膜表面图案化是一种新兴的物理法膜污染控制技术。该技术通过改变膜表面形貌来调控膜界面水力学条件，进而控制污染物在膜表面的输运和沉积，达到延缓膜污染的目的。由于缺乏合适观测手段，现有研究对图案膜与水界面区域内污染物运动的表征仍很粗略，对于颗粒运动与流场的关联关系也缺乏深入认识。此外，图案膜的制备方法也有待完善。因此本研究探索并比较了不同波纹图案膜的制备方法，并结合计算流体动力学（CFD）流场模拟结果构建了新型图案膜流场原位实时观测系统；在这两方面工作的基础上，对不同进水条件下，不同图案膜表面示踪颗粒的运动行为进行了在线观测研究；最后，根据界面流场与颗粒运动的相关关系分析，初步探讨了图案膜形貌的优化方案。本研究的主要内容及结论如下：

（1）图案膜制备与表征：分别采用喷雾非溶剂相转换（s-NIPS）、相分离微成形（PSμM）制膜方法并结合3D打印技术，通过调控铸膜液组成、浓度、延流速度和喷雾速度等条件，制备出了具有不同表面形状特征的波纹膜。表征结果说明，PSμM膜和s-NIPS膜具有不同的膜孔结构，但所有膜的最大孔径都在0.6 mm以下，属于微滤膜。PSμM膜比s-NIPS膜具有更好的图案保真度，当铸膜液组分的重量百分比为聚偏氟乙烯（PVDF）：H₂O：聚乙烯吡咯烷酮（PVP）=15%：1%：5%时，PSμM膜的图案保真度可达95%。

（2）图案膜表面流场模拟与观测系统构建：首先采用CFD模拟技术，对实际制备图案膜表面流场进行仿真模拟，发现在与卷式膜元件接近的运行条件下，流场的最大雷诺数远小于2800，流动状态为层流；同时，图案谷内可出现旋流，而在脊附近出现波状流动，说明膜表面图案可在低雷诺数下，在流体边界层内引起局部紊流，并且谷是出现流场扰动的主要区域。根据模拟结果，图案膜表面流体最大边界层厚度为1.26 mm，图案脊处和谷内的最大切向流速分别为0.04 m/s和0.005 m/s。根据上述结果，选用325 fps帧率的摄像头，并设计专用透明圆柱和矩形膜池，构建了膜表面颗粒运动的原位实时观测系统。

（3）进水条件对膜表面颗粒运动的影响：利用所构建的原位实时观测系统，以聚苯乙烯乳胶颗粒和空心玻璃珠为示踪物，对s-NIPS膜表面的颗粒物运动进行观测，并探究了进水方向、错流速度对膜表面脊和谷区域颗粒运动的影响。结果表明，当进水方向与膜表面波纹走向一致时，图案膜表面的颗粒运动轨迹与平面膜表面相同，均为直线运动；当进水方向垂直于波纹走向时，脊附近运动区域加速跨越脊产生波状运动，谷内颗粒出现振荡运动；错流速度变化会显著影响谷内颗粒运动形式，当错流速度为0.08 m/s（Re≈237）时，颗粒出现螺旋振荡运动，当错流速度为0.1 m/s（Re≈296）时颗粒做快速无规则振荡运动。同时，振荡有利于颗粒离开图案膜的谷区，延缓该区域的颗粒沉积。

（4）图案膜形貌对膜表面颗粒运动的影响：在上述研究基础上，采用不同波纹形貌的PSμM膜，探索了图案膜波纹高度、间距等因素对颗粒振荡运动及其产生的临界错流流速的影响。结果发现，规则波纹形貌的PSμM膜谷中在较低雷诺数下也出现了颗粒螺旋振荡现象，且随雷诺数上升，谷内颗粒振动周期从1.96 s降低至0.88 s；当增加图案高度时，颗粒螺旋振动周期随之降低（振频加快），图案高度从240 μm增大至700 μm时，颗粒振动周期从236 s降低至0.8 s；而颗粒振动幅度受图案高度影响较小，受图案间距影响较大。

（5）颗粒与流场运动关联及图案膜表面形貌优化分析：结合图案膜观测结果与CFD模拟结果，分析了流场特点与颗粒运动的关联关系，发现颗粒振荡运动与谷内旋流有关，此时膜表面出现较强流体剪切力。对比所制备膜的观测结果发现，不规则图案膜比规则图案膜具有更高的表面剪切力，因此在设计膜表面图案时，不规则图案形状也是可选项；对于规则图案膜，图案高度≈ 440 μm的谷底剪切力高于图案高度≈ 700 μm的谷底剪切力，因此图案高度不能过高，需考虑过水通道与图案高度比值。此外，应避免尖角、拐角等不规则图案形状，这些区域难以形成旋流，容易捕集颗粒物并造成膜污染。

