EFFECTS OF TURBULENCE-RADIATION INTERACTIONS IN A NON-PREMIXED TURBULENT METHANE-AIR FLAME

This work studied a turbulent flame and analyzed the interaction between turbulence and radiation (TRI). The problem consists of a non-premixed turbulent methane flame surrounded by a low-velocity air coflow identified as Flame DLR-A. The steady laminar diffusion flamelet (SLDF) model is used to solve the chemical kinetics. To generate the flamelet library, turbulence-chemistry interaction is taken into account through previously assumed probability density functions (PDF) of mean scalars. Radiative heat flux is calculated with the discrete ordinates method, considering the Gray Gas model (GG). Turbulence is solved with k-ε Standard model and TRI methodology is based on temperature self-correlation. The solution is obtained using ANSYS/Fluent code coupled with user-defined functions (UDFs). Results indicated that the temperature and chemical species predictions are little affected by TRI, while the radiative quantities (radiative heat flux on the domain wall) are importantly affect by TRI effects

APPLICATION OF THE WEIGHTED-SUM-OF-GRAY-GASES MODEL TO NON-HOMOGENEOUS H2O/CO2 MIXTURES FOR MEDIA WITH NON-GRAY WALLS

The spectral modeling of the thermal radiation in participating media is a research area that has received constant attention due to its importance in a great number of engineering problems, especially because the highly irregular spectral dependence of the absorption coefficient of a gas with the wavenumber requires the adoption of alternative methods to determine the radiative properties. This work brings a numerical study of a one-dimensional system, bounded by perfectly diffuse and non-gray walls, filled by a non-homogeneous and non-isothermal mixture of water vapor and carbon dioxide. The main objective is to estimate the magnitude of the deviations in treating surfaces that should be considered non-gray as black or gray. The spectral modeling of the problem is performed by the weighted-sum-of-gray-gases (WSGG) model and the accuracy of the solution methodology developed is evaluated by means of comparisons against the results obtained by line-by-line (LBL) integration

ANALYSIS OF THE TURBULENCE-RADIATION INTERACTION IN A METHANE-AIR DIFFUSION FLAME

The phenomenon of turbulence-radiation interaction (TRI) has been demonstrated experimentally, theoretically and numerically to be important in a great number of engineering applications. This paper presents a numerical study on the subject, focusing on a methane-air diffusion flame confined in a rectangular enclosure. An open source, Fortran-based code, Fire Dynamics Simulator, is used for the analysis. Large Eddy Simulation (LES) is adopted to model the turbulence, and to resolve the sub-grid scale terms the dynamic Smagorinsky model is employed. To solve the radiative heat transfer, the finite volume method is used alongside the Weighted-Sum-of-Gray-Gases model. The main objective of the present work is to assess the magnitude of TRI effects for the configuration proposed. For this purpose, the time-averaged wall heat fluxes and volumetric radiative heat source, calculated from the LES results, are compared with those same quantities obtained by independent simulations initialized using mean temperature and species concentration fields. TRI effects are found to be responsible for differences up to 30% between results considering and neglecting turbulent fluctuations. These differences are larger for the radiative heat source and for the radiative heat flux to the walls, smaller for the total heat flux, and almost negligible for the convective heat flux. The influence of the fuel stream Reynolds number on the TRI effects is also evaluated, and a slight decrease on the magnitude of TRI is observed with the increase of that parameter

Transporte de NO3 e NH4 em agregados de Latossolo Vermelho com e sem atividade biológica.

Objetivou-se, com este trabalho, avaliar a influência do tamanho dos agregados de um Latossolo Vermelho distrófico sobre as transformações e transporte do amônio e do nitrato em condições de presença e ausência de atividade biológica. Utilizou-se o fatorial 23 x 4, com fatores e níveis: vegetação de cobertura do solo (cerrado e milho ); atividade biológica (com e sem esterilização do solo); fontes de N da solução com 10 mmol L-1 de N, para saturação das colunas (Ca(NO3)2 e NH4CI) e classes de agregados (2,0 a 1,0; 1,0 a 0,5; 0,5 a 0,25 e 0,25 a 0,105 mm). Na primeira eluição, o efluente das colunas contendo microbiota ativa e saturação com Ca(NO3)2 apresentou teor de NO3 - menor no efluente dos agregados de 0,25 a 0,105 mm; já em condições de esterilização, ocorreu o inverso: maior concentração do NO3 -no efluente dos agregados de 0,25 a 0,105 mm. Para as colunas saturadas com NH4CI, na primeira eluição os teores do NH4+ foram maiores nos efluentes dos agregados de 0,25 a 0,105 mm para todas as combinações de cobertura de solo e esterilização, enquanto na presença da microbiota ativa o efluente dos agregados de 0,25 a 0,105 mm apresentou teor semelhante ao dos agregados de 0,5 a 0,25 mm

Negative Even Grade mKdV Hierarchy and its Soliton Solutions

In this paper we provide an algebraic construction for the negative even mKdV hierarchy which gives rise to time evolutions associated to even graded Lie algebraic structure. We propose a modification of the dressing method, in order to incorporate a non-trivial vacuum configuration and construct a deformed vertex operator for $\hat{sl}(2)$, that enable us to obtain explicit and systematic solutions for the whole negative even grade equations

ANALYSIS OF THE TURBULENCE-RADIATION INTERACTION IN A METHANE-AIR DIFFUSION FLAME

The phenomenon of turbulence-radiation interaction (TRI) has been demonstrated experimentally, theoretically and numerically to be important in a great number of engineering applications. This paper presents a numerical study on the subject, focusing on a methane-air diffusion flame confined in a rectangular enclosure. An open source, Fortran-based code, Fire Dynamics Simulator, is used for the analysis. Large Eddy Simulation (LES) is adopted to model the turbulence, and to resolve the sub-grid scale terms the dynamic Smagorinsky model is employed. To solve the radiative heat transfer, the finite volume method is used alongside the Weighted-Sum-of-Gray-Gases model. The main objective of the present work is to assess the magnitude of TRI effects for the configuration proposed. For this purpose, the time-averaged wall heat fluxes and volumetric radiative heat source, calculated from the LES results, are compared with those same quantities obtained by independent simulations initialized using mean temperature and species concentration fields. TRI effects are found to be responsible for differences up to 30% between results considering and neglecting turbulent fluctuations. These differences are larger for the radiative heat source and for the radiative heat flux to the walls, smaller for the total heat flux, and almost negligible for the convective heat flux. The influence of the fuel stream Reynolds number on the TRI effects is also evaluated, and a slight decrease on the magnitude of TRI is observed with the increase of that parameter

Universal and nonuniversal contributions to block-block entanglement in many-fermion systems

We calculate the entanglement entropy of blocks of size x embedded in a larger system of size L, by means of a combination of analytical and numerical techniques. The complete entanglement entropy in this case is a sum of three terms. One is a universal x and L-dependent term, first predicted by Calabrese and Cardy, the second is a nonuniversal term arising from the thermodynamic limit, and the third is a finite size correction. We give an explicit expression for the second, nonuniversal, term for the one-dimensional Hubbard model, and numerically assess the importance of all three contributions by comparing to the entropy obtained from fully numerical diagonalization of the many-body Hamiltonian. We find that finite-size corrections are very small. The universal Calabrese-Cardy term is equally small for small blocks, but becomes larger for x>1. In all investigated situations, however, the by far dominating contribution is the nonuniversal term steming from the thermodynamic limit.Comment: 6 pages, 3 figure