Orifice

Fixed orifice

 Description The Orifice component models a sharp-edge orifice with a circular opening of a given area.
 Optional Volumes The boolean parameters Use volume A and Use volume B, when true, add optional volumes ${V}_{A}$  and ${V}_{B}$ to ports A and B, respectively. See Port Volumes for details. If two orifices or valves are connected, enabling a volume at the common port reduces the the stiffness of the system and improves the solvability.
 Equations $p={p}_{A}-{p}_{B}=\frac{\mathrm{\pi }}{8}\frac{\mathrm{\rho }\mathrm{\nu }q}{{C}_{d}^{2}{A}_{\mathrm{cs}}\sqrt{\mathrm{\pi }{A}_{\mathrm{cs}}}}{\left(\frac{16{q}^{4}}{{\mathrm{\pi }}^{2}{A}_{\mathrm{cs}}^{2}{\mathrm{\nu }}^{4}}+{\mathrm{\Re }}_{\mathrm{Cr}}^{4}\right)}^{\frac{1}{4}}$ $q={q}_{A}-{q}_{\mathrm{VA}}=-{q}_{B}+{q}_{\mathrm{VB}}$ ${q}_{\mathrm{VA}}=\left\{\begin{array}{cc}\frac{\mathrm{d}{V}_{{f}_{A}}}{\mathrm{d}t}& \mathrm{useVolumeA}\\ 0& \mathrm{otherwise}\end{array}\phantom{\rule[-0.0ex]{2.5ex}{0.0ex}}{q}_{\mathrm{VB}}=\left\{\begin{array}{cc}\frac{\mathrm{d}{V}_{{f}_{B}}}{\mathrm{d}t}& \mathrm{useVolumeB}\\ 0& \mathrm{otherwise}\end{array}$ ${V}_{{f}_{A}}={V}_{A}\left(1+\frac{{p}_{A}}{K}\right)\phantom{\rule[-0.0ex]{3.0ex}{0.0ex}}{V}_{{f}_{B}}={V}_{B}\left(1+\frac{{p}_{B}}{K}\right)$

Variables

 Name Units Description Modelica ID $p$ $\mathrm{Pa}$ Pressure drop from A to B p ${p}_{X}$ $\mathrm{Pa}$ Pressure at port X pX $q$ $\frac{{m}^{3}}{s}$ Flow rate from A to B q ${q}_{\mathrm{VX}}$ $\frac{{m}^{3}}{s}$ Flow rate into port X's optional volume qVX ${V}_{{f}_{X}}$ ${m}^{3}$ Effective volume at port X VfX

Connections

 Name Description Modelica ID $\mathrm{portA}$ Upstream hydraulic port portA $\mathrm{portB}$ Downstream hydraulic port portB

Parameters

General Parameters

 Name Default Units Description Modelica ID $A$ $1·{10}^{-6}$ ${m}^{2}$ Area of opening A ${C}_{d}$ $\frac{7}{10}$ Flow-discharge coefficient Cd ${\mathrm{\Re }}_{\mathrm{Cr}}$ $12$ Reynolds number at critical flow ReCr

Volume Parameters

 Name Default Units Description Modelica ID Use volume A $\mathrm{false}$ When true a hydraulic volume chamber is added to portA useVolumeA ${V}_{A}$ $1·{10}^{-6}$ ${m}^{3}$ Volume of chamber A Va Use volume B $\mathrm{false}$ When true a hydraulic volume chamber is added to portB useVolumeB ${V}_{B}$ $1·{10}^{-6}$ ${m}^{3}$ Volume of chamber B Vb