Function for defining the friction forces using the Darcy friction factor.
function Friction extends Modelica.Icons.Function; import Modelica.Constants.pi; input SI.Velocity v "Flow velocity"; input SI.Diameter D "Pipe diameter"; input SI.Length L "Pipe length"; input SI.Density rho "Density"; input SI.DynamicViscosity mu "Dynamic viscosity of water"; input SI.Height p_eps "Pipe roughness height"; output SI.Force F_f "Friction force"; end Friction;