Deformation behavior of a liquid droplet impinging on hot metallic surfaces above the Leidenfrost temperature

莱顿弗罗斯特温度以上液滴撞击热金属表面的变形行为

• 批准号: 07455287
• 负责人: HATTA Natsuo
• 金额: $ 4.35万
• 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 1996
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07455287/
• 关键词: Leidenfrost temperature; Weber number; numerical analysis; deformation process of droplet; free surface; surface tension; spray cooling; surface material; 変形挙動; 液滴粒子; 表面粗さ

The deformation process of a droplet impacting a hot surface has been investigated by many double exposure photographs on the basis of statistical procedure. When a droplet impacts a hot surface with low Weber numbers, the droplet spreads on the surface, reaches a maximum diameter, recoils and finally rebounds from the surface. For larger Weber numbers, we have found that the droplet breaks up into small parts in the recoiling process. Wiht increasing the Weber number further, the droplet shatters in the spreading process. Also, we have investigated the effect of kind of surface material on the droplet deformation process. The effect of kind of surface material has been hardly recognized in the range of low Weber numbers such that the droplet rebounds from the surface without disintegration. However, it has been found that the critical Weber number whether or not the droplet break up into small parts during the deformation is changeable depending upon the kind of surface material.The deformation behavior of droplet has been analyzed numerically. The system of governing equation is the Navier-Stokes equations for the incompressible viscous fluid flow in the axisymmetric system. The effects of viscosity, gravity and surface tension have been taken into account. The system of governing equations has been solved by the finite differencing method. The deformation process of droplet impinging on a cold surface at room temperature as well as a hot surface above the Leidenfrost temperature has been analyzed. The numerical results have been compared with the experimental data to verify the validation of mathematical model. As a result, the numerical results have been found to agree well with the experimental data. Also, it has been clarified theoretically that the droplet rebounding occurs owing to the effect of surface tension.

本文用大量的二次曝光照片研究了液滴撞击热表面的变形过程。当液滴撞击韦伯数较低的热表面时，液滴在表面上展开，达到最大直径，反冲并最终从表面反弹。对于较大的韦伯数，我们已经发现，液滴在反冲过程中分裂成小部分。随着Weber数的进一步增大，液滴在铺展过程中破碎。此外，我们还研究了表面材料的种类对液滴变形过程的影响。在低韦伯数的范围内，表面材料的种类的影响几乎没有被认识到，使得液滴从表面反弹而不解体。然而，发现液滴在变形过程中是否破碎成小块的临界韦伯数随表面材料的种类而变化，并对液滴的变形行为进行了数值分析。控制方程组是不可压缩粘性流体在轴对称系统中流动的Navier-Stokes方程。考虑了粘度、重力和表面张力的影响。用有限差分法求解了控制方程组。本文分析了液滴撞击冷表面和热表面的变形过程。数值计算结果与实验数据进行了比较，验证了数学模型的有效性。结果表明，数值计算结果与实验数据吻合较好。此外，从理论上阐明了由于表面张力的作用而发生的液滴反弹。

项目成果

藤本 仁: "表面粗さの異なる加熱金属平面に衝突する微小液滴の変形挙動特性" 鉄と鋼. 82. 975-980 (1996)

Hitoshi Fujimoto：“微滴与不同表面粗糙度的加热金属平面碰撞的变形行为特征”Tetsu-to-Hagane 82. 975-980 (1996)。

八田夏夫: "変形を伴う気泡まわりの流れ場の数値解析" 資源と素材. 111. 630-636 (1995)

Natsuo Hatta：“变形气泡周围流场的数值分析”资源和材料 111. 630-636 (1995)。

Natsuo Hatta: "Experimental Study of Deformation Mechanism of a Water Droplet Impinging on Hot Metallic Surfaces above the Leidenfrost Temperature" Trans. ASME J. Fluids Engg.(掲載予定).

Natsuo Hatta：“莱顿弗罗斯特温度以上水滴撞击热金属表面的变形机制的实验研究”，ASME J. Fluids Engg。

N.Hatta et al.: "Experimeutal study of Deformation Mechanism of a water Proplet Impingiing on Hot Mettallic surfaces abore the Leidnfrost Temperatare" Trans.of ASME.J.Fluids Engg. (掲載予定).

N.Hatta 等人：“水推进器撞击莱顿弗罗斯特温度上的热金属表面的变形机制的实验研究”Trans.of ASME.J.Fluids Engg（即将出版）。

Natsuo Hatta: "Deformation Process of a Water Droplet Impinging on a Solid Surface" Trans. ASME. J. Fluids Engg.117. 394-401 (1995)

Natsuo Hatta：“水滴撞击固体表面的变形过程”Trans。