PRESSURE CORRELATIONS ON A ROUGH CONE IN TURBULENT SHEAR-FLOW

A detailed wind tunnel test has been carried out on a rough cone model using an electronically scanned pressure transducer system, enabling almost instantaneous capture of 256 pressure tap signals from 16 level s of 16 equispaced taps at each level. A very complete analysis was pe rformed on a reduced data set consisting of weighted integrations of t he 16 pressure signals forming time series of lift and drag at each le vel. Autospectra of the drag data showed good agreement with the appro ach wind spectra at the same level, and with the von Karman spectral e quation. Local aerodynamic admittance showed less reduction with incre asing fD/V than expected from ''lattice plate'' theory. Drag root-cohe rence could be well described by a modified exponential decay equation , and differed considerably from the root-coherence of the longitudina l component of the onset wind how. The lift autospectra were well fitt ed by the forced-damped-harmonic motion vibration equation. Normalised co-spectra were obtained between reference levels 5, 9, and 12 and ea ch of the other 15 levels and were used to find correlation coefficien ts at the shedding frequency of the reference level. The coefficients collapsed to a single curve when plotted versus non-dimensional separa tion, which could be well fitted by an exponentially damped cosine fun ction, Analysis of the 16 front and 16 rear taps showed that the root- coherence of the front pressures was more similar to the wind coherenc e than the drag pressures, but the root-coherence of the rear tap pres sures was substantially less than the wind for low dimensionless frequ encies.