# unsteady flow - matlab - for loop questions

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 September 5, 2011, 19:03 unsteady flow - matlab - for loop questions #1 Member   Join Date: Jun 2010 Posts: 98 Rep Power: 7 Hi all, I am writing a code for an unsteady flow in maltab. This code is over simplified just to realize where I am going wrong and understand the basic first... n = number of time steps h = number of cells v1 = zeros(h,n+1); %v1(x,t) v1(1,= 0; %boundary condition for j = 1: n+1 for j = 1: h v1(i,j+1) = v1(i,j) + dt*eye(h,h)*2*v(i,j); %Euler time stepping v1(end,j+1)=1; %boundary condition end end Obviously this code does not work. But hopefully it will help in understanding my questions: 1) v1 is mean to be a (h,1) matrix at each time step. but when I apply eye(h,h)*2*v(i,j), the code tries to multiply a (h,h) matrix with a (h,j) matrix, and not a (h,1) matrix. so I get errors. I am not sure how to change that so that eye(h,h) is multiplied by that v of each time... 2) In general, is this a reasonable approach to solve an unsteady flow problem. Thank you in advance!

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