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

流动分离是当流体颗粒减速并不能跟随表面的形状时发生的现象。它对阻力和升力有几个负面影响，对能源消耗和排放、飞机的机动性、涡轮噪音和振动等都是至关重要的。拟议的研究是基于观察到鲨鱼皮肤上的真皮齿状物(坚韧的鳞片)在减少流体动力阻力方面表现出良好的性能。鲨鱼独特的皮肤在鱼类世界中动态响应流动的能力提供了比目前的流动控制技术显著的性能优势。该奖学金旨在对鲨鱼皮牙齿的减阻作用相关的因果机制有一个新的基本理解，同时为常规工业设计推进当前的数值模型。在EPSCoR RII Track-4：NSF奖学金的支持下，PI将学习模拟和分析流体-结构相互作用，并通过在斯坦福大学湍流研究中心(CTR)的培训开发新的数值预报工具模型。该奖学金将加强密西西比大学和斯坦福大学之间的合作，并促进中南部和密西西比州与航空、航空和海军工业相关的新的经济发展机会。鲨鱼齿的弹性锚定使它们在受到分离开始时发生的反向分离流动时能够竖起刷毛，从而阻碍了当地的分离。当Flow附着时，牙齿返回到非刷毛位置并形成肋状纹理，以减少摩擦阻力。这种运动导致牙齿的流动依赖的各向异性(或方向性)功能，这表明被动的、流动激活的分离控制技术。目前针对静止表面粗糙度设计的方法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国际和平协会在CTR的培训和合作研究。培训和研究的重点将是尖端的流固耦合模拟方法，以及用于预测表面微结构所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：(1)产生可移动各向异性微结构上前所未有的流动数据集，(2)对非线性相互作用有一个新的基本理解，(3)综合认识以开发真正可预测的阻力和动量通量模型。这项RII Track-4：NSF奖学金将扩大PI的研究能力，并将他的职业道路转变为流体-固体多物理系统和降阶模型开发的有前途的方向。流动相关的各向异性微结构所实现的独特流动控制技术将极大地改变航空航天、农业、生物医学、能源和环境工程中的许多其他研究领域，在这些领域中，流动控制过程需要应用具有定向功能的结构。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.