/** Spring force with a directional force to align with flow direction. */
static const Vector
edge_force(const Vector& dir, const Vector& hpos, const Vector& tpos)
{
return vec_add(dir, spring_force(hpos, tpos, EDGE_LEN, EDGE_K));
}
void get_forces(struct chain_param *chain_pm, struct monomer *monomers, Float ***velcs_df, int n_step, VSLStreamStatePtr rngstream)
{
extern int n_proc, num_proc;
extern int num_x;
extern int max_x, max_y, max_z;
extern int wall_flag;
int mon_proc;
int num_beads, Nbead;
int i, j;
int n1, n2;
int s_type = 1; /* spring type : 0 = FENE, 1=WLC */
int ev_type = 1; /* ev type: 0=HS, 1=WCA, 2=Gaussian */
int maxsize[DIMS];
int max_N_flag=0;
double send_buffer[2*DIMS+1];
char filename[80];
FILE *stream;
maxsize[0]=max_x;
maxsize[1]=max_y;
maxsize[2]=max_z;
num_beads = chain_pm->num_beads;
Nbead = chain_pm->num_beads / chain_pm->Nchain;
for(j=0; j<DIMS; j++)
monomers[0].force[j] = monomers[0].f_ext[j];
for(n1=1; n1<num_beads; n1++)
for(j=0; j<DIMS; j++)
monomers[n1].force[j] = 0.0;
/* Calculate spring and exc. vol. forces if # of beads > 1 */
if(num_beads > 1) {
spring_force(chain_pm, monomers); /* 0 = FENE, 1=WLC */
/*excluded volume forces */
if(num_beads < 200)
ev_force(monomers[0].radius, chain_pm, monomers);
else {
for(n1=0; n1<num_beads; n1++)
if(monomers[n1].list[0] >= MAX_N-1) max_N_flag = 1;
if(max_N_flag == 1)
ev_force(monomers[0].radius, chain_pm, monomers);
else ev_force_nlist(monomers[0].radius, chain_pm, monomers);
}
}
for(n1=0; n1<num_beads; n1++)
for(j=0; j<DIMS; j++) {
monomers[n1].force[j] *= chain_pm->monmass;
monomers[n1].f_int[j] = monomers[n1].force[j];
}
/*hydrodynamic and fluctuation forces */
hi_force(monomers, velcs_df, chain_pm->fric, chain_pm->MD_steps, chain_pm->dt, num_beads, chain_pm->monmass, rngstream);
if(wall_flag > 0)
wall_force(chain_pm, monomers);
/* send forces and fluid_vel back to proc 0 then broadcast from 0 */
for(n1=0; n1< num_beads; n1++) {
mon_proc = (int)(monomers[n1].pos[0]/num_x);
send_buffer[0]=n1;
for(i=0; i<DIMS; i++) {
send_buffer[i+1]=monomers[n1].force[i];
send_buffer[i+DIMS+1]=monomers[n1].fluid_vel[i];
}
vector_copy(send_buffer, 2*DIMS+1, n_proc, mon_proc, 0);
for(i=0; i<DIMS; i++) {
monomers[(int)send_buffer[0]].force[i]=send_buffer[i+1];
monomers[(int)send_buffer[0]].fluid_vel[i]=send_buffer[i+1+DIMS];
}
}
sync_procs();
for(n1=0; n1< num_beads; n1++) {
broad_cast(monomers[n1].force, DIMS, 0);
broad_cast(monomers[n1].fluid_vel, DIMS, 0);
}
}
void settle_sheet(
tectonic_sheet *ts,
size_t iterations,
float dt,
float equilibrium_distance,
float spring_constant,
int hold_edges
) {
size_t iter, i, j;
size_t idx, idx_a, idx_b, idx_c;
size_t pw, ph;
pw = sheet_pwidth(ts);
ph = sheet_pheight(ts);
vector *a, *b, *c; // the points of the current triangle
vector *f; // the force on the current point
vector tmp; // vector used for intermediate calculations
for (iter = 0; iter < iterations; ++iter) {
// First pass: compute forces by iterating over triangles in the sheet:
for (i = 0; i < ts->width; ++i) {
for (j = 0; j < ts->height; ++j) {
idx_a = sheet_pidx_a(ts, i, j);
idx_b = sheet_pidx_b(ts, i, j);
idx_c = sheet_pidx_c(ts, i, j);
a = &(ts->points[idx_a]);
b = &(ts->points[idx_b]);
c = &(ts->points[idx_c]);
if (i % 2 == j % 2) { // if this triangle points up
// All six forces on all three corners of this triangle:
// a <- b
f = &(ts->forces[idx_a]);
spring_force(b, a, &tmp, equilibrium_distance, spring_constant);
vadd_to(f, &tmp);
// a <- c
spring_force(c, a, &tmp, equilibrium_distance, spring_constant);
vadd_to(f, &tmp);
// b <- a
f = &(ts->forces[idx_b]);
spring_force(a, b, &tmp, equilibrium_distance, spring_constant);
vadd_to(f, &tmp);
// b <- c
spring_force(c, b, &tmp, equilibrium_distance, spring_constant);
vadd_to(f, &tmp);
// c <- a
f = &(ts->forces[idx_c]);
spring_force(a, c, &tmp, equilibrium_distance, spring_constant);
vadd_to(f, &tmp);
// c <- b
spring_force(b, c, &tmp, equilibrium_distance, spring_constant);
vadd_to(f, &tmp);
} else if (i == 0 && (j % 2 == 1)) {
// Both forces on our a <-> b edge:
// a <- b
f = &(ts->forces[idx_a]);
spring_force(b, a, &tmp, equilibrium_distance, spring_constant);
vadd_to(f, &tmp);
// b <- a
f = &(ts->forces[idx_b]);
spring_force(a, b, &tmp, equilibrium_distance, spring_constant);
vadd_to(f, &tmp);
} else if ((i == ts->width - 1) && (j % 2 == 0) ) {
// Both forces on our a <-> c edge:
// a <- c
f = &(ts->forces[idx_a]);
spring_force(c, a, &tmp, equilibrium_distance, spring_constant);
vadd_to(f, &tmp);
// c <- a
f = &(ts->forces[idx_c]);
spring_force(a, c, &tmp, equilibrium_distance, spring_constant);
vadd_to(f, &tmp);
}
}
}
// Second pass: apply forces (iterating over points this time)
for (i = 0; i < pw; ++i) {
for (j = 0; j < ph; ++j) {
idx = sheet_pidx(ts, i, j);
f = &(ts->forces[idx]);
if (
hold_edges
&&
(i == 0 || i == pw - 1 || j == 0 || j == ph - 1)
) {
vzero(f);
continue;
}
vscale(f, dt);
vadd_to(&(ts->points[idx]), f);
vzero(f);
}
}
}
}