CAREER: Numerical Investigations of Biological and Bio-inspired Locomotion

University Of California-Los Angeles, Los Angeles CA

Investigators

Abstract

Abstract CBET-0645228 J. Eldredge, UCLA The proposed program addresses a need for a high-fidelity, computationally efficient tool for simulating flows produced by bodies with moving, deforming surfaces. This tool will be applicable to a wide range of fluid dynamical problems of biological and technological interest, but focus in this program period will be devoted to studying the role of flexibility in biomorphic locomotion in fluids. The proposed research program consists of two parallel components: (1) Development of a simulation tool for three-dimensional unsteady flow coupled with flexible surfaces, and (2) Numerical investigation of active and passive flexibility in a series of biologically-motivated benchmark problems. The research program will address several open questions of locomotion, and the educational component has a paradigm that is easily accessible to students at many levels. Intellectual merit: The grace and agility with which many organisms self-propel and maneuver in fluids is hardly matched by our own attempts of mimicry. We still lack sufficient understanding of the fundamental physics of most forms of biological locomotion to construct vehicles with similar functionality, despite thousands of years of observation. Investigation of these problems is most effective with a multidisciplinary tandem of experimental, computational and theoretical analysis, and recent interest has led to new and exciting advances with each of these tools. Experiments reveal that highly unsteady vortical flow structures and surface flexibility play critical roles in generating the requisite thrust, lift and maneuvering forces in fish and insects. Numerical simulations serve a powerful and necessary role due to the obvious difficulties in obtaining detailed flow measurements from freely-moving organisms. Conventional flow solvers are not naturally suited to the large surface deformations of biological locomotion. In order to circumvent these difficulties and to exploit the important role of vorticity, the simulations in this program will rely on the viscous vortex particle method, with which the PI has extensive experience. In lieu of a fixed grid, this method uses computational particles that automatically adapt to the evolving flow; because particles are only needed where vorticity is present, the method naturally focuses computational resources on a spatially compact region. The tool will be used to address several open questions regarding biological locomotion, with particular attention devoted to the roles of active and passive flexibility in the basic mechanics. A key development will be the construction and investigation of three canonical "flexible-body locomotion" problems. These problems will each be solved through a hierarchical series of sub-problems that give progressively more insight. The results of these studies can be used for later work in trajectory planning and reduced-order modeling, with the ultimate goal of devising control strategies. Broader impacts: The tools and results from this research program will be relevant to other important problems in bio-inspired aquatic and micro air vehicle design and internal biological flows. Furthermore, the results will be distilled and integrated into an educational program that consists of three principal components: development of an undergraduate course on the fluid dynamics of biological systems; visits to local K-12 schools through the UCLA Center for Excellence in Engineering and Diversity; and development and mentoring of undergraduate research projects. Each of these components will use the paradigm of natural locomotion to motivate fundamental concepts in fluid dynamics, and engineering in general. The visits to local schools in the Los Angeles and Inglewood Unified School Districts will focus on drawing students from disadvantaged and traditionally underrepresented groups into science and engineering. The PI and a small group of undergraduate assistants will engage the students by asking questions such as "Why doesn't an airplane fly like an insect?", and then lead interactive discussions and demonstrations that encourage broad participation.