Squashed commit of the following:

commit 510b9353f8cb932a87f1588b17a4dea230c29d3c
Author: mattijs <mattijs>
Date:   Wed Jun 14 16:36:35 2017 +0100

    ENH: timeControl: propagate time-change logic from Time.C

commit 6dc57a8f1e0e7605ea819deb6f11dd4b7874ff30
Author: mattijs <mattijs>
Date:   Thu Jun 1 11:28:56 2017 +0100

    ENH: timeControl: cleanup; avoid division by zero

commit 5ac4bc2dd8c1f4676eef9d7a03215caba23a2e19
Author: mattijs <mattijs>
Date:   Wed May 31 12:04:52 2017 +0100

    ENH: timeControl: allow ramping down as well as up.

commit a6b2db9e791f29258f04f3a9cbd6354aa468977d
Author: mattijs <mattijs>
Date:   Wed May 17 15:29:22 2017 +0100

    ENH: timeControl: limit any timestep change if deltaTCoeff enabled.

commit 004115ee03a6637ae0d23cce303a30d1b3af046f
Author: mattijs <mattijs>
Date:   Wed May 17 11:40:26 2017 +0100

    ENH: setTimeStep: have timeStart, timeEnd controls on time step adjustment.

    Also added smoothly varying time step change (through optional deltaTCoeff)

src/OpenFOAM/db/functionObjects/timeControl/timeControlFunctionObject.H

@@ -25,6 +25,13 @@ Class
     Foam::functionObjects::timeControl
 
 Description
+    Wrapper around functionObjects to add time control.
+
+    Adds
+    - timeStart, timeEnd activation
+    - deltaT modification to hit writeInterval (note: if adjustableRunTime
+      also in controlDict this has to be an integer multiple)
+    - smooth deltaT variation through optional deltaTCoeff parameter
 
 Note
     Since the timeIndex is used directly from Foam::Time, it is unaffected
@@ -85,6 +92,9 @@ class timeControl
             //- De-activation time - defaults to VGREAT
             scalar timeEnd_;
 
+            //- Max time step change
+            scalar deltaTCoeff_;
+
             //- Number of steps before the dump-time during which deltaT
             //  may be changed (valid for adjustableRunTime)
             label nStepsToStartTimeChange_;
@@ -103,6 +113,16 @@ class timeControl
         label executeTimeIndex_;
 
 
+        // For time-step change limiting (deltaTCoeff supplied) only:
+
+            //- Store the old deltaT value
+            scalar deltaT0_;
+
+            //- Store the series expansion coefficient value
+            scalar seriesDTCoeff_;
+
+
+
     // Private Member Functions
 
         //- Read relevant dictionary entries
@@ -111,6 +131,26 @@ class timeControl
         //- Returns true if within time bounds
         bool active() const;
 
+        //- Return expansion ratio (deltaT change) that gives overall time
+        static scalar calcExpansion
+        (
+            const scalar startRatio,
+            const scalar y,
+            const label n
+        );
+
+        //- Calculate deltaT change such that the next write interval is
+        //  obeyed. Updates requiredDeltaTCoeff
+        void calcDeltaTCoeff
+        (
+            scalar& requiredDeltaTCoeff,
+            const scalar wantedDT,
+            const label nSteps,
+            const scalar presentTime,
+            const scalar timeToNextWrite,
+            const bool rampDirectionUp
+        );
+
         //- Disallow default bitwise copy construct
         timeControl(const timeControl&);
 

src/functionObjects/utilities/setTimeStep/setTimeStepFunctionObject.C

@@ -89,7 +89,7 @@ bool Foam::functionObjects::setTimeStepFunctionObject::adjustTimeStep()
         index = time_.timeIndex();
 
         // Set time, allow deltaT to be adjusted for writeInterval purposes
-        const_cast<Time&>(time_).setDeltaT(newDeltaT, true);
+        const_cast<Time&>(time_).setDeltaT(newDeltaT, false);
     }
 
     return true;

src/functionObjects/utilities/setTimeStep/setTimeStepFunctionObject.H

@@ -43,6 +43,9 @@ Usage
     {
         type        setTimeStep;
         libs        ("libutilityFunctionObjects.so");
+
+        deltaT      table ((0 5e-4)(0.01 1e-3));
+
         ...
     }
     \endverbatim
@@ -52,6 +55,10 @@ Usage
         Property     | Description             | Required    | Default value
         type         | Type name: setTimeStep  | yes         |
         enabled      | On/off switch           | no          | yes
+        deltaT       | Time step value         | yes         |
+        timeStart    | Start time              | no          | 0
+        timeEnd      | End time                | no          | GREAT
+        deltaTCoeff  | Time step change limit  | no          | GREAT
     \endtable
 
 SourceFiles