// control temperature by rescale velocities
void control_velocity(int totalAtom, // total atom
struct system_t *sys, // pointer to syatem
struct molecule_t *ptr, // pointer to molecule
double tem){ // temperature
double Ek=0; // total kinetic energy
double lamda; // scaling factor
int i,j; // loop index
// Do not rescale velocity
if(tem<=0){};
// Rescale velocity
if(tem>0){
// calulate total kinetic energy
for(i=0;i<sys->nMolecule;i++){
get_kinetic(sys->mols+i,&Ek);
}
// calculate scaling factor
lamda = sqrt((3/2)*BOLZMANN*tem*totalAtom/Ek);
// rescale velocity
for(i=0;i<sys->nMolecule;i++){
for(j=0;j<ptr->nAtom;j++){
ptr->vx[j] = ptr->vx[j]*lamda;
ptr->vy[j] = ptr->vy[j]*lamda;
ptr->vz[j] = ptr->vz[j]*lamda;
printf("\nvx= %lf vy= %lf vz= %lf",ptr->vx[j],ptr->vy[j],ptr->vz[j]);
}
ptr = ptr+1;
}
}
}
int main(int argc, char **argv){
/*positions of all particles*/
FLOAT *x;
FLOAT *y;
FLOAT *z;
/*velocities of all particles*/
FLOAT *v_x;
FLOAT *v_y;
FLOAT *v_z;
/*accelerations of all particles*/
FLOAT *a_x;
FLOAT *a_y;
FLOAT *a_z;
/*terms for runge-kutta*/
FLOAT *a_x_old;
FLOAT *a_y_old;
FLOAT *a_z_old;
FLOAT *k_1_x;
FLOAT *k_1_y;
FLOAT *k_1_z;
FLOAT *k_1_v_x;
FLOAT *k_1_v_y;
FLOAT *k_1_v_z;
FLOAT *k_2_x;
FLOAT *k_2_y;
FLOAT *k_2_z;
FLOAT *k_2_v_x;
FLOAT *k_2_v_y;
FLOAT *k_2_v_z;
FLOAT *k_3_x;
FLOAT *k_3_y;
FLOAT *k_3_z;
FLOAT *k_3_v_x;
FLOAT *k_3_v_y;
FLOAT *k_3_v_z;
FLOAT *k_4_x;
FLOAT *k_4_y;
FLOAT *k_4_z;
FLOAT *k_4_v_x;
FLOAT *k_4_v_y;
FLOAT *k_4_v_z;
FLOAT *xtemp;
FLOAT *ytemp;
FLOAT *ztemp;
FLOAT *v_xtemp;
FLOAT *v_ytemp;
FLOAT *v_ztemp;
FLOAT *a_xtemp;
FLOAT *a_ytemp;
FLOAT *a_ztemp;
/*masses*/
FLOAT *mass;
/*timestep variables*/
FLOAT h= 0.001;
int n_steps = (int)(100/h);
int n_points = 3;
FLOAT radius = 100.0;
FLOAT unit_mass = 1.0;
FLOAT vel_initial = sqrt((11.0/3.0) * G_GRAV * unit_mass / (sqrt(3.0)*radius));
FLOAT kinetic;
FLOAT potential;
int i,j,k;
/*memory allocation*/
x = get_memory(n_points);
y = get_memory(n_points);
z = get_memory(n_points);
v_x = get_memory(n_points);
v_y = get_memory(n_points);
v_z = get_memory(n_points);
a_x = get_memory(n_points);
a_y = get_memory(n_points);
a_z = get_memory(n_points);
mass = get_memory(n_points);
k_1_x = get_memory(n_points);
k_1_y = get_memory(n_points);
k_1_z = get_memory(n_points);
k_1_v_x = get_memory(n_points);
k_1_v_y = get_memory(n_points);
k_1_v_z = get_memory(n_points);
k_2_x = get_memory(n_points);
k_2_y = get_memory(n_points);
k_2_z = get_memory(n_points);
k_2_v_x = get_memory(n_points);
k_2_v_y = get_memory(n_points);
k_2_v_z = get_memory(n_points);
k_3_x = get_memory(n_points);
k_3_y = get_memory(n_points);
k_3_z = get_memory(n_points);
k_3_v_x = get_memory(n_points);
k_3_v_y = get_memory(n_points);
k_3_v_z = get_memory(n_points);
k_4_x = get_memory(n_points);
k_4_y = get_memory(n_points);
k_4_z = get_memory(n_points);
k_4_v_x = get_memory(n_points);
k_4_v_y = get_memory(n_points);
k_4_v_z = get_memory(n_points);
xtemp = get_memory(n_points);
