Abstract
An ordinary differential equation algorithm was formulated to approximate the solution to the characteristic form of the Saint-Venant equations for one-dimensional, gradually varied, unsteady open-channel flow in prismatic irrigation canals. The algorithm was applied by developing a network of characteristics using difference equations for randomly spaced intervals in the x − t (space–time) plane. Consistency, convergence and numerical stability of the equations are demonstrated, and a method to estimate the error of the predictor–corrector scheme is proposed. A mathematical model was developed to test the algorithm using a hypothetical case of unsteady flow, and it was compared to the results from two other mathematical simulation models, providing a high degree of agreement.
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Abbreviations
- a :
-
interpolation coefficient
- A :
-
cross-sectional flow area
- c :
-
shallow-water wave speed (celerity)
- E :
-
local truncation error
- g :
-
gravitational acceleration constant
- H :
-
total hydraulic head
- J :
-
Jacobian matrix
- n :
-
Manning roughness parameter
- N :
-
number of steps
- p :
-
interpolating polynomial
- Q :
-
volumetric flow rate
- S f :
-
energy loss gradient
- S o :
-
longitudinal bed slope
- t :
-
elapsed time
- T :
-
top width of flow
- V :
-
mean flow velocity
- W p :
-
wetted perimeter
- x :
-
longitudinal distance in downstream direction
- y :
-
water depth
- z :
-
elevation of the channel bed
- α :
-
initial distance or divided difference
- β :
-
polynomial root or divided difference
- λ :
-
constant coefficient
- ξ :
-
integration variable
- μ :
-
temporal variable
- i, j, k :
-
counters
- n :
-
node designator
- (+):
-
positive characteristics
- (−):
-
negative characteristics
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Communicated by P. Waller.
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Chun, S.J., Merkley, G.P. ODE solution to the characteristic form of the Saint-Venant equations. Irrig Sci 26, 213–222 (2008). https://doi.org/10.1007/s00271-007-0087-7
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DOI: https://doi.org/10.1007/s00271-007-0087-7