The investigation of flight dynamics instability, when based on computational fluid dynamics level aerodynamics, is traditionally done in the time domain. It is, however, possible to look to the behavior of the eigenspectrum of the Jacobian of the semidiscrete system to obtain information at a reduced computational cost. The central computational task in this approach is to solve a sparse linear system, with a key issue being the calculation of an effective parallel preconditioner. With a knowledge of the bifurcation angle and the critical eigenvalue/eigenvector, it is possible to develop a reduced-order model which can predict the limit cycle amplitude postbifurcation. In this paper the shifted inverse power method, built on a preconditioned sparse matrix solver, is used to predict the wingrock onset angle of an 80-deg delta wing. The postbifurcation limit cycle oscillations are then calculated using a reduced model which uses knowledge of the critical mode of the system. This problem is considered here as a prototype flight dynamics instability. Superscripts p, q, z = complex conjugate w, = difference from equilibrium solution

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This paper considers the effects of both wind-tunnel walls and a downstream support structure, on the aerodynamics of a 70°delta wing. A RANS model of the flow was used with the wind-tunnel walls and supports being modelled with inviscid wall boundary conditions. A consistent discretisation of the domain was employed such that grid dependence effects were consistent in all solutions, thus any differences occurring were due to varying boundary conditions (wall and support locations). Comparing solutions from windtunnel simulations and simulations with farfield conditions, it has been shown that the presence of tunnel walls moves the vortex breakdown location upstream. It has also been seen that vortex strength, helix angle, and mean incidence also increase, leading to a more upstream breakdown location in wind-tunnels. The secondary separation line was also observed to move outboards. It was observed that for high Reynolds numbers, with a support downstream of the wing, vortex breakdown can be delayed due to blockage effects providing the vortices do not impinge on the support. This was observed to be the case for smaller supports also.