wantmake cureve to flat

this code is related to the transmission line

and when i input this code i got a some figure that like this

but what the want shape is like this one

when my code forward to the ( 0,0) the shape looks like curve but what i wanna is just flat like this pitcture

how can change my code to make this picture?

this is also related to the electromagnetic and transmission line

and a/h is x axis b/h is y axis

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clear all;format compact;

H=0.05;

NT= 100;

A=2.5; B=2.5; D=0.5; W=1.0;

ER=2.35;

EO=8.81E-12;

U=3.0E+8;

NX=A/H;

NY=B/H;

ND=D/H;

NW=W/H;

VD=100.0;

%CALCULATE CHARGE WITH AND WITHOUT DIELECTRIC

ERR=1.0;

for L=1:2

E1=EO;

E2=EO*ERR;

%INITIALIZATION

V=zeros(NX+2,NY+2);

%SET POTENTIAL ON INNER CONDUCTOR(FIXED NODES) EQUAL TO VD

V(2:NW+1,ND+2)=VD;

%CALCULATE POTENTIAL AT FREE NODES

P1=E1/(2*(E1+E2));

P2=E2/(2*(E1+E2));

for K=1:NT

for I=0:NX-1

for J=0:NY-1

if( (J==ND)&(I<=NW))

%do nothing

elseif(J==ND)

%IMPOSE BOUNDARY CONDITION AT THE INTERFACE

V(I+2,J+2)=0.25*(V(I+3,J+2)+V(I+1,J+2))+....

P1*V(I+2,J+3)+P2*V(I+2,J+1);

elseif(I==0)

%IMPOSE SYMMETRY CONDITION ALONG Y-AXIS

V(I+2,J+2)=(2*V(I+3,J+2)+V(I+2,J+3)+V(I+2,J+1))/4.0;

elseif(J==0)

%IMPOSE SYMMETRY CONDITION ALONG X-AXIS

V(I+2,J+2)=(V(I+3,J+2)+V(I+1,J+2)+2*V(I+2,J+3))/4.0

else

V(I+2,J+2)=(V(I+3,J+2)+V(I+1,J+2)+V(I+2,J+3)+V(I+2,J+1))/4.0;

end

end

end

%Animation of calculation

figure(1),surf(V),,colorbar,title([num2str(K),'/',num2str(NT)])

end

end