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Fluid Dynamic Problems in Cold Regions

寒冷地区的流体动力学问题

基本信息

批准号：
63302027
负责人：
KIYA Masaru
金额：
$ 4.35万
依托单位：
Hokkaido University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Co-operative Research (A)
财政年份：
1988
资助国家：
日本
起止时间：
1988 至 1990
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-63302027/
关键词：
Fluid Mechanics Heat Transfer Cold Regions Snow Drifting Ice Formation Snow Fences Model Snow Model Experiment 北方圏熱工学

项目摘要

1. A turbulent separated-and-reattaching flow is one of the most fundamental flows which are associated with the effectiveness of snow fences and shelters, the obstruction of drivers' sight during snow drifting, etc. Two- and three-dimensional separated flows were experimentally studied to obtain the time-mean velocities, turbulence properties, flow unsteadiness due to the shedding of large-scale vortical structure, and means of their manipulation. These results are likely to be similar to those of a wide range of separated-and-reattaching flows.2. An experimental study was made to investigate characteristics of the freezing heat transfer of layered ice-water flow in a circular pipe, in which cooled air and water flow in the same direction. The experiment was performed under a variety of conditions of water discharge, water temperature, tube-wall temperature, air discharge, and water level. Particular attention was focused on photographic visual observation of the developing ice layer … More along the tube wall. It was observed that there were two different regions characterizing the ice formation, one of which was the freeze-off region, and the other was the steady-state region. Conditions for the freezeoff onset were obtained in terms of an empirical formula.3. The formation of ice growth occurring in branched pipes which contained water was made over a range of Reynolds number, and the cooling temperature ratios. From the flow visualization studies, the branched pipe flowing water was first blocked by ice formation ; subsequently the main pipe downstream of the branched portion was frozen off, and eventually the main pipe downstream of the branched portion was blocked by ice formation. This shows that freezing of the remaining water in the branched portion results in the pipe rupture at around the branched portion. The transient behavior of the ice formation was expressed in terms of the pressure loss and Reynolds number for various cooling temperature ratios.4. Flow around a snow shelter consisting of cascade of elliptic wings was numerically studied by solving the Navier-Stokes equations by the use of a body-fitted coordinate to obtain the aerodynamic forces acting on the wing, the velocity distribution, and the effectiveness of blowing off snow on the ground level. Velocity and turbulence measurements were also made in wake of a porous plate to evaluate the extent of detached low-velocity region downstream of the plate. These results gave excellent information on design of effective snow fences and shelters. Less

1. 湍流分离再附着流是最基本的流动之一，与防雪栅栏和避难所的有效性、飘雪时对驾驶员视线的遮挡等有关。对二维和三维分离流进行了实验研究，获得了时间平均速度、湍流特性、大尺度涡结构脱落引起的流动不稳定及其操纵手段。这些结果很可能与大范围的分离再附着流的结果相似。2．对冷却空气和水同向流动的圆管内层状冰水流的冷冻传热特性进行了实验研究。实验在不同的排水量、水温、管壁温度、排气量、水位等条件下进行。特别关注的是沿管壁发展的冰层的摄影目视观察。据观察，存在两个不同的区域来表征冰的形成，其中一个是冻结区域，另一个是稳态区域。根据经验公式得出冻结开始的条件。 3．在含有水的支管中发生冰生长的形成是在雷诺数和冷却温度比的范围内进行的。从流动可视化研究来看，支管流动的水首先被结冰所堵塞；随后，分支部分下游的主管被冻结，最终分支部分下游的主管被结冰堵塞。这表明，分支部分中的剩余水结冰导致分支部分周围的管道破裂。冰形成的瞬态行为用不同冷却温度比下的压力损失和雷诺数来表示。4．通过使用贴体坐标求解纳维-斯托克斯方程，对由椭圆翼级联组成的防雪棚周围的流动进行数值研究，以获得作用在机翼上的气动力、速度分布以及地面吹雪的有效性。还在多孔板后面进行了速度和湍流测量，以评估板下游低速区域的分离程度。这些结果为有效的防雪栅栏和避难所的设计提供了极好的信息。较少的