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FEATool Multiphysics
v1.17.5
Finite Element Analysis Toolbox
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FEATool Multiphysics
v1.17.5
Finite Element Analysis Toolbox
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EX_HEAT_EXCHANGER1 Example of free and forced convection around a heated cylinder.
[ FEA, OUT ] = EX_HEAT_EXCHANGER1( VARARGIN ) Sets up and solves an example of temperature transport in a fluid around a heated cylinder. The model involves both free and forced convection by using the Boussinesq approximation.
Accepts the following property/value pairs.
Input Value/{Default} Description
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hmax scalar {0.0005} Max grid cell size
sf_u string {sflag2} Shape function for velocity
sf_p string {sflag1} Shape function for pressure
sf_T string {sflag1} Shape function for temperature
solver string {} Solver selection default, openfoam, fenics
iplot scalar 0/{1} Plot solution and error (=1)
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Output Value/(Size) Description
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fea struct Problem definition struct
out struct Output struct
cOptDef = { 'hmax', 0.0004;
'sf_u', 'sflag1';
'sf_p', 'sflag1';
'sf_T', 'sflag1';
'solver', '';
'iplot', 1;
'w', 0.0075;
'h', 0.05;
'yc', 0.02;
'r', 0.003;
'rho', 2.2e1;
'miu', 2.8e-3;
'cp', 3.1e3;
'k', 0.55;
'al', 0.26e-3;
'g', 9.81;
'vin', 40e-2;
'Tc', 300;
'Th', 330;
'tol', 0.1;
'fid', 1 };
[got,opt] = parseopt( cOptDef, varargin{:} );
fid = opt.fid;
% Geometry definition.
fea.sdim = { 'x' 'y' };
fea.geom.objects = { gobj_rectangle( 0, opt.w, 0, opt.h, 'R1' ) ...
gobj_circle( [0 opt.yc], opt.r, 'C1' ) };
fea = geom_apply_formula( fea, 'R1-C1' );
% Grid generation.
fea.grid = gridgen( fea, 'hmax', opt.hmax, 'fid', fid );
% Boundary conditions.
dtol = 1e-6;
ib_l = findbdr( fea, ['x<',num2str(dtol)] ); % Right boundary numbers.
ib_r = findbdr( fea, ['x>',num2str(opt.w-dtol)] ); % Left boundary number.
ib_b = findbdr( fea, ['y<',num2str(dtol)] ); % Bottom boundary number.
ib_t = findbdr( fea, ['y>',num2str(opt.h-dtol)] ); % Top boundary number.
ib_c = findbdr( fea, ['sqrt(x.^2+(y-',num2str(opt.yc),').^2)<',num2str(opt.r+dtol)] ); % Cylinder boundary numbers.
% Problem definition.
fea.expr = { 'rho' opt.rho ;
'miu' opt.miu ;
'cp' opt.cp ;
'k' opt.k ;
'alpha' opt.al ;
'g' opt.g ;
'vin' opt.vin ;
'Tc' opt.Tc ;
'Th' opt.Th };
fea = addphys(fea,@navierstokes); % Add Navier-Stokes equations physics mode.
fea.phys.ns.eqn.coef{1,end} = { 'rho' };
fea.phys.ns.eqn.coef{2,end} = { 'miu' };
fea.phys.ns.eqn.coef{4,end} = { 'alpha*g*rho*(T-Tc)' };
fea.phys.ns.bdr.sel(ib_t) = 4; % Set pressure to zero on top boundary segment.
fea.phys.ns.bdr.sel(ib_b) = 2; % Set y-velocity to vin at bottom boundary.
fea.phys.ns.bdr.coef{2,end}{2,ib_b} = 'vin';
fea.phys.ns.sfun = { opt.sf_u opt.sf_u opt.sf_p };
fea = addphys(fea,@heattransfer); % Add heat transfer physics mode.
fea.phys.ht.sfun = { opt.sf_T };
fea.phys.ht.eqn.coef{1,end} = { 'rho' };
fea.phys.ht.eqn.coef{2,end} = { 'cp' };
fea.phys.ht.eqn.coef{3,end} = { 'k' };
fea.phys.ht.eqn.coef{4,end} = { fea.phys.ns.dvar{1} };
fea.phys.ht.eqn.coef{5,end} = { fea.phys.ns.dvar{2} };
fea.phys.ht.bdr.sel = 3*ones( 1, max(fea.grid.b(3,:)) ); % Default to symmetry BCs.
fea.phys.ht.bdr.sel(ib_t) = 2; % Set top boundary to convective flux/outflow.
fea.phys.ht.bdr.sel([ib_c ib_b]) = 1; % Set temperature to bottom and cylinder boundaries.
[fea.phys.ht.bdr.coef{1,end}{ib_b}] = deal('Tc');
[fea.phys.ht.bdr.coef{1,end}{ib_c}] = deal('Th');
% Parse and solve problem.
fea = parsephys(fea);
[fea.bdr.d{1}{[ib_l ib_r]}] = deal(0); % Manually apply slip boundary conditions.
[fea.bdr.d{2}{[ib_l ib_r]}] = deal([]);
[fea.bdr.n{2}{[ib_l ib_r]}] = deal(0);
fea = parseprob(fea);
if( strcmp(opt.solver,'openfoam') )
logfid = fid; if( ~got.fid ), fid = []; end
fea.sol.u = openfoam( fea, 'fid', fid, 'logfid', logfid, 'nproc', 1 );
fid = logfid;
elseif( strcmp(opt.solver,'fenics') )
fea = fenics( fea, 'fid', fid, 'nproc', 1 );
else
fea.sol.u = solvestat( fea, 'fid', fid, 'maxnit', 50 );
end
% Postprocessing.
if( opt.iplot>0 )
figure
subplot(1,2,1)
postplot( fea, 'surfexpr', 'sqrt(u^2+v^2)', 'arrowexpr', {'u' 'v'} )
hold on
fea.grid.p(1,:) = -fea.grid.p(1,:); % Mirror solution.
postplot( fea, 'surfexpr', 'sqrt(u^2+v^2)', 'arrowexpr', {'u' 'v'} )
title('Velocity field')
subplot(1,2,2)
postplot( fea, 'surfexpr', 'T' )
hold on
fea.grid.p(1,:) = -fea.grid.p(1,:); % Mirror solution.
postplot( fea, 'surfexpr', 'T' )
title('Temperature')
end
% Average temperature at outlet.
out.T_av_out = intbdr( 'T*v', fea, ib_t )/intbdr( 'v', fea, ib_t );
out.err = abs(intbdr('T-Tc',fea,3)/0.0075-1.7)/1.7;
out.pass = out.err < opt.tol;
if( nargout==0 )
clear fea out
end