抄録
A very efficient method is presented for calculating the water surface profiles in steady, subcritical flows using an unsteady flow model. A parameter of the unsteady term α in the Saint Venant equations is introduced. To solve the governing differential equations, the Preissmann scheme with a time weighting factor θ is used. The values of the parameter set, α=1 and θ=0.55, represent the difference equations for unsteady flow. By setting parameters at α=0 and θ=1, the difference structure of an unsteady flow equation is easily changed into that of a steady flow equation. For the flow in a nonprismatic channel, the results of this method are found to be in excellent agreement with those of the step method.
