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Investigation on Dissimilarity between Heat and Momentum Transport Processes and Its Numerical Modeling

热与动量传输过程的差异性研究及其数值模拟

基本信息

批准号：
07455097
负责人：
SUZUKI Kenjiro
金额：
$ 4.99万
依托单位：
KYOTO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1997
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07455097/
关键词：
Convective Heat Transfer Turbulent Boundary Layr Square Rod Karman Vortex Dissimilarity Control of Turbulence Numerical Simulation Unsteady Flow 角柱(ブラフ・ボディ)

项目摘要

This research project was conducted for investigation on the mechanism of dissimilarity between heat and momentum transport processes and its numerical modelling. The head investigator originally found the dissimilarity in a flat plate turbulent boundary layr disturbed by a circular cylinder, which means wall heat transfer enhancement and wall skin friction reduction simultaneously occur down stream of the cylinder. Such a bluff body, however, is not a suitable geometrical shape because of a relatively large momentum loss due to its form drag. A thin LEBU (Large Eddy Break-Up) plate, on the other hand, is one of the effective shapes to reduce the skin friction without a serious form drag, although the heat transfer is not enhanced with the plate.In this project, therefore, a flatten cylinder (Case 1) or a square rod attached with a splitter plate (Case 2) were inserted in a flat plate turbulent boundary layr in order to find the best shape to generate strong dissimilarity most effectiv … More ely and also to investigate how the dissimilarity is produced related to Karman vortices generated behind the inserted bodies. It was found for Case 1 that the degree of heat transfer enhancement decreases with an increase in the flatness of the cylinder, while the degree of skin friction reduction does not decreases in such a monotonous way. For Case 2, Karman vortex shed behind the rod was controlled by the splitter plate and suppressed with an increase in the plate length. Quadrant analysis, spectral analysis and wavelet analysis of monitored turbulent signals revealed for both cases that selective intensification of the interactive fluid motions was produced intermittently, synchronized with the Karman vortices. Such a selective intensification could be related to the generation mechanism of the dissimilarity.Unsteady flow and thermal numerical computations were also performed for both laminar and turbulent boundary layrs disturbed by a square rod. It was found that flow unsteadiness strongly depends on the ratio of the clearance between the rod and the plate to the side length of the rod. The dissimilarity was observed statistically in such a manner that heat transfer enhancement and skin friction reduction occur instantaneously at the same region, accompanied with the Karman vortex shedding. Less

本研究旨在探讨热动量输运过程差异的机理及其数值模拟。头部研究人员最初在圆柱体扰动的平板湍流边界层中发现了这种不同之处，即圆柱体下游的壁面换热增强和壁面摩阻减小同时发生。然而，这种钝体并不是一个合适的几何形状，因为它的形状阻力造成了相对较大的动量损失。另一方面，薄LEBU(大涡破裂)板是一种有效的减少表面摩擦的形状，没有严重的形状阻力，尽管它并没有增强传热。因此，在这个项目中，在平板湍流边界层中插入一个扁平的圆柱体(情况1)或一个带有分离板的方棒(情况2)，以找到最好的形状来产生最强的不同最有效的…更多的是为了研究这种差异是如何产生的，与插入的物体后面产生的卡门旋涡有关。结果表明，对于第一种情况，换热强化程度随着圆柱体平面度的增加而减小，而壁面阻力的减小程度并不是以这种单调的方式减小。在第二种情况下，杆后脱落的卡曼涡由分离板控制，并随板长的增加而被抑制。对监测到的湍流信号进行了象限分析、谱分析和小波分析，结果表明，两种情况下流体相互作用运动的选择性增强都是间歇性的，与卡门涡同步。这种选择性强化可能与差异性的产生机制有关。本文还对方棒扰动的层流和湍流边界层进行了非定常流动和热力数值计算。结果表明，流动不稳定强烈地依赖于杆与板之间的间隙与杆的边长之比。在统计上观察到的不同之处在于，换热增强和壁面阻力减小在同一区域同时发生，并伴随着卡门旋涡的脱落。较少