Bottom Friction

Bottom Friction

The mean (short-wave averaged) bed shear stress, ${\tau }_{bi}$, is calculated as

${\tau }_{bi}={\lambda }_{wc}{\tau }_{ci}$ (2-8)

where

${\lambda }_{wc}=$ nonlinear bottom friction enhancement factor $({\lambda }_{wc}\ge 1)$ [-]

${\tau }_c=$ current-related bed shear stress vector [Pa]

The current bed shear stress is given by

${\tau }_{ci}=\rho c_{b}U{U}_i$ (2-9)

where

$\rho =$ water density (~1025 kg/m³)

c_b = bed friction coefficient [-]

$U=$ current magnitude = $\sqrt{U_i^2+U_j^2}$ [m/s]