Development of a Noise Prediction Model for a Cruise Friendly Circulation Control Wing

Abstract

New aircraft concepts that are to meet challenging cruise efficiency, short field takeoff, and noise goals will have to rely on innovative high lift technology. One such technology is the Circulation Control Wing (CCW) which leverages a thin high aspect ratio jet flowing over a curved flap surface to generate tremendous lift coefficients. Of concern is the impact that this technology will have on the overall noise of the aircraft. Some acoustic studies have reported noise characterization of such a CCW with extremely thick airfoils and trailing edges. More practical CCWs must be “cruise friendly”. It is the objective of the current paper to address the noise character of such a CCW configuration and to begin to develop a noise prediction model to assess new aircraft configurations using this technology. A current NASA Fundamental Aeronautics Subsonic Fixed Wing project being conducted by Georgia Tech Research Institute (GTRI) and teammate California Polytechnic State University involves the development of a CCW integrated with engines located over the wing (OTW) to improve the powered high-lift and cruise performance of Cruise Efficient STOL (CESTOL) aircraft. As part of this program, a series of aeroacoustic tests on a 2D model scale CCW are conducted. Far field acoustic data was acquired to quantify the far field noise as a function of aft flyover angles, free stream velocity, and slot jet velocity. It is found that an asymmetrical directivity pattern emerges where higher frequency noise is shielded to observers below the bottom of the flap chord. A 5 order velocity scaling collapses spectra very well for high frequencies and a 6 order works well for lower frequencies. Finally, these data are used as a basis for predicting the community noise of a CESTOL aircraft relative to a conventional take-off and landing aircraft. It was found that using a CCW in conjunction with a STOL trajectory has the potential for reducing overall aircraft noise, however a more complete set of acoustic data on a highly fidelity test article is needed to reduce the uncertainty of the prediction.