FreeFOAM The Cross-Platform CFD Toolkit
gradientDispersionRAS.C
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25 
26 #include <OpenFOAM/error.H>
27 
28 #include "gradientDispersionRAS.H"
30 
31 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
32 
33 namespace Foam
34 {
35 
36 // * * * * * * * * * * * * * * Static Data Members * * * * * * * * * * * * * //
37 
38 defineTypeNameAndDebug(gradientDispersionRAS, 0);
39 
41 (
42  dispersionModel,
43  gradientDispersionRAS,
44  dictionary
45 );
46 
47 
48 // * * * * * * * * * * * * * * * * Constructors * * * * * * * * * * * * * * //
49 
50 // Construct from components
52 (
53  const dictionary& dict,
54  spray& sm
55 )
56 :
57  dispersionRASModel(dict, sm)
58 {}
59 
60 
61 // * * * * * * * * * * * * * * * * Destructor * * * * * * * * * * * * * * * //
62 
64 {}
65 
66 
67 // * * * * * * * * * * * * * * * Member Functions * * * * * * * * * * * * * //
68 
70 {
71 
72  const scalar cps = 0.16432;
73 
74  scalar dt = spray_.runTime().deltaT().value();
75  const volScalarField& k = turbulence().k();
76  volVectorField gradk = fvc::grad(k);
77  const volScalarField& epsilon = turbulence().epsilon();
78  const volVectorField& U = spray_.U();
79 
80  for
81  (
83  elmnt != spray_.end();
84  ++elmnt
85  )
86  {
87  label celli = elmnt().cell();
88  scalar UrelMag = mag(elmnt().U() - U[celli] - elmnt().Uturb());
89 
90  scalar Tturb = min
91  (
92  k[celli]/epsilon[celli],
93  cps*pow(k[celli], 1.5)/epsilon[celli]/(UrelMag + SMALL)
94  );
95  // parcel is perturbed by the turbulence
96  if (dt < Tturb)
97  {
98  elmnt().tTurb() += dt;
99 
100  if (elmnt().tTurb() > Tturb)
101  {
102  elmnt().tTurb() = 0.0;
103 
104  scalar sigma = sqrt(2.0*k[celli]/3.0);
105  vector dir = -gradk[celli]/(mag(gradk[celli]) + SMALL);
106 
107  // numerical recipes... Ch. 7. Random Numbers...
108  scalar x1 = 0.0;
109  scalar x2 = 0.0;
110  scalar rsq = 10.0;
111  while((rsq > 1.0) || (rsq == 0.0))
112  {
113  x1 = 2.0*spray_.rndGen().scalar01() - 1.0;
114  x2 = 2.0*spray_.rndGen().scalar01() - 1.0;
115  rsq = x1*x1 + x2*x2;
116  }
117 
118  scalar fac = sqrt(-2.0*log(rsq)/rsq);
119 
120  // in 2D calculations the -grad(k) is always
121  // away from the axis of symmetry
122  // This creates a 'hole' in the spray and to
123  // prevent this we let x1 be both negative/positive
124  if (spray_.twoD())
125  {
126  fac *= x1;
127  }
128  else
129  {
130  fac *= mag(x1);
131  }
132 
133  elmnt().Uturb() = sigma*fac*dir;
134  }
135  }
136  else
137  {
138  elmnt().tTurb() = GREAT;
139  elmnt().Uturb() = vector::zero;
140  }
141  }
142 }
143 
144 
145 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
146 
147 } // End namespace Foam
148 
149 // ************************ vim: set sw=4 sts=4 et: ************************ //