From cc3b257ce3f7407fe91fa74fbd345c72f65fbb5f Mon Sep 17 00:00:00 2001
From: Will Bainbridge <http://cfd.direct>
Date: Thu, 16 Dec 2021 15:58:54 +0000
Subject: [PATCH] LiquidEvaporation: Added condensation switch

This switch controls whether or not the model clips a droplet's outlet
mass flow rate to zero or permits it to become negative and thereby
represent condensation. By default condensation is not permitted.
---
 .../LiquidEvaporation/LiquidEvaporation.C        | 16 +++++++++++++++-
 .../LiquidEvaporation/LiquidEvaporation.H        |  5 ++++-
 2 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/src/lagrangian/parcel/submodels/Reacting/PhaseChangeModel/LiquidEvaporation/LiquidEvaporation.C b/src/lagrangian/parcel/submodels/Reacting/PhaseChangeModel/LiquidEvaporation/LiquidEvaporation.C
index daa306ae10..4f86af6a7f 100644
--- a/src/lagrangian/parcel/submodels/Reacting/PhaseChangeModel/LiquidEvaporation/LiquidEvaporation.C
+++ b/src/lagrangian/parcel/submodels/Reacting/PhaseChangeModel/LiquidEvaporation/LiquidEvaporation.C
@@ -72,6 +72,14 @@ Foam::LiquidEvaporation<CloudType>::LiquidEvaporation
 :
     PhaseChangeModel<CloudType>(dict, owner, typeName),
     liquids_(owner.thermo().liquids()),
+    condensation_
+    (
+        this->coeffDict().template lookupOrDefault<Switch>
+        (
+            "condensation",
+            false
+        )
+    ),
     activeLiquids_(this->coeffDict().lookup("activeLiquids")),
     liqToCarrierMap_(activeLiquids_.size(), -1),
     liqToLiqMap_(activeLiquids_.size(), -1)
@@ -200,7 +208,13 @@ void Foam::LiquidEvaporation<CloudType>::calculate
         const scalar Cinf = Xc[gid]*pc/(RR*Ts);
 
         // molar flux of vapour [kmol/m2/s]
-        const scalar Ni = max(kc*(Cs - Cinf), 0.0);
+        scalar Ni = kc*(Cs - Cinf);
+
+        // limit if not permitting condensation
+        if (!condensation_)
+        {
+            Ni = max(Ni, 0);
+        }
 
         // mass transfer [kg]
         dMassPC[lid] += Ni*pi*sqr(d)*liquids_.properties()[lid].W()*dt;
diff --git a/src/lagrangian/parcel/submodels/Reacting/PhaseChangeModel/LiquidEvaporation/LiquidEvaporation.H b/src/lagrangian/parcel/submodels/Reacting/PhaseChangeModel/LiquidEvaporation/LiquidEvaporation.H
index 1b4218a154..09c80615a2 100644
--- a/src/lagrangian/parcel/submodels/Reacting/PhaseChangeModel/LiquidEvaporation/LiquidEvaporation.H
+++ b/src/lagrangian/parcel/submodels/Reacting/PhaseChangeModel/LiquidEvaporation/LiquidEvaporation.H
@@ -2,7 +2,7 @@
   =========                 |
   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
    \\    /   O peration     | Website:  https://openfoam.org
-    \\  /    A nd           | Copyright (C) 2011-2020 OpenFOAM Foundation
+    \\  /    A nd           | Copyright (C) 2011-2021 OpenFOAM Foundation
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
 License
@@ -56,6 +56,9 @@ protected:
         //- Global liquid properties data
         const liquidMixtureProperties& liquids_;
 
+        //- Whether or not to permit condensation (default false)
+        Switch condensation_;
+
         //- List of active liquid names
         List<word> activeLiquids_;