Commit 604fb951 authored by andy's avatar andy
Browse files

BUG: Corrected Pilch-Erdman break-up model

parent 0d13d8f1
......@@ -36,7 +36,7 @@ Foam::PilchErdman<CloudType>::PilchErdman
:
BreakupModel<CloudType>(dict, owner, typeName),
B1_(0.375),
B2_(0.236)
B2_(0.2274)
{
if (!this->defaultCoeffs(true))
{
......@@ -90,58 +90,79 @@ bool Foam::PilchErdman<CloudType>::update
scalar& massChild
)
{
scalar semiMass = nParticle*pow3(d);
scalar We = 0.5*rhoc*sqr(Urmag)*d/sigma;
// Weber number - eq (1)
scalar We = rhoc*sqr(Urmag)*d/sigma;
// Ohnesorge number - eq (2)
scalar Oh = mu/sqrt(rho*d*sigma);
scalar Wec = 6.0*(1.0 + 1.077*pow(Oh, 1.6));
// Critical Weber number - eq (5)
scalar Wec = 12.0*(1.0 + 1.077*pow(Oh, 1.6));
if (We > Wec)
{
// We > 1335, wave crest stripping
// We > 2670, wave crest stripping - eq (12)
scalar taubBar = 5.5;
if (We < 1335)
if (We < 2670)
{
if (We > 175.0)
if (We > 351)
{
// sheet stripping - eq (11)
taubBar = 0.766*pow(We - 12.0, 0.25);
}
else if (We > 45)
{
// sheet stripping
taubBar = 0.766*pow(2.0*We - 12.0, 0.25);
// bag-and-stamen breakup - eq (10)
taubBar = 14.1*pow(We - 12.0, 0.25);
}
else if (We > 22.0)
else if (We > 18)
{
// Bag-and-stamen breakup
taubBar = 14.1*pow(2.0*We - 12.0, -0.25);
// bag breakup - eq (9)
taubBar = 2.45*pow(We - 12.0, 0.25);
}
else if (We > 9.0)
else if (We > 12)
{
// Bag breakup
taubBar = 2.45*pow(2.0*We - 12.0, 0.25);
// vibrational breakup - eq (8)
taubBar = 6.0*pow(We - 12.0, -0.25);
}
else if (We > 6.0)
else
{
// Vibrational breakup
taubBar = 6.0*pow(2.0*We - 12.0, -0.25);
// no break-up
taubBar = GREAT;
}
}
scalar rho12 = sqrt(rhoc/rho);
scalar Vd = Urmag*rho12*(B1_*taubBar + B2_*taubBar*taubBar);
// velocity of fragmenting drop - eq (20)
scalar Vd = Urmag*rho12*(B1_*taubBar + B2_*sqr(taubBar));
// maximum stable diameter - eq (33)
scalar Vd1 = sqr(1.0 - Vd/Urmag);
Vd1 = max(Vd1, SMALL);
scalar Ds = 2.0*Wec*sigma/(Vd1*rhoc*sqr(Urmag));
scalar A = Urmag*rho12/d;
scalar dStable = Wec*sigma/(Vd1*rhoc*sqr(Urmag));
scalar taub = taubBar/A;
if (d < dStable)
{
// droplet diameter already stable = no break-up
// - do not update d and nParticle
return false;
}
else
{
scalar semiMass = nParticle*pow3(d);
scalar frac = dt/taub;
// invert eq (3) to create a dimensional break-up time
scalar taub = taubBar*d/(Urmag*rho12);
// update the droplet diameter according to the rate eq. (implicitly)
d = (d + frac*Ds)/(1.0 + frac);
// update droplet diameter according to the rate eq (implicitly)
scalar frac = dt/taub;
d = (d + frac*dStable)/(1.0 + frac);
// correct the number of particles to conserve mass
nParticle = semiMass/pow3(d);
// correct the number of particles to conserve mass
nParticle = semiMass/pow3(d);
}
}
return false;
......
......@@ -2,7 +2,7 @@
========= |
\\ / F ield | OpenFOAM: The Open Source CFD Toolbox
\\ / O peration |
\\ / A nd | Copyright (C) 2011 OpenFOAM Foundation
\\ / A nd | Copyright (C) 2011-2013 OpenFOAM Foundation
\\/ M anipulation |
-------------------------------------------------------------------------------
License
......@@ -25,7 +25,7 @@ Class
Foam::PilchErdman
Description
secondary breakup model
Particle secondary breakup model, based on the reference:
@verbatim
Pilch, M. and Erdman, C.A.
......@@ -35,6 +35,24 @@ Description
Int. J. Multiphase Flows 13 (1987), 741-757
@endverbatim
The droplet fragment velocity is described by the equation:
\f[
V_d = V sqrt(epsilon)(B1 T + B2 T^2)
\f]
Where:
V_d : fragment velocity
V : magnitude of the relative velocity
epsilon : density ratio (rho_carrier/rho_droplet)
T : characteristic break-up time
B1, B2 : model input coefficients
The authors suggest that:
compressible flow : B1 = 0.75*1.0; B2 = 3*0.116
incompressible flow : B1 = 0.75*0.5; B2 = 3*0.0758
\*---------------------------------------------------------------------------*/
#ifndef PilchErdman_H
......
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