BrunDrippingInjection: Calculate drop diameter from the capillary length

The diameter of the drops formed are obtained from the local capillary
length multiplied by the \c dCoeff coefficient which defaults to 3.3.

Reference:
    Lefebvre, A. (1988).
    Atomization and sprays
    (Vol. 1040, No. 2756). CRC press.

src/regionModels/surfaceFilmModels/submodels/kinematic/injectionModel/BrunDrippingInjection/BrunDrippingInjection.C

@@ -25,11 +25,6 @@ License
 
 #include "BrunDrippingInjection.H"
 #include "addToRunTimeSelectionTable.H"
-#include "fvMesh.H"
-#include "Time.H"
-#include "mathematicalConstants.H"
-#include "Random.H"
-#include "volFields.H"
 #include "kinematicSingleLayer.H"
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
@@ -56,17 +51,8 @@ BrunDrippingInjection::BrunDrippingInjection
 :
     injectionModel(type(), owner, dict),
     ubarStar_(coeffDict_.lookupOrDefault("ubarStar", 1.62208)),
-    deltaStable_(readScalar(coeffDict_.lookup("deltaStable"))),
-    particlesPerParcel_(readScalar(coeffDict_.lookup("particlesPerParcel"))),
-    rndGen_(label(0), -1),
-    parcelDistribution_
-    (
-        distributionModels::distributionModel::New
-        (
-            coeffDict_.subDict("parcelDistribution"),
-            rndGen_
-        )
-    ),
+    dCoeff_(coeffDict_.lookupOrDefault("dCoeff", 3.3)),
+    deltaStable_(coeffDict_.lookupOrDefault("deltaStable", 0)),
     diameter_(owner.regionMesh().nCells(), -1.0)
 {}
 
@@ -89,8 +75,6 @@ void BrunDrippingInjection::correct
     const kinematicSingleLayer& film =
         refCast<const kinematicSingleLayer>(this->owner());
 
-    const scalar pi = constant::mathematical::pi;
-
     // Calculate available dripping mass
     tmp<volScalarField> tsinAlpha(film.gNorm()/mag(film.g()));
     const scalarField& sinAlpha = tsinAlpha();
@@ -101,66 +85,47 @@ void BrunDrippingInjection::correct
     const scalarField& sigma = film.sigma();
     const scalar magg = mag(film.g().value());
 
-    scalarField massDrip(film.regionMesh().nCells(), 0.0);
+    scalarField massDrip(film.regionMesh().nCells(), scalar(0));
 
-    forAll(delta, i)
+    forAll(delta, celli)
     {
-        if (sinAlpha[i] > SMALL && delta[i] > deltaStable_)
+        if (sinAlpha[celli] > SMALL && delta[celli] > deltaStable_)
         {
-            scalar lc = sqrt(sigma[i]/(rho[i]*magg));
-            scalar deltaStable = max
+            const scalar lc = sqrt(sigma[celli]/(rho[celli]*magg));
+            const scalar deltaStable = max
             (
-                3*lc*sqrt(1 - sqr(sinAlpha[i]))
-               /(ubarStar_*sqrt(sinAlpha[i])*sinAlpha[i]),
+                3*lc*sqrt(1 - sqr(sinAlpha[celli]))
+               /(ubarStar_*sqrt(sinAlpha[celli])*sinAlpha[celli]),
                 deltaStable_
             );
 
-            Info<< delta[i] << " " << deltaStable << endl;
-            if (delta[i] > deltaStable)
+            if (delta[celli] > deltaStable)
             {
-                const scalar ddelta = max(0.0, delta[i] - deltaStable);
-                massDrip[i] +=
-                    min(availableMass[i], max(0.0, ddelta*rho[i]*magSf[i]));
+                const scalar ddelta = max(delta[celli] - deltaStable, 0);
+                massDrip[celli] +=
+                    min
+                    (
+                        availableMass[celli],
+                        max(ddelta*rho[celli]*magSf[celli], 0)
+                    );
             }
         }
     }
 
