mesh size & urf SIMPLE FVM MATLAB
I have developed a laminar 2D solver for Poiseulle flow using FVM and SIMPLE, and the results match nicely to the Hagen-Poiseulle velocity profile, but if i increase the mesh size, the solution blows up... My results are coming out nicely, but i cannot seem to be able to increase the mesh size beyond 36*36... I have to decrease the pressure under-relaxation to 0.01 to get it to iterate, but then it just oscillates at a continuity residual of around e-2... do you know the reason for this and why it happens? or how to fix it?
I am trying to maybe implement a method such that:
if MassResidual <= 10^-2
alphap = 0.05
disp('alphap is now 0.1')
if MassResidual <= 10^-3
alphap = 0.1
disp('alphap is now 0.3')
in an effort to try and march the process along? is this a correct approach?
I am also solving the equations using Jacobi:
pcheck = pdash;
mx = max(max(max(abs(pcheck-pdash))));
if (kk>50&&mx<10^-6), break, end
and for residuals:
I'd appreciate any assistance!
Apologies, I did not add all of the relevant information...
This is the momentum equation that i solve for, including under-relaxation:
%Solve iteratively using the Jacobi Method to yield u, which will now
%be the most up to date value, i.e. u*
u(i,j)=((biJ(i,j)+uaE(i,j)*u(i+1,j)+uaW(i,j)*u(i-1,j)+uaN(i,j)*u(i,j+1)+uaS(i,j)*u(i,j-1) + (1-alphau)*uaP(i,j)*u(i,j)/alphau))*alphau/uaP(i,j);
kk=kk+1; % Counter
and i correct the pressure with under-relaxation:
%% Correct the Pressure, including under-relaxation
pnew(2:nXp,2:nYp-1) = pstar(2:nXp,2:nYp-1) + alphap*pdash(2:nXp,2:nYp-1);
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