Development of semispan model test techniques

A computational investigation was performed to support the development of a semispan model test capability in the NASA Langley Research Center's National Transonic Facility, This capability is desirable for the testing of advanced subsonic transport aircraft at full-scale Reynolds numbers. A three-dimensional Navier-Stokes solver was used to examine methods to improve the now over a semispan configuration. First, a parametric study is conducted to examine the influence of the standoff height on the flow over the semispan model, It is found that decreasing the standoff height improves the aerodynamic characteristics of the semispan model. Next, active sidewall boundary-layer control techniques are examined, Juncture region blowing jets, upstream tangential blowing, and sidewall suction are found to improve the flow over the aft portion of the semispan model, Both upstream blowing and suction are found to reduce the sidewall boundary-layer separation, The resulting near-surface streamline patterns are improved and found to be quite similar to the full-span results. Both techniques, however, adversely affect the pitching moment coefficient.