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| #include "mypoisson.h"
struct Viscosity {
vector u;
face vector mu;
scalar rho;
double dt;
int nrelax;
scalar * res;
double (* embed_flux) (Point, scalar, vector, double *);
};
#if AXI
// fixme: RHO here not correct
# define lambda ((coord){1., 1. + dt/RHO*(mu.x[] + mu.x[1] + \
mu.y[] + mu.y[0,1])/2./sq(y)})
#else // not AXI
# if dimension == 1
# define lambda ((coord){1.})
# elif dimension == 2
# define lambda ((coord){1.,1.})
# elif dimension == 3
# define lambda ((coord){1.,1.,1.})
#endif
#endif
// Note how the relaxation function uses "naive" gradients i.e. not
// the face_gradient_* macros.
static void relax_diffusion (scalar * a, scalar * b, int l, void * data)
{
struct Viscosity * p = (struct Viscosity *) data;
(const) face vector mu = p->mu;
(const) scalar rho = p->rho;
double dt = p->dt;
vector u = vector(a[0]), r = vector(b[0]);
double (* flux) (Point, scalar, vector, double *) = p->embed_flux;
foreach_level_or_leaf (l) {
double avgmu = 0.;
foreach_dimension()
avgmu += mu.x[] + mu.x[1];
avgmu = dt*avgmu + SEPS;
foreach_dimension() {
double c = 0.;
double d = flux ? flux (point, u.x, mu, &c) : 0.;
scalar s = u.x;
double a = 0.;
foreach_dimension()
a += mu.x[1]*s[1] + mu.x[]*s[-1];
u.x[] = (dt*a + (r.x[] - dt*c)*sq(Delta))/
(sq(Delta)*(rho[]*lambda.x + dt*d) + avgmu);
}
}
#if TRASH
vector u1[];
foreach_level_or_leaf (l)
foreach_dimension()
u1.x[] = u.x[];
trash ({u});
foreach_level_or_leaf (l)
foreach_dimension()
u.x[] = u1.x[];
#endif
}
static double residual_diffusion (scalar * a, scalar * b, scalar * resl,
void * data)
{
struct Viscosity * p = (struct Viscosity *) data;
(const) face vector mu = p->mu;
(const) scalar rho = p->rho;
double dt = p->dt;
double (* flux) (Point, scalar, vector, double *) = p->embed_flux;
vector u = vector(a[0]), r = vector(b[0]), res = vector(resl[0]);
double maxres = 0.;
#if TREE
/* conservative coarse/fine discretisation (2nd order) */
foreach_dimension() {
scalar s = u.x;
face vector g[];
foreach_face()
g.x[] = mu.x[]*face_gradient_x (s, 0);
foreach (reduction(max:maxres)) {
double a = 0.;
foreach_dimension()
a += g.x[] - g.x[1];
res.x[] = r.x[] - rho[]*lambda.x*u.x[] - dt*a/Delta;
if (flux) {
double c, d = flux (point, u.x, mu, &c);
res.x[] -= dt*(c + d*u.x[]);
}
if (fabs (res.x[]) > maxres)
maxres = fabs (res.x[]);
}
}
#else
/* "naive" discretisation (only 1st order on trees) */
foreach (reduction(max:maxres))
foreach_dimension() {
scalar s = u.x;
double a = 0.;
foreach_dimension()
a += mu.x[0]*face_gradient_x (s, 0) - mu.x[1]*face_gradient_x (s, 1);
res.x[] = r.x[] - rho[]*lambda.x*u.x[] - dt*a/Delta;
if (flux) {
double c, d = flux (point, u.x, mu, &c);
res.x[] -= dt*(c + d*u.x[]);
}
if (fabs (res.x[]) > maxres)
maxres = fabs (res.x[]);
}
#endif
return maxres;
}
#undef lambda
double TOLERANCE_MU = 0.; // default to TOLERANCE
trace
mgstats viscosity (struct Viscosity p)
{
vector u = p.u, r[];
scalar rho = p.rho;
foreach()
foreach_dimension()
r.x[] = rho[]*u.x[];
face vector mu = p.mu;
restriction ({mu, rho});
p.embed_flux = u.x.boundary[embed] != antisymmetry ? embed_flux : NULL;
return mg_solve ((scalar *){u}, (scalar *){r},
residual_diffusion, relax_diffusion, &p, p.nrelax, p.res,
minlevel = 1, // fixme: because of root level
// BGHOSTS = 2 bug on trees
tolerance = TOLERANCE_MU);
}
|
