抄録
Present paper describes characters of bottom boundary layer under irregular waves for both laminar and turbulent flow conditions, assessed through numerical computation. To compute flow phenomena in the boundary layer, firstly, irregular waves have been generated. Then those have been applied at the free surface boundary in Jones and Launder original low Reynolds number k-A model. Calculated results indicate that for laminar flow the bottom shear stress is more dominated by high frequency component waves. It has also been observed that high flow inertia close to the bottom produces a double peaked structure in the bottom shear stress in a wave cycle which is unique in irregular waves. The phase difference between bottom shear stress and free stream velocity reduces significantly under turbulent flow condition. A phase difference of about 15 degrees shows a distinct limit between laminar and turbulent regimes. Under turbulent motions, close to the bottom, the turbulent kinetic energy shows a dual dependency on bottom shear stress and on free stream velocity indicating high variability in boundary layer thickness with free stream velocity.
