scholarly journals Discrete Ordinate Method for the Estimation of Downward Solar Flux in Penang, Malaysia

2020 ◽  
Vol 489 ◽  
pp. 012032
Author(s):  
H Yusuf ◽  
N Mohamed Tahrin ◽  
H.S Lim
Keyword(s):  
Solar Flux ◽  
Discrete Ordinate Method ◽  
Discrete Ordinate

scholarly journals Modelling and Simulation of the Radiant Field in an Annular Heterogeneous Photoreactor Using a Four-Flux Model

2018 ◽  
Vol 2018 ◽  
pp. 1-16 ◽  
Author(s):  
O. Alvarado-Rolon ◽  
R. Natividad ◽  
R. Romero ◽  
L. Hurtado ◽  
A. Ramírez-Serrano
Keyword(s):  
Photocatalytic Oxidation ◽  
Reaction Rate ◽  
Comsol Multiphysics ◽  
Discrete Ordinate Method ◽  
Discrete Ordinate ◽  
Cylindrical Coordinates ◽  
Volumetric Rate ◽  
Flux Model ◽  
Reaction Rate Equation ◽  
Good Agreement

This work focuses on modeling and simulating the absorption and scattering of radiation in a photocatalytic annular reactor. To achieve so, a model based on four fluxes (FFM) of radiation in cylindrical coordinates to describe the radiant field is assessed. This model allows calculating the local volumetric rate energy absorption (LVREA) profiles when the reaction space of the reactors is not a thin film. The obtained results were compared to radiation experimental data from other authors and with the results obtained by discrete ordinate method (DOM) carried out with the Heat Transfer Module of Comsol Multiphysics® 4.4. The FFM showed a good agreement with the results of Monte Carlo method (MC) and the six-flux model (SFM). Through this model, the LVREA is obtained, which is an important parameter to establish the reaction rate equation. In this study, the photocatalytic oxidation of benzyl alcohol to benzaldehyde was carried out, and the kinetic equation for this process was obtained. To perform the simulation, the commercial software COMSOL Multiphysics v. 4.4 was employed.

scholarly journals Optimization and parallelization of the discrete ordinate method for radiation transport simulation in OpenFOAM: Hierarchical combination of shared and distributed memory approaches

2021 ◽  
Vol 1 ◽  
pp. 2
Author(s):  
Jose Moreno-SanSegundo ◽  
Cintia Casado ◽  
David Concha ◽  
Antonio S. Montemayor ◽  
Javier Marugán
Keyword(s):  
Distributed Memory ◽  
Radiation Transport ◽  
Computational Time ◽  
Limiting Factor ◽  
Discrete Ordinate Method ◽  
Discrete Ordinate ◽  
Radiation Sources ◽  
Transport Problems ◽  
Volume Models ◽  
Spatial Cell

This paper describes the reduction in memory and computational time for the simulation of complex radiation transport problems with the discrete ordinate method (DOM) model in the open-source computational fluid dynamics platform OpenFOAM. Finite volume models require storage of vector variables in each spatial cell; DOM introduces two additional discretizations, in direction and wavelength, making memory a limiting factor. Using specific classes for radiation sources data, changing the store of fluxes and other minor changes allowed a reduction of 75% in memory requirements. Besides, a hierarchical parallelization was developed, where each node of the standard parallelization uses several computing threads, allowing higher speed and scalability of the problem. This architecture, combined with optimization of some parts of the code, allowed a global speedup of x15. This relevant reduction in time and memory of radiation transport opens a new horizon of applications previously unaffordable.

scholarly journals An Efficient Implementation of the Finite-volume Method For the Solution of Radiation Transport in Circuit Breakers

2017 ◽  
Vol 4 (2) ◽  
pp. 177-181
Author(s):  
A. Mazaheri ◽  
J. Y. Trépanier ◽  
R. Camarero ◽  
P. Robin-Jouan
Keyword(s):  
Finite Volume ◽  
Radiation Transport ◽  
Computation Time ◽  
Discrete Ordinate Method ◽  
Discrete Ordinate ◽  
Circuit Breakers ◽  
Explicit Approach ◽  
Order Of Magnitude ◽  
Implicit Approach ◽  
Volume Method

In this paper, we propose to revisit the method to solve the radiation transport equation in circuit breakers to reduce the computation time. It is based on an explicit approach using a space marching algorithm. The method can further be accelerated using a Cartesian grid and using the axisymmetric assumption. Comparisons performed in terms of accuracy and efficiency between the P1 model, the implicit finite-volume discrete ordinate method and the space-marching finite-volume discrete ordinate method show that the explicit approach is more that an order of magnitude faster than the implicit approach, for the same accuracy.

A Novel Dynamic Quadrature Scheme for Solving Boltzmann Equation with Discrete Ordinate and Lattice Boltzmann Methods

2012 ◽  
Vol 11 (4) ◽  
pp. 1397-1414 ◽  
Author(s):  
C. T. Hsu ◽  
S. W. Chiang ◽  
K. F. Sin
Keyword(s):  
Boltzmann Equation ◽  
Lattice Boltzmann Method ◽  
Lattice Boltzmann ◽  
Physical Space ◽  
Velocity Space ◽  
Discrete Ordinate Method ◽  
Discrete Ordinate ◽  
Mean Velocity ◽  
Quadrature Scheme ◽  
Boltzmann Method

AbstractThe Boltzmann equation (BE) for gas flows is a time-dependent nonlinear differential-integral equation in 6 dimensions. The current simplified practice is to linearize the collision integral in BE by the BGK model using Maxwellian equilibrium distribution and to approximate the moment integrals by the discrete ordinate method (DOM) using a finite set of velocity quadrature points. Such simplification reduces the dimensions from 6 to 3, and leads to a set of linearized discrete BEs. The main difficulty of the currently used (conventional) numerical procedures occurs when the mean velocity and the variation of temperature are large that requires an extremely large number of quadrature points. In this paper, a novel dynamic scheme that requires only a small number of quadrature points is proposed. This is achieved by a velocity-coordinate transformation consisting of Galilean translation and thermal normalization so that the transformed velocity space is independent of mean velocity and temperature. This enables the efficient implementation of Gaussian-Hermite quadrature. The velocity quadrature points in the new velocity space are fixed while the correspondent quadrature points in the physical space change from time to time and from position to position. By this dynamic nature in the physical space, this new quadrature scheme is termed as the dynamic quadrature scheme (DQS). The DQS was implemented to the DOM and the lattice Boltzmann method (LBM). These new methods with DQS are therefore termed as the dynamic discrete ordinate method (DDOM) and the dynamic lattice Boltzmann method (DLBM), respectively. The new DDOM and DLBM have been tested and validated with several testing problems. Of the same accuracy in numerical results, the proposed schemes are much faster than the conventional schemes. Furthermore, the new DLBM have effectively removed the incompressible and isothermal restrictions encountered by the conventional LBM.

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