This function returns the pressure loss dp as function of mass flow rate m_flow for an edged bend. The details of the function are described here.
The bend characteristic is valid for constant density and constant dynamic viscosity. It can be approximately also used for compressible media. This is performed by providing the upstream density and upstream dynamic viscosity. In order to be able to regularize density and dynamic viscosity around zero mass flow rate, the two quantities have to be given if fluid flows from port_a to port_b (d_a, eta_a) and if fluid flows from port_b to port_a (d_b, eta_b).
function pressureLoss extends Modelica.Icons.Function; input SI.MassFlowRate m_flow "Mass flow rate (= port_a.m_flow)"; input Geometry geometry "Geometry of bend"; input SI.Density d_a "Density at port_a when fluid is flowing from port_a to port_b"; input SI.Density d_b "Density at port_b when fluid is flowing from port_b to port_a"; input SI.DynamicViscosity eta_a "Dynamic viscosity at port_a when fluid is flowing from port_a to port_b"; input SI.DynamicViscosity eta_b "Dynamic viscosity at port_b when fluid is flowing from port_b to port_a"; input SI.AbsolutePressure dp_small "Small pressure drop used for regularization if m_flow=f(...,dp_small,..,dp)"; input SI.MassFlowRate m_flow_small "Small mass flow rate used for regularization if dp=f_inv(...,m_flow_small,m_flow)"; output SI.Pressure dp "Pressure loss"; end pressureLoss;