负浮力射流的卷积和失稳特性及其湍流形成机制研究

项目名称： 负浮力射流的卷积和失稳特性及其湍流形成机制研究

项目编号： No.50879074

项目类型： 面上项目

立项/批准年度： 2009

项目学科： 生物科学

项目作者： 林文贤

作者单位： 云南师范大学

项目金额： 32万元

中文摘要： 利用目前处于研究前沿的PIV实验、DNS和标度分析等手段对负浮力射流的卷积和失稳特性及其湍流形成机制，以及负浮力射流撞击固体表面和与其密切相关的非稳态自然对流、储热水箱中的三维流动、太阳能空气集热器和热水器，以及晶体生长中的流动特征展开了深入的研究。结果表明，对于特定的Fr，当Re较小时，射流依然是轴对称和无失稳的；随着Re的增大，射流逐渐演变为三维，轴对称消失，而失稳特征逐渐增强；当Fr小于6时，表征轴对称性失去程度的定量参数和表征二维转变为三维的变化大小的定量参数都随Fr的增加而增加；但当Fr大于6时，它们都不再随Fr的增加而变化;当Re在200和500之间时，两者都随Re的增加而增加;但当Re大于500时，它们都不再随Re的增加而变化;非稳态自然对流边界层的瞬时流动可由一个3区域结构来描述：在起始阶段，流动是一维且与高度无关；但在达到稳态时，流动变为二维且与高度有关；利用标度分析建立了一系列描述边界层在不同发展阶段的流动特征参数与控制参数之间的标度关系，并利用DNS验证和量化了这些标度关系。这些结果揭示了负浮力射流的独特湍流特征及其微观形成机制，为工程应用奠定了坚实的理论基础。

中文关键词： 负浮力射流；失稳；湍流；卷积；自然对流

英文摘要： In this project, the cutting-edge PIV, DNS and scaling analysis techniques have been used to study in depth the entrainment, instability and turbulence generation mechanism in fountains, and fountains impinging on solid surfaces and the relevant fluid behavior in natural convection, three-dimensional flows in heat storage tanks, solar air collectors and water heaters, and crystal growths. The results show that for a fixed Fr, when Re is small, fountains are axisymmetric and stable; when Re increases, fountains gradually evolves into three-dimensional and the axisymmetry disappears and the instability increases; when Fr is smaller than 6, the parameters quantifying the extent of loss of axisymmetry and the change evolving from two-dimensional to three-dimensional increase with Fr; nevertheless, when Fr is larger than 6, these parameters no longer change; when Re is in the range of 200 and 500, these parameters increase with Re; however, when Re is larger than 500, they do not change anymore; The instantaneous flow of an unsteady natural convection boundary layer can be represented by a 3-region structure: in the start-up stage, the flow is one-dimensional and does not depend on the height; but when the flow attains the steady state, the flow becomes two-dimensional and depends on the height; The scaling analysis has been used to develop a series of scaling laws to relate the flow behavior parameters to the control parameters of the flows at different development stages and these scaling laws have been confirmed and quantified by the DNS results. All these research outcomes reveal the unique turbulence generation characteristics in fountains and the relevant flow behavior, which will form a firm theoretical basis for the engineering applications of the flows.

英文关键词： Fountain; Instability; Turbulence; Entrainment; Natural Convection