A hybrid ray-tracing and radiosity method for calculating radiation transport and illuminance distribution in spaces with venetian blinds

Solar Energy ◽  
2012 ◽  
Vol 86 (11) ◽  
pp. 3109-3124 ◽  
Author(s):  
Ying-Chieh Chan ◽  
Athanasios Tzempelikos
2006 ◽  
Vol 128 (9) ◽  
pp. 945-952 ◽  
Author(s):  
Sandip Mazumder

Two different algorithms to accelerate ray tracing in surface-to-surface radiation Monte Carlo calculations are investigated. The first algorithm is the well-known binary spatial partitioning (BSP) algorithm, which recursively bisects the computational domain into a set of hierarchically linked boxes that are then made use of to narrow down the number of ray-surface intersection calculations. The second algorithm is the volume-by-volume advancement (VVA) algorithm. This algorithm is new and employs the volumetric mesh to advance the ray through the computational domain until a legitimate intersection point is found. The algorithms are tested for two classical problems, namely an open box, and a box in a box, in both two-dimensional (2D) and three-dimensional (3D) geometries with various mesh sizes. Both algorithms are found to result in orders of magnitude gains in computational efficiency over direct calculations that do not employ any acceleration strategy. For three-dimensional geometries, the VVA algorithm is found to be clearly superior to BSP, particularly for cases with obstructions within the computational domain. For two-dimensional geometries, the VVA algorithm is found to be superior to the BSP algorithm only when obstructions are present and are densely packed.


2008 ◽  
Vol 4 (S259) ◽  
pp. 103-104 ◽  
Author(s):  
Rolf Kuiper ◽  
Mario Flock ◽  
Hubert Klahr

AbstractWe briefly overview our newly developed radiation transport module for MHD simulations and two actual applications. The method combines the advantage of the speed of the Flux-Limited Diffusion approximation and the high accuracy obtained in ray-tracing methods.


Author(s):  
Mahesh Ravishankar ◽  
Sandip Mazumder

The first-order spherical harmonics method (or P1 approximation) has found prolific usage for approximate solution of the radiative transfer equation (RTE) in participating media. However, the accuracy of the P1 approximation deteriorates as the optical thickness of the medium is decreased. The Modified Differential Approximation (MDA) was originally proposed to remove the shortcomings of the P1 approximation in optically thin situations. This article presents algorithms to apply the MDA to arbitrary geometry—in particular, three-dimensional (3D) geometry with obstructions, and inhomogeneous media. The wall-emitted component of the intensity was computed using a combined view-factor and ray-tracing approach. The Helmholtz equation, arising out of the medium-emitted component, was solved using an unstructured finite-volume procedure. The general procedure was validated against benchmark Monte Carlo results. The accuracy of MDA was found to be far superior to the standard P1 approximation in optically thin situations, and comparable to the P1 approximation in optically thick situations. Calculation and storage of the view-factor matrix was found to be a major shortcoming of the MDA, and several strategies to reduce both memory and computational time are discussed and demonstrated. In addition, for inhomogeneous media, calculation of optical distances requires a ray-tracing procedure, which was found to be a bottleneck from a computational efficiency standpoint.


2010 ◽  
Vol 34 (3) ◽  
pp. 150-156 ◽  
Author(s):  
Mohamad HAMADY ◽  
Michel AUBÈS ◽  
Georges ZISSIS

Author(s):  
Bidisha Bandyopadhyay ◽  
Christian Fendt ◽  
Dominik R G Schleicher ◽  
Christos Vourellis

Abstract In 2019, the Event Horizon Telescope Collaboration (EHTC) has published the first image of a supermassive black hole (SMBH) obtained via the Very Large Baseline Interferometry (VLBI) technique. In the future, it is expected that additional and more sensitive VLBI observations will be pursued for other nearby Active Galactic Nuclei (AGN), and it is therefore important to understand which possible features can be expected in such images. In this paper, we post-process General Relativistic Magneto-Hydrodynamical (GR-MHD) simulations which include resistivity, thus providing a self-consistent jet formation model, including resistive mass loading of a wind launched from a disc in Keplerian rotation. The ray-tracing is done using the General Relativistic Ray-Tracing code GRTRANS assuming synchrotron emission. We study the appearance of the black hole environment including the accretion disc, winds and jets under a large range of condition, varying black hole mass, accretion rate, spin, inclination angle, disc parameters and observed frequency. When we adopt M87-like parameters, we show that we can reproduce a ring-like feature (similar as observed by the EHT) for some of our simulations. The latter suggests that such Keplerian disc models thus could be consistent with the observed results. Depending on their masses, accretion rates, spin and the sensitivity of the observation, we note that other SMBHs may show additional features like winds and jets in the observations.


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