基于超疏水表面的主被动复合防/除冰技术研究进展

介绍了光热、电加热、磁能、声波能与超疏水表面相结合的主被动复合防/除冰技术及其机理与应用，阐述了以上复合型防/除冰技术的优势与不足。其中，光热复合技术具有耗能低、材料选择多样化等优点；电加热复合技术工艺简单，易于规模化制造；磁能复合技术可满足复杂场景的防/除冰应用需求；声波复合技术则具有结构简单的优势。此外，同时复合多种能场可进一步提升防/除冰工作效率，是主被动复合技术的发展趋势之一。最后，阐述了基于超疏水表面的主被动复合防/除冰技术的不足之处，并展望了复合防/除冰技术的应用研究前景。     

Mixing performance of transverse hydrogen/air multi-jet through coaxial injector arrays in supersonic crossflow

Increasing the fuel mixing performance substantially improves the overall performance of the scramjet engine for a long-distance flight. In this paper, the influence of coaxial injector arrays of hydrogen/air multi-jet on the mixing performance of the fuel in supersonic crossflow is fully investigated. Our main goal is to examine the impacts of air and fuel coaxial injector on fuel distribution and penetration downstream of injectors in different operating conditions. In this study, fuel and air are simultaneously injected through coaxial multi-jet at sonic condition while of free-stream Mach number is 4. Computational Fluid Dynamic is applied for simulation of the transverse coaxial jet at supersonic crossflow. The effect of jet diameter with the same mass flow rate of air and hydrogen on fuel mixing is also investigated. The mixing efficiency of different jet spaces and pressures is also examined to obtain an optimum jet arrangement in the combustor chamber. Our study shows that the injection of the coaxial air/hydrogen jet noticeably improves mixing downstream by augmentation of fuel interaction with an air jet. Our results also show that fuel jet space of 7 Dj offers maximum fuel mixing by the formation of multi vortices with uniform strength.     

激光加工超疏水表面抗结冰性能研究进展

在低温环境中，表面结冰会严重影响户外装备的运行效率和安全，基于疏水材料的新型被动式防除冰方法引起了广泛关注。超疏水表面凭借其优越的拒水、抑制冰核形成和降低冰黏附强度等能力，在防除冰技术领域表现出广阔的应用前景。激光加工技术具有高效率和灵活性，成为制备超疏水表面的有效方法，并被进一步用来研究表面的抗结冰性能。首先，概述了固体表面润湿理论和结冰机理。其次，综合评估了激光加工超疏水表面的抗结冰性能，包括静态水滴延迟结冰时间、动态水滴累积、冰黏附强度、延迟结霜与抗冻能力、表面积冰与除冰等方面。静态水滴延迟结冰时间受到水滴与表面接触界面的成核速率和传热速率的影响，动态水滴累积与表面润湿性密切相关，冰黏附强度反映了表面对冰的附着性和除冰的难易程度。超疏水表面具有显著的延迟结冰能力，但在低温高湿条件下，表面的超疏水性可能会减弱，甚至失效。除冰过程也可能破坏超疏水表面的微观结构，进而影响其持续的抗结冰性能。最后，对超疏水表面激光加工与抗结冰性能的未来研究方向进行了展望。     

热敏荧光法用于蒸发液滴近接触线的温度测量

探究静置液滴蒸发的动力学原理在众多的相关工业应用中举足轻重。在过去的数十年间,尽管相关领域的学者进行了大量的研究工作,但仍有一个关键的问题尚未解决,即液滴接触线附近的温度在蒸发过程中到底是如何变化的。通过直接测量的实验方法,报道了液滴在接触线固定不动的蒸发阶段,其接触线附近温度的详细变化过程。利用显微热敏荧光测温技术,其结果表明：液滴接触线附近自由界面的温度将沿径向发生急剧变化,并伴随一组在蒸发过程中不断发生演变的荧光同心圆环,这种荧光条纹带是由于液滴边缘的几何差异性所导致的局部强化蒸发冷却与一组热浮力驱动的对流辊相互作用产生的结果。本研究将为蒸发动力学提供新的认识,并有望在各种对传热系统的应用领域中促成新的进展。     

Effect of hybrid coaxial air and hydrogen jets on fuel mixing at supersonic crossflow

In this research study, a computational method is applied to examine the impacts of coaxial hybrid air and fuel jets on fuel mixing at the supersonic cross-flow of Mach = 4. This study examined the coaxial air and fuel jet effects on main parameters i. e. circulation, mixing efficiency, and fuel penetration. Computational Fluid Dynamic is employed for the modelling of the coaxial jet at cross supersonic flow. Reynolds Average Navier-Stocks equations with SST turbulence model for achieving hydrodynamic feature of the main model. Impacts of air-jet pressure and nozzle configurations on fuel distribution are also presented and the main effective factors for efficient fuel mixing condition are explained. Our results disclosed that injection of coaxial air and fuel jets at supersonic cross airflow significantly improves the fuel penetration and mixing inside the combustion chamber. Flow study analysis shows that the coaxial injector augments the spiral feature of the fuel jet, which surges fuel mixing downstream. Our circulation analysis confirms that circulation strength increases in far away from an injector by the injection of a coaxial air jet.     

