Advancement of Semispan Testing at the National Transonic Facility

Abstract

A need for low-speed, high Reynolds number test capabilities has been identified for the design and development of advanced subsonic transport high-lift systems. In support of this need, multiple investigations have been conducted in the National Transonic Facility (NTF) at NASA Langley Research Center to develop a semispan testing capability that will provide the low-speed, flight Reynolds number data currently unattainable using conventional sting-mounted, full-span models. Although a semispan testing capability will effectively double the Reynolds number capability over full-span models, it does come at the expense of contending with the issue of the interaction of the flow over the model with the wind-tunnel wall boundary layer. To address this issue, the size and shape of the semispan model mounting geometry has been investigated, and the results are presented herein. The cryogenic operating environment of the NTF produced another semispan test technique issue in that varying thermal gradients have developed on the large semispan balance. The suspected cause of these thermal gradients and methods to eliminate them are presented