An Experimental Investigation of Forces Induced on Cylinders by Random Oscillatory Flow

Abstract

Results are presented from experiments investigating hydrodynamic forces induced on fixed circular cylinders by random oscillatory flows. The oscillatory flow was generated in a water tunnel and the inline and transverse forces induced on the cylinders were measured simultaneously. Analysis of the measured forces shows that significant differences exist when comparing drag and inertia coefficients to those measured under sinusoidal flow conditions, particularly in the inertia/ drag regime of the Keulegan-Carpenter number. The comparison of results for random versus sinusoidal flow conditions generated in the same experimental apparatus quantifies the difference in the physical mechanisms, specifically the vortex shedding and pairing, which influence the induced forces. A study is also made of the dependence of measured force power spectral densities on the statistical Keulegan-Carpenter number, Reynold’s number and on the spectral width of the flow velocity auto-power spectrum.