Aerodynamic Characteristics of Perforated Walls for Transonic Wind Tunnels

A combined experimental-theoretical approach is developed for determination of the crossflow characteristics of ventilated walls. The technique is based on measurement of static pressures at the boundaries of a two-dimensional flow, calculation of the interior flow properties with Murman- Cole type finite difference techniques, and calculation of the boundary-layer development on and mass flux distribution through the ventilated wall using Patankar-Spalding type solution techniques. Results verify the validity of assuming proportionality between local pressure and flow angle as a boundary condition for wall interference estimates. However, it is also shown that the thickness of the boundary layer represents a dominant influence on the perforated wall characteristics, with both the slope and intercept of the characteristic being dependent on the boundary layer. The effects on the wall characteristics of suppressing the edgetone noise by use of screen overlays or splitter plates within discrete holes are documented.