Re: Particle movement question

[Anonymous Monk]

More info please... are there only 9 different particles, or are there lots of different kinds of particles and each cell can only hold up to nine at a time, etc.? What's your code so far?

my @grid_a; # there are only 9 particles
my @grid_b; # there are lots of particles
for my $x (0..9) {
  for my $y (0..9) {
    for my $particle (0..8) {
      $grid_a[$x][$y][$particle] = 1;
      $grid_b[$x][$y]{$particle} = 1;
    }
    my $pcount = keys %{$grid_b[$x][$y]};
  }
}

use Data::Dumper;
print Dumper(\@grid_a, \@grid_b);

perlreftut, perldsc

[koda123]

The basis is that within a grid, there is a rectangular portion, approximately one fifth of the total x distance and the entire y distance containing a number of particles, del_x distance apart (representing a fluid). At the initial position each grid has a horizontal velocity, and a vertical velocity. I am trying to simulate a scenario where the right boundary of the rectangle is suddenly removed, releasing all of the "fluid" So by assigning each grid unit within the rectangle 9 particles, I would essentially be assigning values to the free boundary (The right and top boundary), performing my calculations, resulting in a new horizontal and vertical velocity, determine the new velocity at a time n+1, and then compute the particle position. the problem would be creating a particle that would be tracked.

[Anonymous Monk]

Show us your code so far.

[koda123]

so here is my code. Clearly it doesn't work right now, and it's very long. Getting it to calculate velocities would be a good start, and i'm pretty sure my flagging is not correct.

$xlength=10;
$ylength=4;

$N=100;

my @u;     #Horizontal Velocity
my @v;    #Vertical Velocity
my @p;
my @F;
my @G;
my $eps=.001;
 
my @grid;



$imax=25;
$jmax=10;


for $i (0..$imax) {
    for $j (0..$jmax) {

$u[$i][$j]=0;
$v[$i][$j]=0;
$p[$i][$j]=0;

}}

for $i (1..$imax){
    for $j (1..$jmax) {

$u[0][$j]=0;
$v[$i][$jmax]=0;


$v[0][$j]=$v[1][$j];
$u[$i][$jmax+1]=$u[$i][$jmax];


}}

for $i (1..$imax) {                
    for $j (1..$jmax) {

$u[$i][1]=100;
$u[$imax][$j]=100;
$v[$i][1]=100;
$v[$imax][$j]=100;
$p[$i][1]=100;
$p[$imax][$j]=100;
}}

$gx=0;
$gy=-1;
$delx=1;
$dely=1;
$RE=10;
$time_step=.5;

print "$v[10][1]\n";


##### Assigning Flags######



#Begin Time loop####
for ($t=0; $t <$tend; $t +=$time_step) {

for $i (0..$N) {

    for $j (0..$N) {

if ($v[$i][$j] and $u[$i][$j] > 0 ){$flag=CF;}
if ($v[$i][$j] and $u[$i][$j] = 0) {$flag=CE;}

for $flag (CF) {
    


if( $v[$i][$j-1]=0 or $u[$i][$j-1]=0){$flag='C_N';}
if( $v[$i][$j+1]=0 or $u[$i][$j+1]=0) {$flag='C_S';}

if ($u[$i-1][$j]=0 or $v[$i-1][$j]=0){$flag='C_W';}
if ($u[$i+1][$j]=0 or $v[$i+1][$j]=0) {$flag='C_E';}

if ($u[$i][$j-1]=0 and $u[$i][$j+1]=0 or  $v[$i][$j-1]=0 and  $v[$i][$
+j+1]=0){$flag='C_NS';}
if ($u[$i-1][$j]=0and $u[$i+1][$j]=0 or $v[$i-1][$j]=0and $v[$i+1][$j]
+=0){$flag='C_WE';}

if ($u[$i][$j-1]=0 and $u[$i-1][$j]=0 or $v[$i][$j-1]=0 and $v[$i-1][$
+j]=0){$flag='C_NW';}
if ($u[$i][$j-1]=0 and $u[$i+1][$j]=0 or $v[$i][$j-1]=0 and  $v[$i+1][
+$j]=0){$flag='C_NE';}


if ($u[$i][$j+1]=0 and $u[$i-1][$j]=0 or  $v[$i][$j+1]=0 and $v[$i-1][
+$j]=0){$flag='C_SW';}
if ($u[$i][$j+1]=0 and $u[$i+1][$j]=0 or  $v[$i][$j+1]=0 and $v[$i+1][
+$j]=0){$flag='C_SE';}

if ($u[$i][$j-1]=0 and $u[$i-1][$j]=0 and $u[$i+1][$j]=0 or  $v[$i][$j
+-1]=0 and $v[$i-1][$j]=0 and $v[$i+1][$j]=0){$flag='C_NWE';}
if ($u[$i][$j-1]=0 and $u[$i][$j+1]=0 and $u[$i+1][$j]=0 or  $v[$i][$j
+-1]=0 and  $v[$i][$j+1]=0 and $v[$i+1][$j]=0){$flag='C_NSE';}
if ($u[$i][$j-1]=0 and $u[$i][$j+1]=0 and $u[$i-1][$j]=0 or  $v[$i][$j
+-1]=0 and  $v[$i][$j+1]=0  and $v[$i-1][$j]=0){$flag='C_NSW';}
if ($u[$i+1][$j]=0 and $u[$i][$j+1]=0 and $u[$i-1][$j]=0 or $v[$i+1][$
+j]=0 and  $v[$i][$j+1]=0 and $v[$i-1][$j]=0){$flag='C_SWE';}

if ($u[$i][$j-1]=0 and $u[$i-1][$j]=0 and $u[$i][$j+1]=0  and $u[$i+1]
+[$j]=0 or $v[$i][$j-1]=0 and $v[$i-1][$j]=0 and  $v[$i][$j+1]=0 and $
+v[$i+1][$j]=0){$flag='C_NWSE';}

for $i (1..$imax) {                
    for $j (1..$jmax) {
if ($flag eq 'C_N', 'C_S', 'C_E', 'C_W'){
$p[$i][$j]=2/$RE*(($u[$i][$j]-$u[$i-1][$j])/$delx);

