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Accession Number:
ADA281075
Title:
Numerical Simulation of Transient Vortex Breakdown above a Pitching Delta Wing
Descriptive Note:
Final rept. 1 Jan-31 Dec 1992
Corporate Author:
WRIGHT LAB WRIGHT-PATTERSON AFB OH
Report Date:
1994-05-04
Pagination or Media Count:
43.0
Abstract:
Computational results are presented for transient vortex breakdown above a delta wing subject to a pitch-and-hold maneuver to high angle of attack. The flows are simulated by solving the full three-dimensional Navier-Stokes equations on a moving grid using the implicit Beam-Warming algorithm. An assessment of the effects of numerical resolution, and favorable comparison with experimental data suggest the computational approach captures the basic dynamics of this transient breakdown. The pressure gradient along the vortex axis is found to play a dominant role in the initiation of breakdown. A description of the three-dimensional instantaneous structure of the flow field is provided for the first time using critical-point theory. The reversed-flow region in the vortex core is associated with pairs of opposite spiralsaddle critical points. At its onset, the vortex breakdown is fairly axisymmetric however, as it proceeds upstream and a stronger transition takes place along the axis, asymmetric effects become important and result in the formation of a bubble-type breakdown. This bubble structure is open and contains within itself a pair of stagnation points which are diametrically opposed and which rotate in the same sense as the base flow. Vortex breakdown, Delta wings, Unsteady aerodynamics, Computational fluid dynamics.
Distribution Statement:
APPROVED FOR PUBLIC RELEASE
