Ray Effect Mitigation Through Reference Frame Rotation

Tencer, John

doi:10.1115/1.4033699

Cited by 18 publications

(10 citation statements)

References 22 publications

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“…Several methods have been proposed to simultaneously satisfy conservation of energy and maintain the shape of the phase function [58], [59]. Modifications of the angular discretization procedure have been used to reduce the ray effects, namely by averaging the computed solution for several reference frame orientations [60], by employing a goal-based angular adaptivity method [61] or a goal-oriented regional angular adaptive algorithm [62]. The application to problems with specular reflection was addressed in Refs.…”

Section: Discrete Ordinates and Finite Volume Methodsmentioning

confidence: 99%

The impact of radiative heat transfer in combustion processes and its modeling – with a focus on turbulent flames

Liu

Consalvi

Coelho

et al. 2020

Fuel

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Radiative heat transfer (RHT) is often the dominant mode of heat transfer in flames, fires, and combustion systems and affects significantly temperature distributions directly and kinetically controlled chemical processes indirectly. Modeling RHT accurately in multidimensional flames and combustion systems is challenging mainly due to the highly spectral dependence of radiative properties of combustion products, the high computational cost of solving the radiative transfer equation (RTE), and the strong turbulence and radiation interactions (TRI). Significant progress has been made in all the three aspects in the last three decades and the state-of-the-art models and methods have been incorporated into CFD practice for modeling fires, turbulent jet flames, and turbulent combustion in combustion systems. In this article, we first discuss the coupling between RHT and combustion and the important role played by RHT in some fundamental flame phenomena. Then we discuss the state-of-the-art radiation models with a focus on RTE solvers, radiative property models and TRI. Next, we review the recent simulations of turbulent combustion systems involving these state-of-the-art radiation models. Finally, we provide concluding remarks and some potential research areas to advance RHT modeling in multiphase reacting flows. Nomenclature, , area normal to directions x, y and z [m 2 ] non-grey stretching factor for WSGG, SLW, and FSK methods absorption cross-section of a soot primary particle [m 2 ] absorption cross-section of a soot aggregate [m 2 ] diameter [m] , , integral over a control angle of the direction cosines relative to x, y and z-axis particle size parameter [-] radiant fraction [-] array of variables defining the absorption coefficient, = { , , , } Ω solid angle [sr] Subscript Fuel direction j spectral line S soot at a given wavenumber Superscript aggregate lth direction (DOM) or lth control angle (FVM) mth direction (DOM) or mth control angle (FVM) primary particle Operators 〈 〉 Reynolds averaged quantity ′ Reynolds fluctuating quantity ̅ filtered (or resolved) quantity ′′ subgrid-scale (or residual) fluctuation Recently, quasi-MC methods [43], [44] were employed to solve RHT problems in 3D participating media, aimed at the improvement of the convergence rate, and therefore the computational efficiency. In these methods, the random numbers are replaced by low-

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Section: Discrete Ordinates and Finite Volume Methodsmentioning

confidence: 99%

The impact of radiative heat transfer in combustion processes and its modeling – with a focus on turbulent flames

Liu

Consalvi

Coelho

et al. 2020

Fuel

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“…In terms of ray effects, in addition to increase discrete directions, to modify direction layout is another common remedy [11][12][13][14][15]. Numerical experiments have been conducted by Li et al [11] showing that ray effects can be reduced by modifying direction layouts, and three corresponding countermeasures were proposed in their paper.…”

Section: Introductionmentioning

confidence: 99%

“…Numerical experiments have been conducted by Li et al [11] showing that ray effects can be reduced by modifying direction layouts, and three corresponding countermeasures were proposed in their paper. Tencer [12] proposed a ray effects mitigation technique by averaging the computed results of various direction layouts, which are generated by arbitrarily rotating the reference layout. Quadrature rotation was also applied to solve time-dependent transport and results showed that ray effects were reduced significantly, including for small numbers of quadrature points [13].…”

Section: Introductionmentioning

confidence: 99%

Ray Effects and False Scattering in Improved Discrete Ordinates Method

Cheng¹,

Yang²,

Huang³

2021

Energies

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The improved discrete ordinates method (IDOM) developed in our previous paper is extended to solve radiative transfer in three-dimensional radiative systems with anisotropic scattering medium. In IDOM, radiative intensities in a large number of new discrete directions are calculated by direct integration of the conventional discrete ordinates method (DOM) results, and radiative heat flux is obtained by integrating radiative intensities in these new discrete directions. Ray effects and false scattering, which tend to compensate each other, are investigated together in IDOM. Results show that IDOM can mitigate both of them effectively with high computation efficiency. Finally, the effect of scattering phase function on radiative transfer is studied. Results of radiative heat flux at boundaries containing media with different scattering phase functions are compared and analyzed. This paper indicates that the IDOM can overcome the shortages of the conventional DOM well while inheriting its advantages such as high computation efficiency and easy implementation.

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“…More sophisticated strategies to mitigate ray effects make use of biased quadrature sets, which reflect the importance of certain ordinates [1]. In [23], the angular flux is computed for several differently oriented quadrature sets and ray effects are then mitigated by averaging over all solutions. Moreover, a method combining S N and P N to reduce rays has been introduced in [10] with further refinements given in [9,21,18].…”

Section: Introductionmentioning

confidence: 99%

Ray effect mitigation for the discrete ordinates method through quadrature rotation

Camminady

Frank

Küpper

et al. 2019

Journal of Computational Physics

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Solving the radiation transport equation is a challenging task, due to the high dimensionality of the solution's phase space. The commonly used discrete ordinates (S N ) method suffers from ray effects which result from a break in rotational symmetry from the finite set of directions chosen by S N . The spherical harmonics (P N ) equations, on the other hand, preserve rotational symmetry, but can produce negative particle densities. The discrete ordinates (S N ) method, in turn, by construction ensures non-negative particle densities.In this paper we present a modified version of the S N method, the rotated S N (rS N ) method. Compared to S N , we add a rotation and interpolation step for the angular quadrature points and the respective function values after every time step. Thereby, the number of directions on which the solution evolves is effectively increased and ray effects are mitigated. Solution values on rotated ordinates are computed by an interpolation step. Implementation details are provided and in our experiments the rotation and interpolation step only adds 5% to 10% to the runtime of the S N method. We apply the rS N method to the line-source and a lattice test case, both being prone to ray effects. Ray effects are reduced significantly, even for small numbers of quadrature points. The rS N method yields qualitatively similar solutions to the S N method with less than a third of the number of quadrature points, both for the line-source and the lattice problem. The code used to produce our results is freely available and can be downloaded [4].

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Ray Effect Mitigation Through Reference Frame Rotation

Cited by 18 publications

References 22 publications

The impact of radiative heat transfer in combustion processes and its modeling – with a focus on turbulent flames

The impact of radiative heat transfer in combustion processes and its modeling – with a focus on turbulent flames

Ray Effects and False Scattering in Improved Discrete Ordinates Method

Ray effect mitigation for the discrete ordinates method through quadrature rotation

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