Prediction of instantaneous bottom shear stress for smooth turbulent bottom boundary layers under irregular waves

Abstract

A method has been proposed to compute instantaneous turbulent bottom shear stress from the variation in free stream velocity under irregular waves for hydraulically smooth plane bed condition. Instantaneous free stream velocity and a modified relationship for turbulent wave friction factor have been introduced as the basis for the correlation with bottom shear stress. Turbulent friction factor and phase difference, obtained through spectral analysis of generated free stream velocity and corresponding bottom shear stress from k–e model computation, corresponds quite well to those from laboratory data. Instantaneous bottom shear stress computed by the proposed method has been compared with those from experimental data for irregular waves. The proposed method presents a high degree of accuracy and has been found to be very convenient in defining the asymptotic behavior of bottom shear stress variation under smooth plane bed condition