Function to gather mesh information from gmesh files

Description

function [O1,O2,O3,O4,O5,O6,O7,O8,O9,O10]=getMesh(input) %Function to gather mesh information from gmesh files %--------------------------- % DEFINE SHORT-NAME OUTPUTS: %--------------------------- % O1=msh; Mesh file from gmesh % O2=Mdpts; Midpoint Database % O3=cons; Various important constants % O4=solidpts; Nodes (vertices and midpoints) on solid domain % O5=fluidpts; Nodes (vertices and midpoints) on fluid domain % O6=solperimeter; Nodes (vertices and midpoints) on solid/fluid bdry % O7=outerbdrynodes; Vertices on the outer boundary % O8=ELsolid; Global element numbers of vertices on solid domain % O9=ELfluid; Global element numbers of vertices on fluid domain % O10=edgetri; List of global element #'s in solid touching bdry %-------------------------------------------------------------------------- global searchtriangles global solidbdrynodes disp('Gathering mesh information...') %Choose particular mesh to use: if input==1 usemesh='solidfluid.msh'; elseif input==2 usemesh='solidfluid2.msh'; elseif input==3 usemesh='solidfluid3.msh'; elseif input==4 usemesh='solidfluid4.msh'; elseif input==5 usemesh='solidfluid5.msh'; elseif input==6 usemesh='solidfluid6.msh'; elseif input==7 usemesh='solidfluid7.msh'; elseif input==-1 % <----debugging with mesh by hand usemesh='fixedhandmesh1.msh'; elseif input==-2 % <----debugging with mesh by hand usemesh='fixedhandmesh2.msh'; else usemesh='solidfluid.msh'; end disp([' - Using Mesh: ',usemesh]) msh = load_gmsh2(usemesh,[1 2]); % [1,2] requests variables for lines and triangles only M=msh.nbNod; % Number of nodes in mesh NODECO=(1/3)*msh.POS(1:M,1:2); % NODE COordinates msh.POS(1:M,1:2)=NODECO; L=msh.nbTriangles; % Number of elements (triangular) ELNODE=msh.TRIANGLES(1:L,1:4); % Global node numbers for all elements; element domain chtype=ELNODE(1,end); % get tag for domain type; assume first type listed is fluid k=0; j=0; for i=1:L % get a list of elements in each domain if ELNODE(i,4)~=chtype k=k+1; ELsolid(k,1:3)=ELNODE(i,1:3); %coordinates of elements in solid domain else j=j+1; ELfluid(j,1:3)=ELNODE(i,1:3); %coordinates of elements in fluid domain end end nELsolid=k; % number of elements in the solid domain nELfluid=j; % number of elements in the fluid domain % The following information can be used to subdivide the boundary into segments %global L1 %L1=msh.nbLines; % Number of element edges on the natural boundary %global BDRYEDGES BDRYEDGES=msh.LINES; % EDGES (node, node, ...) [nBdryNodes,dum]=size(BDRYEDGES); % total number of nodes on a boundary k=1; k2=1; chtype=BDRYEDGES(1,end); for i=1:nBdryNodes if BDRYEDGES(i,end)==chtype outerbdrynodes(k,1)=BDRYEDGES(i,1); k=k+1; else solidbdrynodes(k2,1)=BDRYEDGES(i,1); k2=k2+1; end end %---------------------- %Determine fluid/solid nodes %---------------------- nfluidpts=0; nsolidpts=0; temp=ELfluid(:,1:3); temp2=ELsolid(:,1:3); for k=1:M check=isempty(find(k==temp)); if check==0 nfluidpts=nfluidpts+1; fluidpts(nfluidpts)=k; end check=isempty(find(k==temp2)); if check==0 nsolidpts=nsolidpts+1; solidpts(nsolidpts)=k; end end otherDim=nfluidpts; nsolidnodes=nsolidpts; %------------------- % Midpoint Database %------------------- function [out]=mdptcalc(v1,v2) % Gives midpoint (x,y) coordinates between global nodes v1 and v2 % also places a flag for the domain % out(3)=0 means pt in interior of solid % out(3)=1 means pt on solid bdry % out(3)=2 means pt outside solid domain not on solid bdry v1coord=NODECO(v1,1:2); v2coord=NODECO(v2,1:2); out(1)=.5*(v1coord(1)+v2coord(1)); out(2)=.5*(v1coord(2)+v2coord(2)); out(3)=0; check1=isempty(find(v1==fluidpts)); %is