火灾羽流直接数值模拟-安全技术及工程专业论文.docxVIP

摘要关键词：火灾轴对称羽流平面羽流直接数值模拟无量纲参数涡量涡旋 摘要 关键词：火灾轴对称羽流平面羽流直接数值模拟无量纲参数涡量涡旋 AbstractAbstract Abstract Abstract Fire，which cause heavy casualties and tremendous property loss，is kind of catastrophic uncontroIlable combustion phenomenon and brings great hazards to human society．Thus people should discover and recognize the phenomenon and the rule and mechanism of fire process．The research on fre plume is significant in the field of fire science and there are two kinds of research methods including experimental and numerical one．Numerical simulation based on mathematical and physical model is popular among the researchers for many advantages，such as flexible parameters setting，good repeatability,low cost,etc．Due to its ability to capture most accurate temporal and spatial scales，DNS was employed in this paper to simulate fire plume，including thermal buoyancy plume and reactive plume． Thermal buoyancy plume simulation was investigated in the article．The comparative analysis between planar plume and axisymmetric plume was performed． The results show that the averaged radia!veIocity and vorticity of axisymmetric plume are lower than those ofplanar plume，while pulsation ffequency is higher than that of planar plume．Base on the vorticity transport equation,this phenomenon was analyzed and we came to a conclusion that plume vortex decreases and mixing intensity reduces because the stretching term ov／r of axisymmetric plume is negative． The article simulated axisymmetric plume involved chemical reaction,Studies the influence on plume by non—dimensional parameter Oh、忍、Fr、Da、Ze． Combustion model use one-step chemical reaction with the Arrhenius kinetics．The influence on vortex structure by heat released caused by chemical reaction is analyzed first．The results siloW that,vortex structure occurs in the case without buoyancy and chemical reaction,which caused by the instability of Kelvin-HelmhoItz．Budgets of the vortic ity transport are examined to understand the mechanism It can be t