Measurement and prediction of bottom boundary layer hydrodynamics under modulated oscillatory flows

Velocities are measured using LDA within the bottom boundary layer for 10 oscillatory flow tunnel experiments involving regular and amplitude modulated flows over a gravel-rough bed sand-rough bed. Corresponding were equivalent in terms of rms velocity, period, skewness asymmetry. The experimental results compared with predictions based on 1DV RANS model k?? turbulence closure. effects modulation hydrodynamics individual half-cycles time-averaged analysed. Turbulence is carried from one half-cycle to following but main hydrodynamic properties (boundary thickness, peak turbulent kinetic energy, stress) show little or no dependence prior conditions. propagation vertical profiles skewness, asymmetry, energy stress remarkably effect modulation. Modulation does not affect shape velocity profile generated by non-symmetric flows, it reduce magnitude. shows generally good agreement above about grain diameter bed, but, because its assumption rough flow, poorly predicts low-velocity