt.

Large X-ray mirrors are required for beam transport at both present-day and future free-electron lasers (FELs) and synchrotron sources worldwide. The demand for large mirrors with lengths up to 1 m single layers consisting of light or heavy elements has increased during the last few decades. Accordingly, surface finishing technology is now able to produce large substrate lengths with micro-roughness on the sub-nanometer scale. At the Helmholtz-Zentrum Geesthacht (HZG), a 4.5 m-long sputtering facility enables us to deposit a desired single-layer material some tens of nanometers thick. For the European XFEL project, the shape error should be less than 2 nm over the whole 1 m X-ray mirror length to ensure the safe and efficient delivery of X-ray beams to the scientific instruments. The challenge is to achieve thin-film deposition on silicon substrates, benders and gratings without any change in mirror shape. Thin films of boron carbide and platinum with a thickness in the range 30-100 nm were manufactured using the HZG sputtering facility. This setup is able to cover areas of up to 1500 mm × 120 mm in one step using rectangular sputtering sources. The coatings produced were characterized using various thin-film methods. It was possible to improve the coating process to achieve a very high uniformity of the layer thickness. The movement of the substrate in front of the sputtering source has been optimized. A variation in B4C layer thickness below 1 nm (peak-to-valley) was achieved at a mean thickness of 51.8 nm over a deposition length of 1.5 m. In the case of Pt, reflectometry and micro-roughness measurements were performed. The uniformity in layer thickness was about 1 nm (peak-to-valley). The micro-roughness of the Pt layers showed no significant change in the coated state for layer thicknesses of 32 nm and 102 nm compared with the uncoated substrate state. The experimental results achieved will be discussed with regard to current restrictions and future developments.

Application of comprehensive geophysical prospecting method in groundwater exploration

In order to solve the problem of shortage of water resources in northern Shaanxi, we selected rectangular large loop source transient electromagnetic method with high water affinity, and radioactive α measurement method which can delineate the water storage structure, comprehensive geophysical prospecting methods to look for groundwater. Algorithm has established a forward model, and compared all-time apparent resistivity in late-time apparent resistivity is better than late. We can find out the exact location of the groundwater and thus improving wells rate by comparatively using these two kinds of geophysical prospecting method. Hydrogeology drilling confirmed water inflow of a single well can be up to 40 m3/h, it can fully cover native Domestic and Agricultural water, and provide an important basis for groundwater exploration.

Flame extension area of unconfined thermal ceiling jets induced by rectangular-source jet fire impingement

Flame extension area is a significant parameter of thermal ceiling jet, which directly determines the strong heat transfer area between the thermal plume and the building ceiling. Experiment was conducted to investigate the flame extension area induced by rectangular source fires in this work. Results show that the flame extension area data sets can not be precisely predicted by former correlations. The aspect ratio of rectangular fire source has an influence on flame extension area; the fire source with smaller aspect ratio leads to a larger flame extension area. Finally, a global non-dimensional correlation combined the effects of source-ceiling height, heat release rate, source aspect rations are proposed to predict the flame extension area of flat unconfined ceiling jets. The new proposed correlation can also provide reference for the flame extension area beneath the confined tunnel ceiling during a tunnel fire. This work can supply added results to complement the existing knowledge of flame extension beneath the building roof and it can also provide directions for the fire risk assessment and fire protection design of buildings.

Integration of deployable fluid lenses and reflectors with endoluminal therapeutic ultrasound applicators: Preliminary investigations of enhanced penetration depth and focal gain.

Catheter-based ultrasound applicators can generate thermal ablation of tissues adjacent to body lumens, but have limited focusing and penetration capabilities due to the small profile of integrated transducers required for the applicator to traverse anatomical passages. This study investigates a design for an endoluminal or laparoscopic ultrasound applicator with deployable acoustic reflector and fluid lens components, which can be expanded after device delivery to increase the effective acoustic aperture and allow for deeper and dynamically adjustable target depths. Acoustic and biothermal theoretical studies, along with benchtop proof-of-concept measurements, were performed to investigate the proposed design. The design schema consists of an array of tubular transducer(s) situated at the end of a catheter assembly, surrounded by an expandable water-filled conical balloon with a secondary reflective compartment that redirects acoustic energy distally through a plano-convex fluid lens. By controlling the lens fluid volume, the convex surface can be altered to adjust the focal length or collapsed for device insertion or removal. Acoustic output of the expanded applicator assembly was modeled using the rectangular radiator method and secondary sources, accounting for reflection and refraction at interfaces. Parametric studies of transducer radius (1-5 mm), height (3-25 mm), frequency (1.5-3 MHz), expanded balloon diameter (10-50 mm), lens focal length (10-100 mm), lens fluid (silicone oil, perfluorocarbon), and tissue attenuation (0-10 Np/m/MHz) on beam distributions and focal gain were performed. A proof-of-concept applicator assembly was fabricated and characterized using hydrophone-based intensity profile measurements. Biothermal simulations of endoluminal ablation in liver and pancreatic tissue were performed for target depths between 2 and 10 cm. Simulations indicate that focal gain and penetration depth scale with the expanded reflector-lens balloon diameter, with greater achievable performance using perfluorocarbon lens fluid. Simulations of a 50 mm balloon OD, 10 mm transducer outer diameter (OD), 1.5 MHz assembly in water resulted in maximum intensity gain of ~170 (focal dimensions: ~12 mm length × 1.4 mm width) at ~5 cm focal depth and focal gains above 100 between 24 and 84 mm depths. A smaller (10 mm balloon OD, 4 mm transducer OD, 1.5 MHz) configuration produced a maximum gain of 6 at 9 mm depth. Compared to a conventional applicator with a fixed spherically focused transducer of 12 mm diameter, focal gain was enhanced at depths beyond 20 mm for assembly configurations with balloon diameters ≥ 20 mm. Hydrophone characterizations of the experimental assembly (31 mm reflector/lens diameter, 4.75 mm transducer radius, 1.7 MHz) illustrated focusing at variable depths between 10-70 mm with a maximum gain of ~60 and demonstrated agreement with theoretical simulations. Biothermal simulations (30 s sonication, 75 °C maximum) indicate that investigated applicator assembly configurations, at 30 mm and 50 mm balloon diameters, could create localized ellipsoidal thermal lesions increasing in size from 10 to 55 mm length × 3-6 mm width in liver tissue as target depth increased from 2 to 10 cm. Preliminary theoretical and experimental analysis demonstrates that combining endoluminal ultrasound with an expandable acoustic reflector and fluid lens assembly can significantly enhance acoustic focal gain and penetration from inherently smaller diameter catheter-based applicators.

