Low wavenumber turbulent boundary layer fluctuating wall shear stress measurements from vibration data on a cylinder in pipe flow

摘要

Fluctuating wall shear stress under turbulent boundary layer (TBL) excitation is studied inthis experimental investigation. A cylindrical shell with a smooth internal surface issubjected to TBL excitation from water in fully developed pipe flow at 6.1 m/s. Thevibration response of the cylinder is used to inversely determine low wavenumber TBLshear stress levels. Both the cross-flow and streamwise directions are examined usingdirectionally uncoupled low-order cylinder modes in the circumferential and axialdirections. This data addresses a critical gap in available literature regarding experimentallow wavenumber shear stress data. The low wavenumber shear stress levels in both thecross-flow and streamwise directions are determined to be roughly 10 dB higher than thoseof normal pressure. As is the case for various models of TBL pressure, these measurementssuggest that a nearly constant value for normalized shear stress at low wavenumber is validover a broad range of frequencies. A simple wavenumber white model form established forlow wavenumber TBL surface pressure is also shown to be appropriate for shear stress.