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Chung, P. M.

Publications and source records attributed to Chung, P. M..

17 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

An analysis of turbulent diffusion flame in axisymmetric jet

The kinetic theory of turbulent flow was employed to study the mixing limited combustion of hydrogen in axisymmetric jets. The integro-differential equations in two spatial and three velocity coordinates describing the combustion were reduced to a set of hyperbolic partial differential equations in the two spatial coordinates by a binodal approximation. The MacCormick's finite difference method was then employed for solution. The flame length was longer than that predicted by the flame-sheet analysis, and was found to be in general agreement with a recent experimental result. Increase of the turbulence energy and scale resulted in an enhancement of the combustion rate and, hence, in a shorter flame length. Details of the numerical method as well as of the physical findings are discussed.

Chung, P. M.↗
NASA NTRS1979

Turbulent flow and pumping in the cavity of a chemical laser

The kinetic theory of turbulent flow is employed to estimate an upper bound on the production rates of the lasing species in a free turbulent mixing layer. The maximum production rate is found to be about one third to one half of that predicted by a flame-sheet theory. The effects of turbulence scale and energy on the overall reaction rates are discussed and the gross structure of the combustion zone is determined.

Hayday, A. A.↗
NASA NTRS1976

Diffusivity in turbulent fluid containing two dominant scales, and compressible shear layer according to a kinetic theory

The solution of the two nonequilibrium-degree kinetic equation was first determined for the effective length scale and turbulence energy for a spatially homogeneous turbulence field with two characteristic length scales, where the source for one family of eddies exists. This solution was applied to the evaluation of the eddy diffusivity in the combustion chamber of an internal combustion engine. The result was compared with another existing solution. This was carried out to demonstrate the feasibility of obtaining an effective length-scale equation within the context of the kinetic theory. A formulation and partial solution of the compressible plane shear layer are also presented.

Chung, P. M.↗
NASA NTRS1976

A kinetic-theory approach to turbulent chemically reacting flows

The paper examines the mathematical and physical foundations for the kinetic theory of reactive turbulent flows, discussing the differences and relation between the kinetic and averaged equations, and comparing some solutions of the kinetic equations obtained by the Green's function method with those obtained by the approximate bimodal method. The kinetic method described consists essentially in constructing the probability density functions of the chemical species on the basis of solutions of the Langevin stochastic equation for the influence of eddies on the behavior of fluid elements. When the kinetic equations are solved for the structure of the diffusion flame established in a shear layer by the bimodal method, discontinuities in gradients of the mean concentrations at the two flame edges appear. This is a consequence of the bimodal approximation of all distribution functions by two dissimilar half-Maxwellian functions, which is a very crude approximation. These discontinuities do not appear when the solutions are constructed by the Green's function method described here.

Chung, P. M.↗
NASA NTRS1973

Turbulent shear flow of continuum plasma.

The turbulence structure of weakly ionized, continuum plasma is analyzed with emphasis on the turbulent fluctuation and the transport properties of the ionized species. The mean gradients of the velocity and ionized-species concentrations are considered to be uniform. It is assumed that the turbulence Reynolds number is small and that the turbulence field is homogeneous in order to close the dynamic equations of turbulence. It was found that the ratio of the Debye shielding length to the local integral scale of turbulence must be sufficiently small in order for the detailed quasi-neutrality to prevail. The condition of the detailed quasi-neutrality is necessary, in addition to the equal mean concentrations of electrons and ions, in order for the turbulence properties involving the electrons to be the same as those involving the ions.

Chung, P. M.↗
NASA NTRS1972

Diffusion flame in homologous turbulent shear flows.

The simplifed statistical theory developed previously is employed to analyze the equilibrium and near-equilibrium combustion of initially unmixed reactants. It is found that the flame zone in the limit of large Damkohler numbers is very thick and is of the order of the local integral scale of turbulence. This is in contrast to the existing phenomenological theories which predict the infinitesimally thin flame sheet, in the same limit, as it is with the laminar diffusion flame. Qualitative agreements with the available experimental results are shown. It is found that singularities exist at the edges of the flame which are removed as Damkohler number is reduced. Also, it is found that the heat transfer may take place against the local mean temperature gradient in certain regions within the flame.

Chung, P. M.↗
NASA NTRS1972

Turbulent properties of a continuum plasma in shear flow.

The detailed turbulence structure of a weakly ionized, continuum plasma is analyzed. This analysis, when extended to high Reynolds number turbulent boundary layers, shows that the ratio of the electron to ion saturation currents decreases by an order of magnitude as compared to the laminar case.

Marcisz, T. J.↗
NASA NTRS1971

A turbulence description of couette flow

Statistical mechanics for wall shear turbulence in couette flow based on Brownian motion and comparison with stochastic theory based on Navier-Stokes equation

Chung, P. M.↗