From aa8b1ae0f886e45b16c09962de599fd0f3fb1a9a Mon Sep 17 00:00:00 2001
From: Kai Bao <kai.bao@sintef.no>
Date: Mon, 2 Oct 2017 14:51:54 +0200
Subject: [PATCH] giving the friction pressure loss a direction.

---
 opm/autodiff/MultisegmentWell_impl.hpp | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/opm/autodiff/MultisegmentWell_impl.hpp b/opm/autodiff/MultisegmentWell_impl.hpp
index 1b97d9d69..51444f487 100644
--- a/opm/autodiff/MultisegmentWell_impl.hpp
+++ b/opm/autodiff/MultisegmentWell_impl.hpp
@@ -1644,7 +1644,9 @@ namespace Opm
         const double area = segmentSet()[seg].crossArea();
         const double diameter = segmentSet()[seg].internalDiameter();
 
-        return mswellhelpers::frictionPressureLoss(length, diameter, area, roughness, density, mass_rate, visc);
+        const double sign = mass_rate < 0. ? 1.0 : - 1.0;
+
+        return sign * mswellhelpers::frictionPressureLoss(length, diameter, area, roughness, density, mass_rate, visc);
     }