Méthodes adaptatives pour les déformations localisées

Structure materials carry the loads that are applied to them, often by developing very localized behaviour near geometric singularities like joints (welds, rivets, etc.), thickness variations or various notches. Computations accuracy requires then meshes that would be prohibitive if they were uniformly refined without knowing a priori the aforementioned areas. Adaptive methods with shape functions enrichment allows to focus the computational cost in these regions. Herein, the error estimation problem is addressed as well as various mesh and model enrichment possibilities in particular hierarchical enrichment, for example for joints between three-dimensional and shell structure. The interest of such an analysis for crack propagation in ductile material is examined. Finally several numerical examples are presented to emphasize the efficiency of the approach.     

微液滴/注液表面黏附行为的主被动控制及机理

目的 提出一种微液滴/注液表面黏附行为主/被动控制方法，探究在电压和流体黏度耦合作用下微液滴/注液表面黏附行为动态可调机理。方法 在P型硅片表面制备超疏水层，注入黏度分别为10、50、100 mm²/s的聚二甲基硅油制得注液表面，使用固液界面行为测试仪探究不同黏度和外加电压下微液滴/注液表面的黏附行为。结果 当聚二甲基硅油黏度从10 mm²/s增加到100 mm²/s，微液滴/注液界面润湿力从194 μN减小到123 μN，最大相互作用力从129 μN减小到94 μN，分离力从101 μN减小到82 μN;当电压从0 V增加到240 V时，润湿力从156 μN增加到322 μN左右，最大相互作用力从120 μN增加到178 μN左右，分离力从85 μN减小到53 μN左右，实现了黏附力的动态调节。结论 高黏度聚二甲基硅油内部具有较强的剪切力，但是长链会增强微液滴/注液表面氢键作用，在2种作用形式的耦合下，润湿力、最大相互作用力以及分离力随黏度的增加而减小。在电压作用下，微液滴在注液表面产生电润湿行为，有效界面能随电压发生非线性响应，实现了固液界面黏附力的实时调节。微液滴/注液表面可以通过改变电压与润滑油的黏度实现黏附行为的主/被动的调节。     

硫醇改性超疏水铜表面的耐候性及失效机理

目的 探究户外环境中导致硫醇改性超疏水铜表面失效的因素及其超疏水性失效的机制。方法 通过化学刻蚀法在铜表面构筑纳米结构，利用正十二硫醇进行表面改性，得到具有超疏水性的铜表面。将该表面置于户外进行耐候性研究，并通过4种模拟户外环境实验探究超疏水性失效的原因，包括组合循环实验（循环条件含紫外辐射、淋雨和凝露）、紫外辐射实验、水环境实验和温度实验。结果 超疏水铜表面经过10 d的户外实验后，其接触角由初始状态的158.5°降至131.1°，表明该表面的超疏水性能已失效。经过2次组合循环实验（每次循环的时间为12 h）、20 d紫外辐射实验及30 d水环境实验后，该表面的接触角分别降至130.3°、124.5°、131.7°，表明该表面均已失去超疏水性；经过40 d高温实验后，表面的超疏水性开始失效。XPS谱图表明，在超疏水性失效后该表面不存在硫元素，即正十二硫醇已经脱离表面。结论 超疏水铜表面的硫醇分子脱落是超疏水性失效的根本原因。紫外辐射、水和高温是导致超疏水铜表面超疏水性失效的主要因素。其中，紫外辐射或水对超疏水性的破坏速度比高温快。相较于单一因素（紫外辐射、水或高温），三者的协同作用更...     

Sustainable Droplet Manipulation on Ultrafast Lubricant Self-Mediating Photothermal Slippery Surfaces

Designing intelligent slippery surfaces for droplet manipulation is critical for many applications from drug delivery to bio-analysis, while is of great challenging in sustainability for inescapable wastage of lubricant layer. Herein, an ultrafast lubricant self-mediating (self-replenishing/-absorbing) photothermal slippery surface is designed that achieves sustainable transport of droplet under the irradiation of near infrared light (NIL) even if the lubricant layer is wiped clean completely, as well as at other man-made extreme conditions. The ultrafast lubricant self-mediating performance is caused by synergistic effects of interconnection of porous structure and photothermal expansion of the material. When lubricant on surface is lost, photothermal expansion of material can quickly squeeze the lubricant inside the base to flow into and out of the interconnected porous structure to generate a fresh lubricant layer. Attractively, when the NIL is turned off, the rebuilt lubricant layer can be swiftly self-absorbed into the porous to inhibit unnecessary wastage. Moreover, an arbitrary split of droplet in desired configurations can be achieved by controlling the NIL irradiating route. This sustainable droplet manipulation induced by ultrafast lubricant self-mediating can be extensively applied in microfluidics and micro-reactor settings.