过渡区内喷泉流动的直接数值模拟与分析  

Direct numerical simulation and analysis of transitional fountain flows

作　　者：罗川旭[1] 林文贤[1] 刘滔[1] 高文峰[1] 李明[1] 马煜[1] 郑勤红[1] 

机构地区：[1]云南师范大学太阳能研究所,昆明650092

出　　处：《水动力学研究与进展（A辑）》2008年第3期244-254,共11页Chinese Journal of Hydrodynamics

基　　金：973计划前期研究专项(2007CB216405);国家自然科学基金(10262003);云南省自然科学基金(2003E0004Z);教育部"新世纪优秀人才支持计划"(NCET-04-0918)资助项目

摘　　要：对于具有中等数值的Fr和Re值的处于从层流向湍流过渡的过渡区内的喷泉流动而言,了解其流动机理,尤其是卷吸和湍流开始出现时的流动机理,将有助于我们掌握湍流在负浮力射流中的形成机制以及湍流与负浮力射流之间的相互作用。本文对处于过渡区内(1≤Fr≤10,100≤Re≤1000)的负浮力射流进行了直接数值模拟。结果表明,当Re≤200时,在上升流动与回落流动、回落流动与环境流体之间的交界面上均只有微弱的卷吸现象出现,甚至当Fr较大时(如Fr=8)也是如此。但当Re>200时,在上述交界面上不但出现了卷吸现象,并且其程度随Re的增大而增大,尤其在Re≥400时,回落流动与环境流体之间的卷吸现象变得很强烈。这些结果表明卷吸的产生主要是由于Re的影响,而相比之下Fr对于卷吸的产生的影响就要小得多。结果还表明,由于卷吸的作用,喷泉的最大穿透高度即使在喷泉流动达到稳态时仍然有上下波动,其平均值在1<Fr≤8和100≤Re≤800的范围内与Fr3/2Re1/4存在比例关系。Fountains with moderate Froude （Fr） and Reynolds （Re） numbers are of interest,especially for understanding the mechanism of turbulence and entrainment in the early stages of turbulent fountains. However there has been little investigation work to be done about the behavior of these transitional fountains. In this paper,the transient behavior of axisymmetric fountains with 1≤Fr≤10 and 100≤Re≤1000 was studied by direct numerical simulation. It is found that when Re≤200,there is little mixing between the downflow of the fountain and the ambient,even for Fr=8. However,when Re≥200,the mixing between the fountain downflow and the ambient becomes stronger,indicating that the entrainment and the turbulence are mainly due to Reynolds number and the contribution from Fr number is much smaller,and the mixing becomes very strong especially when Re≥400. The maximum fountain penetration height fluctuates,even when the flow reaches the quasi-steady state,due to the interaction between the downflow and the bottom boundary and/or the entrainment between the downflow and the ambient,with its averaged value scales to Fr^3/2Re^1/4 for 1〈Fr≤8 and 100≤Re≤800.

关 键 词：负浮力射流 直接数值模拟 过渡区 湍流 卷吸 

分 类 号：O358[理学—流体力学]