ENH: Pair collision model - added ramp time to bleed-in force contributions

src/lagrangian/intermediate/submodels/Kinematic/CollisionModel/PairCollision/PairModel/PairModel/PairModel.C

@@ -3,7 +3,7 @@
   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
    \\    /   O peration     |
     \\  /    A nd           | Copyright (C) 2011 OpenFOAM Foundation
-     \\/     M anipulation  |
+     \\/     M anipulation  | Copyright (C) 2018 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -37,7 +37,11 @@ Foam::PairModel<CloudType>::PairModel
 :
     dict_(dict),
     owner_(owner),
-    coeffDict_(dict.subDict(type + "Coeffs"))
+    coeffDict_(dict.subDict(type + "Coeffs")),
+    forceRampTime_
+    (
+        this->coeffDict().template lookupOrDefault<scalar>("forceRampTime", -1)
+    )
 {}
 
 
@@ -66,13 +70,28 @@ const Foam::dictionary& Foam::PairModel<CloudType>::dict() const
 
 
 template<class CloudType>
-const Foam::dictionary&
-Foam::PairModel<CloudType>::coeffDict() const
+const Foam::dictionary& Foam::PairModel<CloudType>::coeffDict() const
 {
     return coeffDict_;
 }
 
 
+template<class CloudType>
+Foam::scalar Foam::PairModel<CloudType>::forceCoeff
+(
+    typename CloudType::parcelType& pA,
+    typename CloudType::parcelType& pB
+) const
+{
+    if (forceRampTime_ < 0)
+    {
+        return 1;
+    }
+
+    return min(min(pA.age(), pB.age())/forceRampTime_, 1);
+}
+
+
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
 #include "PairModelNew.C"

src/lagrangian/intermediate/submodels/Kinematic/CollisionModel/PairCollision/PairModel/PairModel/PairModel.H

@@ -3,7 +3,7 @@
   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
    \\    /   O peration     |
     \\  /    A nd           | Copyright (C) 2011-2016 OpenFOAM Foundation
-     \\/     M anipulation  |
+     \\/     M anipulation  | Copyright (C) 2018 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -63,6 +63,21 @@ class PairModel
         //- The coefficients dictionary
         const dictionary coeffDict_;
 
+        //- Time to bleed-in collision forces; default = 0 (no delay)
+        scalar forceRampTime_;
+
+
+protected:
+
+    // Protected Member Functions
+
+        //- Return the force coefficient based on the forceRampTime_
+        scalar forceCoeff
+        (
+            typename CloudType::parcelType& pA,
+            typename CloudType::parcelType& pB
+        ) const;
+
 
 public:
 

src/lagrangian/intermediate/submodels/Kinematic/CollisionModel/PairCollision/PairModel/PairSpringSliderDashpot/PairSpringSliderDashpot.C

@@ -3,7 +3,7 @@
   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
    \\    /   O peration     |
     \\  /    A nd           | Copyright (C) 2011-2017 OpenFOAM Foundation
-     \\/     M anipulation  |
+     \\/     M anipulation  | Copyright (C) 2018 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -193,7 +193,10 @@ void Foam::PairSpringSliderDashpot<CloudType>::evaluatePair
 
     if (normalOverlapMag > 0)
     {
-        //Particles in collision
+        // Particles in collision
+
+        // Force coefficient
+        scalar forceCoeff = this->forceCoeff(pA, pB);
 
         vector rHat_AB = r_AB/(r_AB_mag + VSMALL);
 
@@ -224,6 +227,8 @@ void Foam::PairSpringSliderDashpot<CloudType>::evaluatePair
                 *rHat_AB;
         }
 
+        fN_AB *= forceCoeff;
+
         pA.f() += fN_AB;
         pB.f() += -fN_AB;
 
@@ -278,6 +283,8 @@ void Foam::PairSpringSliderDashpot<CloudType>::evaluatePair
                 fT_AB = - kT*tangentialOverlap_AB - etaT*USlip_AB;
             }
 
+            fT_AB *= forceCoeff;
+
             pA.f() += fT_AB;
             pB.f() += -fT_AB;