Transonic Stall/Choke Flutter Analysis of Cascades by a Navier-Stokes Solution-Adaptive Approach

In this paper, the stall and choke flutter analyses of NACA 0006 unstaggered cascades in transonic viscous flows are presented by using a time domain approach. For the present time domain approach, a solution-adaptive finite volume method with rigid-deformable dynamic mesh treatment is adopted to solve the two-dimensional unsteady Navier-Stokes equations. The structural model equations, where each blade is treated as a typical section having plunging and pitching degrees of freedom, are integrated to obtain the blade displacements by an explicit four-stage Runge-Kutta scheme. In the present calculations, the Baldwin-Lomax turbulence model and two transition formulations are used. The instantaneous meshes, vorticity contours, pressure contours and velocity vectors around the trailing edge clearly indicate the flow phenomena, such as the vortex shedding and λ shocks with separation bubbles. From the histories of blade displacements and total energy, the flutter phenomena are studied. Furthermore, the Fast Fourier Transformation (FFT) and modal identification techniques are introduced to investigate the aeroelastic behaviors in present transonic stall and choke flutter problems.