56        temperature = clamp(temperature, 1e-9, 500.0); 
 
   57        pressure = clamp(pressure, 0.0, 1e8); 
 
   63        const Scalar M_x = 1e3*Xylene::molarMass(); 
 
   64        const Scalar M_a = 1e3*Air::molarMass(); 
 
   65        const Scalar Tb_x = 412.0;        
 
   66        const Scalar sigma_a = 3.711;     
 
   67        const Scalar T_scal_a = 78.6;     
 
   68        const Scalar V_B_x = 140.4;       
 
   69        const Scalar sigma_x = 1.18*pow(V_B_x, 0.333);     
 
   70        const Scalar sigma_ax = 0.5*(sigma_a + sigma_x);
 
   71        const Scalar T_scal_x = 1.15*Tb_x;
 
   72        const Scalar T_scal_ax = sqrt(T_scal_a*T_scal_x);
 
   75        Scalar T_star = temperature/T_scal_ax;
 
   76        T_star = max(T_star, 1e-5); 
 
   78        const Scalar Omega = 1.06036/pow(T_star, 0.1561) + 0.193/exp(T_star*0.47635)
 
   79            + 1.03587/exp(T_star*1.52996) + 1.76474/exp(T_star*3.89411);
 
   80        const Scalar B_ = 0.00217 - 0.0005*sqrt(1.0/M_a + 1.0/M_x);
 
   81        const Scalar Mr = (M_a + M_x)/(M_a*M_x);
 
   82        const Scalar D_ax = (B_*pow(temperature,1.5)*sqrt(Mr))
 
   83                           /(1e-5*pressure*power(sigma_ax, 2)*Omega);