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Numerical validations
We present first some unsteady Navier-Stokes results obtained with the 2.5D solver for an isolated profile and the rectilinear cascade.
3.1 Isolated PFSU profile
The aerodynamic conditions for this 2D computation are an upstream Mach number value of 0.75, a total pressure of 1108121 Pa, and a total temperature of 299.8 Kelvin. The steady angle-of-attack of the ft>w is 3 degrees. The chord of the profile is 0.3 meter. The profile is moving in pitch at a frequency of 40Hz, with an amplitude of 0.25 degree. Navier-Stokes steady and unsteady computations were run using the turbulence model of Michel and that of Spalart-Allmaras. We used a 300×100 C-like mesh.
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Figure 1 Steady and Harmonic analysis of the pressure coefficient |
The unsteady run needed the computation of 4 periods of about 50000 iterations using a uniform time step at a maximum CFL value of 10. The previous sketch shows the mean and unsteady pressure coefficients on the profile (Fig. 1) and a comparison of steady velocity profiles for three axial positions (Fig. 2). Spalart-Allmaras results and available experimental data compare fairly well. Algebraic turbulent model seems to be insufficient to get a good description of the leading edge separated zone.
