棘齿形热表面液滴自输运机理及实验研究

The main objective of this work is to understand the driving mechanism of self-propelling Leidenfrost liquid droplets on ratchets surface by using experimental and theoretical study.Property and experimental study of the contact line or interface between the drop and the film are experimentally recorded by using a high-speed video camera for each droplet to be extracted frame by frame. Numerical analysis of the evaporating flows over a ratchet surface will suggests new insights into the mechanism of motion rectification that are incorporated into the simplest equations of motion for a Leidenfrost body. The significance of thermally-driven flows for the propulsion of Leidenfrost droplets on a ratchet surface is studied based on a numerical solution of the Boltzmann equation. A simple method is used to examine the driving force with ratchets of micrometer period, and the velocity of Leidenfrost droplets was derived by using the model established under different conditions. The mechanism responsible for the force acting on the drop on superheated ratchets has been recently under debate. Different ratchets with different sharpness of teeth will be analyzed by using the numerical methods, and some ratchets with better results will be fabricated on separate blocks of brass and experimentally studied. The focus point of this proposal is unique, and one of the innovation is the use of the analytic mehtod for the liquid-vapor interface, and the other is the assumption of ratchets with surface morphology, which will generate higher droplet velocity. This work will provide theoretical and experimental supports of the mechanism for the Leidenfrost droplets.

本项目针对Leidenfrost液滴高速自输运这一现象，开展液滴自输运机理的研究，拟据此推动该项技术在相关领域的应用。主要研究内容及方案包括：①液滴与汽膜的作用界面形状的实验及理论研究，拟建立汽液接触线的适用理论模型，该部分内容以实验研究为主，辅以理论分析开展；②汽膜内的气流特性，通过这部分内容可以揭示气流对液滴运动的作用规律。以理论分析和数值模拟为主开展，辅以实验研究；③棘齿形貌对气流的影响，通过改变热源表面形状，通过数值模拟和实验研究，寻求能够有利于汽流导流并对液滴提供强大动力的表面形状及参数。本研究的聚焦点独特，创新点之一在于运用解析方法求解汽液界面，同时提出通过改变棘齿表面形貌以利于液滴更高速输运的研究设想。研究最终将明确棘齿形热表面液滴膜沸腾自输运现象的作用机理，为液滴高速自输运机理提供理论和实验支持。

本项目针对Leidenfrost液滴高速自输运现象，开展了棘齿形表面液滴自输运机理的研究，主要的研究内容及成果包括：（1）自主设计搭建了棘齿形热表面液滴自输运实验系统；（2）通过对液滴与汽膜作用界面形状的实验及理论研究，建立了汽液接触线的适用理论模型；（3）通过研究汽膜内的气流特性，揭示了气流对液滴运动的作用规律；（4）通过改变热源表面形状，研究了棘齿形貌对气流的影响，获得了能够有利于汽流导流并对液滴提供强大动力的表面形状及参数。本项目研究结果揭示了棘齿形热表面液滴膜沸腾自输运现象的作用机理。结果表明，通过改变棘齿表面形貌可以让液滴具有更高速的输运特性。研究成果为液滴高速自输运机理提供了理论和实验支持。