Author
HaeOk S. Lee
Bio: HaeOk S. Lee is an academic researcher from Glenn Research Center. The author has contributed to research in topics: Radiative transfer & Scattering. The author has an hindex of 10, co-authored 17 publications receiving 1405 citations.
Papers
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TL;DR: In this paper, a finite-volume (FV) method for computing radiation heat transfer processes is presented. But the main ingredients of the calculation procedure were presented by Chai et al. The resulting method has been tested, refined and extended to account for various geometrical and physical complexities.
Abstract: This chapter presents a finite-volume (FV) method for computing radiation heat transfer processes The main ingredients of the calculation procedure were presented by Chai et al [1] The resulting method has been tested, refined and extended to account for various geometrical and physical complexities
552 citations
TL;DR: In this article, a discussion on the ray effect and false scattering occurring in discrete ordinates solution of the radiative transfer equation is presented, and four sample problems are used to explain these two effects.
Abstract: A discussion on the ray effect and false scattering occurring in discrete ordinates solution of the radiative transfer equation is presented in this article. Ray effect arises from the approximation of a continuously varying angular nature of radiation by a specified set of discrete angular directions. It is independent of the spatial discretization practice. False scattering, on the other hand, is a consequence of the spatial discretization practice and is independent of the angular discretization practice. In multidimensional computations, when a beam is not aligned with the grid line, false scattering smears the radiative intensity field. It reduces the appearance of unwanted bumps, but does not eliminate ray effect. An inappropriate view of false scattering is also presented. Four sample problems are used to explain these two effects.
286 citations
TL;DR: In this article, a finite volume method for irregular geometries is presented, and the capability of the procedure is tested using five test problems using transparent, absorbing, emitting, and anisotropic scattering media.
Abstract: A finite volume method for irregular geometries is presented in this article. The capability of the procedure is tested using five test problems. In these tests, transparent, absorbing, emitting, and anisotropically scattering media are examined. The solutions indicate that the finite volume method is a viable solution procedure for radiative heat transfer processes.
141 citations
TL;DR: In this paper, a blocked-off region procedure was proposed to model radiative transfer in irregular geometries using a Cartesian coordinates finite-volume method (FVM) for straight-edged, inclined and curved boundaries.
Abstract: This article presents a blocked-off-region procedure to model radiative transfer in irregular geometries using a Cartesian coordinates finite-volume method (FVM). Straight-edged, inclined and curved boundaries can be treated. It is capable of handling participating or transparent media enclosed by black or reflecting walls. With this procedure, irregular geometries can be specified through the problem specification portion of the program. Four test problems are used to show that the procedure is capable of reproducing available results for inclined and curved walls, transparent, nonscattering, and anisotropically scattering media.
118 citations
TL;DR: In this paper, three popular spatial differencing practices for the discrete ordinates method are examined in detail for a basic two-dimensional Cartesian coordinates problem, including positive, step, and diamond schemes.
Abstract: Three popular spatial differencing practices for the discrete ordinates method are examined in detail for a basic two-dimensional Cartesian coordinates problem. These differencing schemes are 1) positive, 2) step, and 3) diamond schemes. The diamond scheme is shown to produce negative intensities under certain conditions irrespective of the number of control volumes employed, requiring some form of negative intensity fix-up. In absorbing-emitting or absorbing-emitting-scattering media, grid refinement can result in negative intensities when the diamond scheme is used. The diamond scheme and a positive scheme, which sets the negative intensities encountered in the diamond scheme to zero or very small number for purely absorbing media, can also produce physically unrealistic overshoots. The step scheme, although not considered as accurate as the diamond scheme, gives physically realistic results for the basic problem considered. Further evaluation of Fiveland's positive conditions, and variable weight and exponential-type schemes indicate a need for alternate spatial differencing schemes that describe the physics of radiative heat transfer more accurately.
88 citations
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TL;DR: In this paper, a finite-volume (FV) method for computing radiation heat transfer processes is presented. But the main ingredients of the calculation procedure were presented by Chai et al. The resulting method has been tested, refined and extended to account for various geometrical and physical complexities.
Abstract: This chapter presents a finite-volume (FV) method for computing radiation heat transfer processes The main ingredients of the calculation procedure were presented by Chai et al [1] The resulting method has been tested, refined and extended to account for various geometrical and physical complexities
552 citations
TL;DR: In this article, a new algorithm for modeling radiative transfer in inhomogeneous three-dimensional media is described, which uses a spherical harmonic angular representation to reduce memory use and time computing the source function.
Abstract: A new algorithm for modeling radiative transfer in inhomogeneous three-dimensional media is described. The spherical harmonics discrete ordinate method uses a spherical harmonic angular representation to reduce memory use and time computing the source function. The radiative transfer equation is integrated along discrete ordinates through a spatial grid to model the streaming of radiation. An adaptive grid approach, which places additional points where they are most needed to improve accuracy, is implemented. The solution method is a type of successive order of scattering approach or Picard iteration. The model computes accurate radiances or fluxes in either the shortwave or longwave regions, even for highly peaked phase functions. Broadband radiative transfer is computed efficiently with a k distribution. The results of validation tests and examples illustrating the efficiency and accuracy of the algorithm are shown for simple geometries and realistic simulated clouds.
509 citations
TL;DR: In this article, a discussion on the ray effect and false scattering occurring in discrete ordinates solution of the radiative transfer equation is presented, and four sample problems are used to explain these two effects.
Abstract: A discussion on the ray effect and false scattering occurring in discrete ordinates solution of the radiative transfer equation is presented in this article. Ray effect arises from the approximation of a continuously varying angular nature of radiation by a specified set of discrete angular directions. It is independent of the spatial discretization practice. False scattering, on the other hand, is a consequence of the spatial discretization practice and is independent of the angular discretization practice. In multidimensional computations, when a beam is not aligned with the grid line, false scattering smears the radiative intensity field. It reduces the appearance of unwanted bumps, but does not eliminate ray effect. An inappropriate view of false scattering is also presented. Four sample problems are used to explain these two effects.
286 citations
TL;DR: Wang et al. as mentioned in this paper provided a critical overview of the key parameters that influence the performance of the photobioreactors, including light, mixing, mass transfer, temperature, pH, and capital and operating costs.
283 citations
TL;DR: In this paper, a cell-based numerical scheme is devised for computing radiative heat transfer using meshes composed of arbitrary unstructured polyhedra, which is shown to be robust and accurate through comparisons with published solutions.
Abstract: The e nite volume method has been shown to accurately predict radiative heat transfer in absorbing, emitting, and scattering media. However, computations have for the most part been restricted to structured, body-e tted meshes. In this paper a conservative cell-based numerical scheme is devised for computing radiative heat transfer using meshes composed of arbitrary unstructured polyhedra. The method is shown to be robust and accurate through comparisons with published solutions.
279 citations