Predicting the main geometrical features of horizontal rectangular source fuel jet fires

The main geometrical features of horizontal jet fire with rectangular source fuel have seldom been revealed in the past, especially the rectangular orifice with same area but different aspect ratios. In order to better understand the rectangular jet fire, a set of numerical simulations were carried out by rectangular source fuel with same rectangular orifice area S (4 cm2) but different aspect ratios (orifice length to orifice width: L/W = 1, 2, 4) to investigate the flame shape, flame length and flame width. The simulated flame lengths and flame widths were compared with previous experimental data and calculated values using the Thornton model. The non-dimensional flame length and flame width were defined, in which the flame geometrical features were found in relation to the orifice aspect ratio and fuel jet velocity. Results show that the flame length and flame width increases with fuel jet velocity, while the flame length decreases with aspect ratio n for same orifice area, but the flame width increases simultaneously. The simulated data agree well with previous experimental data, but the predictions by Thornton model are larger than simulated and previous experimental values. The modified Thornton model is proposed considering both orifice shape and aspect ratio to apply to rectangular jet fire.

Microgravity changes at the Laguna del Maule volcanic field: Magma‐induced stress changes facilitate mass addition

Time‐dependent, or 4‐D, microgravity changes observed at the Laguna del Maule volcanic field, Chile, since 2013, indicate significant (1.5 × 1011 kg) ongoing mass injection. Mass injection is focused along the Troncoso fault, and subparallel structures beneath the lake at 1.5–2 km depth, and is best modeled by a vertical rectangular prism source. The low‐density change (156 to 307 kg/m3) and limited depth extent suggest a mechanism of hydrothermal fluid intrusion into existing voids, or voids created by the substantial uplift, rather than deeper‐sourced dike intrusion of rhyolite or basalt magma. Although the gravity changes are broadly spatially coincident with ongoing surface deformation, existing models that explain the deformation are deeper sourced and cannot explain the gravity changes. To account for this discrepancy and the correspondence in time of the deformation and gravity changes, we explore a coupled magmatectonic interaction mechanism that allows for shallow mass addition, facilitated by deeper magma injection. Computing the strain, and mean, normal, and Coulomb stress changes on northeast trending faults, caused by the opening of a sill at 5 km depth, shows an increase in strain and mean and normal stresses along these faults, coincident with the areas of mass addition. Seismic swarms in mid‐2012 to the west and southwest of the mass intrusion area may be responsible for dynamically increasing permeability on the Troncoso fault, promoting influx of hydrothermal fluids, which in turn causes larger gravity changes in the 2013 to 2014 interval, compared to the subsequent intervals.

Maximum temperature of thermal plume beneath an unconfined ceiling with different inclination angles induced by rectangular fire sources

The maximum temperature of thermal plume beneath an unconfined ceiling with different inclination angles induced by rectangular fire sources were investigated experimentally and theoretically. The experimental results show that the maximum temperature rise at the ceiling level with different ceiling inclination angles is proportional to that of a free fire thermal plume; and the maximum temperature rise increases according to the ceiling inclination angle when other experiment conditions remain unchanged for a given fire source; A new global non-dimensional correlation combined the effects of source-ceiling height, heat release rate, source aspect ratio and especially the ceiling inclination angle are proposed to predict the maximum temperature rise. The new proposed correlation can predict the maximum temperature rise beneath the ceiling induced by axisymmetric, rectangular and line fire sources uniformly. This work provides supplementary results over previous knowledge of temperature distribution beneath the inclined ceilings. It can also provide guidance for thermal risk assessment and fire safety design of open-styled spaces.