Dynamic Characterization of Force Transducers for Wind Tunnel Measurements
Open Access
- Author:
- Trowbridge, Garrett
- Area of Honors:
- Aerospace Engineering
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Nicholas A Vlajic, Thesis Supervisor
Sven Schmitz, Thesis Honors Advisor - Keywords:
- Dynamics
Wind Tunnels
Force Reconstruction
Hypersonics - Abstract:
- Dynamic forces are increasingly present as wind tunnel speed increases. However, problems arise with the calibration of dynamic forces. Dynamic forces that are calibrated like the traditional static forces will not read accurately. The current investigation explores two new methods to calibrate and measure dynamic forces by means of adding accelerometers in addition to static transducers. The approaches involve determining inertial, damping, and static coefficients from acceleration, velocity, and position data. The first method simultaneously solves for all three coefficients from a known force and respective data. The second method involves conducting a static calibration. The static force is then subtracted from the dynamic force and the other coefficients can be solved for. A computational simulation yields errors less than 0.1 percent for both methods, and around 1 percent error when noise is added. A two degree-of-freedom balance was designed to model a lift-pitch system and test the methods experimentally. A static calibration was conducted by hanging weights, measuring voltages reported by strain gauges, and computing calibration coefficients. Dynamic forces were simulated with a modal impact hammer. Velocity data was found by numerically integrating the acceleration data. The dynamic force reported by the modal impact hammer along with the position, velocity, and acceleration data was used to determine the calibration coefficients. These coefficients were used to reconstruct a static force, which was simulated by cutting string attached to static weights.