本研究实现了图案膜表面颗粒污染物运动的实时观测，初步揭示了颗粒运动与膜界面流场的关联关系。研究成果对于新型图案膜的设计和优化具有重要指导意义。

Membrane surface patterning is an emerging physical membrane fouling control technology. This technology regulates the hydraulic conditions of the membrane interface by changing the surface morphology of the membrane, thereby controlling the transport and deposition of pollutants on the membrane surface, and achieving the purpose of alleviating membrane fouling. Due to the lack of appropriate observation methods, the existing researches are still very rough in the characterization of the movement of pollutants in the interface area between the patterned membrane and the water, and lack of in-depth understanding of the relationship between particle movement and the flow field. In addition, the preparation method of patterned membrane also needs to be improved. Therefore, this study explored and compared the preparation methods of different ripple patterned membranes, and constructed a new in-situ real-time observation system for the flow field of patterned membranes combined with the CFD flow field simulation results. On the basis of these two aspects of work, the movement behavior of tracer particles on the surface of different patterned membranes under different influent conditions was observed online. Finally, according to the correlation analysis of interfacial flow field and particle motion, the optimization scheme of patterned membrane morphology was preliminarily discussed. The main contents and conclusions of this study are as follows:

(1) Preparation and characterization of patterned membranes: Spray non-solvent phase conversion (s-NIPS) and phase separation microforming (PSμM) membrane preparation methods, combined with 3D printing technology, were used to prepare corrugated membranes with different surface shape characteristics by adjusting the composition, concentration of casting solution, casting speed and spray speed. The characterization results show that PSμM membrane and s-NIPS membrane have different pore structures, but the maximum pore size of all membranes is below 0.6 μm, belonging to microfiltration membranes. The pattern fidelity of PSμM membrane is better than that of s-NIPS membrane, and the pattern fidelity of PSμM membrane can reach 95% when the weight percentage of the casting solution component is poly vinylidene fluoride (PVDF) : H₂O: polyvinylpyrrolidone (PVP) =15% : 1% : 5%.

(2) Flow field simulation and observation system construction on the surface of patterned membrane: Firstly, CFD simulation technology was used to simulate the flow field on the surface of the actual patterned membrane. It was found that the maximum Re of the flow field was much less than 2800 and the flow state was laminar flow under the operating conditions close to that of the spiral wound membrane modules. At the same time, swirling flow can occur in the pattern valley, while wavy flow can occur near the ridge, indicating that the pattern on the membrane surface can cause local turbulence in the fluid boundary layer at low Reynolds number, and valley is the main area of flow field disturbance. According to the simulation results, when the maximum boundary layer thickness of the fluid on the surface of the patterned membrane is 1.26 mm, and the maximum tangential flow velocity at the ridge of the pattern and in the valley is 0.04 m/s and 0.005 m/s, respectively. According to the above results, an in situ real-time observation system of particle movement on the surface of a film was constructed by selecting a camera with frame rate above 25 fps and designing a special transparent cylinder and rectangular membrane cell.

(3) The influence of influent conditions on the particle movement on the membrane surface: The in-situ real-time observation system was constructed to observe the particle movement on the s-NIPS membrane surface with polystyrene latex particles and hollow glass beads as tracers, and the influence of influent direction and cross-flow velocity on the particle movement in the ridges and valleys on the membrane surface was investigated. The results show that when the water inlet direction is consistent with the corrugation trend on the surface of the membrane, the particle trajectory on the surface of the patterned membrane is the same as that on the surface of the flat membrane, and the motion is linear. When the water inlet direction is perpendicular to the corrugation trend, the moving area near the ridge accelerates across the ridge and produced wavy motion, and the particles oscillated in the valley. The change of the cross-flow velocity will significantly affect the motion form of the particles in the valley. When cross-flow velocity was 0.08 m/s (Re ≈ 237), particles appear spiral oscillation motion, and when cross-flow velocity increase to 0.1 m/s (Re ≈ 296), particles perform fast and irregular oscillation motion. At the same time, the oscillation is beneficial for particles to leave the valley region of patterned membrane and alleviate the deposition of particles in this region.

(4) Influence of patterned membrane morphology on particle movement on membrane surface: Based on the above research, PSμM membranes with different corrugated morphologies were used to explore the influence of factors such as corrugation height and spacing of patterned membrane on particle oscillation motion and the critical cross-flow velocity. The results show that the particle spiral oscillation also occurs in the PSμM membrane valley with regular corrugation morphology at a lower Reynolds number, and the particle vibration period decreases from 1.96 s to 0.88 s with the increase of Reynolds number. When the pattern height increases, the spiral vibration period decreases (vibration frequency increases), and when the pattern height increases from 240 μm to 700 μm, the particle vibration period decreases from 236 s to 0.8 s. The amplitude of particle vibration is less affected by pattern height and more affected by pattern spacing.

(5) Correlation between particles and flow field motion and optimization analysis of patterned membrane surface topography: Combined with the observation results of patterned membrane and CFD simulation, the correlation between flow field characteristics and particle motion was analyzed. It was found that the particle oscillation movement was related to swirling flow in valley, and strong fluid shear force appeared on the membrane surface. Compared with the observed results of the prepared films, it is found that the surface shear stress of irregular patterned membrane is higher than that of regular patterned membrane, so the irregular pattern shape is optional when designing the surface pattern of the membrane. For regular patterned membranes, the valley bottom shear stress of pattern height about 440 μm is higher than that of pattern height about 700 μm. Therefore, the pattern height should not be too high, and the ratio of water channel to pattern height should be considered. In addition, irregular pattern shapes such as sharp corners and corners should be avoided. These areas are difficult to form swirling currents, which are easy to trap particles and cause membrane fouling.

In this study, the movement of particles on the surface of the patterned membrane was observed in real time, and the correlation between the movement of particles and the flow field at the membrane interface was preliminarily revealed. The research results have important guiding significance for the design and optimization of novel patterned membranes.