Unable to perform assignment because the size of the left side is 1-by-1 and the size of the right side is 1-by-2.

I am getting an error on line that is in bold, italics, and underlined stating that I have different sized matrixes but have no clue how this could've happened. I thought I used the same methodology for both sides and should therefore they should be the same size. Any help you can provide would be greatly appreciated.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

clear

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% properties of flow

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

r = 0.2; % meters, radius of cylinder

vFreeStream = 5; % m/s, free stream velocity

lpus = 50; % N/m, lift per unit span

rho = 1.18; % k/m^3, air density of free-stream

tol = 1.0e-6; % tolerance

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% kutta-juokowski circulation equation

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

gamma = lpus / (vFreeStream*rho); % circulation

cl = lpus / (0.5*r*rho*(vFreeStream^2)) % lift coefficient

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% this section will help us print later in the code

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

minX = -1; % m, minimum location of x

maxX = 1; % m, max location of x

numX = 101; % number of spots

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% do the same for y values

minY = -1;

maxY = 1;

numY = 101;

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% mesh spacing & loop

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

dx = (maxX-minX) / (numX-1);

dy = (maxY-minY) / (numY-1);

for ii = 1:numX % loop over x values

for jj = 1:numY

xVals(ii,jj) = minX+dx*(ii-1);

yVals(ii,jj) = minY+dy*(jj-1);

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% Polar coordinates with assumed origin

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

r2 = (xVals(ii,jj)^2+yVals(ii,jj)^2); % p-thag

r2 = max(r2,tol);

r2 = sqrt(r);

theta = atan2(yVals(ii,jj),xVals(ii,jj));

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% applying potential flow theory

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% cyclinder with freestream velocity

psi(ii,jj) = vFreeStream*r2*sin(theta)*(1-(r/r2)^2);

phi(ii,jj) = vFreeStream*r2*cos(theta)*(1+(r/r2)^2);

vr = (1-(r/r2)^2)*vFreeStream*cos(theta);

vTheta = -(1+(r/r2)^2)*vFreeStream*sin(theta);

% vortex

phi(ii,jj) = phi(ii,jj)-gamma/(2.*pi)*theta;

psi(ii,jj) = psi(ii,jj)+gamma/(2.*pi)*log(r2/r);

vr = vr+0;

vTheta = vTheta-gamma/(2.*pi*r2);

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% source terms

lamb = -2.*pi*r*vr; %lambda term

vr(ii,jj) = lamb/(2.*pi*r);

phi(ii,jj) = lamb*log(r)/(2.*pi);

psi(ii,jj) = lamb*theta/(2.*pi);

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

if(r2<r)

vmag(ii,jj) = -1;

cp(ii,jj) = 2;

else

vmag(ii,jj) = sqrt(vr.^2+vTheta.^2);

cp(ii,jj) = 1-(vmag(ii,jj)/vFreeStream)^2;

end

end

end

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% plotting (directly from report, with changed variables for my code)

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

figure(1)

clf(1)

hold on

[c1,h1]=contour(xVals(:,:),yVals (:,:), psi(:,:),'k','LineWidth',4,[-10:1:10]); %plots the x vs t

clabel (c1, h1, -10:2:10, "fontsize", 24);

[c2,h2]=contour(xVals(:,:),yVals (:,:), cp(:,:),'g','LineWidth',4,[-2:0.1:1]); %plots the x vs t

clabel (c2, h2, -2:0.2:1, "fontsize", 24);

hold off

t1=title('Coplot of Stream Function (\psi) and C_p')

x1=xlabel('Position, x (m)') %x-axis label

y1=ylabel('Position, y (m)') %y-axis label

set(t1,'FontSize',24) %change fontsize

set(x1,'FontSize',24) %change fontsize

set(y1,'FontSize',24) %change fontsize

%Now only plot the Vel Mag, what does it look like

figure(2)

clf(2)

hold on

[c2,h2]=contourf(xVals(:,:),yVals (:,:), vmag(:,:),'k','LineWidth',0.5,[0:0.5:8]); %plots the x vs t

clabel (c2, h2, 0:1:8, "fontsize", 24);

t1=title('Velocity Mag(|V|)')

x1=xlabel('Position, x (m)') %x-axis label

y1=ylabel('Position, y (m)') %y-axis label

set(t1,'FontSize',24) %change fontsize

set(x1,'FontSize',24) %change fontsize

set(y1,'FontSize',24) %change fontsize

%Now only plot the Cp, what does it look like

figure(3)

clf(3)

hold on

[c2,h2]=contourf(xVals(:,:),yVals (:,:), cp(:,:),'k','LineWidth',0.5,[-2:0.1:1]); %plots the x vs t

clabel (c2, h2, -2:0.2:1, "fontsize", 24);

t1=title('Pressure Coefficent(C_p)')

x1=xlabel('Position, x (m)') %x-axis label

y1=ylabel('Position, y (m)') %y-axis label

set(t1,'FontSize',24) %change fontsize

set(x1,'FontSize',24) %change fontsize

set(y1,'FontSize',24) %change fontsize

%Now one more, a coplot of Psi and Phi

figure(4)

clf(4)

hold on

[c1,h1]=contour(xVals(:,:),yVals (:,:), psi(:,:),'k','LineWidth',4,[-10:1:10]); %plots the x vs t

clabel (c1, h1, -10:2:10, "fontsize", 24);

[c2,h2]=contour(xVals(:,:),yVals (:,:), phi(:,:),'r','LineWidth',4,[-10:1:10]); %plots the x vs t

clabel (c2, h2, -10:2:10, "fontsize", 24);

t1=title('Coplot of Stream Function (\psi) and Velocity Potential (\phi)')

x1=xlabel('Position, x (m)') %x-axis label

y1=ylabel('Position, y (m)') %y-axis label

set(t1,'FontSize',24) %change fontsize

set(x1,'FontSize',24) %change fontsize

set(y1,'FontSize',24) %change fontsize

Answer 1

[Voss]

This line, which is a few lines above the line with the error:

vr(ii,jj) = lamb/(2.*pi*r);

makes vr a 1-by-2 vector when it is executed when ii = 1 and jj == 2.

That's what causes the error a little later on, because this expression

sqrt(vr.^2+vTheta.^2)

will now return a 1-by-2 vector, which cannot be stored in the scalar "slot" given by

vmag(ii,jj)

I guess the solution is to change vr here:

vr(ii,jj) = lamb/(2.*pi*r);

to some other variable name, say vr_all:

vr_all(ii,jj) = lamb/(2.*pi*r);

because it seems like you want to store vr for all ii and all jj, but vr is already a scalar variable you are using inside the loops.