SCALING AND EXTRAPOLATING SMALL-SCALE IN-FLOW WIND TUNNEL JET NOISE TO FULL-SCALE FLYOVER JET NOISE

In the development of noise suppressor nozzles and other aircraft systems, it is often cost effective and appropriate to build and test small-scale prototype systems instead of expensive full-scale systems. The difficulty with this approach lies in the interpretation of the scale model data in terms of quantities that would be produced by an actual fullscale nozzle. This paper will discuss a procedure for predicting the full-scale flyover noise of jet nozzles/suppressors from in-flow acoustic wind tunnel measurements of small-scale nozzle/suppressor models. Before data manipulations are considered, requirements for the set-up of the small-scale experiment are reviewed. The data manipulations are then discussed in four parts: removal of test day and test set-up effects, scaling to full scale, extrapolation to simulation distance, and flight simulation.