Quantitative and Qualitative Testing on a Model of the Prandtl-D Research Glider to Validate its Geometry

As part of an effort to elucidate the mechanisms behind the Prandtl-D research glider's novel aerodynamic behaviors, an experimental study has been designed and is being implemented. The initial test model was found not to behave as was numerically predicted, so the model was rebuilt, and the test setup was carefully and thoroughly recalibrated. The data acquisition system was updated to new hardware and software and the external force balance used for aerodynamic force measurements was recalibrated using a carefully designed, 824-point static calibration. Tests on the rebuilt test model included aerodynamic force measurements, the use of trailing edge streamers, and a series of surface oil flow visualization tests. Force measurements showed that the rebuilt test model behaves very similarly to the original model, having a maximum lift coefficient deficit of greater than 10% as compared to NASA simulations, among other discrepancies. Trailing edge streamers clearly show the position of the trailing vortices on the test model moved inboard precisely at the predicted angle of attack. Ongoing surface oil flow visualizations are being carried out to examine the stalling characteristics of the test model.