Dissertation Defenses

Doctoral Dissertation Announcement

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Candidate: Srinivasa Pantula

Degree of: Doctor of Philosophy

Department: Mechanical and Aeronautical Engineering

Title: Modeling Fluid Structure Interaction over a Fin Attached to a Naca0012 Airfoil

Committee:
Dr. William Liou, Chair
Dr. Tianshu Liu
Dr. Iskender Sahin
Dr. Ray Hixon

Date: Wednesday, November 5, 2008 10:00 a.m. - 12:00 p.m.
D204 Parkview Campus

Abstract:
Flow separation control is of immense importance to the performance of air vehicles and other technologically important systems involving fluids. Generally, it is desired to postpone separation so that the form drag is reduced, stall is delayed, lift is enhanced, and pressure recovery is improved. This work explores a new concept of post-stall flow control for airfoils and wings by using a thin flexible fin attached on the upper surface of an airfoil to passively manipulate flow structures in the fully separated flows for drag reduction, lift enhancement, and oscillation/flutter suppression. The flow induced oscillations allied with the shape deformations change the overall pressure distribution on the fin, which in turn affect the fin dynamics. This mutual effect of inertial and elastic forces can also be considered through fluid-structure interactions (FSI). In order to study this problem, an in-house Navier-Stokes finite difference solver is coupled with an in-house subdivision finite element solver in a segregated manner. The moving interface (i.e. fin) is modeled by a new class of non-boundary conforming methods called Immersed Boundary Methods (IBM) where the governing equations are solved on fixed meshes and the boundary, either moving or stationary, can be accounted by introducing external force into the momentum equation, which ensures that fluid satisfies the no-slip boundary condition on solid boundary.
In this dissertation the in-house CFD code and the in-house CSD code are validated. The immersed boundary method is used to compute steady and unsteady flows around stationary and moving boundaries. The order of convergence tests performed show that the immersed boundary method converges at a rate close to second order. The coupled CFD-CSD solver is first used to model flow induced flapping flat plate with a 50 angle of attack at Re = 20,000. Finally, the coupled solver is used to simulate flow over a NACA0012 airfoil with a passive flexible flapping fin attached to the upper surface of the airfoil with a 180 angle of attack at Re = 63,000.