From 7142917d06cfe9efee8a9b73745514092faf1e32 Mon Sep 17 00:00:00 2001
From: Henry Weller <http://cfd.direct>
Date: Sat, 25 Mar 2023 14:49:58 +0000
Subject: [PATCH] solvers::functions: Added optional subSolverTime controlDict
 entry

Class
    Foam::solvers::functions

Description
    Solver module to execute the \c functionObjects for a specified solver

    The solver specified by either the \c subSolver or if not present the \c
    solver entry in the \c controlDict is instantiated to provide the physical
    fields needed by the \c functionObjects.  The \c functionObjects are then
    instantiated from the specifications are read from the \c functions entry in
    the \c controlDict and executed in a time-loop also controlled by entries in
    \c controlDict and the \c maxDeltaT() returned by the sub-solver.

    The fields and other objects registered by the sub-solver are set to
    NO_WRITE as they are not changed by the execution of the functionObjects and
    should not be written out each write-time.  Fields and other objects created
    and changed by the execution of the functionObjects are written out.

    When restarting from a time directory which does contain the \c subSolver
    fields the optional \c controlDict entry \c subSolverTime may be provided to
    specify which time the \c subSolver should be instantiated for, after which
    time is reset to \c startTime for the restart.
---
 .../solvers/modules/functions/functions.C     | 21 +++++++++++++++++++
 .../solvers/modules/functions/functions.H     |  5 +++++
 2 files changed, 26 insertions(+)

diff --git a/applications/solvers/modules/functions/functions.C b/applications/solvers/modules/functions/functions.C
index 76a1c77573..8fa1244653 100644
--- a/applications/solvers/modules/functions/functions.C
+++ b/applications/solvers/modules/functions/functions.C
@@ -52,9 +52,30 @@ Foam::solvers::functions::functions(fvMesh& mesh)
       : runTime.controlDict().lookup("solver")
     );
 
+    Time& time(const_cast<Time&>(runTime));
+    const TimeState ts(time);
+    bool startTimeChanged = false;
+
+    if (runTime.controlDict().found("subSolverTime"))
+    {
+        const scalar subSolverTime
+        (
+            runTime.controlDict().lookup<scalar>("subSolverTime")
+        );
+
+        time.setTime(subSolverTime, 0);
+
+        startTimeChanged = true;
+    }
+
     // Instantiate the selected solver
     solverPtr = (solver::New(solverName, mesh));
 
+    if (startTimeChanged)
+    {
+        time.setTime(ts, ts.timeIndex());
+    }
+
     // Set all registered objects to NO_WRITE
     // so only those created by the functionObjects are written
     for
diff --git a/applications/solvers/modules/functions/functions.H b/applications/solvers/modules/functions/functions.H
index aff28709d6..2b32a0ceba 100644
--- a/applications/solvers/modules/functions/functions.H
+++ b/applications/solvers/modules/functions/functions.H
@@ -39,6 +39,11 @@ Description
     should not be written out each write-time.  Fields and other objects created
     and changed by the execution of the functionObjects are written out.
 
+    When restarting from a time directory which does contain the \c subSolver
+    fields the optional \c controlDict entry \c subSolverTime may be provided to
+    specify which time the \c subSolver should be instantiated for, after which
+    time is reset to \c startTime for the restart.
+
 SourceFiles
     functions.C