Physical and Computer Models of Multiquality Networks

Solute transport in a multiquality water network is a complicated process, which recently gained increasing attention in view of the interest in environmental problems and the increased use of brackish water. A reduced‐scale physical model of a multiquality water system has been developed. The model is constructed of small‐diameter plastic irrigation pipes, which simulate the prototype pipeline network, and a computerized data‐acquisition system, which continuously records signals from pressure transducers, flow‐rate gages, and salinity sensors. Similitude analysis was conducted and the following scale factors where chosen: for pipe length, 0.05; for time, 0.25; for velocity, 0.4; and for pipe diameter, 0.05. A multiquality irrigation network of a farm in Israel is simulated using the reduced‐scale physical model and a theoretical computer model developed earlier by Shah and Sinai. Steady state flow rates and salinities are measured in several locations of that network and are found to agree with the simulated ones. Dynamics of salt front transportation lag and reservoir response are also tested. The dynamic response of pond to step change in input salinity is found to behave in a similar manner to the simple first‐order delay assumed in the theoretical model. Combined use of these two models is suggested for the analysis of multiquality water systems. The physical model is most effectively used for testing physical phenomena and for examination of real control systems. The computer model is more suitable for sensitivity analysis and quick checks.