电渗流动与传热的耗散粒子动力学研究

发布时间：2018-05-12 23:43

  本文选题：电渗流 + 多场耦合　； 参考：《哈尔滨工业大学》2016年硕士论文

【摘要】：电渗流是微流控技术和微全分析系统中最为重要的流体驱动方式之一,因其简单高效而得到了较为普遍的应用。随着流体控制技术逐渐向着复杂化和微型化发展,其内部流动细节及微观结构逐渐成为人们所关注的重点。由分子动力学(MD)演化而来的能量守恒耗散粒子动力学(eDPD)是一种基于粒子的新兴拉格朗日数值方法,相比MD具有更高的效率和更强的灵活性,对于模拟复杂流体的流动与传热问题具有先天性的优势。作为一种新兴的介观方法,eDPD的发展和应用目前还较为有限,对于多物理场耦合的流动传热问题更是鲜有涉及。本文研究的主要目的就是将其用于电场、流场及温度场耦合下的电渗流动与传热的模拟。首先详细地介绍了电渗流动与传热的控制方程及eDPD方法模拟复杂流动与传热问题的理论基础,并阐明了eDPD系统中实现多物理场耦合的一般方法,通过模拟简单微通道内的纯电渗流及有压差驱动下的混合电渗流动与传热过程,将得到的结果分别与理论解及有限元方法(FEM)对比,验证了该方法的正确性。微混合技术在微流体控制及输运中起着强化传质与传热的核心作用,对于设备的微型化和集成化具有重要的意义。本文通过改变微通道壁面的异质电势分布结构,采用eDPD方法分别对横向和纵向电场作用下的电渗微混合与传热问题进行了模拟,分析了压力梯度及壁面电势等对微混合产生的相关影响。研究发现不同方向电场作用下的微混合流态具有较大的差异,而压力梯度的增加会导致电渗混合与传热的整体效果逐渐减弱。诱导电渗流是近十几年才被发现和提出的一种电动新现象,与传统电渗流相比能够对微流体产生更好的驱动效果,而其内部规律尚未被完全了解,因此具有很高的研究价值。本文首次将eDPD方法应用于圆柱电极诱导电渗流动与传热问题的研究,分析了有压差存在下电极材料结构变化时的诱导电渗流动与换热特性,发现电极材料结构对其附近的流态有较大的影响,左侧导体材料诱导产生的电渗涡流削弱了压力梯度的作用,而右侧涡流对压力驱动流则具有一定的促进效果。本文的研究充实了介观尺度下的电动力学理论,成功地将eDPD方法应用于多物理场耦合复杂流动与换热问题的研究,拓展了其模型的应用领域并充分证明了其可靠性及灵活性,为其在相关方向的发展奠定了一定的基础。
[Abstract]:Electroosmotic flow (EOF) is one of the most important fluid driving methods in microfluidic control technology and micro-total analysis system. It has been widely used because of its simplicity and efficiency. With the development of fluid control technology towards complexity and miniaturization, the internal flow details and microstructure gradually become the focus of attention. The energy conservation dissipative particle dynamics (PDD) evolved from molecular dynamics (MD) is a new Lagrangian numerical method based on particles, which is more efficient and more flexible than MD. It has an inherent advantage in simulating the flow and heat transfer of complex fluids. As a new mesoscopic method, the development and application of eDPD is still limited, and the heat transfer problem of multi-physical field coupling flow is rarely involved. The main purpose of this study is to simulate the electroosmotic flow and heat transfer under the coupling of electric field, flow field and temperature field. Firstly, the governing equations of electroosmotic flow and heat transfer and the theoretical basis of eDPD method for simulating complex flow and heat transfer are introduced in detail, and the general method to realize multi-physical field coupling in eDPD system is also expounded. By simulating the pure electroosmotic flow and the mixed electroosmotic flow and heat transfer process driven by pressure difference in a simple microchannel, the results obtained are compared with the theoretical solution and the finite element method (FEMM), respectively, and the correctness of the method is verified. Micro mixing technology plays a key role in enhancing mass transfer and heat transfer in micro fluid control and transportation. It is of great significance for the miniaturization and integration of the equipment. In this paper, the electroosmotic micromixing and heat transfer under transverse and longitudinal electric field are simulated by changing the heterogeneity potential distribution structure of microchannel wall. The effects of pressure gradient and wall potential on the micromixing are analyzed. It is found that there are great differences in the micro-mixing flow states under the action of electric field in different directions, and the increase of pressure gradient will lead to the gradual weakening of the overall effect of electroosmotic mixing and heat transfer. Induction electroosmotic flow (EOF) is a new electrokinetic phenomenon which has been discovered and proposed in recent years. Compared with traditional electroosmotic flow (EOF), it can produce better driving effect on micro-fluid, but its internal law has not been fully understood, so it has high research value. In this paper, the eDPD method is applied to the study of electroosmotic flow and heat transfer induced by cylindrical electrode for the first time, and the induced electroosmotic flow and heat transfer characteristics are analyzed when the structure of electrode material changes under pressure difference. It is found that the structure of electrode material has a great influence on the flow state near the electrode. The electroosmotic eddy current induced by the left conductor material weakens the pressure gradient, while the right eddy current has a certain promoting effect on the pressure driven flow. The research in this paper enriches the theory of electrodynamics at mesoscopic scale and successfully applies the eDPD method to the study of coupled complex flow and heat transfer problems in multiple physical fields. The application field of the model is expanded and its reliability and flexibility are fully proved. It has laid a certain foundation for its development in the related direction.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TK124
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本文编号：1880703