36 lines
922 B
Matlab
36 lines
922 B
Matlab
function [K, F] = ApplyRobinBC_mult_rot(model, K, F, alpha, u_out)
|
|
mesh = model.Mesh;
|
|
nodes = mesh.Nodes;
|
|
elements = mesh.Elements;
|
|
|
|
edgesAll = [elements([1 2],:), elements([2 3],:), elements([3 1],:)];
|
|
edgesSorted = sort(edgesAll,1);
|
|
[edgesUnique,~,ic] = unique(edgesSorted','rows');
|
|
counts = accumarray(ic,1);
|
|
boundaryEdges = edgesUnique(counts==1,:);
|
|
|
|
for k = 1:size(boundaryEdges,1)
|
|
i = boundaryEdges(k,1);
|
|
j = boundaryEdges(k,2);
|
|
|
|
ri = nodes(1,i);
|
|
rj = nodes(1,j);
|
|
|
|
%find the edges on the axis -> homogeneous Neumann BC, no Robin contribution
|
|
if ri == 0 && rj == 0
|
|
continue;
|
|
end
|
|
|
|
xi = nodes(:,i);
|
|
xj = nodes(:,j);
|
|
|
|
L = norm(xi - xj);
|
|
rbar = 0.5 * (xi(1) + xj(1)); % r at edge midpoint
|
|
|
|
Ke = rbar * alpha * L / 6 * [2 1; 1 2];
|
|
Fe = rbar * alpha * u_out * L / 2 * [1; 1];
|
|
|
|
K([i j],[i j]) = K([i j],[i j]) + Ke;
|
|
F([i j]) = F([i j]) + Fe;
|
|
end
|
|
end
|