Dear All,
I just completed modify the program code from Sukop’s book to model phase separation phenomenon.
But, when I plotted the results, the density field did not change too much from the initial value (200+rand())
I attach here the code.
Can you help me find the bug?
Thank you
parameter(ly=200,lx=200)
integer is_solid_node(ly,lx)
real rho(ly,lx),f(ly,lx,9),ftemp(ly,lx,9),ex(9),ey(9),
+ u_x(ly,lx),u_y(ly,lx),x(ly,lx),y(ly,lx),feq(ly,lx,9)
real psi(ly,lx),forcex(ly,lx),forcey(ly,lx)
real psi_x, psi_y
tau = 1.
C Set solid nodes at walls on top and bottom
is_solid_node=0
C Set initial density
do j=1,ly
do i=1,lx
rho(j,i)=200.+ rand()
end do
end do
do j=1,ly
do i=1,lx
f(j,i,1) = (4./9. )*rho(j,i)
f(j,i,2) = (1./9. )*rho(j,i)
f(j,i,3) = (1./9. )*rho(j,i)
f(j,i,4) = (1./9. )*rho(j,i)
f(j,i,5) = (1./9. )*rho(j,i)
f(j,i,6) = (1./36.)*rho(j,i)
f(j,i,7) = (1./36.)*rho(j,i)
f(j,i,8) = (1./36.)*rho(j,i)
f(j,i,9) = (1./36.)*rho(j,i)
enddo
enddo
C Define lattice velocity vectors
ex(1)= 0
ey(1)= 0
ex(2)= 1
ey(2)= 0
ex(3)= 0
ey(3)= 1
ex(4)=-1
ey(4)= 0
ex(5)= 0
ey(5)=-1
ex(6)= 1
ey(6)= 1
ex(7)=-1
ey(7)= 1
ex(8)=-1
ey(8)=-1
ex(9)= 1
ey(9)=-1
C Time loop
do ts=1,300
write(*,*) ts
C Computing macroscopic density, rho, and velocity, u=(ux,uy).
do j=1,ly
do i=1,lx
u_x(j,i) = 0.0
u_y(j,i) = 0.0
rho(j,i) = 0.0
if(is_solid_node(j,i).eq.0) then
do k=1,9
rho(j,i) = rho(j,i) + f(j,i,k)
u_x(j,i) = u_x(j,i) + ex(k)*f(j,i,k)
u_y(j,i) = u_y(j,i) + ey(k)*f(j,i,k)
enddo
u_x(j,i) = u_x(j,i)/rho(j,i)
u_y(j,i) = u_y(j,i)/rho(j,i)
endif
enddo
enddo
C Compute Force term
do j=1,ly
do i=1,lx
if(is_solid_node(j,i).eq.0) then
psi(j,i) = 4.0*exp(-200./rho(j,i))
end if
end do
end do
do j=1,ly
if (j.gt.1) then
jn = j-1
else
jn = LY
endif
if (j.lt.ly) then
jp = j+1
else
jp = 1
endif
do i=1,lx
if (i.gt.1) then
in = i-1
else
in = LX
endif
if (i.lt.LX) then
ip = i+1
else
ip = 1
endif
-
neighbor 2 psi_x = (1./9. )*ex(2)*psi(j,ip) psi_y = (1./9. )*ey(2)*psi(j,ip)
-
neighbor 3 psi_x = psi_x + (1./9. )*ex(3)*psi(jp,i) psi_y = psi_y + (1./9. )*ey(3)*psi(jp,i)
-
neighbor 4 psi_x = psi_x + (1./9. )*ex(4)*psi(j,in) psi_y = psi_y + (1./9. )*ey(4)*psi(j,in)
-
neighbor 5 psi_x = psi_x + (1./9. )*ex(5)*psi(jn,i) psi_y = psi_y + (1./9. )*ey(5)*psi(jn,i)
-
neighbor 6 psi_x = psi_x + (1./36. )*ex(6)*psi(jp,ip) psi_y = psi_y + (1./36. )*ey(6)*psi(jp,ip)
-
neighbor 7 psi_x = psi_x + (1./36. )*ex(7)*psi(jp,in) psi_y = psi_y + (1./36. )*ey(7)*psi(jp,in)
-
neighbor 8 psi_x = psi_x + (1./36. )*ex(8)*psi(jn,in) psi_y = psi_y + (1./36. )*ey(8)*psi(jn,in)
-
neighbor 9 psi_x = psi_x + (1./36. )*ex(9)*psi(jn,ip) psi_y = psi_y + (1./36. )*ey(9)*psi(jn,ip) forcex(j,i) = -120.*psi(j,i)*psi_x forcey(j,i) = -120.*psi(j,i)*psi_y enddo enddo
C Compute the equilibrium distribution function, feq.
