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PGRC Cascade
We next present Navier-Stokes computations dealing with a high subsonic unsteady fbw over a PGRC profile cascade. The upstream Mach number is 0.9. The fbw angle of attack is 12 degrees. The computation was performed for a total pressure of 159881 Pa and a total temperature of 285.16 K. For this computation, a 3 domain HCH grid was designed for a single channel using a total of 16433 nodes. Continuity boundary conditions were used in the steady case at channel interfaces. We present in Fig. 3 the steady isomach lines map obtained by PIV technique and by the computation, over 2 channels.
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Figure 3 Steady iso-Mach lines and Pressure distribution. |
The unsteady computations have been performed for 5 inter-blade phase angles. The dual timestep technique has been used with a CFL number of 4.
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Figure 4 Harmonic analysis of the pressure coefficient |
At each physical timestep, the first component of the fOw field must decrease of two order. To describe a cycle we need 64 time-steps. When the inter-blade phase angle is different from zero, we need to run about 20 periods ( 6 periods are enough for the zero inter-blade phase angle).We present the unsteady results, for a pitching motion of the central blade at a frequency of about 300 Hz, compared to experimental data. A rather good agreement with the experimental distribution can be noticed.
