Turbulent Combined Wave-Current Boundary Layer Model

Accurately predicting transport processes, including sediment transport, in the coastal environment is impossible without correct current velocity and shear stress information. A combined wave-current boundary layer theory is necessary to predict these quantities, and while the previous Grant-Madsen type boundary layer models are effective, they inconsistently apply a discontinuous two layer eddy viscosity structure to the wave and current problems. We have therefore developed a new continuous three layer model which consistently applies all three layers and leads to a strong coupling between the wave and current solutions. Boundary layer models require an estimate of the movable bed roughness, and while this roughness is scaled by the sand grain diameter for flat beds, in the coastal environment it is often the case that either wave-generated ripples cover the bed or the near-bed sediment is transported as sheet flow, in which case the roughness is much larger and less straightforward t