CFD Online Discussion Forums - simplified nse in cynlinderic coordinates (matlab)

hey.
my problem is
$\frac{\partial u}{\partial t} = \frac{\eta}{\rho} \frac{\partial u}{\partial r} \frac{1}{r} + \frac{\partial^2 u}{\partial r^2}+f(P)$
with
du(0)/dr =0
u(t=0)=0
u(r)=0

u should be a profile of flow (incompressible & laminar)

f(P) is a periodic impuls of pressure.

my problem is when r=0 , u should be max. but my programm doesnt do that.
i'm using finite difference. the discretization should be okay.

Quote:

function []=inststromzy(N,om,per)
format long
ro=820;
eta=0.002;
R=0.0005;
p0=10^6;
u=zeros(N+1,1);

uavg=0;
dr=R/N;
dt=om/100;
X=[0:dr:R];
epsi=eta*dt/ro;

d = 4*ones(N+1,1);
li= -2*ones(N+1,1);
re= -2*ones(N+1,1);
li= -dr./X' + li;
re= dr./X' + re;
li(1)=-2;
A=speye(N+1)+epsi/(2*dr^2)*spdiags([li d re],-1:1,N+1,N+1);
A(N+1,N)=0;
A(N+1,N+1)=1;

v=1;

t=0;

for i=1: per

t=0;

while t < om

v=v+1;
fv(1)=0;
fv(N+1)=0;
fv(2:N-1)=-p0/ro*(exp(-2000^2*(t-1/4*om).^2));

u=A\(u-dt*fv');

figure(1)

plot(X,u)

title(['t=',num2str(t)])
axis ([0 R 0 6])
pause(0.1);

t=t+dt;

end

end

end

it would be nice,if someone could help me

thanks.