Some further studies on the transition to turbulent convection
Some further studies on the transition to turbulent convection
复制标题
DOI：
10.1017/s0022112073000170
复制
发表时间：
1973-09
影响因子：
3.7
通讯作者：
R. Krishnamurti
中科院分区：
文献类型：
--
作者：
R. Krishnamurti
在水平对流流体层中，对于给定的普朗特数Pr，在某些不同的瑞利数R处会发生几个不同的转变。状态图已经扩展到包括普朗特数范围2·5 × 10−2 [les ] Pr [les ] 0·85 × 104。特别是，我们发现即使在Pr = 2·5 × 10−2时，热流曲线的斜率也会发生明显的变化。流量在R = Rt = 2·4 × 10 ~ 3时是稳定的。当R > Rt时，振荡周期与Busse的理论值作了比较。当Pr = 0·71时，热流曲线的斜率既增加又减小。对于R刚大于Rc，在各种侧壁几何形状的辊的优选取向进行了研究。对于高普朗特数，滚转轴的曲率的影响，迫使弯曲的侧壁，在RII的第二个转变后的影响进行了研究。据发现，曲率，以及先前讨论的效果，导致降低RII。这些结果，沿着观察到的滞后，支持的观点，有亚稳态有限振幅不稳定性。最后，在Hele-Shaw盒中研究了大R和高Prandtl数下的时间相关流动的性质。它明确地表明，在一个固定的点所观察到的周期性是由于热或冷的羽流移动过去的点。
In a horizontal convecting layer of fluid, several distinct transitions occur at certain distinct Rayleigh numbers R, for a given Prandtl number Pr. The regime diagram has been extended to include the Prandtl-number range 2·5 × 10−2 [les ] Pr [les ] 0·85 × 104. In particular it is found that distinct changes in the slope of the heat-flux curve occur even for Pr = 2·5 × 10−2. The flow is steady up to R = Rt = 2·4 × 103. For R > Rt, the period of oscillation is compared with the theoretical values of Busse. For Pr = 0·71 decreases as well as increases in the slope of the heat-flux curve are observed. For R just greater than Rc, the preferred orientation of rolls in various side-wall geometries is investigated. For high Prandtl number, the effect of curvature of the roll axis, forced by curved side walls, upon the second transition at RII is investigated. It is found that curvature, as well as previously discussed effects, leads to a lowering of RII. These results, along with the observed hysteresis, support the view that there are metastable states attainable by finite amplitude instability. Finally the nature of the time-dependent flow at large R and high Prandtl number is investigated in a Hele-Shaw cell. It is shown unequivocally that the observed periodicity at a fixed point is due to hot or cold plumes moving past the point.