The Zone Method: A New Explicit Matrix Relation to Calculate the Total Exchange Areas in Anisotropically Scattering Medium Bounded by Anisotropically Reflecting Walls

2002 ◽  
Vol 124 (4) ◽  
pp. 696-703 ◽  
Author(s):  
J. M. Goyhe´ne`che ◽  
J. F. Sacadura
Keyword(s):  
Complex Geometry ◽  
Anisotropic Scattering ◽  
Radiative Properties ◽  
Scattering Medium ◽  
Zone Method ◽  
Indirect Exchange ◽  
Matrix Relation ◽  
Definition Of ◽  
New Formulation ◽  
Total Exchange

A new explicit matrix relation for the calculation of the total exchange areas (TEA) in emitting, absorbing and anisotropically scattering semi-transparent medium bounded by emitting, absorbing and anisotropically reflecting walls has been established. It has been used to directly determine the TEA as a function of radiative properties and geometry of the medium and its boundaries. Computation calls for direct exchange areas (DEA) and indirect exchange areas (IEA). A new definition of these exchange areas reduces their integration order and provides practical energy balance relations for their computation in the case of complex geometry elements. The new formulation is applied in the case of an emitting, absorbing and linearly anisotropic scattering semi-transparent slab bounded by black surfaces. This method is also applicable to nongray medium using the weighted sum of gray gases model.

scholarly journals Large-Eddy Simulation Analyses of Heated Urban Canyon Facades

Energies ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3078
Author(s):  
Carlo Cintolesi ◽  
Francesco Barbano ◽  
Silvana Di Sabatino
Keyword(s):  
Urban Canopy ◽  
Pollutant Removal ◽  
Present Contribution ◽  
Convective Flows ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Isothermal Case ◽  
Definition Of ◽  
New Formulation ◽  
Heating Up

Thermal convective flows are common phenomena in real urban canyons and strongly affect the mechanisms of pollutant removal from the canyon. The present contribution aims at investigating the complex interaction between inertial and thermal forces within the canyon, including the impacts on turbulent features and pollutant removal mechanisms. Large-eddy simulations reproduce infinitely long square canyons having isothermal and differently heated facades. A scalar source on the street mimics the pollutant released by traffic. The presence of heated facades triggers convective flows which generate an interaction region around the canyon-ambient interface, characterised by highly energetic turbulent fluxes and an increase of momentum and mass exchange. The presence of this region of high mixing facilitates the pollutant removal across the interface and decreases the urban canopy drag. The heating-up of upwind facade determines favourable convection that strengthens the primary internal vortex and decreases the pollutant concentration of the whole canyon by 49% compare to the isothermal case. The heating-up of the downwind facade produces adverse convection counteracting the wind-induced motion. Consequently, the primary vortex is less energetic and confined in the upper-canyon area, while a region of almost zero velocity and high pollution concentration (40% more than the isothermal case) appears at the pedestrian level. Finally, numerical analyses allow a definition of a local Richardson number based on in-canyon quantities only and a new formulation is proposed to characterise the thermo-dynamics regimes.

scholarly journals FEM Simulations for the Optimization of the Inlet Gate System in Rapid Investment Casting Process for the Realization of Heat Exchangers

2021 ◽  
Author(s):  
D. Almonti ◽  
G. Baiocco ◽  
E. Mingione ◽  
N. Ucciardello
Keyword(s):  
Investment Casting ◽  
Heat Exchangers ◽  
Complex Geometry ◽  
Heat Pipes ◽  
Casting Process ◽  
Added Value ◽  
Cad Models ◽  
Gate System ◽  
Definition Of ◽  
Metallic Parts

AbstractOver the last decades, additive manufacturing (AM) has become the principal production technology for prototypes and components with high added value. In the production of metallic parts, AM allows producing complex geometry with a single process. Also, AM admits a joining of elements that could not be realized with traditional methods. In addition, AM allows the manufacturing of components that could not be realized using other types of processes like reticular structures in heat exchangers. A solid mold investment casting that uses printed patterns overcomes typical limitations of additive processes such as expensive machinery and challenging process parameter settings. Indeed, rapid investment casting provides for a foundry epoxy pattern reproducing the component to exploit in the lost wax casting process. In this paper, aluminium radiators with flat heat pipes seamlessly connected with a cellular structure were conceived and produced. This paper aims at defining and investigating the principal foundry parameters to achieve a defect-free heat exchanger. For this purpose, different device CAD models were designed, considering four pipes’ thickness and length. Finite element method numerical simulations were performed to optimize the design of the casting process. Three different gate configurations were investigated for each length. The numerical investigations led to the definition of a castability range depending on flat heat pipes geometry and casting parameters. The optimal gate configuration was applied in the realization of AM patterns and casting processes

scholarly journals Formulation of scale transformation in a stochastic data assimilation framework

