Instability of the flow in the vicinity of trailing edge of a class of thin aerofoils


Turkyilmazoglu M.

COMPUTERS & FLUIDS, cilt.32, sa.3, ss.353-371, 2003 (SCI İndekslerine Giren Dergi) identifier identifier

  • Yayın Türü: Makale / Tam Makale
  • Cilt numarası: 32 Konu: 3
  • Basım Tarihi: 2003
  • Doi Numarası: 10.1016/s0045-7930(01)00088-3
  • Dergi Adı: COMPUTERS & FLUIDS
  • Sayfa Sayıları: ss.353-371

Özet

A numerical study has been undertaken to investigate the notion of absolute/convective instability in laminar incompressible trailing edge flows past wedge-like shapes with curved boundaries of the form y = alpha(-x)(m). The effects of various trailing edge shapes m and relative thickness a on the flow separation and the development of instabilities in the vicinity of trailing edge are investigated. The nonlinear viscous-inviscid interaction equations, which have been derived by means of the asymptotic theory of flow separation, are solved first numerically to construct genuine mean velocity profiles representing the correct flow in the vicinity of the trailing edge. The absolute/convective nature of the asymptotically formed velocity profiles via a composite expansion is then ascertained by using a spatio-temporal analysis based on the Briggs-Bers pinching criterion. Although no absolute growth is encountered upstream of the trailing edge of the airfoil shapes considered, in particular the wake region behind the trailing edge of Joukowski type profiles is found to be persistently susceptible to absolute instability. It is found that separation is enhanced as the relative thickness of the airfoil gets bigger. This, in turn, is shown to lead to an additional enhancement of the absolute instability character by both increasing the absolute growth rate as well as the extent of the unstable region. Shedding frequency of the Karman vortex street is also determined behind the trailing edge shapes considered. (C) 2002 Elsevier Science Ltd. All rights reserved.