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% BELINT - compute shape function information for a FEM domain |
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% |
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% BELINT(FEM_GRID_STRUCT) computes shape function |
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% information to be used in element finding (FINDELE). |
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% BELINT must return a new structure containing the input |
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% structure and adding the new components. The returned |
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% structure now includes:... |
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% |
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% INPUT : fem_grid_struct - (from LOADGRID, see FEM_GRID_STRUCT) |
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% |
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% OUTPUT : new_struct (REQ) - new structure with areas |
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% |
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% CALL : >>new_struct=belint(fem_grid_struct); |
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% |
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% Written by : Brian O. Blanton |
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% Summer 1997 |
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% |
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function ret_struct=el_areas(fem_grid_struct) |
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% VERIFY INCOMING STRUCTURE |
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% |
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if ~is_valid_struct(fem_grid_struct) |
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error(' Argument to EL_AREAS must be a valid fem_grid_struct.') |
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end |
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% NEED ONE OUT ARG |
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% |
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if nargout~=1 |
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error(' BELINT must have 1 output argument.') |
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end |
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% BREAK DOWN INCOMING STRUCTURE |
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% |
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e=fem_grid_struct.e; |
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x=fem_grid_struct.x; |
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y=fem_grid_struct.y; |
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% COMPUTE GLOBAL DY |
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% |
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dy=[y(e(:,2))-y(e(:,3)) y(e(:,3))-y(e(:,1)) y(e(:,1))-y(e(:,2))]; |
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% COMPUTE ELEMENTAL AREAS |
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% |
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AR=(x(e(:,1)).*dy(:,1)+x(e(:,2)).*dy(:,2)+x(e(:,3)).*dy(:,3))/2.; |
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% COMPUTE ARRAYS FOR ELEMENT FINDING |
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% |
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n1 = e(:,1); |
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n2 = e(:,2); |
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n3 = e(:,3); |
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A(:,1)=x(n3)-x(n2); |
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A(:,2)=x(n1)-x(n3); |
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A(:,3)=x(n2)-x(n1); |
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B(:,1)=y(n2)-y(n3); |
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B(:,2)=y(n3)-y(n1); |
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B(:,3)=y(n1)-y(n2); |
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A0(:,1)=.5*(x(n2).*y(n3)-x(n3).*y(n2)); |
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A0(:,2)=.5*(x(n3).*y(n1)-x(n1).*y(n3)); |
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T(:,1)=A0(:,1)*2; |
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T(:,2)=A0(:,2)*2; |
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T(:,3)=2*AR-T(:,1)-T(:,2); |
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%Create return structure and attach element areas to ret_struct |
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% |
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ret_struct=fem_grid_struct; |
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ret_struct.A=A; |
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ret_struct.B=B; |
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ret_struct.A0=A0; |
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ret_struct.T=T; |
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% |
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% Brian O. Blanton |
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% Curriculum in Marine Sciences |
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% Ocean Processes Numerical Modeling Laboratory |
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% 15-1A Venable Hall |
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% CB# 3300 |
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% Uni. of North Carolina |
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% Chapel Hill, NC |
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% 27599-3300 |
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% |
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% 919-962-4466 |
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% blanton@marine.unc.edu |
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% |
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% October 1995 |
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% |
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