From 0e20dd4be175d47148f8ed8a954fbade507883ac Mon Sep 17 00:00:00 2001
From: Chris Greenshields <https://cfd.direct>
Date: Mon, 25 Jul 2022 12:04:04 +0100
Subject: [PATCH] BirdCarreau viscosity model: default the 'a' coefficient

---
 .../strainRateViscosityModels/BirdCarreau/BirdCarreau.C         | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/MomentumTransportModels/momentumTransportModels/laminar/generalisedNewtonian/generalisedNewtonianViscosityModels/strainRateViscosityModels/BirdCarreau/BirdCarreau.C b/src/MomentumTransportModels/momentumTransportModels/laminar/generalisedNewtonian/generalisedNewtonianViscosityModels/strainRateViscosityModels/BirdCarreau/BirdCarreau.C
index c22ad783b1..22ab199d2e 100644
--- a/src/MomentumTransportModels/momentumTransportModels/laminar/generalisedNewtonian/generalisedNewtonianViscosityModels/strainRateViscosityModels/BirdCarreau/BirdCarreau.C
+++ b/src/MomentumTransportModels/momentumTransportModels/laminar/generalisedNewtonian/generalisedNewtonianViscosityModels/strainRateViscosityModels/BirdCarreau/BirdCarreau.C
@@ -93,7 +93,7 @@ read
     }
 
     n_.read(coeffs);
-    a_.read(coeffs);
+    a_.readIfPresent(coeffs);
 
     return true;
 }