From 42e71682cc80824336655471bb85fc56751bce3c Mon Sep 17 00:00:00 2001
From: Will Bainbridge <http://cfd.direct>
Date: Fri, 3 Nov 2023 11:07:56 +0000
Subject: [PATCH] modules/isothermalFluid: Consistent handling of rhoU_0 and
 rhoUf_0

---
 applications/modules/isothermalFluid/isothermalFluid.C | 4 ++--
 applications/modules/isothermalFluid/isothermalFluid.H | 4 ----
 applications/modules/isothermalFluid/moveMesh.C        | 3 +--
 3 files changed, 3 insertions(+), 8 deletions(-)

diff --git a/applications/modules/isothermalFluid/isothermalFluid.C b/applications/modules/isothermalFluid/isothermalFluid.C
index f81ce8bbf3..4d13684207 100644
--- a/applications/modules/isothermalFluid/isothermalFluid.C
+++ b/applications/modules/isothermalFluid/isothermalFluid.C
@@ -314,9 +314,9 @@ void Foam::solvers::isothermalFluid::preSolve()
     {
         rhoU = new volVectorField("rhoU", rho*U);
 
-        if (rhoUf().nOldTimes() > 1)
+        for (label i = 1; i <= rhoUf().nOldTimes(false); ++ i)
         {
-            rhoU0 = new volVectorField("rhoU_0", rho.oldTime()*U.oldTime());
+            rhoU().oldTime(i) == rho.oldTime(i)*U.oldTime(i);
         }
     }
 
diff --git a/applications/modules/isothermalFluid/isothermalFluid.H b/applications/modules/isothermalFluid/isothermalFluid.H
index 1800c38172..7ad3945fd5 100644
--- a/applications/modules/isothermalFluid/isothermalFluid.H
+++ b/applications/modules/isothermalFluid/isothermalFluid.H
@@ -156,10 +156,6 @@ protected:
         //  used for mesh-change to set rhoUf for introduced faces
         autoPtr<volVectorField> rhoU;
 
-        //- Pointer to the old-time vol momentum field
-        //  used for mesh-change to set rhoUf.oldTime() for introduced faces
-        autoPtr<volVectorField> rhoU0;
-
         //- Pointer to the surface momentum field
         //  used to recreate the flux after mesh-change
         autoPtr<surfaceVectorField> rhoUf;
diff --git a/applications/modules/isothermalFluid/moveMesh.C b/applications/modules/isothermalFluid/moveMesh.C
index e6879bf983..ec9289ba78 100644
--- a/applications/modules/isothermalFluid/moveMesh.C
+++ b/applications/modules/isothermalFluid/moveMesh.C
@@ -36,10 +36,9 @@ void Foam::solvers::isothermalFluid::moveMesh()
         // Move the mesh
         mesh_.move();
 
-        // The rhoU and rhoU0 fields can be cleared following mesh-motion
+        // The rhoU field can be cleared following mesh-motion
         // now the mesh has been re-stitched as necessary
         rhoU.clear();
-        rhoU0.clear();
 
         if (mesh.changing())
         {