Friction drag and other design parameters for acoustic face sheets

Design changes and subsequent structural effects incurred in reducing jet noise are reviewed, together with test results from evaluations of the effects on aerodynamic drag produced by acoustic liner designs. The controlling factors in acoustic design are the face-sheet open area (POA), the face-sheet thickness, and the honeycomb thickness. Attention is given to the use of perforated materials of various types, the choice of hole diameters, and the application of a microporous cover on the POA-perforate. Design optimization is discussed, taking into account weight, the composites used, and the drag effects. Comparisons are made with test results for the drag coefficients of aluminum, titanium, porous and honeycomb liners for varying subsonic grazing speeds.