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|Title:||Numerical Simulation of Leading Edge Vortex Rollup and Bursting|
|Author(s):||Brandt, Steven Allan|
|Department / Program:||Aeronautical and Astronautical Engineering|
|Discipline:||Aeronautical and Astronautical Engineering|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Abstract:||Vortex aerodynamics has played an important role in the development of high performance aircraft in recent years. Although computer codes which solve the three dimensional Euler equations have been used extensively to study vortex flows, they don't include physical viscosity effects associated with vortex flows. The Euler solvers do, however, contain numerical viscosity. As a result, viscosity effects in the Euler solutions such as vortex core size, vortex burst location, leading edge separation, and vortex rollup often do not agree quantitatively with results of physical experiments. The present work defines models for these physical viscosity effects which can be coupled with an Euler solver to improve modeling of vortex physics.
A vortex core model is derived from the steady, incompressible Navier-Stokes equations written in cylindrical coordinates. The core model is coupled with an Euler solver and tested on a variety of delta wings over a range of angles of attack. The resulting surface pressure distributions and vortex burst locations are shown to be much closer to wind tunnel data and results from Navier-Stokes solutions than results from Euler codes alone.
A second model is defined for viscosity effects in the viscous shear layer near the rounded leading edge of a highly swept wing based on an analogy to the boundary layer on a flat plate. The model is incorporated into an Euler code through the surface boundary condition and source terms in the boundary cells. The modified code is tested on several highly swept wings with rounded leading edges. Results are also shown to be in closer agreement with wind tunnel data for the same wing geometry than results from an unmodified Euler code.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1988.
|Date Available in IDEALS:||2014-12-15|