Experimental determination of the two-dimensional aerodynamic admittances of a 5:1 rectangular cylinder in streamwise sinusoidal flows

Abstract The aerodynamic loadings of a 5:1 rectangular cylinder in one-dimensional sinusoidal flows are experimentally tested in a multiple-fan active control wind tunnel. A series of single-frequency streamwise sinusoidal flows, which are fully coherent in the spanwise direction, are generated by changing the frequency and amplitude. Spectral analysis indicates that the total drag, lift forces, and pitching moment contain the inflow-induced components as well as those induced by vortex shedding. To identify the two-dimensional aerodynamic admittances (2D AAF), the vortex-induced components are separated from the inflow-induced components by using the POD method. Subsequently, the 2D AAFs of the drag, lift forces and pitching moment are identified and compared with the empirical or theoretical models. Results show that the inflow amplitude has a limited influence on the 2D AAFs, while the angle of attack (AoA) can cause significant changes in them. At a zero AoA, the 2D drag AAF is in alignment with the Davenport function and the 2D lift AAF is close to Horlock’s AAF at low frequencies. Meanwhile, the 2D drag AAF is less influenced by the AoA than the lift and moment AAFs. The relationships between the inflow-induced and vortex shedding-induced components of the total forces are also discussed.