ytemp = get_memory(n_points);
ztemp = get_memory(n_points);
v_xtemp = get_memory(n_points);
v_ytemp = get_memory(n_points);
v_ztemp = get_memory(n_points);
a_xtemp = get_memory(n_points);
a_ytemp = get_memory(n_points);
a_ztemp = get_memory(n_points);
initialize_pos(x,y,z, n_points, radius);
initialize_vel(v_x,v_y,v_z, n_points, vel_initial, radius);
initialize_mass(mass, n_points, unit_mass);
/*implementation of a second order runge kutta integration*/
FILE *in;
in = fopen("3cuerpos.dat","w");
for(i=0;i<n_steps;i++){
a_x_old = a_x;
a_y_old = a_y;
a_z_old = a_z;
get_acceleration(a_x, a_y, a_z, x, y, z, mass, n_points);
for(j=0;j<n_points;j++){
k_1_x[j] = v_x[j];
k_1_y[j] = v_y[j];
k_1_z[j] = v_z[j];
k_1_v_x[j] = a_x[j];
k_1_v_y[j] = a_y[j];
k_1_v_z[j] = a_z[j];
//FIRST STEP
xtemp[j] = x[j] + (h/2.0)*k_1_x[j];
ytemp[j] = y[j] + (h/2.0)*k_1_y[j];
ztemp[j] = z[j] + (h/2.0)*k_1_z[j];
v_xtemp[j] = v_x[j] + (h/2.0)*k_1_v_x[j];
v_ytemp[j] = v_y[j] + (h/2.0)*k_1_v_y[j];
v_ztemp[j] = v_z[j] + (h/2.0)*k_1_v_z[j];
k_2_x[j] = v_xtemp[j];
k_2_y[j] = v_ytemp[j];
k_2_z[j] = v_ztemp[j];
}
get_acceleration(a_xtemp,a_ytemp,a_ztemp,xtemp,ytemp,ztemp, mass, n_points);
for(j=0;j<n_points;j++){
k_2_v_x[j] = a_xtemp[j];
k_2_v_y[j] = a_ytemp[j];
k_2_v_z[j] = a_ztemp[j];
//SECOND STEP
xtemp[j] = x[j] + (h/2.0)*k_2_x[j];
ytemp[j] = y[j] + (h/2.0)*k_2_y[j];
ztemp[j] = z[j] + (h/2.0)*k_2_z[j];
v_xtemp[j] = v_x[j] + (h/2.0)*k_2_v_x[j];
v_ytemp[j] = v_y[j] + (h/2.0)*k_2_v_y[j];
v_ztemp[j] = v_z[j] + (h/2.0)*k_2_v_z[j];
k_3_x[j] = v_xtemp[j];
k_3_y[j] = v_ytemp[j];
k_3_z[j] = v_ztemp[j];
}
get_acceleration(a_xtemp,a_ytemp,a_ztemp,xtemp,ytemp,ztemp, mass, n_points);
for(j=0;j<n_points;j++){
k_3_v_x[j] = a_xtemp[j];
k_3_v_y[j] = a_ytemp[j];
k_3_v_z[j] = a_ztemp[j];
//THIRD STEP
xtemp[j] = x[j] + h*k_3_x[j];
ytemp[j] = y[j] + h*k_3_y[j];
ztemp[j] = z[j] + h*k_3_z[j];
v_xtemp[j] = v_x[j] + h*k_3_v_x[j];
v_ytemp[j] = v_y[j] + h*k_3_v_y[j];
v_ztemp[j] = v_z[j] + h*k_3_v_z[j];
k_4_x[j] = v_xtemp[j];
k_4_y[j] = v_ytemp[j];
k_4_z[j] = v_ztemp[j];
}
get_acceleration(a_xtemp,a_ytemp,a_ztemp,xtemp,ytemp,ztemp, mass, n_points);
for(j=0;j<n_points;j++){
k_4_v_x[j] = a_xtemp[j];
k_4_v_y[j] = a_ytemp[j];
k_4_v_z[j] = a_ztemp[j];
//FOURTH STEP
x[j] = x[j] + h*(1.0/6.0)*(k_1_x[j]+2*k_2_x[j]+2*k_3_x[j]+k_4_x[j]);
y[j] = y[j] + h*(1.0/6.0)*(k_1_y[j]+2*k_2_y[j]+2*k_3_y[j]+k_4_y[j]);
z[j] = z[j] + h*(1.0/6.0)*(k_1_z[j]+2*k_2_z[j]+2*k_3_z[j]+k_4_z[j]);
v_x[j] = v_x[j] + h*(1.0/6.0)*(k_1_v_x[j]+2*k_2_v_x[j]+2*k_3_v_x[j]+k_4_v_x[j]);
v_y[j] = v_y[j] + h*(1.0/6.0)*(k_1_v_y[j]+2*k_2_v_y[j]+2*k_3_v_y[j]+k_4_v_y[j]);
v_z[j] = v_z[j] + h*(1.0/6.0)*(k_1_v_z[j]+2*k_2_v_z[j]+2*k_3_v_z[j]+k_4_v_z[j]);
}
for(k=0;k<n_points;k++){
fprintf(in," %f %f %f ", x[k], y[k], z[k]);
}
kinetic = get_kinetic(x, y, z, v_x, v_y, v_z, a_x, a_y, a_z, mass, n_points);
potential = get_potential(x, y, z, v_x, v_y, v_z, a_x, a_y, a_z, mass, n_points);
fprintf(in,"%f %f \n",kinetic, potential);
}
fclose(in);
}