twoPhaseMixtureThermo: Fix for collated file operation

twoPhaseMixtureThermo writes the temperatures during construction only
for them to be read again immediately after by construction of the
individual phases' thermo models. When running with collated file
handling this behaviour is not thread safe. This change deactivates
threading for the duration of this behaviour.

Patch contributed by Mattijs Janssens

applications/solvers/multiphase/compressibleInterFoam/twoPhaseMixtureThermo/twoPhaseMixtureThermo.C

@@ -26,7 +26,7 @@ License
 #include "twoPhaseMixtureThermo.H"
 #include "gradientEnergyFvPatchScalarField.H"
 #include "mixedEnergyFvPatchScalarField.H"
-
+#include "collatedFileOperation.H"
 
 // * * * * * * * * * * * * * * Static Data Members * * * * * * * * * * * * * //
 
@@ -50,6 +50,12 @@ Foam::twoPhaseMixtureThermo::twoPhaseMixtureThermo
     thermo1_(nullptr),
     thermo2_(nullptr)
 {
+    // Note: we're writing files to be read in immediately afterwards.
+    //       Avoid any thread-writing problems.
+    float bufSz =
+        fileOperations::collatedFileOperation::maxThreadFileBufferSize;
+    fileOperations::collatedFileOperation::maxThreadFileBufferSize = 0;
+
     {
         volScalarField T1
         (
@@ -80,6 +86,10 @@ Foam::twoPhaseMixtureThermo::twoPhaseMixtureThermo
         T2.write();
     }
 
+    fileOperations::collatedFileOperation::maxThreadFileBufferSize =
+        bufSz;
+
+
     thermo1_ = rhoThermo::New(U.mesh(), phase1Name());
     thermo2_ = rhoThermo::New(U.mesh(), phase2Name());