f1=3.
f2=9./2.
f3=3./2.
do j=1,ly
do i=1,lx
if(is_solid_node(j,i).eq.0) then
rt0 = (4./9. )*rho(j,i)
rt1 = (1./9. )*rho(j,i)
rt2 = (1./36.)*rho(j,i)
ueqxij = u_x(j,i)+tau*forcex(j,i)/rho(j,i)
ueqyij = u_y(j,i)+tau*forcey(j,i)/rho(j,i)
uxsq = ueqxij * ueqxij
uysq = ueqyij * ueqyij
uxuy5 = ueqxij + ueqyij
uxuy6 = -ueqxij + ueqyij
uxuy7 = -ueqxij -ueqyij
uxuy8 = ueqxij -ueqyij
usq = uxsq + uysq
feq(j,i,0+1) = rt0*(1. - f3*usq)
feq(j,i,1+1) = rt1*(1.+ f1*ueqxij+f2*uxsq - f3*usq)
feq(j,i,2+1) = rt1*(1.+ f1*ueqyij+f2*uysq - f3*usq)
feq(j,i,3+1) = rt1*(1.- f1*ueqxij+f2*uxsq - f3*usq)
feq(j,i,4+1) = rt1*(1.- f1*ueqyij+f2*uysq - f3*usq)
feq(j,i,5+1) = rt2*(1.+ f1*uxuy5 +f2*uxuy5*uxuy5-f3*usq)
feq(j,i,6+1) = rt2*(1.+ f1*uxuy6 +f2*uxuy6*uxuy6-f3*usq)
feq(j,i,7+1) = rt2*(1.+ f1*uxuy7 +f2*uxuy7*uxuy7-f3*usq)
feq(j,i,8+1) = rt2*(1.+ f1*uxuy8 +f2*uxuy8*uxuy8-f3*usq)
endif
enddo
enddo
C Collision step.
do j=1,ly
do i=1,lx
if(is_solid_node(j,i).eq.1) then
C Standard bounceback
temp= f(j,i,1+1)
f(j,i,1+1) = f(j,i,3+1)
f(j,i,3+1) = temp
temp= f(j,i,2+1)
f(j,i,2+1) = f(j,i,4+1)
f(j,i,4+1) = temp
temp= f(j,i,5+1)
f(j,i,5+1) = f(j,i,7+1)
f(j,i,7+1) = temp
temp= f(j,i,6+1)
f(j,i,6+1) = f(j,i,8+1)
f(j,i,8+1) = temp
else
C Regular collision
do k=1,9
f(j,i,k) = f(j,i,k)-( f(j,i,k) - feq(j,i,k))/tau
enddo
endif
enddo
enddo
C Streaming step; subtle changes to periodicity here due to indexing
do j=1,ly
if (j.gt.1) then
jn = j-1
else
jn = LY
endif
if (j.lt.ly) then
jp = j+1
else
jp = 1
endif
do i=1,lx
if (i.gt.1) then
in = i-1
else
in = LX
endif
if (i.lt.LX) then
ip = i+1
else
ip = 1
endif
ftemp(j,i,0+1) = f(j,i,0+1)
ftemp(j,ip,1+1) = f(j,i,1+1)
ftemp(jp,i,2+1) = f(j,i,2+1)
ftemp(j,in,3+1) = f(j,i,3+1)
ftemp(jn,i ,4+1) = f(j,i,4+1)
ftemp(jp,ip,5+1) = f(j,i,5+1)
ftemp(jp,in,6+1) = f(j,i,6+1)
ftemp(jn,in,7+1) = f(j,i,7+1)
ftemp(jn,ip,8+1) = f(j,i,8+1)
enddo
enddo
f=ftemp
C End time loop
enddo
open(unit=20,file='rho.dat',status='unknown')
do j=1,ly
do i=1,lx
write(20,*) rho(j,i)
enddo
enddo
end