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Dissipation Model (dissipation + model)

Distribution by Scientific Domains

Engineering	75%

Selected Abstracts

Predicting toxic gas concentrations resulting from enclosure fires using local equivalence ratio concept linked to fire field models

FIRE AND MATERIALS, Issue 1 2007
Z. Wang
Abstract A practical CFD method is presented in this study to predict the generation of toxic gases in enclosure fires. The model makes use of local combustion conditions to determine the yield of carbon monoxide, carbon dioxide, hydrocarbon, soot and oxygen. The local conditions used in the determination of these species are the local equivalence ratio (LER) and the local temperature. The heat released from combustion is calculated using the volumetric heat source model or the eddy dissipation model (EDM). The model is then used to simulate a range of reduced-scale and full-scale fire experiments. The model predictions for most of the predicted species are then shown to be in good agreement with the test results. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Adaptive strategy of the supersonic turbulent flow over a backward-facing step

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 11 2004
Shih-Ying YangArticle first published online: 16 MAR 200
Abstract An adaptive strategy incorporating mesh remeshing and refining is developed to study the supersonic turbulent flow over a backward-facing step on a mixed quadrilateral,triangular mesh. In the Cartesian co-ordinate system, the unsteady Favre-averaged Navier,Stokes equations with a low-Reynolds-number k,,turbulence model are solved using a locally implicit scheme with an anisotropic dissipation model. In the present adaptive strategy, two error indicators for both mesh remeshing and refining, respectively, are presented. The remeshing error indicator incorporates unified magnitude of substantial derivative of pressure and that of vorticity magnitude, whereas the refining error indicator incorporates unified magnitude of substantial derivative of pressure and that of weighted vorticity magnitude. To assess the present approach, the transonic turbulent flow around an NACA 0012 airfoil is performed. Based on the comparison with the experimental data, the accuracy of the present approach is confirmed. According to the high-resolutional result on the adaptive mesh, the structure of backstep corner vortex, expansion wave and oblique shock wave is distinctly captured. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Reactor performance with primary/secondary swirl intensity and direction in coal gasification process

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 13 2001
Han Chang Cho
Abstract In order to evaluate the effect of swirl direction and intensity of primary/secondary stream on pulverized coal gasification performance, a numerical study was conducted. Eulerian and Lagrangian approaches are used for the gas and solid phase, respectively. The computation code was formulated with PSI-cell method, k,, model for turbulence flow, Monte-Carlo method for radiative heat transfer, and eddy dissipation model for gas-phase reaction rate. A one-step two-reaction model is employed for the devolatilization of Kideco coal. Flow and reactor performance are varied by primary/secondary swirl intensity and direction. For weak primary swirl, the WSF region is minimized at the secondary vane angle beginning generation of internal recirculation zone and having peak coal burnout. The flame stability is improved at counterswirl rather than coswirl due to its intense shear. Meanwhile, for strong primary swirl, flow distribution and coal burnout are the reverse trend with those of weak swirl and the flame stability is somewhat enhanced at coswirl rather than counterswirl. To improve coal burnout and flame stability, it is confirmed that the swirl condition be proposed for moving the flame front position toward upstream. Copyright © 2001 John Wiley & Sons, Ltd. [source]

A turbulence dissipation model for particle laden flow

AICHE JOURNAL, Issue 6 2009
John D. Schwarzkopf
Abstract A dissipation transport equation for the carrier phase turbulence in particle-laden flow is derived from fundamental principles. The equation is obtained by volume averaging, which inherently includes the effects of the particle surfaces. Three additional terms appear that reveal the effect of the particles; these terms are evaluated using Stokes drag law. Two of the terms reduce to zero and only one term remains which is identified as the production of dissipation due to the particles. The dissipation equation is then applied to cases where particles generate homogeneous turbulence, and experimental data are used to evaluate the empirical coefficients. The ratio of the coefficient of the production of dissipation (due to the presence of particles) to the coefficient of the dissipation of dissipation is found to correlate well with the relative Reynolds number. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source]