functionObjects::stopAtTimeStep: New functionObject to stop the run if the time-step becomes too small

This is useful to write results before a case fails due to uncontrollable
automatic time-step reduction, usually caused by unstable pressure-velocity
coupling.

Class
    Foam::functionObjects::stopAtTimeStep

Description
    Stops the run if the time-step drops below the specified value in seconds
    and optionally write results before stopping.

    The following actions are supported:
    - noWriteNow
    - writeNow (default)
    - nextWrite

    Examples of function object specification:
    \verbatim
    stop
    {
        type            stopAtTimeStep;

        libs            ("libutilityFunctionObjects.so");

        minDeltaT       1e-8;
        action          writeNow;
    }
    \endverbatim
    will write the fields and stop if the time-step drops below 1e-8s.

Usage
    \table
        Property  | Description               | Required | Default value
        type      | type name: stopAtTimeStep | yes      |
        minDeltaT | Minimum time-step [s]     | yes      |
        action    | Action executed           | no       | writeNow
    \endtable

src/functionObjects/utilities/Make/files

@@ -8,6 +8,7 @@ systemCall/systemCall.C
 stopAt/stopAt.C
 stopAt/stopAtFile/stopAtFile.C
 stopAt/stopAtClockTime/stopAtClockTime.C
+stopAt/stopAtTimeStep/stopAtTimeStep.C
 removeRegisteredObject/removeRegisteredObject.C
 writeDictionary/writeDictionary.C
 writeObjects/writeObjects.C

src/functionObjects/utilities/stopAt/stopAt.C

@@ -2,7 +2,7 @@
   =========                 |
   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
    \\    /   O peration     | Website:  https://openfoam.org
-    \\  /    A nd           | Copyright (C) 2020 OpenFOAM Foundation
+    \\  /    A nd           | Copyright (C) 2020-2023 OpenFOAM Foundation
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
 License
@@ -86,10 +86,6 @@ bool Foam::functionObjects::stopAt::read(const dictionary& dict)
     {
         action_ = actionTypeNames_.read(dict.lookup("action"));
     }
-    else
-    {
-        action_ = actionType::nextWrite;
-    }
 
     return true;
 }

src/functionObjects/utilities/stopAt/stopAtTimeStep/stopAtTimeStep.C

@@ -0,0 +1,90 @@
+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+   \\    /   O peration     | Website:  https://openfoam.org
+    \\  /    A nd           | Copyright (C) 2023 OpenFOAM Foundation
+     \\/     M anipulation  |
+-------------------------------------------------------------------------------
+License
+    This file is part of OpenFOAM.
+
+    OpenFOAM is free software: you can redistribute it and/or modify it
+    under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    OpenFOAM is distributed in the hope that it will be useful, but WITHOUT
+    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+    for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.
+
+\*---------------------------------------------------------------------------*/
+
+#include "stopAtTimeStep.H"
+#include "Time.H"
+#include "addToRunTimeSelectionTable.H"
+
+// * * * * * * * * * * * * * * Static Data Members * * * * * * * * * * * * * //
+
+namespace Foam
+{
+namespace functionObjects
+{
+    defineTypeNameAndDebug(stopAtTimeStep, 0);
+
+    addToRunTimeSelectionTable
+    (
+        functionObject,
+        stopAtTimeStep,
+        dictionary
+    );
+}
+}
+
+
+// * * * * * * * * * * * * * Private Member Functions  * * * * * * * * * * * //
+
+bool Foam::functionObjects::stopAtTimeStep::condition() const
+{
+    return time_.deltaTValue() < minDeltaT_;
+}
+
+
+// * * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * //
+
+Foam::functionObjects::stopAtTimeStep::stopAtTimeStep
+(
+    const word& name,
+    const Time& runTime,
+    const dictionary& dict
+)
+:
+    stopAt(name, runTime, dict),
+    minDeltaT_(0)
+{
+    action_ = actionType::writeNow;
+    read(dict);
+}
+
+
+// * * * * * * * * * * * * * * * * Destructor  * * * * * * * * * * * * * * * //
+
+Foam::functionObjects::stopAtTimeStep::~stopAtTimeStep()
+{}
+
+
+// * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
+
+bool Foam::functionObjects::stopAtTimeStep::read(const dictionary& dict)
+{
+    stopAt::read(dict);
+    dict.lookup("minDeltaT") >> minDeltaT_;
+
+    return true;
+}
+
+
+// ************************************************************************* //

src/functionObjects/utilities/stopAt/stopAtTimeStep/stopAtTimeStep.H

@@ -0,0 +1,141 @@
+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+   \\    /   O peration     | Website:  https://openfoam.org
+    \\  /    A nd           | Copyright (C) 2023 OpenFOAM Foundation
+     \\/     M anipulation  |
+-------------------------------------------------------------------------------
+License
+    This file is part of OpenFOAM.
+
+    OpenFOAM is free software: you can redistribute it and/or modify it
+    under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    OpenFOAM is distributed in the hope that it will be useful, but WITHOUT
+    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+    for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.
+
+Class
+    Foam::functionObjects::stopAtTimeStep
+
+Description
+    Stops the run if the time-step drops below the specified value in seconds
+    and optionally write results before stopping.
+
+    The following actions are supported:
+    - noWriteNow
+    - writeNow (default)
+    - nextWrite
+
+    Examples of function object specification:
+    \verbatim
+    stop
+    {
+        type            stopAtTimeStep;
+
+        libs            ("libutilityFunctionObjects.so");
+
+        minDeltaT       1e-8;
+        action          writeNow;
+    }
+    \endverbatim
+    will write the fields and stop if the time-step drops below 1e-8s.
+
+Usage
+    \table
+        Property  | Description               | Required | Default value
+        type      | type name: stopAtTimeStep | yes      |
+        minDeltaT | Minimum time-step [s]     | yes      |
+        action    | Action executed           | no       | writeNow
+    \endtable
+
+SourceFiles
+    stopAtTimeStep.C
+
+\*---------------------------------------------------------------------------*/
+
+#ifndef functionObjects_stopAtTimeStep_H
+#define functionObjects_stopAtTimeStep_H
+
+#include "stopAt.H"
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+namespace Foam
+{
+namespace functionObjects
+{
+
+/*---------------------------------------------------------------------------*\
+                       Class stopAtTimeStep Declaration
+\*---------------------------------------------------------------------------*/
+
+class stopAtTimeStep
+:
+    public stopAt
+{
+    // Private Data
+
+        //- Minimum time-step, below which the run is stopped
+        scalar minDeltaT_;
+
+
+    // Private Member Functions
+
+        //- Return true when the stop condition is achieved
+        virtual bool condition() const;
+
+
+public:
+
+    //- Runtime type information
+    TypeName("stopAtTimeStep");
+
+
+    // Constructors
+
+        //- Construct from Time and dictionary
+        stopAtTimeStep
+        (
+            const word& name,
+            const Time& runTime,
+            const dictionary&
+        );
+
+        //- Disallow default bitwise copy construction
+        stopAtTimeStep(const stopAtTimeStep&) = delete;
+
+
+    //- Destructor
+    virtual ~stopAtTimeStep();
+
+
+    // Member Functions
+
+        //- Read the dictionary settings
+        virtual bool read(const dictionary&);
+
+
+    // Member Operators
+
+        //- Disallow default bitwise assignment
+        void operator=(const stopAtTimeStep&) = delete;
+};
+
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+} // End namespace functionObjects
+} // End namespace Foam
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+#endif
+
+// ************************************************************************* //