Description

EX_HEATTRANSFER2 1D Stationary heat transfer with radiation.

[ FEA, OUT ] = EX_HEATTRANSFER2( VARARGIN ) NAFEMS T2 benchmark example for heat transfer with radiation [1]. The left end of a 0.1 m rod is held at a temperature of 1000 K while the right end is radiating with an emissivity, em = 0.98, and Stefan-Bolzmann constant, sigma = 5.67e-8 Wm^2/K^4.

       +---------- L=0.1m ----------+ T(0.1)?
   T=1000K                   q_n = em*sigma*(T_amb^4-T^4)

The rod is made of iron with density 7850 kg/m^3, heat capacity 460 J/kgK, and thermal conductivity 55.563 W/mK. The steady state temperature at the left end is sought when the surrounding ambient temperature is 300 K.

Reference

  [1] The Standard NAFEMS Benchmarks,
      The National Agency for Finite Element Standards, UK, 1990.

Accepts the following property/value pairs.

Input       Value/{Default}        Description
-----------------------------------------------------------------------------------
hmax        scalar {0.02}          Grid cell size
sfun        string {sflag1}        Finite element shape function
solver      string fenics/{}       Use FEniCS or default solver
istat       scalar {1}/0           Use stationary (=1), or time dependent solver
iplot       scalar {1}/0           Plot solution (=1)
                                                                                  .
Output      Value/(Size)           Description
-----------------------------------------------------------------------------------
fea         struct                 Problem definition struct
out         struct                 Output struct

Code listing

 cOptDef = { 'hmax',     0.02;
             'sfun',     'sflag1';
             'solver',   '';
             'istat',    1;
             'iplot',    1;
             'fid',      1 };
 [got,opt] = parseopt(cOptDef,varargin{:});


% Grid generation.
 L        = 0.1;
 nx       = round(L/opt.hmax);
 fea.grid = linegrid( nx, 0, L );


% Problem definition.
 fea.sdim  = { 'x' };                      % Space coordinate name.
 fea = addphys( fea, @heattransfer );      % Add heat transfer physics mode.
 fea.phys.ht.sfun = { opt.sfun };          % Set shape function.

% Equation coefficients.
 fea.phys.ht.eqn.coef{1,end} = 7850;       % Density
 fea.phys.ht.eqn.coef{2,end} =  460;       % Heat capacity.
 fea.phys.ht.eqn.coef{3,end} =   55.563;   % Thermal conductivity.
 fea.phys.ht.eqn.coef{6,end} = { 1000 };   % Initial temperature.

% Boundary conditions.
 fea.phys.ht.bdr.sel = [ 1 4 ];
 fea.phys.ht.bdr.coef{1,end} = { 1000 [] };
 fea.phys.ht.bdr.coef{4,end}{2}{4} = '0.98*5.67e-8';
 fea.phys.ht.bdr.coef{4,end}{2}{5} = 300;


% Parse physics modes and problem struct.
 fea = parsephys(fea);
 fea = parseprob(fea);


% Compute solution.
 if( strcmp(opt.solver,'fenics') )
   fea = fenics( fea, 'fid', opt.fid, 'nproc', 1, ...
                 'tstep', 10, 'tmax', 1000, 'ischeme', 2*(~opt.istat) );
 else
   if( opt.istat )
     fea.sol.u = solvestat( fea, 'fid', opt.fid, 'init', {'T0_ht'} );
   else
     [fea.sol.u, tlist] = solvetime( fea, 'fid', opt.fid, 'init', {'T0_ht'}, ...
                                     'tmax', 1000, 'tstep', 10 );
   end
 end


% Postprocessing.
 if( opt.iplot>0 )
   postplot( fea, 'surfexpr', 'T', 'axequal', 0 )
   title('Temperature')
   xlabel('x')
   ylabel('T')
 end


% Error checking.
 T_sol = evalexpr( 'T', 0.1, fea );
 T_ref = 926.97;
 out.err  = abs(T_sol-T_ref)/T_ref;
 out.pass = out.err<6e-4;


 if( nargout==0 )
   clear fea out
 end