The discrete ordinates method is used to develop a solution to an inverse radiation problem of source term in one-dimensional semitransparent plane-parallel media with opaque and specularly reflecting boundaries. It i...The discrete ordinates method is used to develop a solution to an inverse radiation problem of source term in one-dimensional semitransparent plane-parallel media with opaque and specularly reflecting boundaries. It is assumed that, with the exception of the inhomogeneous source term, all aspects of the radiation transport problem are known. A method is developed to determine the inhomogeneous source term from specified incident radiation intensities on the boundaries. The inverse problem is solved using conjugate gradient method that minimizes the error between the incident radiation intensities calculated and the experimental data. The effects of singl-scattering albedo, scattering asymmetry parameter, wall emissivity, the diffuse fraction of reflectivity, and the optical thickness on the accuracy of the inverse are investigated. The results show that the source term can be estimated accurately, even with noisy data.展开更多
This paper presents a method(F method)for determining the optical constants and the thicknesses of semi- transparent thin films.It has the following distinctive features:high precision;rapid determination of the measu...This paper presents a method(F method)for determining the optical constants and the thicknesses of semi- transparent thin films.It has the following distinctive features:high precision;rapid determination of the measured quantities;wide range of convergence of solutions;capable of judging whether or not the results are reasonable.In order to meet the needs of application and engineering design,a family of curves designated Fig.n-F was prepared.Using it n,k,d of the films can be conveniently and accurately determined.From the optical constants and the thicknesses of the films determined by the F method,all important thermal radiation properties of the semi-transparent films needed in application can be obtained.展开更多
The importance of radiative heat transfer in the simulation of indoor-fire has been studied.Computer codes have been developed based on four-flux model and discrete transfer model,respectively.Evaluation of the codes ...The importance of radiative heat transfer in the simulation of indoor-fire has been studied.Computer codes have been developed based on four-flux model and discrete transfer model,respectively.Evaluation of the codes against exact analytic solution and experimental data shows that the discrete transfer model gives numerical results with acceptable accuracy while the four-flux model underpredicts the heat fluxes although the gen- eral trend is reasonable.Numerical studies have been performed of two-dimensional,axisymmetric turbulent, buoyancy-controlled indoor fire.The computational results show that neglecting radiation in the simulation can cause overprediction of 500K in the maximum temperature and less uniform velocity field compared to the prediction by discrete transfer model.The four-flux method has been found to produce less uniform velocity and temperature values than discrete transfer model,but is more economic in computation.展开更多
文摘The discrete ordinates method is used to develop a solution to an inverse radiation problem of source term in one-dimensional semitransparent plane-parallel media with opaque and specularly reflecting boundaries. It is assumed that, with the exception of the inhomogeneous source term, all aspects of the radiation transport problem are known. A method is developed to determine the inhomogeneous source term from specified incident radiation intensities on the boundaries. The inverse problem is solved using conjugate gradient method that minimizes the error between the incident radiation intensities calculated and the experimental data. The effects of singl-scattering albedo, scattering asymmetry parameter, wall emissivity, the diffuse fraction of reflectivity, and the optical thickness on the accuracy of the inverse are investigated. The results show that the source term can be estimated accurately, even with noisy data.
文摘This paper presents a method(F method)for determining the optical constants and the thicknesses of semi- transparent thin films.It has the following distinctive features:high precision;rapid determination of the measured quantities;wide range of convergence of solutions;capable of judging whether or not the results are reasonable.In order to meet the needs of application and engineering design,a family of curves designated Fig.n-F was prepared.Using it n,k,d of the films can be conveniently and accurately determined.From the optical constants and the thicknesses of the films determined by the F method,all important thermal radiation properties of the semi-transparent films needed in application can be obtained.
基金Sponsored by the National Natural Science Foundation of China
文摘The importance of radiative heat transfer in the simulation of indoor-fire has been studied.Computer codes have been developed based on four-flux model and discrete transfer model,respectively.Evaluation of the codes against exact analytic solution and experimental data shows that the discrete transfer model gives numerical results with acceptable accuracy while the four-flux model underpredicts the heat fluxes although the gen- eral trend is reasonable.Numerical studies have been performed of two-dimensional,axisymmetric turbulent, buoyancy-controlled indoor fire.The computational results show that neglecting radiation in the simulation can cause overprediction of 500K in the maximum temperature and less uniform velocity field compared to the prediction by discrete transfer model.The four-flux method has been found to produce less uniform velocity and temperature values than discrete transfer model,but is more economic in computation.
