"Turbulent Transport Mechanismsof Natural Convection over Upward-Facing Horizontal, Heated plate"

“向上的水平加热板自然对流的湍流传输机制”

基本信息

批准号：
09650237
负责人：
KITAMURA Kenzo
金额：
$ 1.73万
依托单位：
Toyohashi University of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1998
项目状态：
已结题

项目摘要

Natural convection induced over the upward-facing horizontal, heated plate have been investigated both experimentally and analytically. Special concerns are directed to the turbulent transition mechanisms and the local heal transfer characteristics in the transitional region. The investigations have been carried out with water at room-temperature and with the test plate of constant wall heat flux, In order to obtain basic insight into the flow and temperature fields over the plate, the flow over the plate and the surface temperatures of the plate were visualized with dye and liquid crystal thermometry. The results showed that the following phenomena occur over the plates : (i) The laminar boundary layer flow develops over the plate in the vicinity of the leading edge. (ii) The flow separates three-dimensionally at certain distance from the edge. (iii) The separated flow, then, fluctuate irregularly and a fully turbulent state is realized in the central portion of the plate when the plate is wide enough. Among these phenomena, the three-dimensional separation and the succeeding turbulent transition are of particular importance, because these regions occupy considerable portion of the total surface area. Thus, we next carried out the numerical simulation on these phenomena. A time-dependent, three-dimensional analysis has been developed for this purpose. The results are quite satisfactory. Present analysis well predicted the occurrence of the flow separation and the succeeding transition to turbulence. Moreover, the local heat transfer coefficients are in good agreement between the analysis and experiment.

在实验和分析上已经研究了在面向向上的水平，加热板上引起的自然对流。特殊问题针对过渡区域的湍流过渡机制和局部治愈转移特性。为了获得对板上的流动和温度场，板上的流量和恒温场的基本见解，在室温下和恒定壁热通量的测试板进行了研究用染料和液晶温度法观察板。结果表明，以下现象出现在板上：（i）层层边界层流在前缘附近的板上发展。（ii）流量在距边缘的一定距离处分离三维。（iii）然后，分离的流动不规则地波动，当板足够宽时，在板的中央部分实现了完全湍流的状态。在这些现象中，三维分离和随后的湍流过渡尤其重要，因为这些区域占据了总表面积的相当一部分。因此，我们接下来对这些现象进行了数值模拟。为此，已经开发了时间依赖的三维分析。结果非常令人满意。目前的分析很好地预测了流动分离的发生以及随后的湍流过渡。此外，局部传热系数在分析和实验之间非常吻合。