sandbox/cselcuk/balistic-sphere.c

    Balistic test case, a sphere with initial transversal velocity and subject to gravity

    # include "grid/octree.h"
# define DLM_Moving_particle 1
# define NPARTICLES 1
# define DLM_alpha_coupling 1

    Parameters related to the spatial resolution

    # define LEVEL 4 
# define adaptive 1
# if adaptive
# define MAXLEVEL (LEVEL + 8)
# endif

    Physical parameters

    The characteristic velocity scale is U_c = \sqrt(gD) with D the sphere’s diameters (characteristic length scale).The Reynolds number based on U_c is Re = 25.

    # define rhoval 1000. // fluid density
# define rhosolid 1140. // particle's density 
# define gravity_y -9.81 // gravity acceleration
# define Lc (0.01)  // characteristic length - particle diameter
# define tval 0.125284 // fluid dynamic viscosity, here Re = 25
# define Uc 0.31321 // sqrt(grav*Lc)
# define Tc (Lc/Uc) // characteristic time

/* output and numerical parameters */
# define mydt  (Tc/50) //time-step
# define maxtime (100*mydt) // simulation time

    Fictitious domain implementation with toy model granular solver

    # include "dlmfd-toygs.h"
# include "navier-stokes/perfs.h"

double deltau;
scalar un[];

int main () {
  
  origin (0., 0., 0.);
 
  L0 = 120*Lc;
   
  /* set time step */
  DT = mydt;

  /* initialise a uniform grid */
  init_grid (1 << LEVEL);

  /* boundary conditions */
  u.t[left]   = dirichlet(0.); //v
  u.r[left]   = dirichlet(0.); //w
  u.n[left]   = dirichlet(0.); //u
  uf.t[left]   = dirichlet(0.); //v
  uf.r[left]   = dirichlet(0.); //w
  uf.n[left]   = dirichlet(0.); //u

  u.t[right]  = dirichlet(0.); //v
  u.r[right]  = dirichlet(0.); //w
  u.n[right]  = dirichlet(0.); //u
  uf.t[right]  = dirichlet(0.); //v
  uf.r[right]  = dirichlet(0.); //w
  uf.n[right]  = dirichlet(0.); //u

  
  u.n[bottom] = dirichlet(0.); //v
  u.t[bottom] = dirichlet(0.); //w
  u.r[bottom] = dirichlet(0.); //u
  uf.n[bottom] = dirichlet(0.); //v
  uf.t[bottom] = dirichlet(0.); //w
  uf.r[bottom] = dirichlet(0.); //u
 
  u.n[top]    = dirichlet(0.); //v
  u.t[top]    = dirichlet(0.); //w
  u.r[top]    = dirichlet(0.); //u
  uf.n[top]    = dirichlet(0.); //v
  uf.t[top]    = dirichlet(0.); //w
  uf.r[top]    = dirichlet(0.); //u
  
  u.n[front]  = dirichlet(0.); //w
  u.t[front]  = dirichlet(0.); //u
  u.r[front]  = dirichlet(0.); //v
  uf.n[front]  = dirichlet(0.); //w
  uf.t[front]  = dirichlet(0.); //u
  uf.r[front]  = dirichlet(0.); //v

  u.n[back]   = dirichlet(0.); //w
  u.t[back]   = dirichlet(0.); //u
  u.r[back]   = dirichlet(0.); //v
  uf.n[back]   = dirichlet(0.); //w
  uf.t[back]   = dirichlet(0.); //u
  uf.r[back]   = dirichlet(0.); //v

  
  // Convergence criteria for the N-S solver
  TOLERANCE = 1e-4; 
  NITERMIN = 2;
  run();
}


event init (i = 0) {
  
  particle * p = particles;
 
  /* Initial condition for the fluid */
  foreach() {
    foreach_dimension() {
      u.x[] = 0.;
    }
    un[] = u.x[];
  }

  double diam = Lc;

  for (int k = 0; k < NPARTICLES; k++) {   

    /* initial condition: particle's position */
    GeomParameter gp = {0};
    gp.center.x = 20*diam;
    gp.center.y = L0-20*diam;
    gp.center.z = L0/2;
    gp.radius = diam/2.;
    
    p[k].g = gp;
    
    /* initial condition: particle's velocities */
    coord c = {0., 0., 0.}; 
    c.x = 1.; p[k].U = c;
    c.x = 0.; p[k].w = c;   
  }
}

event output_data (t += Tc; t <= maxtime)
{
  dump(file = "dump");
  particle * p = particles;
  dump_particle(p);
  
}
 
event last_output (t=end) {
  p.nodump = false;
  dump("dump");
}

    Results

    set grid
show grid
Lc = 0.01
Uc = 0.31321
tc = Lc/Uc
set xlabel "t/t_c"
set ylabel "t_c*\omega"
plot "particle-data-0" u ($1/tc):($8*tc) w l title "t_c\omega^p_x", "particle-data-0" u ($1/tc):($9*tc) w l title "\omega^p_y t_c", "particle-data-0" u ($1/tc):($10*tc) w l title "\omega^p_z t_c"
    dimensionless particle angular velocities t_c\omega^p_x, t_c\omega^p_y , t_c\omega^p_z (script)

    dimensionless particle angular velocities t_c\omega^p_x, t_c\omega^p_y , t_c\omega^p_z (script)

    reset
set grid
show grid
Lc = 0.01
Uc = 0.31321
tc = Lc/Uc
set xlabel "t/t_c"
set ylabel "u/Uc"
plot  "particle-data-0" u ($1/tc):($5/Uc) w l title "U_x/Uc","particle-data-0" u ($1/tc):($6/Uc) w l title "U_y/Uc", "particle-data-0" u ($1/tc):($7/Uc) w l title "U_z/Uc"
    dimensionless particle translational velocities U_x/Uc, U_y/Uc, U_z/Uc (script)

    dimensionless particle translational velocities U_x/Uc, U_y/Uc, U_z/Uc (script)

    reset
diam = 0.01
show grid
set xlabel "x/diam"
set ylabel "y/diam"
plot "particle-data-0" u ($2/diam):($3/diam) w l title "trajectory"
    particle trajectory in x-y plane at z=L0/2 (script)

    particle trajectory in x-y plane at z=L0/2 (script)