Application of Operational Modal Analysis for Wind-Tunnel Testing of an Aircraft Wing Model with Control-Surface

Kurzfassung

Operational modal analysis (OMA) is applied to experimental data from a transonic wind-tunnel test of an aircraft wing model with control-surface. Airflow turbulence and control-surface excitation via hydraulic rotational actuators driven by shaped and burst random signals are employed as natural and artificial excitation for the model structure. Altogether 27 sets of data were measured and processed with different test conditions, e.g. Mach numbers, angles of attack of wing section and angles of the control-surface, static pressure, etc. A novel narrow-band OMA procedure based on frequency-spatial domain decomposition (SFDD) is adopted to identify modal parameters from all different data sets. Mode shapes are identified by frequency domain (FD) principle component analysis (PCA) via SVD of processed power spectrum density (PSD) matrix. A spatial domain modal filter is devised to isolate individual modes, followed by FD curve fitting to estimate relevant modal frequencies and damping ratios from enhanced PSD in the selected narrow-band. Altogether 8 to 12 modes are clearly defined and modal parameters are then identified in the frequency band of 50~350 Hz, including all the "rigid-body" modes of the 2-D airfoil plus flexible modes exhibiting 3-D motion of the assumed 2-D model. Modal parameter changes, especially for modal damping and frequencies, with different wind-tunnel test conditions are clearly observed and their physical reasoning is discussed.