Environmental Engineering Reference
In-Depth Information
Table 7.11. Data required by SETRIC before the start of any simulation of the hydraulic
and sediment calculations.
Physical geometry of the canal and network includes:
•
layout of the canal network with main and secondary canals (laterals), number of canal
sections, location of control and other structures, offtakes, bifurcations and confluences;
•
chainage and length of the canal sections;
•
for each section the bottom width, roughness, bottom slope, side slope, starting bottom
level and drops;
•
base flow and discharge per lateral and the roughness (Chézy, Manning, Strickler);
•
maintenance activities, characteristics for the weed factors and other constants;
•
number, location and type of structures: overflow, flume, siphon-culvert and undershot;
•
dimensions of the structures;
•
total number cannot be more than the number of sections;
•
water depth upstream of the control structure at the downstream boundary.
Characteristics of the water flow
•
base flow (discharge) at the upstream boundary;
•
operation mode, either continuous or intermittent;
•
type of canal maintenance; none, good or ideal maintenance;
•
lateral flow and location of the laterals from the head of the parent canal;
•
flow options for the laterals, either continuous or in time series;
•
option for simulation of sediment in the lateral; laterals will get the same sediment
characteristics as the parent canal;
•
only 1 lateral can start from 1 node;
•
geometrical dimensions to be included in the same way as for the parent canal.
Characteristics of the incoming sediment include:
•
incoming sediment is non-colloidal;
•
sediment particles are characterized by 1 size (d
50
);
•
size and gradation of the sediment constant along the whole canal length, either
continuous or in time series;
•
total concentration (bed load and suspended) in ppm by weight; either continuous or
in time series;
•
type of sediment predictor: Ackers-White, Brownlie or Engelund-Hansen;
•
no sediment deposition in the structures, the sediment inflow is equal to the sediment
outflow;
•
only previously deposited sediment can be eroded, the original canal bed is different
from the inflowing sediment; cannot be eroded.
Details of the required calculation steps should be known before the simulation:
•
time step
t
has to be known before the simulation starts,
t
is a function of the
adaptation time
T
A
and is also related to the Courant number; length step
x
depends
on the required accuracy for the numerical solution and should be much smaller than
the adaptation length
L
A
and should be smaller than 0.67 times the smallest length of
a reach with structures at both nodes.
which gives the actual sediment concentration at any point under non-
equilibrium conditions. The mass balance equation for the total sediment
transport is solved by Lax's modified method, assuming steady conditions
for the sediment concentration.
The actual (non-equilibrium) sediment concentration depends on
c
0
,
L
A
,
T
A
,
x
and
c
e
. The value of
c
0
depends on the inflowing sediment
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