2017 ◽  
Vol 24 (2) ◽  
pp. 279-291 ◽  
Author(s):  
Feng Liu ◽  
Xin Li
Keyword(s):  
Data Assimilation ◽  
Spatial Scale ◽  
Measure Theory ◽  
Stochastic Calculus ◽  
Scale Transformation ◽  
Earth Observations ◽  
Model Unit ◽  
Stochastic Data ◽  
Definition Of ◽  
New Formulation

Abstract. Understanding the errors caused by spatial-scale transformation in Earth observations and simulations requires a rigorous definition of scale. These errors are also an important component of representativeness errors in data assimilation. Several relevant studies have been conducted, but the theory of the scale associated with representativeness errors is still not well developed. We addressed these problems by reformulating the data assimilation framework using measure theory and stochastic calculus. First, measure theory is used to propose that the spatial scale is a Lebesgue measure with respect to the observation footprint or model unit, and the Lebesgue integration by substitution is used to describe the scale transformation. Second, a scale-dependent geophysical variable is defined to consider the heterogeneities and dynamic processes. Finally, the structures of the scale-dependent errors are studied in the Bayesian framework of data assimilation based on stochastic calculus. All the results were presented on the condition that the scale is one-dimensional, and the variations in these errors depend on the differences between scales. This new formulation provides a more general framework to understand the representativeness error in a non-linear and stochastic sense and is a promising way to address the spatial-scale issue.

scholarly journals Analysis of Equivalent Diaphragm Vault Structures in Masonry Construction under Horizontal Forces

Heritage ◽  
2020 ◽  
Vol 3 (3) ◽  
pp. 989-1017
Author(s):  
Pier Silvio Marseglia ◽  
Francesco Micelli ◽  
Maria Antonietta Aiello
Keyword(s):  
Seismic Design ◽  
Complex Geometry ◽  
Geometrical Parameters ◽  
Masonry Building ◽  
Masonry Construction ◽  
Horizontal Connections ◽  
Historical Masonry ◽  
Side Walls ◽  
Definition Of ◽  
The Ideal

In seismic areas, masonry construction is prone to brittle failures due to the mechanical behavior of the constituent materials and to the low capacity of force redistributions. The redistribution capacity is mainly due to the presence of horizontal connections upon the walls and to the stiffness of the roof, which is typically a vaulted structure. The modeling of the global behavior of a masonry building, taking into account the accurate stiffness of the vaults, is a major issue in seismic design and assessment. The complex geometry of the vaults can be considered as an equivalent plate, able to replicate the stiffness behavior and the force redistribution capacity of the real vault. In this study, the efforts of the authors are addressed to the definition of a plate, able to replace the vaulted surfaces in a global numerical model. The ideal diaphragm is considered as a generally orthotropic plate with the same footprint and the same thickness of the original vault. An extended parametric study was conducted in which the mechanical and geometrical parameters were varied, such as the vault thickness, its dimensions, the constraint conditions, and the possible presence of side walls. The results are presented and discussed herein, with the aim of providing useful information to the researchers and practitioners involved in seismic analyses of historical masonry construction.

scholarly journals Effective radiative properties of bounded cascade absorbing clouds: Definition of an effective single-scattering albedo

2000 ◽  
Vol 105 (D16) ◽  
pp. 20635-20648 ◽  
Author(s):  
Frédéric Szczap ◽  
Harumi Isaka ◽  
Marcel Saute ◽  
Bernard Guillemet ◽  
Andrey Ioltukhovski
Keyword(s):  
Single Scattering ◽  
Single Scattering Albedo ◽  
Radiative Properties ◽  
Definition Of

scholarly journals A Fourier approach to the inverse source problem in an absorbing and anisotropic scattering medium

2019 ◽  
Vol 36 (1) ◽  
pp. 015005 ◽  
Author(s):  
Hiroshi Fujiwara ◽  
Kamran Sadiq ◽  
Alexandru Tamasan
Keyword(s):  
Anisotropic Scattering ◽  
Inverse Source Problem ◽  
Scattering Medium
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