24
J. Lou· T. Wolf· W. Rosenthal
model will be briefly described. The new numerical model was then applied to
Cleveland Bay, Australia, and the Oder Estuary, which straddles the border
between Germany and Poland. In this chapter the model predictions are discussed and tested against the field data.
2
Wave-Current Bottom Stresses
Bottom stresses required for sediment transport modeling are calculated by a
bottom boundary layer model. The calculated stresses are then used in the
bottom boundary condition for the sediment transport model. The influence
of wave-current interaction on the bottom shear stress is calculated using an
iterative procedure based on the concept of Grant and Madsen (1979). A similar method was used by Signell et al. (1990), but with a different definition of
wave friction.
The maximum bottom stress Tb,max for wave-current combinations is defined as:
(1)
in which p is the water density, few is an unknown effective friction factor under combined wave-current movement, U8 is the maximum near bottom wave
orbital velocity which may be determined from linear wave theory, U e is the
current velocity near the sea bed, and ¢e is the angle between wave propagation and the current direction.
The calculation of the effective friction coefficient.few begins by determining
the oscillatory component of the stress Tw, whereby:
(2)
with fw as the wave friction factor whose value can be obtained by using the
relationship ofJonsson (1966).
With U*w determined, an iterative procedure is used to calculate.few at the
upper edge of the wave-current boundary layer as briefly described below:
(i) Starting with an initial guess of .few> the steady shear velocity component
U*e is obtained by:
(3)
(ii) The combined wave-current friction velocity U*ew is defined as:
(4)
and can be obtained by the wave-related and current-related friction velocities:
J. Lou· T. Wolf· W. Rosenthal
model will be briefly described. The new numerical model was then applied to
Cleveland Bay, Australia, and the Oder Estuary, which straddles the border
between Germany and Poland. In this chapter the model predictions are discussed and tested against the field data.
2
Wave-Current Bottom Stresses
Bottom stresses required for sediment transport modeling are calculated by a
bottom boundary layer model. The calculated stresses are then used in the
bottom boundary condition for the sediment transport model. The influence
of wave-current interaction on the bottom shear stress is calculated using an
iterative procedure based on the concept of Grant and Madsen (1979). A similar method was used by Signell et al. (1990), but with a different definition of
wave friction.
The maximum bottom stress Tb,max for wave-current combinations is defined as:
(1)
in which p is the water density, few is an unknown effective friction factor under combined wave-current movement, U8 is the maximum near bottom wave
orbital velocity which may be determined from linear wave theory, U e is the
current velocity near the sea bed, and ¢e is the angle between wave propagation and the current direction.
The calculation of the effective friction coefficient.few begins by determining
the oscillatory component of the stress Tw, whereby:
(2)
with fw as the wave friction factor whose value can be obtained by using the
relationship ofJonsson (1966).
With U*w determined, an iterative procedure is used to calculate.few at the
upper edge of the wave-current boundary layer as briefly described below:
(i) Starting with an initial guess of .few> the steady shear velocity component
U*e is obtained by:
(3)
(ii) The combined wave-current friction velocity U*ew is defined as:
(4)
and can be obtained by the wave-related and current-related friction velocities: