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

该研究项目是为了投资热与动量传输过程之间的差异机制及其数值建模。头部研究人员最初发现在平板湍流边界中的差异受到圆形圆柱的影响，这意味着壁热的增强和壁皮的还原简化只是出现在圆柱体的流下。然而，由于其形态阻力，这种虚张声势的身体并不是合适的几何形状。另一方面，薄薄的lebu（大涡流）板是一种有效的形状之一，可以减少没有严重形式的皮肤摩擦，尽管没有用板块增强热传递。并研究如何产生与插入物体后面产生的业力涡流有关的差异。在病例1中发现，随着圆柱体平坦度的增加，传热增强的程度降低，而皮肤摩擦减少的程度不会以这种单调的方式降低。对于情况2，Karman Vortex在杆后面的脱落由分离板控制，并随着板长的增加而抑制。两种情况下，象限分析，光谱分析和小波分析揭示了两种情况下，与Karman涡流同步进行了间歇性地产生相互作用流体运动的选择性强化。这种选择性的强化可能与差异性的发电机理有关。对层流和湍流边界均受到方形杆的干扰，也进行了不稳定流量和热数值计算。发现流动不稳定在很大程度上取决于杆和板之间的间隙与杆的侧面长度的比率。从统计学上观察到差异性，以使热转移增强和皮肤摩擦减少在同一区域瞬间发生，并伴有Karman涡流脱落。较少的