Numerical investigation on irregular wave bottom boundary layer under laminar motion

Laminar plane bed bottom boundary layer properties under irregular waves have been investigated through numerical computation. irregular waves have first been generated and later used for now computation in the boundary layer applying Jones and Launder original low Reynolds number k-epsilon model. Generation of irregular waves show satisfactory result when compared with input spectral properties. Model results have been compared with experiment data and an excellent agreement has been obtained. Results from different Reynolds number conditions have been utilized for detailed analysis of bottom shear stress variation with free stream velocity. It has been observed that bottom shear stress is more dominated by high frequency component waves. High flow inertia dose to the bottom also causes a double peaked structure in the bottom shear stress, a rather unique feature in irregular waves. A comparison of irregular wave bottom shear stress with that of sinusoidal wave shows that the significant bottom shear stress closely corresponds to the maximum of sinusoidal wave when the later is computed with the highest two-fifth of wave heights (H-2/5) of the former.