Type of Document Dissertation Author Luton, J. Alan URN etd-10052007-143040 Title Numerical simulations of vortices near free and solid surfaces Degree PhD Department Engineering Mechanics Advisory Committee
Advisor Name Title Ragab, Saad A. Committee Chair Devenport, William J. Committee Member Mook, Dean T. Committee Member Nayfeh, Ali H. Committee Member Telionis, Demetri P. Committee Member Keywords
- short wavelength instability
- Crow instability
- vortex rebound
- airplane wakes
Date of Defense 1996-08-05 Availability restricted Abstract
The interaction of vortices passing near free and solid surfaces has been examined using direct numerical simulation (DNS). A computer code was developed which solves the unsteady, three-dimensional Navier-Stokes equations for incompressible flow. A critical element of the numerical scheme is the efficient solution of Poisson's equation. A state of the art solver based on multigrid techniques was developed which gives excellent convergence rates. The result is a tool capable of modeling complex three-dimensional flows in a variety of configurations.
Three different flow fields have been examined in order to determine some of the complex interactions involved between a vortex and a surface. The first concerns the two-dimensional interaction between a boundary layer and a convecting vortex. The size and height above the wall of the vortex are the same order of magnitude as the boundary layer thickness. A strong primary vortex creates a secondary vortex which causes the rebound of the primary, a response observed in many previous studies. However, weaker vortices as well do not follow the inviscid trajectory despite the absence of a secondary vortex. Rather than creating vorticity at the wall, a weaker vortex mainly redistributes the vorticity of the boundary layer. The redistributed vorticity alters the path of the vortex in ways not seen for vortex/wall interactions.
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