diff --git a/src/fvOptions/sources/derived/fanMomentumSource/fanMomentumSource.C b/src/fvOptions/sources/derived/fanMomentumSource/fanMomentumSource.C
index 92bd6e558f..a99982396d 100644
--- a/src/fvOptions/sources/derived/fanMomentumSource/fanMomentumSource.C
+++ b/src/fvOptions/sources/derived/fanMomentumSource/fanMomentumSource.C
@@ -6,6 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2022 Louis Vittoz, SimScale GmbH
+    Copyright (C) 2023 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -263,7 +264,7 @@ Foam::fv::fanMomentumSource::fanMomentumSource
     upstreamPatchFaceInfo_(),
     cellsInZones_(),
     fanCurvePtr_(Function1<scalar>::New("fanCurve", coeffs_, &mesh)),
-    UName_(coeffs_.get<word>("U")),
+    UName_(coeffs_.getOrDefault<word>("U", "U")),
     flowDir_(coeffs_.get<vector>("flowDir")),
     thickness_(coeffs_.get<scalar>("thickness")),
     gradPFan_(0.0),
diff --git a/src/fvOptions/sources/derived/fanMomentumSource/fanMomentumSource.H b/src/fvOptions/sources/derived/fanMomentumSource/fanMomentumSource.H
index e1baa7572f..52d11a5139 100644
--- a/src/fvOptions/sources/derived/fanMomentumSource/fanMomentumSource.H
+++ b/src/fvOptions/sources/derived/fanMomentumSource/fanMomentumSource.H
@@ -6,6 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2022 Louis Vittoz, SimScale GmbH
+    Copyright (C) 2023 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -54,6 +55,7 @@ Usage
         // Optional entries
         gradient            <scalar>;
         rho                 <scalar>;
+        U                   <word>;
 
         // Inherited entries
         ...
@@ -71,6 +73,7 @@ Usage
       thickness | Thickness of the fan [m]          | scalar | yes | -
       gradient  | Initial pressure gradient         | scalar | no  | -
       rho       | Reference density for incompressible flow | scalar | no  | -
+      U         | Name of velocity field            | word   | no  | U
     \endtable
 
     The inherited entries are elaborated in: