IDR: Phononic Surfaces for Flow Control

这个跨学科研究项目提出了一个新的概念，表面与流体相互作用-柔性表面，可以设计成流体弹性或气动弹性相互作用与边界层流动在一个有利的方式，导致阻力的减少。其基本思想是在凝聚态物理学的启发下，在表面的内核处具有周期性的晶格结构，因此称为声子表面。该表面将主要设计为延迟层流到湍流的过渡和分离，并且还导致充分发展的湍流的阻力减小。可以同时实现的其他功能是减少整体振动和结构噪声排放。研究计划包括调查一个有效的，系统的和综合的方法建模，分析和设计的建议声子表面。对于周期性晶格晶胞能带结构计算，将利用基于模态分析的新颖且高效的计算方案。将为单位单元优化创建专门的遗传算法算子。将进行表面中的流动和弹性波运动的直接数值模拟。单元格设计将独立于完全耦合的固体-流体模拟进行，从而提供关键的计算节省。研究的跨学科性质，在动力系统，凝聚态物理学和流体动力学的交叉路口，将丰富计划研究的各个方面。阐明固体表面内和之下的色散周期波与非线性和不稳定的流体波之间相互作用的性质将构成涉及基本物理现象的新发现。这些知识的后续利用有望为流量控制开辟一个新的方向。对于流线型船舶和飞机，或一般车辆，建议的减阻概念将大大提高燃料效率，从而带来经济和环境效益。还可以实现不同种类涡轮机性能的提高。

This Interdisciplinary Research project presents a new concept for surfaces interacting with fluids - flexible surfaces that can be designed to hydroelastically or aeroelastically interact with boundary-layer flow in a favorable manner leading to reduction of drag forces. The basic idea, which is inspired by condensed matter physics, is to have a periodic lattice structure at the inner core of the surface, hence the phrase phononic surface. The surface will be primarily designed to delay laminar-to-turbulence transition and separation, and also to cause drag reduction for fully developed turbulent flow. Other functions that can be simultaneously realized are reduction of overall vibrations and structural noise emission. The research plan involves investigation of an efficient, systematic and integrated methodology for modeling, analysis and design of the proposed phononic surfaces. For the periodic lattice unit cell band structure calculation, a novel and efficient computational scheme based on modal analysis will be utilized. Specialized genetic algorithm operators will be created for the unit cell optimization. Direct numerical simulation of the flow and the elastic wave motion in the surface will be carried out. The unit-cell design will be performed independently of the full coupled solid-fluid simulations thus providing crucial computational savings. The interdisciplinary nature of the research, at the cross-roads of dynamical systems, condensed matter physics and fluid dynamics will enrich the various aspects of the planned research. Elucidating the nature of the interaction between the dispersive periodic waves in and beneath the solid surface and the nonlinear and unstable fluid waves will constitute a new discovery involving fundamental physical phenomena. The subsequent utilization of this knowledge promises to open a new direction in flow control. For streamlined ships and aircrafts, or vehicles in general, the proposed drag-reduction concept will bring about substantial improvements in fuel efficiency and hence economic and environmental benefits. Gains to the performance of turbines of different sorts could also be realized.