-
     // Collect the data to be transferred
     forAll(massDrip, celli)
     {
         if (massDrip[celli] > 0)
         {
-            // Set new particle diameter if not already set
-            if (diameter_[celli] < 0)
-            {
-                diameter_[celli] = parcelDistribution_->sample();
-            }
-
-            scalar& diam = diameter_[celli];
-            scalar rhoc = rho[celli];
-            scalar minMass = particlesPerParcel_*rhoc*pi/6*pow3(diam);
+            const scalar rhoc = rho[celli];
+            const scalar diam = dCoeff_*sqrt(sigma[celli]/(rhoc*magg));
+            diameter_[celli] = diam;
 
-            if (massDrip[celli] > minMass)
-            {
-                // All drip mass can be injected
-                massToInject[celli] += massDrip[celli];
-                availableMass[celli] -= massDrip[celli];
+            massToInject[celli] += massDrip[celli];
+            availableMass[celli] -= massDrip[celli];
 
-                // Set particle diameter
-                diameterToInject[celli] = diam;
-
-                // Retrieve new particle diameter sample
-                diam = parcelDistribution_->sample();
-
-                addToInjectedMass(massDrip[celli]);
-            }
-            else
-            {
-                // Particle mass below minimum threshold - cannot be injected
-                massToInject[celli] = 0;
-                diameterToInject[celli] = 0;
-            }
+            diameterToInject[celli] = diam;
+            addToInjectedMass(massDrip[celli]);
         }
         else
         {

src/regionModels/surfaceFilmModels/submodels/kinematic/injectionModel/BrunDrippingInjection/BrunDrippingInjection.H

@@ -27,10 +27,10 @@ Class
 Description
     Film Dripping mass transfer model.
 
-    If the film thickness exceeds the critical value needed to generate a valid
-    parcel, the equivalent mass is removed from the film.  The critical film
-    thickness is calculated from the Rayleigh-Taylor stability analysis
-    of film flow on an inclined plane by Brun et.al.
+    If the film thickness exceeds the critical value needed to generate one or
+    more drops, the equivalent mass is removed from the film.  The critical film
+    thickness is calculated from the Rayleigh-Taylor stability analysis of film
+    flow on an inclined plane by Brun et.al.
 
     Reference:
     \verbatim
@@ -39,7 +39,15 @@ Description
         Physics of Fluids (1994-present), 27(8), 084107.
     \endverbatim
 
-    New parcel diameters are sampled from a PDF.
+    The diameter of the drops formed are obtained from the local capillary
+    length multiplied by the \c dCoeff coefficient which defaults to 3.3.
+
+    Reference:
+    \verbatim
+        Lefebvre, A. (1988).
+        Atomization and sprays
+        (Vol. 1040, No. 2756). CRC press.
+    \endverbatim
 
 SourceFiles
     BrunDrippingInjection.C
@@ -50,8 +58,6 @@ SourceFiles
 #define BrunDrippingInjection_H
 
 #include "injectionModel.H"
-#include "distributionModel.H"
-#include "cachedRandom.H"
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
@@ -84,24 +90,19 @@ protected:
     // Protected data
 
         //- Critical non-dimensional interface velocity
-        //  Coefficient in the film angle stability function
-        // defaults to 1.62208
+        //  Coefficient in the film angle stability function.
+        //  Defaults to 1.62208
         scalar ubarStar_;
 
+        //- Coefficient relating the diameter of the drops formed to
+        //  the capillary length.
+        //  Defaults to 3.3
+        scalar dCoeff_;
+
         //- Stable film thickness - drips only formed if thickness
         //  execeeds this threhold value
         scalar deltaStable_;
 
-        //- Number of particles per parcel
-        scalar particlesPerParcel_;
-
-        //- Random number generator
-        cachedRandom rndGen_;
-
-        //- Parcel size PDF model
-        const autoPtr<distributionModels::distributionModel>
-            parcelDistribution_;
-
         //- Diameters of particles to inject into the dripping
         scalarList diameter_;