Monday  |  Salon 10  |  03:00 PM–03:20 PM

#16481–Reconstruction of Unsteady Lift Force Measurements using Non-Dimensional Scaling Optimization

When measuring the external loads exerted on a flexible test structure, the response of a force measurement device is often influenced by the dynamics of the test structure itself (e.g., resonant behavior). These structural dynamics can make it difficult to measure dynamic forces over a large bandwidth. To remove these structural effects from the measured force, we present a force reconstruction approach using optimization wherein the optimization criteria is based on non-dimensional scaling laws. If the amplitude and bandwidth of the applied forces obey a scaling law, as is true for unsteady forces measured at different flow speed conditions, power spectral densities (PSDs) of the non-dimensionally scaled forces collapse to a single curve. This work utilizes this scaling through two novel optimization approaches, namely, minimizing the variance between the non-dimensional force curves or fitting parameters to a functional form of the non-dimensional forcing function. In the presented formulation, a modal superposition is used to construct the frequency response function (FRF) of the test structure, wherein the modal participation factors are found in the optimization routine. Other modal parameters for the FRF, such as the natural frequency and loss factors, are obtained through operational modal analysis (OMA). The force reconstruction technique presented here is first performed on a simulation model to show the tractability of the optimization criteria. Results are also shown in an experimental apparatus that is used to validate different force reconstruction techniques.

Zachary Jones   Pennsylvania State University
Nicholas Vlajic   Pennsylvania State University