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Adaptive Time Stepping

AdH has several time stepping options that help during run time. Users can simply timestep through a hydrograph by specifying timesteps during the run. These can be constant or varying, as the user specifies. Users can also select the steady state timestep option or the automatic timestep option. These options allow the code to determine the best timestep based on initial residual calculations. The steady stats not time accurate since it is intended for use when modeling steady conditions. The automatic timestep option is time accurate and is best used for dam or levee breach applications where the initial iteration is the most difficult of the problem. More information can be found in the Journal of Hydraulic Engineering Vol. 137, Issue 9, September 2011.

Additionally, AdH will not stop running if a timestep does not converge. AdH will cut the timestep size to one-quarter of the previous timestep and attempt to solve the timestep again. This will continue until it does converge. The next timestep is doubled, allowing for the timestep size to return to the original size.