Contaminant and sediment transport by advection and diffusion 227
hplot=-h(i);
plot(i,hoplot,'','Linewidth',1.5)
hold on
plot(i,h1plot,'r','Linewidth',1.5)
plot(i,hplot,'g','Linewidth',1.5)
xlabel('Longitudinal distance 2 x [m]')
ylabel('Depth of dredge below the bed [m]')
text(58,-3.8,'Time: t = 0')
text(75,-3.0,'Time: t = 1 day')
text(120,-2.6,'Time: t = 2 days')
PROBLEM 8.5
Solve the same problem by making the suggested modifications while keeping the rest of the data constant:
1. Change the water discharge from 2 m 3 /m/s to 0.5, 1.0, 1.5 and
2.5 m 3 /m/s.
2. Change the sediment transport coefficient from 0.01 s 2 /m to 0.001,
0.005 and 0.15 s 2 /m.
3. Change the distance from the centre of the dredge to the canal
entrance to 62 m, and change the shape to trapezoidal with bottom
width 4 m, top width 16 m and a depth 1 m below the bed.
4. Put two dredges of the size and shape of part (c) with their centres at
120 and 280 meters.
5. Change the exponent of the bed load (Equation 8.31) from 3 to 2.5
and 3.5.
Run the simulations, compare the results and comment on the changes
observed regarding the movement and shape of the dredge.
Example 8.6
This application qualifies the scouring/deposition processes around
a breakwater structure in a horizontal two-dimensional domain.
The bathymetry and the velocities field are the same to those used in
Example 8.1. Other data used for the model are as follows:
Mean particle diameter = 0.001 m
Sediment density = 2500 kg/m 3
Bed friction coefficient = 0.001
Spatial step = 5 m
Time step = 1 s
The model is based on the sediment transport continuity equation (Equation 8.26) and the Engelund-Hansen formula (Equation
8.29). The simulation started with a flat bed and deformed under the