Wake Generators

The wake generators, which provide the aerodynamic forcing function in the present work, are symmetric airfoils without camber. They have a blunt trailing edge and are intended to produce wakes that are representative of the wakes shed from modern, highly loaded, low-aspect-ratio front stages. Such wakes are stronger and decay more slowly than those shed by high-aspect-ratio stages [10]. WG vane counts of 0 (clean inlet), 12, 24, or 40 may be chosen. In addition, the axial distance between the WG row and the rotor can be adjusted, via interchangeable spacers, to 12%, 26%, or 56% of the mean WG chord, which is 3.5 in (89 mm).

In the present study, the 26% chord spacing was chosen as being represen­tative of axial gaps found in typical fans and compressors [10]. Figure 5 illus­trates this spacing. To minimize the complexity of the TEB system plumbing and external compressed air consumption, the 12 WG configuration was se­lected. The WGs thus produce an aerodynamic gust forcing function at the twelfth engine-order (12E) and higher harmonics (24E, 36E, etc.).