电热对流格子-Boltzmann模拟及其不稳定性分析

The electro-thermo-convection, as one of fundamental research topics of electrohydrodynamics and heat transfer, is described to be a distinctive flow and heat transfer process driven by Coulomb force combined with buoyancy in dielectric liquids. The project will build a unified lattice Boltzmann model for electro-thermo-flow multi-physics coupled transport in dielectric liquids and an experimental platform for electro-thermo-convection, numerically simulate electro(-thermo)-convection and enhanced heat transfer by electro-thermo-convection, and carry out corresponding experimental research. This project will reproduce the whole evolution process of electro-thermo-convection from the steady hydrodynamic state to linear and nonlinear critical points then bifurcation and multi-solution region until the chaos structure, and investigate the effects of different dimensionless parameters such as electric Rayleigh number, fluid Rayleigh number, injection intensity and geometric parameters el al. on the charge transport, fluid flow and heat transfer. Linear and nonlinear stability theory will be introduced to make a thorough analysis of instability and bifurcation phenomena in electro-thermo-convection, and the induced mechanism of instability phenomena in electro(-thermo)-convection will be revealed. Also, the research will clarify how the initial disturbance influence the evolution of 3D flow field and steady-state characteristic flow structure. The project will examine synergistic effects of flow field, thermal field and electric field on convective heat transfer, and reveal physical mechanism of heat transfer enhancement by electro-thermo-convection. The project will develop effective experimental scheme by which the special flow structure of electro-thermo-convection is observed, and enhancing effects of electro-convection on heat transfer are measured.

电热对流描述的是介电液体在库仑力和浮升力共同作用下形成的独特流动和传热过程，是电流体动力学与传热学的基础研究课题。拟建立介电液体电、热、流多物理场耦合输运的统一格子-Boltzmann模型并搭建电热对流实验台，对电（热）对流及其强化传热进行数值模拟与实验研究。还原电（热）对流从流体静力学状态到线性与非线性稳定临界点，再到分叉和多解区域，直至出现混沌结构的整个演变过程，考察不同无量纲控制参数如电动瑞利数、流动瑞利数、注入强度及几何参数对电荷输运、流体流动与传热过程的影响。引入线性与非线性稳定性理论深入分析电（热）对流的不稳定性和分叉现象，揭示电（热）对流不稳定现象的诱发机制，明确初始扰动对三维流场演变及稳态特征流场结构的影响规律。考察流场、热场、电场对电热对流传热的协同影响，揭示电热对流强化传热的物理机制。发展有效的实验手段，观测电热对流特殊的流动结构及电对流对传热的强化效果。

电热对流描述的是介电液体在库仑力和浮升力共同作用下形成的独特流动和传热过程，是电流体动力学与传热学的基础研究课题。利用电热对流实现流动和传热的控制无需机械运动部件且具有低能耗和低噪声、快速而智能的优点，其在强化传热、航天器热管理、精密仪器、空气净化以及微机械系统等多个领域具有广阔的应用前景。但电热对流的理论分析和数值模拟存在较大研究难度和诸多研究空白。本项目主要研究内容包括电热对流数值算法、电热对流线性失稳与分岔、电热对流二次失稳及非线性动力学、多相电流体流动与传热传质、非牛顿流体电热对流、电对流实验等工作，取得了如下研究成果。..导出了固-液两相电热对流在流体静力学状态下各物理场的理论解，建立了电、热、流、相场耦合输运统一介观模型，构造了基于LBM的单相/两相电热对流通用数值仿真平台；揭示了电场强化传热规律及电场激发相变过程对流不稳定性机制，明晰了表面电荷对流对气-液两相EHD的定量影响。..率先数值复现了电对流蜂窝状六边形流型，明晰了电对流流型演化及线性失稳机制，搭建了理论分析与实验测量间的桥梁；探索了从稳态到混沌过渡过程中流体动力学特征的演化，确定了几种可能存在的混沌转捩路径；考察了弹性作用对电对流一次失稳模式和非线性演化的影响，发现电场与弹性场的耦合将引入新的不稳定性模式和全新的机理。..搭建了电场作用下介电液体流动的实验平台，实现流场以及电压-电流信息的同步测量。基于该实验系统开展了针-板电极介电液体电对流研究，揭示了介电液体在不同的电场作用下自由电荷产生及输运机制。..该项目发表论文19篇，其中SCI检索18篇，包括Phys. Rev. Fluids 2篇、Phys. Fluids 7篇、Phys. Rev. E 1篇、IJHMT 2篇，其中1篇文章被POF选为当期封面并被美国联合会专题报道，1篇文章被POF选为Featured article，1篇文章被POF选为Editor’s Pick；另外在《中国科学：技术科学》发表论文1篇。