59 static Evaluation
gasDiffCoeff(Evaluation temperature, Evaluation pressure)
64 temperature = max(temperature, 1e-9);
65 temperature = min(temperature, 500.0);
66 pressure = max(pressure, 0.0);
67 pressure = min(pressure, 1e8);
71 const double Tb_m = 437.9;
72 const double sigma_a = 3.711;
73 const double T_scal_a = 78.6;
74 const double V_B_m = 162.6;
75 const double sigma_m = 1.18*std::pow(V_B_m, 0.333);
76 const double sigma_am = 0.5*(sigma_a + sigma_m);
77 const double T_scal_m = 1.15*Tb_m;
78 const double T_scal_am = std::sqrt(T_scal_a*T_scal_m);
80 Evaluation T_star = temperature/T_scal_am;
81 T_star = max(T_star, 1e-5);
83 const Evaluation Omega = 1.06036/pow(T_star, 0.1561) + 0.193/exp(T_star*0.47635)
84 + 1.03587/exp(T_star*1.52996) + 1.76474/exp(T_star*3.89411);
85 const double B_ = 0.00217 - 0.0005*std::sqrt(1.0/M_a + 1.0/M_m);
86 const double Mr = (M_a + M_m)/(M_a*M_m);
87 const Evaluation D_am = (B_*pow(temperature, 1.5) * std::sqrt(Mr))
88 /(1e-5*pressure*std::pow(sigma_am, 2.0) * Omega);