考虑壁面粗糙度效应的气固两相流颗粒趋壁行为机理研究

Particle flow towards the wall in gas-solid two phase flow is common in nature and engineering.Due to the complexity of gas-solid two-phase flow,cause the mechanism particle-wall interaction mechanism is difficult to grasp,also the effect of wall roughness increase the complexity of particle flow towards the wall.By means of theoretical analysis and experimental research, develop the further study on particle flow towards the wall in gas-solid two phase flow through rough passage.Based on the Fractal Theory, the three-dimensional random rough surface model accounting for fractal dimension and scale dependency will be established.High-precision numerical model based on coupled CFD-DEM considering forces on particle,particle deposition collision model,interaction coupling way under the synergistic effect of hydrodynamics of gas-solid and kinetics of particle deposition is proposed.Through the analysis of the impact of roughness elements structure, flow condition, particle scale, particle properties and other factors on particle flow towards the wall mechanism,the 3d visualization of particle deposition process will be realized ,the random rough surface deposition characteristic will be explored,and the particle flow towards the wall mechanism through rough passage will be revealed.This project enlarges the gas-solid two phase fluid dynamics research.It is of great siginificance for solving particle deposition,diffusion and common problems in energy conservation and environmental protection area.

气固两相流颗粒趋壁行为在自然界和工程上普遍存在，由于气固两相流动的复杂性，使颗粒-壁面相互作用机理难以把握，而壁面粗糙度效应使颗粒趋壁行为更加复杂。本课题采用理论分析和实验研究的方法，对粗糙壁面气固两相流动颗粒趋壁行为机制进行深入研究。基于分形理论建立考虑分型维数和尺度特征的三维随机粗糙表面模型；考虑气固两相动力学和颗粒沉积动力学特性协同作用下的颗粒受力和碰撞沉积模型及相间作用耦合方式，构造基于CFD-DEM耦合的高精度的数值模型；探索粗糙元结构、流动状态、颗粒尺度、颗粒物性等因素对颗粒趋壁行为的影响机制，实现颗粒沉积过程的三维可视化，阐明随机粗糙表面颗粒沉积规律，揭示粗糙壁面的颗粒趋壁行为机理。本课题扩充了气固两相流体动力学研究领域，对解决节能、环保领域的颗粒沉积、扩散等共性问题具有重要的理论意义。

气固两相流颗粒趋壁行为在自然界和工程上普遍存在，由于气固两相流动的复杂性，使颗粒-壁面相互作用机理难以把握，而壁面粗糙度效应使颗粒趋壁行为更加复杂。本项目利用PIV激光粒子成像测速系统，结合现代化的数据处理手段，对周期性粗糙壁面流道内气固两相流动的三维全流场进行测试和分析；针对不同颗粒尺度、颗粒物性以及不同参数的周期性粗糙流道，分析颗粒在粗糙元处的时均速度、脉动速度和颗粒运动轨迹；数值模拟能够精确预测湍流流场信息以及颗粒沉积中的可视化过程，本项目采用两种粗糙模型，周期性粗糙壁面和随机粗糙壁面。对于周期性粗糙壁面，分析纵横比、高跨比、碰撞恢复系数、颗粒质量浓度对沉积的影响；对于随机粗糙壁面，基于分形理论，根据Weierstrass-Mandelbort分形函数，分析分形维数和尺度参数对随机粗糙壁面的影响。采用CFD-DEM耦合的数值模拟方法，合理的相间作用及耦合方式，全面考虑离散相、连续相各种因素对气固流动颗粒趋壁沉积行为的影响。