Experimental and Analytical Study of Rippled Trailing Edge Airfoils for Compressor Application

Abstract : Research was conducted to assess potential benefits of using the Rippled Trailing Edge (RTE) concept on compressor airfoils for separation alleviation and wake mixing enhancement. An empirically designed RTE was tested in a highly loaded, simulated compressor cascade that had demonstrated large scale suction side separation with a baseline circular trailing edge. The original RTE design resulted in a 50% increase of the chordwise extent of the separated flow compared to the baseline trailing edge. Extensive modifications to the RTE resulted in a fairing that eliminated separation, indicating that RTEs have potential for separation alleviation on compressor trailing edges. However, failure of the first design shows the weaknesses of the empirical RTE design procedure that was used, and that many unknowns still exist regarding the 3-D boundary layer relief concept. Further testing of ripples on more basic, isolated airfoils is suggested to develop further understanding of the 3-D boundary layer relief mechanism, without having to consider the inherent problems associated with the cascade testing. After developing such a data base, RTEs can then be evaluated for application to the more complex case where curvature and three-dimensional effects are significant.