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Explain the timestepping

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Adds developer documentation about the timestepping procedure.
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Håkon Hægland 2025-01-20 23:01:39 +01:00
parent b4192b06c3
commit 18d35cb820
1 changed files with 30 additions and 0 deletions
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opm/simulators/timestepping/AdaptiveTimeStepping_impl.hpp
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@ -579,6 +579,36 @@ reservoirCouplingSlave_()
#endif
#ifdef RESERVOIR_COUPLING_ENABLED
// Description of the reservoir coupling master and slave substep loop
// -------------------------------------------------------------------
// The master and slave processes attempts to reach the end of the report step using a series of substeps
// (also called timesteps). Each substep have an upper limit that is roughly determined by a combination
// of the keywords TUNING (through the TSINIT, TSMAXZ values), NEXSTEP, WCYCLE, and the start of the
// next report step (the last substep needs to coincide with this time). Note that NEXTSTEP can be
// updated from an ACTIONX keyword. Although, this comment focuses on the maximum substep limit,
// note that there is also a lower limit on the substep length. And the substep sizes will be adjusted
// automatically (or retried) based on the convergence behavior of the solver and other criteria.
//
// When using reservoir coupling, the upper limit on each substep is further limited to: a) not overshoot
// next report date of a slave reservoir, and b) to keep the flow rate of the slave groups within
// certain limits. To determine this potential further limitation on the substep, the following procedure
// is used at the beginning of each master substep:
// - First, the slaves sends the master the date of their next report step
// - The master receives the date of the next report step from the slaves
// - If necessary, the master computes a modified substep length based on the received dates
// TODO: explain how the substep is limited to keep the flow rate of the slave groups within certain
// limits. Since this is not implemented yet, this part of the procedure is not explained here.
//
// Then, after the master has determined the substep length using the above procedure, it sends it
// to the slaves. The slaves will now use the end of this substep as a fixed point (like a mini report
// step), that they will try to reach using a single substep or multiple substeps. The end of the
// substep received from the master will either conincide with the end of its current report step, or
// it will end before (it cannot not end after since the master has already adjusted the step to not
// exceed any report time in a slave). If the end of this substep is earlier in time than its next report
// date, the slave will enter a loop and wait for the master to send it a new substep.
// The loop is finished when the end of the received time step conincides with the end of its current
// report step.
template <class TypeTag>
template <class Solver>
SimulatorReport