Amir Gat

Biography

Dr. Amir Gat is a theoretical fluid dynamicist and an expert in the field of low-Reynolds-number fluid-structure-interaction. He obtained his B.Sc. (2005, Summa Cum Laude) and Ph.D. (2010) from the Faculty of Aerospace Engineering, Technion. He then proceeded to a postdoc position at Gharib's group at Caltech (2010-2012) and is with the faculty of Mechanical Engineering since October 2012. Dr. Gat's research approach focuses on theoretical analysis, supplemented by small-scale experiments and numerical computations. The central subject of Amir's research is the analysis of transient dynamics of fluid-solid composite structures. This is an interdisciplinary research subject, which lies on the border between theoretical fluid mechanics, soft-robotics and composite-structures. The results of Amir's research can be applied to define the required geometric and physical properties of solid-fluid structures in order to achieve specific responses to external excitations, thus allowing to leverage elastic-viscous dynamics to create novel soft-actuators and fluid-solid composite materials with unconventional mechanical properties.

Abstract

Dynamics and Instabilities of Shape-Morphing Airfoil

We model a shape-morphing airfoil as two, rear and front, Euler-Bernoulli beams connected to a rigid support at an arbitrary location along the chord. The setup is contained within a uniform potential flow field and the aerodynamic loads are modelled by thin airfoil theory. The aim of this work is to study the dynamics and stability of such soft shape-morphing configurations and specifically the modes of interaction between the front and rear airfoil segments. Initially we present several steady-state solutions, such as canceling of deflection due to aerodynamic forces and transition between two predefined cambers via continuous actuation of the airfoil. The steady results are validated by numerical calculations based on commercially available software. We then examine stability and transient dynamics by assuming small deflections and applying multiple-scale analysis to obtain a stability condition. The condition is attained via the compatibility equations of the orthogonal spatial modes of the first-order correction. The results yield the maximal stable speed as a function of elastic damping, fluid density and location of clamping. The results show that the interaction between the front and rear segments is the dominant mechanism for instability for various discrete locations of clamping. Instabilities due to interaction dynamics between the front and rear segments become more significant as the location of clamping approaches the leading edge. Several transient dynamics are presented for stable and unstable configurations, as well as instability dynamics initiated by cyclic actuation at the natural frequency of the airfoil.