than the weakly nonlinear model and should only be used to investigate
highly asymmetric waves in shallow water, wave-induced currents, and
Wave Breaking Option (Y/N) Wave breaking should be enabled if the
significant wave height is going to be greater than half the water depth in the
shallowest regions of the computational area (Hmo > hmin/2).
Turbulent Length Scale, lt (m) Controls the rate of wave energy dissipation
for breaking waves. Should be set equal to the significant wave height (lt =
Hmo) for irregular waves or the wave height (lt = H) for regular waves.
Smagorinsky Constant Cs Eddy viscosity coefficient for subgrid turbulence.
To avoid excessive dissipation of the waves, Cs should be kept between 0 and
0.5. The default value is 0.0.
Wave Runup Option (Y/N) The runup scheme used in the numerical model
is designed to simulate subcritical flow conditions on mild slopes. It cannot
resolve details of supercritical flow on steep slopes. The runup option should
only be used with the fully nonlinear model equation option.
Minimum Flooding Depth Parameter used control the stability of runup
computations. Its value should be of the order of one-hundredth of the
incident wave height (H/100).
Step 9. Output Data
BOUSS-2D calculates the time-dependent evolution of the water-surface eleva-
tion and horizontal velocities over a rectangular grid. For most simulations, it
would require an excessive amount of disk space to store the surface elevation
and velocity data at every grid point for all the simulation time-steps. To mini-
mize disk storage requirements, the program outputs the time-averaged values of
the variables over the entire grid or time-histories of the variables at specified
grid points in the computational domain. All output files start with a prefix (xxx)
specified by the user. The different output file options are given in the following
2-D Spatial Output
Mean water level η ( x, y) distribution over the computational grid
(xxx_mwl.grd) The free surface fluctuations are averaged over the duration
of the synthesized or input time record, tw, specified in Step 6, i.e.,
∑η( x, y, t )
η ( x, y) =
N ts -tw
where N = tw/∆t and ts is the duration of the numerical simulation specified in
Step 8. The user should make sure that the duration of the numerical simula-
tion is long enough to establish steady-state conditions in the numerical wave
Chapter 4 Setting Up and Running BOUSS-2D