Large-eddy simulation of fully developed turbulent flow over a wavy surface

Large eddy simulation(LES) is used to study flow over a sinusoidal bottom wall, with amplitudewavelength ratio 2a/λ=0.1 and bulk velocity based Reynolds number Reb=6760. Different from a conventional flat channel, flow over a wavy lower surface is affected by the bottom wall in terms of form drag, leading to the change of both mean and instantaneous fields. Wall bounded flow turns into a separation flow with the increasing of Reynolds number, changing the way in which momentum flux transports and mixes. Statistical properties, transient flow fields as well as surface drag are studied. Averaged fields and turbulent structures are different from those of a flat channel. Distribution and shape of streamwise vortex are closely related to the configuration of the lower surface. Comparison of averaged fields with 2a/λ=0.2 shows the dependence of flow characteristics on the wave steepness.