Transonic Buffet over Symmetric Airfoils

Self-sustained oscillations and bifurcations of transonic flow past simple airfoils

“…was studied in [10]. Computations confirmed the existence of bifurcations obtained previously for an inviscid flow.…”

“…Nevertheless, the diagram C L (M ∞ ) depicted in Fig. 3 for airfoil (2a)-(2c) with h = 0.08 is similar to that for airfoil (1) [10]. This shows that the existence of bifurcations depends mainly on the length of the airfoil midportion with zero or small curvature rather than on the shape of the bow or aft parts.…”

“…The values of C L calculated in Maximums and minimums of the lift coefficient CL for an oscillatory flow past airfoil (2a)-(2c) of thickness h = 0.08 at α = 0 and Re = 5.2 · 10 6 : domains corresponding to flow regimes with different numbers of local supersonic zones are indicated by I-IV (four zones in domain I, three zones in domains II and III, and two zones in domain IV).asymmetric regimes of an inviscid flow differ only by 10-25% from the average of C L,max and C L,min obtained for an oscillating turbulent flow. We notice that, for airfoil (1), the neglect of turbulent viscosity resulted, on the contrary, in an expansion of the bifurcation interval[10].3. Flow Past a 7% Thick Airfoil.…”

Bifurcations and buffet of transonic flow past flattened surfaces

“…A numerical simulation of the turbulent flow past the airfoil (3) confirmed the existence of bifurcations at a ¼ 0 and, in addition, demonstrated self-sustained oscillations of the terminating shock waves and separated boundary layers (the buffet onset) [16]. Frequencies of the oscillations were of the same order as those documented in previous studies of transonic buffet for a circular-arc airfoil [17,18] and wavy airfoils [19].…”

“…Solutions of the unsteady Reynolds-averaged Navier-Stokes equations were obtained with a finite volume solver in which the equations are discretized in space on unstructured meshes using the Roe scheme and a MUSCL reconstruction [16]. The time derivatives are approximated with the second-order backward Euler scheme.…”