Hello Daniel,
From the provided information, I understand that you are getting error in your code while trying to plot the drag and lift force of a square prism using the Navier-stokes equation.
As I can see, in the ‘force calculation’ part of your code, the initialization of the variables ‘F_fric’, ‘tau’, ‘F_L’ and ‘F_d’ is not done properly before using them in the equation inside the loop.
Here is how you can modify your code to resolve the error:
% Force calculation
for i=1:nx
for j=1:ny
F_fric(1:nx,1:ny) = 0; % Proper initialization of F_fric
tau(1:nx,1:ny) = 0; % Proper initialization of tau
F_L(1:nx,1:ny) = 0; % Proper initialization of F_L
F_d(1:nx,1:ny) = 0; % Proper initialization of F_d
if (i==1)
tau(i,j)=0;
F_fric(i,j)=0;
F_L(i,j)=0;
I hope this helps!
