title: Spatiotemporal spectral analysis of a forced cylinder wake.
abstract: The wake of a circular cylinder performing rotary oscillations is studied using hydrodynamic tunnel experiments at Re=100. Two-dimensional particle image velocimetry on the midplane perpendicular to the axis of a cylinder is used to characterize the spatial development of the flow and its stability properties. The lock-in phenomenon that determines the boundaries between regions of the forcing parameter space where the wake is globally unstable or convectively unstable [see Thiria and Wesfreid, J. Fluids Struct. 25, 654 (2009) for a review] is scrutinized using the experimental data. A method based on the analysis of power density spectra of the flow allows us to give a detailed description of the forced wake, shedding light on the energy distribution in the different frequency components and in particular on a cascade-like mechanism evidenced for a high amplitude of the forcing oscillation. In addition, a calculation of the drag from the velocity field is performed, allowing us to relate the resulting force on the body to the wake properties.
authors.affiliation: Facultad de Ingeniería Universidad de Buenos Aires (CONICET), Buenos Aires, Argentina. jdadamo@fi.uba.ar
authors.forename: Juan
authors.initials: J
authors.lastname: D'Adamo
authors.forename: Ramiro
authors.initials: R
authors.lastname: Godoy-Diana
authors.forename: José Eduardo
authors.initials: JE
authors.lastname: Wesfreid
mesh_terms: D000465:Algorithms; D057446:Hydrodynamics; D015233:Models, Statistical; D009068:Movement; D009991:Oscillometry / Q000379:methods*; D010825:Physics / Q000379:methods*; D012212:Rheology / Q000379:methods; D013314:Stress, Mechanical; D013997:Time Factors