v1 in fluid domain, 0=yes,1=no check2=isempty(find(v2==fluidpts)); %is v2 in fluid domain, 0=yes,1=no if check1+check2==0 %if both vertices are in fluid domain index1=find(v1==solidbdrynodes); % where is v1 on solid bdry if at all? index2=find(v2==solidbdrynodes); check3=isempty(index1); check4=isempty(index2); if check3+check4==0 %if both vertices are on the solid bdry if abs(index1-index2)==1 || abs(index1-index2)==length( solidbdrynodes)-1 out(3)=1; end else out(3)=2; end end end disp('Generating midpoint database...') disp(' ') %Mdpts= [x-coord, y-coord, bdry?, local node #1, global elem #1, local node #2, % global element #2, fluid/solid] % loctype is from 1-6 depending on what node is across % midpoint could be used twice, so have 2 loctype and node2 % If a point is in both domains, notated as 1, fluid=2, solid=0 tol=10^(-8); Mdpts=zeros(3*M,8); %pre-allocate space since no more than triple the nodes for mdpts Mdpts(:,3)=ones(3*M,1); %assume midpoint is on boundary until proven not nMdpts=1; % will count the number of unique midpoints in the mesh for i=1:L % cycle through each triangle (can we skip solid domain midpts?) v1=ELNODE(i,1); v2=ELNODE(i,2); v3=ELNODE(i,3); mid=zeros(3,4); mid(1,1:3)=mdptcalc(v2,v3); %organize midpoints in same way as local basis phi's mid(2,1:3)=mdptcalc(v3,v1); mid(3,1:3)=mdptcalc(v1,v2); mid(:,4)=[4;5;6]; %Check to see if any of the above are repeats for j=1:3 vec=ones(nMdpts,1); diff_x=abs(mid(j,1)*vec-Mdpts(1:nMdpts,1)); diff_y=abs(mid(j,2)*vec-Mdpts(1:nMdpts,2)); check=min(diff_x+diff_y); if check>tol Mdpts(nMdpts,1:2)=mid(j,1:2); Mdpts(nMdpts,4)=mid(j,4); Mdpts(nMdpts,5)=i; Mdpts(nMdpts,8)=mid(j,3); nMdpts=nMdpts+1; else [dum,place]=min(diff_x+diff_y); Mdpts(place,6:7)=[j+3,i]; Mdpts(place,3)=0; %mark that your midpoint isn't on bdry end end end nMdpts=nMdpts-1; Mdpts=Mdpts(1:nMdpts,1:8); %---------------------------------------- %Determine the fluid/solid midpoints %---------------------------------------- temp=Mdpts(:,8); count=0; clear solperimeter for k=1:nMdpts if temp(k)~=0 nfluidpts=nfluidpts+1; fluidpts(nfluidpts)=k+M; end if temp(k)~=2 nsolidpts=nsolidpts+1; solidpts(nsolidpts)=k+M; if temp(k)==1 count=count+1; solperimeter(count,1)=k+M; end end end solperimeter=[solidbdrynodes; solperimeter]; nsolperimeter=length(solperimeter); %Build a list of global node numbers that intersect the solid boundary, %edgetri edgetri=zeros(0,2); count=0; chtype=ELNODE(1,end); % get tag for domain type; assume first type listed is fluid for q=1:L if ELNODE(q,end)~=chtype % if we are looking at an element in solid domain count=count+1; v1=ELNODE(q,1); test1=isempty(find(v1==solidbdrynodes)); %see if any of the vertices are on solid bdry v2=ELNODE(q,2); test2=isempty(find(v2==solidbdrynodes)); %test=0 means yes on the bdry v3=ELNODE(q,3); test3=isempty(find(v3==solidbdrynodes)); if test1+test2+test3==1 % if two are on bdry edgetri=[edgetri;[q,count]]; %record the global element number and solid global element number end end end nedgetri=length(edgetri); % number of solid elements on bdry cons=[nELsolid,nELfluid,otherDim,nsolidpts,nfluidpts,nMdpts,nsolperimeter, nedgetri]; searchtriangles=[Mdpts(:,5),Mdpts(:,7)]; %Global element numbers for each midpoint % DEFINE SHORT-NAME OUTPUTS: O1=msh; O2=Mdpts; O3=cons; O4=solidpts; O5=fluidpts; O6=solperimeter; O7=outerbdrynodes; O8=ELsolid; O9=ELfluid; O10=edgetri; https://matlab1.com/jupyter-using-it-and-its-great-functions/ http://gmsh.info/doc/texinfo/gmsh.html 

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