טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentKleiman Alexander
SubjectNonlinear Spatio-Temporal Fluid-Structure Interaction of
an Elastic Panel in a Uniform Flow
DepartmentDepartment of Mechanical Engineering
Supervisor Professor Oded Gottlieb
Full Thesis textFull thesis text - English Version


Abstract

The field of fluid-structure interaction (FSI) incorporates a wide range of phenomena that are of great scientific and engineering interest in various disciplines. The essence of this interaction is in the information transfer between the structure and surrounding fluid, where the fluid exerts loads on the structure, which in turn complies and disturbs the flow in its vicinity. One of the highly investigated FSI problems is the complex motion of an elastic rectangular panel immersed in a uniform stream parallel to the longitudinal panel direction.

In the present research we investigated two different configurations: (i) a panel that is clamped/simply-supported along the leading-edge with the other edges in a free configuration, such as a flag, and (ii) an infinite plate comprised of periodic rectangular panels with all edges hinged, and the flow is bounded by two rigid walls, bellow and above the elastic panel.

A nonlinear inextensible Euler-Bernoulli cantilever panel with a Lighthill slender body reactive force and an innovative high order aerodynamic dissipation model is implemented to investigate the subcritical flutter observed in experiments. An asymptotic multiple-scales analysis of the reduced-order dynamical system with model-based estimated quintic damping reveals the necessity of including high-order dissipation to account for the subcritical nature of the flutter.

A computational investigation of hinged rigid-body and elastic panels in viscous and compressible laminar flow is carried out using finite-difference flow and structural solvers. A rigid-body panel investigation reveals an intricate bifurcation structure of coexisting periodic ultrasubharmonic, quasiperiodic and chaotic solutions for moderate Reynolds numbers. The numerical investigation of the elastic panel reveals an intricate bifurcation structure for Re>100, where beyond the flutter threshold a secondary transition to nonstationary solutions with spatial complexity is discovered. It is also found that the panel oscillations undergo a transition from 2nd mode to 4th mode flutter around Re=500. The transition in oscillation regimes is complemented by a wake transition from "P" type to "2P" formation.

An investigation of a two and three mode dynamical system describing the self-excited dynamics of a periodically simply-supported panel in a bounded incompressible flow reveals a complex bifurcation structure governed by multiple Hopf-bifurcations augmented by coexisting periodic and non-stationary limit-cycles.