$u[$i][$j]=$u[$i-1][$j]-($delx/$dely)*($v[$i][$j]-$v[$i][$j-1]);

$v[$i+1][$j-1]=$v[$i][$j-1]-($delx/$dely)*($u[$i][$j]-$u[$i][$j-1]);

print "$u[10][1]\n"
}
if ($flag='C_NE','C_SW'){

$u[$i][$j]=$u[$i-1][$j];

$v[$i][$j-1]=$v[$i][$j];

$p[$i][$j]= 1/2*$RE*((($u[$i][$j+1]+$u[$i-1][$j+1]-$u[$i][$j]-$u[$i-1]
+[$j])/$dely)+(($v[$i][$j]+$v[$i][$j-1]-$v[$i-1][$j]-$v[$i-1][$j-1])/$
+delx));
}

if ($flag='C_NW','C_SE') {

$u[$i][$j]=$u[$i+1][$j];

$v[$i][$j+1]=$v[$i][$j];

$p[$i][$j]= -1/2*$RE*(($u[$i][$j+1]+$u[$i-1][$j+1]-$u[$i][$j]-$u[$i-1]
+[$j])/$dely)+(($v[$i][$j]+$v[$i][$j-1]-$v[$i-1][$j]-$v[$i-1][$j-1])/$
+delx);
}
if ($flag='C_WE', 'C_NS') {

$u[$i][$j]=$u[$i][$j]+$time_step*$gx;
$u[$i-1][$j]=$u[$i-1][$j]+$time_step*$gx;
$v[$i][$j]=$v[$i][$j]+$time_step*$gy;
$v[$i][$j-1]=$v[$i][$j-1]+$time_step*$gy;
$p[$i][$j]=0;
}
if ($flag='C_NSE','C_NSW','C_SWE','C_NWE'){

$p[$i][$j]=0;
}

if ($flag='C_NWSE'){

$u[$i][$j]=$u[$i][$j+1];
$p[$i][$j]=0;
$v[$i][$j]=$v[$i-1][$j];

}

}

}



for $i (1..$imax-1){

    for $j(1..$jmax){

$F[$n][$i][$j]=$u[$i][$j]+$time_step*(1/$RE*(($u[$i][$j]/($xlength*$xl
+ength))+($u[$i][$j]/($ylength*$ylength)))-(($u[$i][$j]*$u[$i][$j])/$x
+length)-(($u[$i][$j]*$v[$i][$j])/$ylength)+$gx);

$G[$n][$i][$j]=$v[$i][$j]+$time_step*(1/$RE*(($u[$i][$j]/($xlength*$xl
+ength))+($u[$i][$j]/($ylength*$ylength)))-(($u[$i][$j]*$v[$i][$j])/$x
+length)-(($u[$i][$j]*$u[$i][$j])/$ylength)+$gy);
}
}
##### more boundary conditions for RHS ######
for $i (1..$imax) {
    for $j (1..$jmax){

$p[0][$j]=$p[1][$j];
$p[$imax+1][$j]=$p[$imax][$j];
$p[$i][0]=$p[$i][1];
$p[$i][$jmax+1]=$p[$i][$jmax];

$Fn[0][$j]=$u[0][$j];
$Fn[$imax][$j]=$u[$imax][$j];

$Gn[$i][0]=$v[$i][0];
$Gn[$i][$jmax]=$v[$i][$jmax];
}}

####RHS Calc###
for $i (1..$imax){
    for $j(1..$jmax){
$RHS[$i][$j]=(1/$time_step)*(($Fn[$i][$j]-$Fn[$i-1][$j])/$delx+($Gn[$i
+][$j]-$Gn[$i][$j-1])/$dely);
if ($i=1){
    $eW=0;
}elsif ($i>1) {
    $eW=1;
}elsif ($i<$imax){
    $eE=1;
}elsif ($i=$imax) {
    $eE=0;
}
if ($j=1){
    $eS=0;
}elsif ($j>1){
    $eS=1;
}elsif ($j<$jmax){
    $eN=1;
}elsif ($j=$jmax){
    $eN=0;
}
}
    }

####SOR #####

#$itmax=20;
#$omg=1;
#do 

#{
    #for $it (1..$itmax){

    #for $i (1..$imax) {

        #for $j (1..$jmax) {
#$P[$i][$j]=(1-$omg)*$p[$i][$j]+($omg/(($eE+$eW)/($delx*$delx))+($eN+$
+eS)/($dely*$dely)))*((($eE*$p[$i+1][$j]+$eW*$P[$i-1][$j])/($delx*$del
+x))+(($eN*$p[$i][$j+1]+$eS*$P[$i][$j-1])/($dely*$dely)-$RHS[$i][$j]);


#$rit[$i][$j]=((($eE*($p[$i+1][$j]-$p[$i][$j])-$eW*($p[$i][$j]-$p[$i-1
+][$j]))/($delx*$delx))+(($eN*($p[$i][$j+1]-$p[$i][$j])-$eS*($p[$i][$j
+]-$p[$i][$j-1])/($dely*$dely))-$RHS[$i][$j]));



#}while ($it<$itmax or abs($rit) gt $eps);
#}
#}


#}





}}}
}