... spatial discretization, utilizing a Galerkin-Fourier expansion in the azimuthal coordinate θ and Chebyshev collocation in r and z The radial dependence of the variables is approximated by a Chebyshev ... equations (Mercader, Net and Falqués 1991) In this study, the aspect ratio Λ was fixed at 2.5 and variations in Re, A and ωf were considered 96 spectral modes in z, 64 in r, and up to 24 in θ ... QUENCHING OF UNSTEADY VORTEX BREAKDOWN Fig 6. 12 Phase portraits (with Wa and Ww as the horizontal and vertical axes, respectively) at Re = 2800, Λ = 2.5, ωf = 0.5 (ωf /ω0 ≈ 2.88) and A as indicated...