From 63bd3ed52b83ce4af9dc97ec8c9039a1951b5468 Mon Sep 17 00:00:00 2001
From: Hrvoje Jasak <h.jasak@wikki.co.uk>
Date: Thu, 28 Mar 2019 15:49:14 +0000
Subject: [PATCH] Bugfix: Use Sf normal rather than n in moving immersed
 boundary: they are not parallel due to Marooney maneouvre

---
 .../movingImmersedBoundaryVelocityFvPatchVectorField.C       | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/immersedBoundary/immersedBoundary/immersedBoundaryFvPatchFields/derived/movingImmersedBoundaryVelocity/movingImmersedBoundaryVelocityFvPatchVectorField.C b/src/immersedBoundary/immersedBoundary/immersedBoundaryFvPatchFields/derived/movingImmersedBoundaryVelocity/movingImmersedBoundaryVelocityFvPatchVectorField.C
index c79ac392d..6248707db 100644
--- a/src/immersedBoundary/immersedBoundary/immersedBoundaryFvPatchFields/derived/movingImmersedBoundaryVelocity/movingImmersedBoundaryVelocityFvPatchVectorField.C
+++ b/src/immersedBoundary/immersedBoundary/immersedBoundaryFvPatchFields/derived/movingImmersedBoundaryVelocity/movingImmersedBoundaryVelocityFvPatchVectorField.C
@@ -189,7 +189,10 @@ void Foam::movingImmersedBoundaryVelocityFvPatchVectorField::updateCoeffs()
         scalarField phip =
             p.patchField<surfaceScalarField, scalar>(fvc::meshPhi(U));
 
-        vectorField n = p.nf();
+        // Warning: cannot use patch normal but the real face normal
+        // THEY MAY NOT BE THE SAME!  HJ, 28/Mar/2019
+        vectorField n = p.Sf()/(p.magSf());
+
         const scalarField& magSf = p.magSf();
         scalarField Un = phip/(magSf + VSMALL);