Wind Tunnel Testing and Aerodynamic Characterization

This subteam produces the measured aerodynamic data that the learning and identification projects use as ground truth. A small single-propeller UAV representative of our airframe is mounted in the Boeing Wind Tunnel at Purdue and tested for lift and drag in steady level flight, with the balance calibrated beforehand against known one to ten pound weights so that the recorded forces trace back to a physical standard rather than to a trusted zero. Because the aircraft is powered, the test separates propulsive force from aerodynamic drag by first sweeping the propeller from twenty percent to full throttle in the absence of wind and recording the resulting thrust history, then repeating the sweep with the tunnel running so that the two contributions can be disentangled. Freestream velocity is measured twice over, once from Pitot dynamic pressure and once from a hot film anemometer, and the disagreement between the two is itself a diagnostic. Each test condition is run three times for averaging. The scientific value lies in the comparison downstream: where the tunnel measurements and the parameters fit from flight logs disagree, that disagreement localizes error in the model and tells the SysID team where its assumptions break down.

The existing procedure fixes the aircraft at zero angle of attack, which is sufficient for the steady level flight case but not for populating a coefficient table across the flight envelope. Extending the test to angle of attack and control surface deflection sweeps, and adding pitch and roll moment reduction to the lift and drag already recorded, is open work for this subteam, as is the question of what Reynolds number scaling and tunnel wall corrections do to the numbers before they are handed to the digital twin.

Expected activities include: 1) Literature review on low-speed wind tunnel methods, blockage corrections, and Reynolds number scaling 2) Force balance calibration and verification 3) Model preparation, mounting, and tunnel safety procedures 4) Execution of the powered and unpowered throttle sweeps with repeat trials 5) Reduction of the twelve-channel LabVIEW output into lift and drag coefficients with uncertainty estimates 6) Cross-checking of Pitot and anemometer velocity measurements 7) Extension of the test matrix beyond zero angle of attack 8) Comparison against SysID parameter estimates and publication of the resulting coefficient set for the digital twin.

Team members will work with the Boeing Wind Tunnel, its LabVIEW data acquisition VI and force balance transducers, Pitot and hot film instrumentation, and Python data reduction pipelines. This subteam suits students who want hands-on experimental work and a direct line from measurement to model.