M.Sc Thesis | |

M.Sc Student | Dunaevich Lev |
---|---|

Subject | Flutter of a Cavity-Backed Plate with a Cutout |

Department | Department of Mechanical Engineering |

Supervisor | PROFESSOR EMERITUS Pinhas Bar-Yoseph |

Full Thesis text |

Fluid-Structure Interaction (FSI) problems arise in many practical problems, ranging from the motion of a flag in the wind to the flutter of aircraft wings. In this research a new geometry for FSI is studied. The geometry consists of an elastic plate with a cutout at its center, placed over a rigid rectangular cavity. The cavity is embedded in an infinite rigid wall. The model is reduced to two dimensions and a cross-section is solved numerically. The flow is considered laminar and incompressible.

It was found that assuming infinite plate rigidity, Rossiter modes are
observed, which are a type of shear layer instability. The Rossiter modes were
governed by the ratio of momentum thickness (*q**)
to cavity opening length (*A*), where for *A/**q*<58* the flow was stable, for *60<A/**q*<*95 the shear layer oscillated at the second
Rossiter mode, and for *95<A/**q*<*180
the flow oscillated at the third Rossiter mode.

When the plate is elastic flutter is observed. For constant *A/**q**, the flutter was studied as a function of flow velocity
normalized by the plates’ rigidity, giving a non-dimensional velocity (*V**).
It was observed that for low *V** the flow behaves as it does for a rigid
plate. Increasing the non-dimensional velocity *V** above 3.3 causes
flutter, and further increase of *V** causes the plate to flutter at the
second (*V*>4.7*) and third (*V*>10*) modes. The flutter is
also dependent on momentum thickness, which influences the critical velocity at
which flutter occurs.

Mapping the flutter stability threshold as a function of *A/**q** and *V** shows a map with four
regions. For *A/**q**<*12*,
the flow was undisturbed by the cavity and the plate. For *12< A/**q*<58* and *V*>3.3*, the flow is dominated by the plate
flutter. For *A/**q**>*58*
and *V*<3*, the flow
is dominated by Rossiter modes, while for *A/**q**>*58* and *V*>3.3* a highly nonlinear mixed region exists.