How can I solve in the error?

clear all, clc; % clear all memory and variables

x = linspace(-1,1); % create linear spacing in x-direction

y = linspace(-1,1); % create linear spacing in y-direction

%initialise velocity

U = 1.; %freestream velocity

%looping in i and j-directions

for i = 1:length(x)

for j = 1:length(y)

%create x & y space

xx(i,j) = x(i);

yy(i,j) = y(j);

%calculate radius from x & y

rad(i,j) = sqrt(x(i)^2 + y(j)^2);

% calculate angle from x and y

if x(i) > 0

theta(i,j) = atan(y(j)/x(i));

elseif x(i) <0 && y(j) >= 0

theta(i,j) =atan(y(j)/x(i))+pi;

elseif x(i) < 0 && y(j) < 0

theta(i,j) = atan(y(j)/x(i))-pi;

elseif x(i) == 0 && y(j) < 0

theta(i,j) = pi/2;

else

theta(i,j) = – pi/2;

end

% calculate stream function using polar coordinate system

psi(i,j) = U *rad(i,j)*sin(theta(i,j));

% calculate velocity potential using polar coordinate system

phi(i,j) = U*rad(i,j)*cos(theta(i,j));

end

end

%plotting

contourf(xx,yy,psi,-1:0.2:1,’k’,’LineWidth’,1.5), hold on % plot stream function for range -1:0.1:1

contour(xx,yy,phi,-1:0.2:1,’r’,’LineWidth’,1.5) % plot velocity potential for range -1:0.2:1

axis image, hold off

legend(‘streamlines’,’potential’)

title(‘Uniform stream in x-direction’)

xlabel(‘x-coordinate’), ylabel(‘y-coordinate’)

axis square;

% end of Octave program

[Karim]

Which error?

After correcting the apostrophes and the minus sign the code appears to run without issues?

[Myo Gyi]

Thank you sir... Can You repair for my code sir.

Answer 1

[Stephan]

%clear all, clc; % clear all memory and variables

x = linspace(-1,1); % create linear spacing in x-direction
y = linspace(-1,1); % create linear spacing in y-direction

%initialise velocity
U = 1.; %freestream velocity

%looping in i and j-directions
for i = 1:length(x)
for j = 1:length(y)

%create x & y space
xx(i,j) = x(i);
yy(i,j) = y(j);

%calculate radius from x & y
rad(i,j) = sqrt(x(i)^2 + y(j)^2);

% calculate angle from x and y
if x(i) > 0
theta(i,j) = atan(y(j)/x(i));
elseif x(i) <0 && y(j) >= 0
theta(i,j) =atan(y(j)/x(i))+pi;
elseif x(i) < 0 && y(j) < 0
theta(i,j) = atan(y(j)/x(i))-pi;
elseif x(i) == 0 && y(j) < 0
theta(i,j) = pi/2;
else
theta(i,j) = -pi/2;
end

% calculate stream function using polar coordinate system
psi(i,j) = U *rad(i,j)*sin(theta(i,j));
% calculate velocity potential using polar coordinate system
phi(i,j) = U*rad(i,j)*cos(theta(i,j));
end
end

%plotting
contourf(xx,yy,psi,-1:0.2:1,'k','LineWidth',1.5), hold on % plot stream function for range -1:0.1:1
contour(xx,yy,phi,-1:0.2:1,'r','LineWidth',1.5) % plot velocity potential for range -1:0.2:1

axis image, hold off
legend('streamlines','potential')
title('Uniform stream in x-direction')
xlabel('x-coordinate'), ylabel('y-coordinate')

axis square;

[Myo Gyi]

Thanks Sir.... Can I get more pitcure like this side

https://people.utm.my/ridhwan/teaching/skme-3333-aerodynamics/potential-flow/