RII Track-4: NSF: Simulation and Modeling of Turbulent Flow Control via Flow-Dependent Anisotropic Surface Textures

流动分离是一种现象，当流体粒子速度减慢，不能跟随表面的形状时发生。它对阻力和升力有几个负面影响，对能源消耗和排放、飞机机动性、涡轮噪声和振动等至关重要。这项研究的动机是观察到鲨鱼皮肤上的真皮小齿（坚韧的鳞片）在减少水动力阻力方面表现出有希望的性能。在鱼类世界中，鲨鱼独特的皮肤动态响应水流的能力比目前的水流控制技术提供了显著的性能优势。该奖学金旨在获得与鲨鱼皮小齿减阻作用相关的因果机制的新的基本理解，同时推进当前常规工业设计的数值模型。在EPSCoR RII Track-4:NSF奖学金的支持下，PI将通过在斯坦福大学湍流研究中心（CTR）的培训，学习模拟和分析流-结构相互作用，并开发新的数值预测工具模型。该奖学金将加强密西西比大学和斯坦福大学之间的合作，并促进与中南部和密西西比州的航空、航天和海军工业相关的新经济发展机会。鲨鱼牙的弹性锚定使它们在受到分离开始时发生的反向分离流时竖起鬃毛，从而阻碍了局部分离。当流体附着时，小齿返回到非刚毛位置，并形成锯齿状纹理，以减少摩擦阻力。这种运动导致了牙齿的流动依赖各向异性（或方向）功能，这表明了一种被动的、流动激活的分离控制技术。目前的方法是为固定表面粗糙度设计的，不足以理解或预测由可移动微结构调制的复杂流动。该奖学金的首要目标是支持PI在CTR的培训和合作研究。培训和研究将侧重于前沿的流固耦合模拟方法，以及用于预测表面微结构代表的复杂效应的新型壁面模型的开发和验证。具体目标包括：(i)生成一个前所未有的可移动各向异性微结构流动数据集，（ii）获得对非线性相互作用的新的基本理解，（iii）综合理解以开发真正的阻力和动量通量预测模型。该奖学金将扩大PI的研究能力，并将他的职业道路转向流固多物理系统和降阶模型开发的有前途的方向。由流动相关的各向异性微结构实现的独特的流动控制技术将对航空航天、农业、生物医学、能源和环境工程等许多其他研究领域产生重大影响，这些领域需要具有定向功能的结构来进行流动控制过程。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Flow separation is the phenomenon that occurs when a fluid particle is slowed down and cannot follow the shape of the surface. It has several negative effects on drag and lift that are critical to energy consumption and emissions, aircraft maneuverability, turbine noise, and vibration, etc. The proposed research is motivated by the observation that dermal denticles (tough scales) on shark skin show promising performance in reducing hydrodynamic drag. The ability of sharks’ unique skin in the fish world to dynamically respond to the flow offers a significant performance advantage over current flow control techniques. This fellowship aims at gaining a new fundamental understanding of the causal mechanisms associated with the drag reduction role of shark skin denticles and simultaneously advancing current numerical models for routine industrial design. With the support of an EPSCoR RII Track-4:NSF Fellowship, the PI will learn to simulate and analyze fluid-structure interactions and develop new models for numerical predictive tools through the training at the Center for Turbulence Research (CTR) at Stanford University. The fellowship will strengthen collaboration between the University of Mississippi and Stanford, and promote new economic development opportunities related to aeronautics, aerospace, and naval industries in the mid-south and in the State of Mississippi.The elastic anchoring of shark denticles enables them to bristle when subjected to the reversing separated flow that occurs at the onset of separation, thus hindering local separation. When flow is attached, denticles return to the non-bristled position and form a riblet-like texture to reduce friction drag. This motion leads to a flow-dependent anisotropic (or directional) function of the denticles that indicates a passive, flow-activated separation control technique. Current approaches, designed for stationary surface roughness, are insufficient to understand or predict the complex flows modulated by movable microstructures. The overarching goal of this fellowship is to support the PI’s training and collaborative research at the CTR. The training and research will focus on the cutting-edge fluid-structure interaction simulation methods and the development and validation of a novel wall model for the prediction of complex effects represented by surface microstructures. Specific objectives include: (i) to generate an unprecedented dataset of flows over movable anisotropic microstructures, (ii) to gain a new fundamental understanding about non-linear interactions, (iii) to synthesize the understanding to develop truly predictive models for drag and momentum flux. This RII Track-4:NSF fellowship will expand the PI’s research capacity and transform his career path towards a promising direction in the fluid-solid multi-physics system and reduced-order model development. The unique flow control techniques achieved by the flow-dependent anisotropic microstructure will be highly transformative to many other research areas in aerospace, agricultural, biomedical, energy, and environmental engineering where the application of structures with directional function is needed for the flow control process.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.