The near field dynamics of buoyant reactive jets with adjacent sidewalls is investigated by time-dependent three-dimensional direct simulations. The physical problem is a fuel jet issuing vertically into an oxidant am...The near field dynamics of buoyant reactive jets with adjacent sidewalls is investigated by time-dependent three-dimensional direct simulations. The physical problem is a fuel jet issuing vertically into an oxidant ambient envi- ronment in a corner configuration with sidewall boundaries. Simulation results are presented for two cases with different jet nozzle geometries: a corner-round reactive jet and a cor- ner-square reactive jet with the same cross-sectional area on the nozzle plane. Buoyancy-induced large vortical structures evolve spatially in the flow field and transition to turbulence occurs downstream. Calculation of the mean flow properties shows that entrainment of the corner-round jet is stronger than that of the corner-square jet due to the stronger vortex deformation in the corner-round case.展开更多
A computational model of three-dimensional, time-dependent flame spread in microgravity environment is presented. The solid is assumed to be a thermally-thin, pyrolysing cellulosic sheet. The gas phase model includes ...A computational model of three-dimensional, time-dependent flame spread in microgravity environment is presented. The solid is assumed to be a thermally-thin, pyrolysing cellulosic sheet. The gas phase model includes the full Navier-Stokes equations with density and pressure variations and six-flus model of radiation heat transfer. The solid phase model consists of continuity and energy eqllations whose solution provides boundary conditions for the gas phase equations. In the numerical procedure, the gas-and solid-phase equations are solved sepaxately and iteratively at each time step. Predictions have been made of flame spread in slow forced flow under gravitational acceleration normal to fuel surface and flame spread in a quiescent environment in an enclosed chamber under gravitational acceleration parallel to fuel surface. Numerical simulations show that, under microgravity, slow-flow conditions, flame spread process is highly unsteady with the upstream flame spreads faster than the downstream flame after a period of ignition. It has also been shown that the level of microgravity has a significant effect on the name spread process.展开更多
The theory of three-dimensional discrete transfer radiation model is expounded in detail in this paper. The computer program has also been written using this method here. Two kinds of radiation heat transfer problemS...The theory of three-dimensional discrete transfer radiation model is expounded in detail in this paper. The computer program has also been written using this method here. Two kinds of radiation heat transfer problemS have been simulate with numerical method using the computer program, and the predictions carried out are quite in agreement with the exed results. It shows that the threedimensional discrete transfer radiation model is one of the suitable way to obtain heat flux and temperature in various applications.展开更多
This paper presents the zone modeling analysis of a single compartment flashover fire. Two criteria are ap- plied in the model to judge the onset of ignition for different combustibles. By calculating the total receiv...This paper presents the zone modeling analysis of a single compartment flashover fire. Two criteria are ap- plied in the model to judge the onset of ignition for different combustibles. By calculating the total received energy through radiation or the surface temperature of the combus- tible, the fire growth can be quantitatively determined. The improved zone fire model shows the influence of different combustibles upon the fire growth. This model is better than the traditional zone model because the common criteria of flashover, i.e. an upper layer temperature of 600℃ and the heat radiation intensity received by the floor of 20 kW/m2, have not been applied in it.展开更多
Based on the basic idea of zone modeling method, a two-layer zone model is developed and programmed to calculate the fire growth and smoke spread in a multi-room building subjected to a fire.The related predictiVe equ...Based on the basic idea of zone modeling method, a two-layer zone model is developed and programmed to calculate the fire growth and smoke spread in a multi-room building subjected to a fire.The related predictiVe equations, numerical simulation method and sub-models implemented in this model are concisely described. A set of experimental data from Cooper’s work at NIST for a two-room compatment fire are chosen for comparison with the model and program, and the numerical results fundamentally agree well with the experimental data. Then, an example of numerical calculation of a two-story building fire is presented, and the relevant output results are given and analyzed.展开更多
文摘The near field dynamics of buoyant reactive jets with adjacent sidewalls is investigated by time-dependent three-dimensional direct simulations. The physical problem is a fuel jet issuing vertically into an oxidant ambient envi- ronment in a corner configuration with sidewall boundaries. Simulation results are presented for two cases with different jet nozzle geometries: a corner-round reactive jet and a cor- ner-square reactive jet with the same cross-sectional area on the nozzle plane. Buoyancy-induced large vortical structures evolve spatially in the flow field and transition to turbulence occurs downstream. Calculation of the mean flow properties shows that entrainment of the corner-round jet is stronger than that of the corner-square jet due to the stronger vortex deformation in the corner-round case.
文摘A computational model of three-dimensional, time-dependent flame spread in microgravity environment is presented. The solid is assumed to be a thermally-thin, pyrolysing cellulosic sheet. The gas phase model includes the full Navier-Stokes equations with density and pressure variations and six-flus model of radiation heat transfer. The solid phase model consists of continuity and energy eqllations whose solution provides boundary conditions for the gas phase equations. In the numerical procedure, the gas-and solid-phase equations are solved sepaxately and iteratively at each time step. Predictions have been made of flame spread in slow forced flow under gravitational acceleration normal to fuel surface and flame spread in a quiescent environment in an enclosed chamber under gravitational acceleration parallel to fuel surface. Numerical simulations show that, under microgravity, slow-flow conditions, flame spread process is highly unsteady with the upstream flame spreads faster than the downstream flame after a period of ignition. It has also been shown that the level of microgravity has a significant effect on the name spread process.
文摘The theory of three-dimensional discrete transfer radiation model is expounded in detail in this paper. The computer program has also been written using this method here. Two kinds of radiation heat transfer problemS have been simulate with numerical method using the computer program, and the predictions carried out are quite in agreement with the exed results. It shows that the threedimensional discrete transfer radiation model is one of the suitable way to obtain heat flux and temperature in various applications.
基金This work was supported by the China NKBRSF Project(No.2001CB409603).
文摘This paper presents the zone modeling analysis of a single compartment flashover fire. Two criteria are ap- plied in the model to judge the onset of ignition for different combustibles. By calculating the total received energy through radiation or the surface temperature of the combus- tible, the fire growth can be quantitatively determined. The improved zone fire model shows the influence of different combustibles upon the fire growth. This model is better than the traditional zone model because the common criteria of flashover, i.e. an upper layer temperature of 600℃ and the heat radiation intensity received by the floor of 20 kW/m2, have not been applied in it.
文摘Based on the basic idea of zone modeling method, a two-layer zone model is developed and programmed to calculate the fire growth and smoke spread in a multi-room building subjected to a fire.The related predictiVe equations, numerical simulation method and sub-models implemented in this model are concisely described. A set of experimental data from Cooper’s work at NIST for a two-room compatment fire are chosen for comparison with the model and program, and the numerical results fundamentally agree well with the experimental data. Then, an example of numerical calculation of a two-story building fire is presented, and the relevant output results are given and analyzed.
