The plot below shows the imaginary unsteady pressure coefficient on the suction surface for the off-design test case. The interblade phase angle is 180 degrees. The reduced frequency (full chord) is 0.309. The data from Sbardella & Imregun was digitally extracted from figures in their paper titled Linearized Unsteady Viscous Turbomachinery Flows Using Hybrid Grids, in The Journal of Turbomachinery, Volume 123, pages 568 to 582. The experimental data is from tests performed at the EPFL and the data is available from the KTH site .