Jump to navigation
An experimental investigation of the prandtl-d research gliders aerodynamic characteristics
Zelenka, Bradley Joseph
Miller, FletcherJacobs, Gustaaf
The work presented herein serves as the foundation for an effort to elucidate the mechanisms behind the Prandtl-D research glider’s novel aerodynamic behaviors using a highly detailed Stereoscopic Particle Image Velocimetry (SPIV) flow survey. As preparation, wind tunnel testing of a Prandtl-D model was carried out. The full-scale Prandtl-D sees flow with a Reynolds number of 337,000: present testing achieves 180,000 and 210,000 using an 8.3% scale model. The force balance was calibrated using a carefully developed 824-point static calibration with a set of newly NIST-traceable calibrated weights in 50% load limit increments. The optimal math model was determined using the NASA BALFIT multivariate analysis tool, producing a 40-term balance calibration model. Observed measurement error standard deviations were far less than 1.0% of the balance’s limits, and each of the six calibration curves are presented. The data acquisition system was modernized to achieve 16-bit reading resolution and 1.25 MHz maximum single-channel sampling rate among other improvments. New software was written, integrating digital recording of the angle of attack, flow temperature, and freestream dynamic pressure. The test model performs as predicted over a significant range within the test envelope. Trailing edge streamers demonstrated the existence of inboard trailing vortices precisely as NASA simulations predict. However, the test model was found to have a manufacturing defect posited to have significantly affected its aerodynamic performance: a sharp leading edge. Lift measurements show two degrees angle of attack early stall onset with a maximum lift coefficient discrepancy of greater than 10%. Similarly, drag measurements behave largely as predicted, but diverge near stall. Pitching moment measurements are offset from their predicted values, presumably due to uncertainty in the moment reference center location on the order of 0.1 inches. Lateral performance coefficients varied far more than anticipated especially at zero sideslip angle. The future SPIV measurement campaign will study the test model posed at 8 degrees angle of attack, which is determined from NASA simulations along with present flow visualizations and aerodynamic force measurements. Prior to this phase, the model will be rebuilt and further validated using similar techniques in addition to surface oil flow visualizations.
San Diego State University
Master of Science (M.S.) San Diego State University, 2021
© 2015 SDSU Library & Information Access. All Rights Reserved.