From 6584fa6ce07f892b99b1fe84e197ae4980214c53 Mon Sep 17 00:00:00 2001
From: Henry Weller <http://openfoam.org>
Date: Tue, 17 Oct 2017 12:17:24 +0100
Subject: [PATCH] functionObjects::wallHeatFlux: More efficient evaluation of
 heat-flux

which avoids the need for field interpolation and snGrad specification and
evaluation.

Resolves patch request https://bugs.openfoam.org/view.php?id=2725
---
 .../field/wallHeatFlux/wallHeatFlux.C              | 14 ++++++--------
 1 file changed, 6 insertions(+), 8 deletions(-)

diff --git a/src/functionObjects/field/wallHeatFlux/wallHeatFlux.C b/src/functionObjects/field/wallHeatFlux/wallHeatFlux.C
index f0f824b9dd..a347cfb43b 100644
--- a/src/functionObjects/field/wallHeatFlux/wallHeatFlux.C
+++ b/src/functionObjects/field/wallHeatFlux/wallHeatFlux.C
@@ -65,20 +65,18 @@ void Foam::functionObjects::wallHeatFlux::calcHeatFlux
     volScalarField& wallHeatFlux
 )
 {
-    surfaceScalarField heatFlux
-    (
-        fvc::interpolate(alpha)*fvc::snGrad(he)
-    );
-
     volScalarField::Boundary& wallHeatFluxBf =
         wallHeatFlux.boundaryFieldRef();
 
-    const surfaceScalarField::Boundary& heatFluxBf =
-        heatFlux.boundaryField();
+    const volScalarField::Boundary& heBf =
+        he.boundaryField();
+
+    const volScalarField::Boundary& alphaBf =
+        alpha.boundaryField();
 
     forAll(wallHeatFluxBf, patchi)
     {
-        wallHeatFluxBf[patchi] = heatFluxBf[patchi];
+        wallHeatFluxBf[patchi] = alphaBf[patchi]*heBf[patchi].snGrad();
     }
 
     if (foundObject<volScalarField>("qr"))