Hivel2D users manual
grav 32.18900
| GRAVITY (FT/(SEC*SEC))
mcon 2.20800
| MANNING CONVERSION
turb 0.1000 0.2000
| CB FOR VISCOSITY SMOOTH, AND JUMP
time 1.0000 1.0000
| TIME STEP, TEMPORAL DIFF
step 20 20
| TIME STEPS, OUTPUT INTERVAL
iter 4 0.00500
|NUMB. OF ITER, CONV CRITERIA
bin 1 2 60.000
0.000 1 3.000
bin 2 2 60.000
0.000 1 3.000
bin 3 2 60.000
0.000 1 3.000
bos 2 0 -14.8 6
333
334
335
336
337
338
mtyp 2
| NUMBER OF ELEMENT TYPES(FOR ROUGHNESS)
1 0.0150
2
0.0250
Figure D5. Initial hydrodynamic input file (example1.flo).
was chosen to be first-order since the interest is in steady-state results only. Even though
the downstream boundary is intended to be supercritical and no boundary condition is
needed, experience has shown that the model sometimes will converge to a different
solution or be unstable unless a very good starting guess at the solution was made.
Therefore, until the model settles down, a tailwater elevation is specified corresponding to
flow that is slightly subcritical. Two different element types and Manning's roughness
coefficients have been designated. The convergent section is steeper and rougher in this
example. The model will run 20 time-steps resulting in a simulation time of 20 sec. The
time-step size is then increased. Later the downstream tailwater condition is effectively
removed by specifying an elevation that is below the bed elevation. The nodes 1, 2, and 3
are the upstream boundary nodes (designated by BIN in the hydrodynamic flow file), and
nodes 333-338 are the downstream boundary nodes (designated by BOS in the
hydrodynamic flow file).
The next input file is run to raise the time-step now that the model has settled down
from startup. The time-step has been raised to 3.0 sec. The
second input file is shown in Figure D6.
The final input file (Figure D7) removes the tailwater constraint. This run was repeated
one time.
Figures D8 and D9 are the steady-state results of the model run for water-surface and
velocity contours, respectively. These were generated by SMS. There are many options
available such as vectors and time-series plots. The results show that the bridge pier is a
49
Appendix D Example problem
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