Unsteady Free-Surface Flow, CHAN

The program CHAN may be used to model unsteady flows (such as surges), floods and storm runoff in a system of channels, streams, sewers, tunnels and other constructed water conveyance structures, and in closed conduits flowing partially full. The unsteady flow may be produced by runoff from precipitation, i.e., rainfall, snow-melt, etc., failure of levees, dams, and other control structures, or opening and/or closing of control gates. In addition, the program may be used to compute the variation of air pressure above the free-water surface in partially full closed conduits and air inflow and outflow through vent shafts during the transient conditions.

The program CHAN is written in FORTRAN. The channel system may be a series or a branching system. With the current DIMENSION statement, systems having up to 100 channels, 15 gates, 15 inflow and outflow hydrographs, 15 weirs, 5 upstream and 5 downstream constant-level reservoirs. Each channel may be divided into as many as 1000 equal-length reaches. To facilitate data input, free format is used. Several options are available for printing the program output. The computed flow conditions may be stored for post-processing and plotting by using any other program.

Either English or SI units may be used for the system parameters.

The program computes initial steady-state conditions by numerically integrating the gradually varied flow equation. The explicit finite-difference (Lax diffusive scheme) is used to compute the unsteady flows. Control devices and other appurtenances are simulated by using procedures outlined in Open-Channel Flow, 2nd ed., by M. H. Chaudhry, Springer, New York, NY., 2008. The software has been verified by comparing the computed results with those measured in the laboratory or in the field.

In the User’s Manual, Chapter 1 describes the specification of the system. The arrangement of input data, definition of various variables, and different options for the printing and plotting of computed results are presented in Chapter 2. Chapter 3 includes a typical example to illustrate the use of the program for application to the drainage tunnel system of Greater Vancouver Regional District, Vancouver, BC, Canada for January 29, 1997 rainstorm.