function 
 
 
   gas 
 
 
   % specifies the working gas properties (he, h2, air) 
 
 
   % Israel Urieli 4/20/02 
 
 
   global 
 
 
   rgas 
 
 
   % gas constant [J/kg.K] 
 
 
   global 
 
 
   cp 
 
 
   % specific heat capacity at constant pressure [J/kg.K] 
 
 
   global 
 
 
   cv 
 
 
   % specific heat capacity at constant volume [J/kg.K] 
 
 
   global 
 
 
   gama 
 
 
   % ratio: cp/cv 
 
 
   global 
 
 
   mu0 
 
 
   % dynamic viscosity at reference temp t0 [kg.m/s] 
 
 
   global 
 
 
   t0 t_suth 
 
 
   % reference temperature [K], Sutherland constant [K] 
 
 
   global 
 
 
   prandtl 
 
 
   % Prandtl number 
 
 
   global 
 
 
   new fid 
 
 
   % new data file 
 
 
   gas_type = 
 
 
   'un' 
 
 
   ; 
 
 
   while 
 
 
   (strncmp(gas_type, 
 
 
   'un' 
 
 
   ,2)) 
 
 
   if 
 
 
   (strncmp(new, 
 
 
   'y' 
 
 
   ,1)) 
 
 
   fprintf( 
 
 
   'Available gas types are:\n' 
 
 
   ); 
 
 
   fprintf( 
 
 
   '   hy)drogen)\n' 
 
 
   ); 
 
 
   fprintf( 
 
 
   '   he)lium\n' 
 
 
   ); 
 
 
   fprintf( 
 
 
   '   ai)r\n' 
 
 
   ); 
 
 
   gas_type = input( 
 
 
   'enter gas type: ' 
 
 
   , 
 
 
   's' 
 
 
   ); 
 
 
   gas_type = [gas_type(1), gas_type(2)]; 
 
 
   fprintf(fid, 
 
 
   '%s\n' 
 
 
   , gas_type); 
 
 
   else 
 
 
   fscanf(fid, 
 
 
   '%c' 
 
 
   ,1); 
 
 
   % bypass the previous newline character 
 
 
   gas_type = fscanf(fid, 
 
 
   '%c' 
 
 
   ,2); 
 
 
   end 
 
 
   if 
 
 
   (strncmp(gas_type, 
 
 
   'hy' 
 
 
   ,2)) 
 
 
   fprintf( 
 
 
   'gas type is hydrogen\n' 
 
 
   ) 
 
 
   gama = 1.4; 
 
 
   rgas = 4157.2; 
 
 
   mu0 = 8.35e-6; 
 
 
   t_suth = 84.4; 
 
 
   elseif 
 
 
   (strncmp(gas_type, 
 
 
   'he' 
 
 
   ,2)) 
 
 
   fprintf( 
 
 
   'gas type is helium\n' 
 
 
   ) 
 
 
   gama = 1.67; 
 
 
   rgas = 2078.6; 
 
 
   mu0 = 18.85e-6; 
 
 
   t_suth = 80.0; 
 
 
   elseif 
 
 
   (strncmp(gas_type, 
 
 
   'ai' 
 
 
   ,2)) 
 
 
   fprintf( 
 
 
   'gas type is air\n' 
 
 
   ) 
 
 
   gama = 1.4; 
 
 
   rgas = 287.0; 
 
 
   mu0 = 17.08e-6; 
 
 
   t_suth = 112.0; 
 
 
   else 
 
 
   fprintf( 
 
 
   'gas type is undefined\n' 
 
 
   ) 
 
 
   gas_type = 
 
 
   'un' 
 
 
   ; 
 
 
   end 
 
 
   end 
 
 
   cv = rgas/(gama - 1); 
 
 
   cp = gama*cv; 
 
 
   t0 = 273; 
 
 
   prandtl = 0.71;