6 Matching Results

Search Results

Advanced search parameters have been applied.

Parallel computation of 3-D small-scale turbulence via additive turbulent decomposition

Description: Implementation and parallelization of additive turbulent decomposition is described for the small-scale incompressible Navier-Stokes equations in 3-D generalized coordinates applied to the problem of turbulent jet flow. It is shown that the method is capable of producing high-resolution local results, and that it exhibits a high degree of parallelizability. Results are presented for both distributed- and shared-memory architectures, and speedups are essentially linear with number of processors in both cases.
Date: December 31, 1995
Creator: Mukerji, S. & McDonough, J.M.
Partner: UNT Libraries Government Documents Department

A data-fitting procedure for chaotic time series

Description: In this paper the authors introduce data characterizations for fitting chaotic data to linear combinations of one-dimensional maps (say, of the unit interval) for use in subgrid-scale turbulence models. They test the efficacy of these characterizations on data generated by a chaotically-forced Burgers` equation and demonstrate very satisfactory results in terms of modeled time series, power spectra and delay maps.
Date: October 1, 1998
Creator: McDonough, J.M.; Mukerji, S. & Chung, S.
Partner: UNT Libraries Government Documents Department

Radiation turbulence interactions in pulverized coal flames: Chaotic map models of soot fluctuations in turbulent diffusion flames. Quarterly report, October 1995--December 1995

Description: In this paper, we introduce a methodology to characterize soot volume fraction fluctuations in turbulent diffusion flames via chaotic maps. The approach is based on the hypothesis that the fluctuations of properties in turbulent flames is deterministic in nature, rather than statistical. Out objective is to develop models to mimic these fluctuations. The models will be used eventually in comprehensive algorithms to study the true physics of turbulent flames and the interaction of turbulence with radiation. To this extent, we measured the time series of soot scattering coefficient in an ethylene diffusion flame from light scattering experiments. Following this, corresponding power spectra and delay maps were calculated. It was shown that if the data were averaged, the characteristics of the fluctuations were almost completely washed out. The psds from experiments were successfully modeled using a series of logistic maps.
Date: December 31, 1995
Creator: McDonough, J.M.; Menguc, M.P.; Mukerji, S.; Swabb, S.; Manickavasagam, S. & Ghosal, S.
Partner: UNT Libraries Government Documents Department

Chaotic map models of soot fluctuations in turbulent diffusion flames

Description: In this paper, the authors introduce a methodology to characterize time-dependent soot volume fraction fluctuations in turbulent diffusion flames via chaotic maps. The approach is based on the hypothesis that fluctuations of properties in turbulent flames are deterministic in nature, rather than statistical. The objective is to develop models of these fluctuations to be used in comprehensive algorithms to study the nature of turbulent flames and the interaction of turbulence with radiation. To this end the authors measured the time series of soot scattering coefficient in an ethylene diffusion flame from light scattering experiments and fit these data to linear combinations of chaotic maps of the unit interval. Both time series and power spectra can be modeled with reasonable accuracy in this way.
Date: October 1, 1998
Creator: Mukerji, S.; McDonough, J.M.; Menguec, M.P.; Manickavasagam, S. & Chung, S.
Partner: UNT Libraries Government Documents Department

Radiation/turbulence interactions in pulverized-coal flames. Second year technical progress report, September 30, 1994--September 30, 1995

Description: Our goal in this project is to investigate the interaction of radiation and turbulence in coalfired laboratory scale flames and attempt to determine the boundaries of the ``uncertainty domain`` in Figure 3 more rigorously. We have three distinct objectives: (1) To determine from experiments the effect of turbulent fluctuations on the devolatilization/pyrolysis of coal particles and soot yield, and to measure the change in the ``effective`` radiative properties of particulates due to turbulence interactions; (2) To perform local small-scale simulations to investigate the radiation-turbulence interactions in coal-fired flames starting from first principles; and (3) To develop a thorough and rigorous, but computationally practical, turbulence model for coal flames, starting from the experimental observations and small scale simulations.
Date: December 31, 1995
Creator: Menguec, M.P.; McDonough, J.M.; Manickavsagam, S.; Mukerji, S.; Wang, D.; Ghosal, S. et al.
Partner: UNT Libraries Government Documents Department

Radiation turbulence interactions in pulverized coal flames. Technical progress report, third year, second quarter, December 15, 1995--March 15, 1996

Description: In this paper, the authors discuss an experimental and theoretical methodology to characterize soot volume fraction fluctuations in turbulent diffusion flames via chaotic maps. The approach is based on the hypothesis that the fluctuations of properties in turbulent flames is deterministic in nature, rather than statistical. To this extent, the authors measured the time series of soot scattering coefficient in an ethylene diffusion flame from light scattering experiments. Following this, corresponding power spectra and delay maps were calculated. It was shown that if the data were averaged, the characteristics of the fluctuations were almost completely washed out. The psds from experiments were successfully modeled using a series of logistic maps.
Date: September 1, 1996
Creator: Menguec, M.P.; McDonough, J.M.; Manickavasagam, S.; Mukerji, S.; Swabb, S. & Ghosal, S.
Partner: UNT Libraries Government Documents Department