权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

Double Diffusive Natural Convection in Crystal Growth

晶体生长中的双扩散自然对流

基本信息

批准号：
06044171
负责人：
OZOE Hiroyuki
金额：
$ 3.84万
依托单位：
KYUSHU UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for international Scientific Research
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1995
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-06044171/
关键词：
double diffusion crystal growth oscillatory convection concentration convection temperature convection micro structure low Prandtl number gas phase convection

项目摘要

In the process of crystal growing of pure materials, very small amount of impurities are accumulated just outside of the solidification front. This induces the concentration gradient an concentration natural convection. The cooling temperature gradient and concentration gradient induce so to speak double diffusive natural convection.This is the theme of the present research. At the beginning, two phase layrs were adopted as a most simple system of double diffusion. The lower half layr is a dense salt water layr and the upper half layr a pure water layr. Both layrs are heated from the one vertical side and cooled from opposing vertical side. After two layrs are strted to be heated and cooled, salt component is continuously diffused to the upper layr and the salt-thick plume is raised upward along the heated wall. Because of the high Lewis number of the system, the thick concentration boundary layr is kept for long and the core regime is relatively pure water for many hours. This induces oscillatory convection both in the upper and lower layrs. The temperature dependence of the properties were found to move the two-layr interface constantly upward. The mass transfer rate was correlated by a single equation. It is determined not by the concentration differece but by the diffusion coefficient. Various systems for the buoyant forces due to temperature and concentration either opposite or the same directions were studied for the oscillatory convection characterstics.

在纯材料的晶体生长过程中，只有极少量的杂质在凝固前沿外积累。这导致了浓度梯度和浓度自然对流.冷却温度梯度和浓度梯度诱导了所谓的双扩散自然对流，这是本研究的主题。一开始，采用两相层作为最简单的双扩散系统。下半部为致密咸水层，上半部为纯水层。两层都是从一个垂直侧加热，从相对的垂直侧冷却。经过两层加热和冷却后，盐组分不断扩散到上层，盐厚的羽流沿着受热壁向上上升。由于系统的高Lewis数，厚的浓度边界层长时间保持，核心区域是相对纯净的水长达数小时。这在上层和下层都引起了振荡对流。研究发现，这些性质的温度依赖性使双层界面不断向上移动。传质速率可用单一方程关联。它不是由浓度差决定的，而是由扩散系数决定的。为了研究振荡对流特性，研究了温度和浓度相反或相同方向的浮力的不同系统。