Unsteady Aerodynamic Force Sensing from Strain Data

A simple approach for computing unsteady aerodynamic forces from simulated measured strain data is proposed in this study. First, the deflection and slope of the structure are computed from the unsteady strain. Velocities and accelerations of the structure are computed using the autoregressive moving average model, online parameter estimator, low-pass filter, and a least-squares curve fittingmethod, togetherwith analytical derivativeswith respect to time. Finally, aerodynamic forces over the wing are computed using modal aerodynamic influence coefficient matrices, a rational function approximation, and a time-marching algorithm.A cantilevered rectangularwing is used to validate the simple approach. Unsteady aerodynamic forces as well as wing deflections, velocities, accelerations, and strains are computed using the CFL3D computational fluid dynamics code and the MSC/NASTRAN finite element analysis code; and these CFL3D/NASTRAN-based results are assumed as measured quantities. Computed deflections, velocities, accelerations, and unsteady aerodynamic forces are compared with the CFL3D/NASTRANbased results. Computed aerodynamic forces based on lifting-surface theory at subsonic speeds are in goodagreement with the target aerodynamic forces generated usingCFL3Dcodewith theEuler equation.This researchdemonstrates the feasibility of obtaining induceddrag and lift forces through the use of distributed sensor technologywithmeasured strain data.