Implementation of a Wall Interference Correction Method at the National Full-Scale Aerodynamics Complex

Abstract

A wall interference correction software package was implemented in the 40– by 80–foot wind tunnel of the National Full–Scale Aerodynamics Complex at NASA Ames Research Center. The software uses a modified version of the wall signature method that combines wall pressure and lift/pitching moment measurements with a singularity representation of the test article in order to assess wall interference corrections. First, the calculation of a perturbation velocity database is reviewed that relates location and strength of a test article singularity to both the measured wall pressure signature and the wall interference corrections. Then, the implementation of different software modules is discussed that establish a data exchange between the data system of the 40– by 80–foot wind tunnel and the correction software and also compute corrections. In the next step, a wind tunnel test data simulation is discussed that was successfully used for the initial verification of the wall interference correction software. Finally, correction results from an actual wind tunnel test are discussed. It appears that the software computes angle of attack corrections correctly. Blockage corrections, however, do not show expected trends. This observation may be related to the fact that the walls of the test section of the 40– by 80–foot wind tunnel are covered with porous acoustic panels that were mathematically represented by using the closed wall boundary condition. In addition, the wind tunnel’s wall pressure measurements may not be compatible with the wall signature method. They are currently obtained on the bottom of isolated acoustic cavities instead of being recorded on the surface of the test section.