function lossConstant_D_zeta extends Modelica.Icons.Function; input SI.Diameter D "Diameter at port_a or port_b"; input Real zeta "Constant pressure loss factor with respect to D (i.e., either port_a or port_b)"; output Real k "Loss constant (= 8*zeta/(pi^2*D^4))"; end lossConstant_D_zeta;