Published online by Cambridge University Press: 04 July 2016
A turbulent boundary layer, subjected to a freestream velocity which changes sinusoidally with time around a spatially uniform mean value has been studied experimentally. The experiments were conducted in a specially designed unsteady-flow water tunnel. A two-component laser Doppler anemometer was used to measure the instantaneous velocities, and hence the turbulent stresses, in the periodic boundary layer. A surface-mounted heat-flux gauge was used to measure the unsteady wall shear stress. The experiments were conducted at relatively high amplitudes of oscillation (≈ 40% of the mean) and over a wide range of reduced frequencies (1.7-28). While the present data on the oscillatory flow properties generally confirm previously known trends the information on the turbulent shear stress and skin friction obtained in the present studies is more complete than previously available. The experimental data, all of which has been archived on magnetic tape, form a comprehensive base for the development and verification of predictive models for unsteady turbulent boundary layers.