Fig. 4. Comparison of the measurements of unsteady coefficients of lift (red) and drag (blue) with the cross-flow vortex model. The steady measurements are also included. Tow speed is 1.34 m s^–1. Motion parameters are ₀=30°, ₀=15°, f=1.25 Hz, U=1.34 m s^–1, span=20 cm, _Bias=0°, St=0.26. St is Strouhal number defined as 2f₀R_avg/U, where f is the frequency of oscillation.