added comments

src/postProcessing/functionObjects/utilities/timeActivatedFileUpdate/timeActivatedFileUpdate.H

@@ -26,6 +26,27 @@ Class
     Foam::timeActivatedFileUpdate
 
 Description
+    Performs a file copy/replacement once a specified time has been reached.
+
+    Example usage to update the fvSolution dictionary at various times
+    throughout the calculation:
+
+        fileUpdate1
+        {
+            type              timeActivatedFileUpdate;
+            functionObjectLibs ("libutilityFunctionObjects.so");
+            outputControl     timeStep;
+            outputInterval    1;
+            fileToUpdate      "$FOAM_CASE/system/fvSolution";
+            timeVsFile
+            (
+                (-1 "$FOAM_CASE/system/fvSolution.0")
+                (0.10 "$FOAM_CASE/system/fvSolution.10")
+                (0.20 "$FOAM_CASE/system/fvSolution.20")
+                (0.35 "$FOAM_CASE/system/fvSolution.35")
+            );
+        }
+
 
 SourceFiles
     timeActivatedFileUpdate.C
@@ -60,6 +81,7 @@ class timeActivatedFileUpdate
         //- Name of this set of timeActivatedFileUpdate objects
         word name_;
 
+        //- Owner database
         const objectRegistry& obr_;
 
         //- On/off switch