sandbox/cselcuk/stencil_colision_test.c
Two cylinders freely rotating in a sheared-flow with DLMFD
Two cylinders, next to each other and twice as heavy as the surrounding fluid, are freely rotating in a shear-flow.
We place the cylinders this way to test how the stencils are constructed when they close to colision.
# define LEVEL 7
# include "grid/quadtree.h"
# define DLM_Moving_particle 1
# define TRANSLATION 0
# define ROTATION 1
# define DLM_alpha_coupling 1
# define adaptive 1
# define NPARTICLES 2
# if adaptive
# define MAXLEVEL (LEVEL)
# endifPhysical parameters
# define Uc 1. //caracteristic velocity
# define rhoval 1. // fluid density
# define diam (0.5) // particle diameter
# define ReD (10) // Reynolds number based on the particle's diameter
# define Ldomain 1.0
# define rhosolid 2.0 //particle density
# define tval (rhoval*Uc*Ldomain/ReD) //fluid dynamical viscosityOutput and numerical parameters
# define Tc (diam/Uc) // caracteristic time scale
# define mydt (Tc/200) // maximum time-step
# define maxtime (1.0)
# define tsave (Tc/1.)We include the ficitious-domain implementation
# include "dlmfd.h"
# include "view.h"
double deltau;
scalar un[];
int main() {
L0 = Ldomain;
/* set time step */
DT = mydt;
/* initialize grid */
init_grid(1 << (LEVEL));
/* boundary conditions */
u.n[left] = dirichlet(-Uc + 2*y*Uc/L0);
u.t[left] = dirichlet(0);
u.n[right] = dirichlet(-Uc + 2*y*Uc/L0);
u.t[right] = dirichlet(0);
u.n[top] = dirichlet(0);
u.t[top] = dirichlet(Uc);
u.n[bottom] = dirichlet(0);
u.t[bottom] = dirichlet(-Uc);
/* Convergence criteria */
TOLERANCE = 1e-4;
run();
}We initialize the fluid and particle variables.
event init (i = 0) {
/* set origin */
origin (0, 0);
if (!restore (file = "dump")){
/* fluid initial condition: */
foreach() {
u.x[] = -Uc + 2*y*Uc/L0;
un[] = u.x[];
}
/* initial condition: particles position */
particle * p = particles;
for (int k = 0; k < NPARTICLES; k++) {
GeomParameter gp = {0};We place the cylinders close to each others to test how the stencils are constructed when they close to colision.
if (k == 0) {
gp.center.x = L0/4;
gp.center.y = L0/2;
gp.radius = diam/2;
}
else {
gp.center.x = 3*L0/4;
gp.center.y = L0/2;
gp.radius = diam/2;
}
p[k].g = gp;
/* initial condition: particle's velocity */
coord c = {0., 0., 0.};
p[k].w = c;
}
} else {
// restart run, the default init event will take care of it
}
}We log the number of iterations of the multigrid solver for pressure and viscosity.
event logfile (i++) {
deltau = change (u.x, un);
fprintf (stderr, "log output %d %g %d %d %g %g %g %ld\n", i, t, mgp.i, mgu.i, mgp.resa, mgu.resa, deltau, grid->tn);
}
event output_data (t += 0.01; t < maxtime) {
stats statsvelox;
/* scalar omega[]; */
view (fov = 22.3366, quat = {0,0,0,1}, tx = -0.465283, ty = -0.439056, bg = {1,1,1}, width = 890, height = 862, samples = 1);
/* vorticity(u, omega); */
statsvelox = statsf (flagfield);
clear();
squares ("flagfield", map = cool_warm, min = statsvelox.min, max = statsvelox.max);
cells();
save ("movie.mp4");
}
event output_data_2 (t += 0.01; t < maxtime) {
stats statsvelox;
/* scalar omega[]; */
view (fov = 22.3366, quat = {0,0,0,1}, tx = -0.465283, ty = -0.439056, bg = {1,1,1}, width = 890, height = 862, samples = 1);
/* vorticity(u, omega); */
statsvelox = statsf (u.x);
clear();
squares ("u.x", map = cool_warm, min = statsvelox.min, max = statsvelox.max);
cells();
save ("movie1.mp4");
}Results
set grid
show grid
plot "particle-data-0" u 1:6 w l, "particle-data-1" u 1:6 w l 
set grid
show grid
plot "sum_lambda-0" u 1:3 w l, "sum_lambda-1" u 1:3 w l
