Comprehensive method of characteristics models for flow simulation

The use of the specified time interval (STI) numerical schemes has been popular in applying the method of characteristics (MOC) to unsteady open‐channel flow problems. Studies and analyses of several variants of the STI schemes have led to the derivation of a new scheme, referred to herein as the multimode scheme, which combines implicit, temporal reachback, spatial reachback, and classical schemes into one. Three numerical models have been developed to implement the implicit and multimode schemes. The IMOCDS model uses an implicit scheme, with which the time step is no longer subject to the Courant constraint. The remaining two models, NEWMOC and SPRMOC, are two versions of the multimode scheme. The NEWMOC and SPRMOC models demonstrate all the advantages previously provided by individual STI schemes, cover the combined flow range of the various schemes involved, and, in addition, display newly acquired benefits such as robustness. Numerical analyses, numerical experiments, and field applications that verify, support, and demonstrate the enhanced model capabilities are presented.