Development of a Self-Streamlining Flexible Walled Transonic Test Section

This design eliminates the uncertainties found in data from conventional ventilated transonic test sections. The sidewalls are rigid, and the flexible floor and ceiling are positioned by motorized jacks controlled by an online computer to minimize tunnel setting times. The tunnel-computer combination is self-streamli ning without reference to the model. Data are taken from the model only when the walls are good streamlines, and can be corrected for the small known but inevitable residual interferences. Two-dimensional validation testing in the Mach range up to about 0.85 where the walls are just supercritical shows good agreement with reference data using a height-chord ratio of 1.5. The work has demonstrated the feasibility of almost eliminating wall interferences, allowing advantage to be taken of the improved flow quality and reduced power requirements or increased Reynolds number inherent with a shallow unventilated test section.