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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

本研究项目旨在研究热量和动量输运过程之间的不相似性机制及其数值模拟。研究者最初发现了圆柱扰动平板湍流边界层的不同之处，即圆柱下游同时发生壁面传热强化和壁面摩阻降低。然而，这样的海崖体不是合适的几何形状，因为由于其形状阻力而导致相对大的动量损失。瘦瘦的LEBU另一方面，（大涡破碎）板是减少表面摩擦而没有严重形状阻力的有效形状之一，尽管板没有增强传热。因此，在本项目中，一个扁平的圆柱体（案例1）或一个带有分离板的方形杆（案例2）在平板湍流边界层中，为了找到最有效地产生强相异性的最佳形状， ...更多信息伊利研究了插入体后产生的卡门涡是如何产生相异性的。结果发现，对于情况1，传热增强的程度随着圆柱体的平坦度的增加而减小，而表面摩擦减少的程度并不以这种单调的方式减小。对于第二种情况，分离板控制了杆后的卡门涡脱落，并随着分离板长度的增加而抑制。象限分析，频谱分析和小波分析的监测湍流信号显示，在这两种情况下，选择性强化的相互作用的流体运动间歇性地产生，与卡门涡同步。这种选择性强化可能与相异性的产生机制有关。本文还对方杆扰动层流和湍流边界层进行了非定常流动和热力数值计算。研究发现，流动不稳定性强烈地依赖于杆和板之间的间隙与杆的边长的比率。统计上观察到的差异，以这样一种方式，即传热增强和表面摩擦减少瞬间发生在同一区域，伴随着卡门涡脱落。少