Hydraulic orifice with constant cross-sectional area
The Fixed Orifice block models a sharp-edged constant-area orifice, flow rate through which is proportional to the pressure differential across the orifice. The model accounts for the laminar and turbulent flow regimes by monitoring the Reynolds number (Re) and comparing its value with the critical Reynolds number (Recr). The flow rate is determined according to the following equations:
|pA,pB||Gauge pressures at the block terminals|
|CD||Flow discharge coefficient|
|A||Orifice passage area|
|DH||Orifice hydraulic diameter|
|ν||Fluid kinematic viscosity|
The block positive direction is from port A to port B. This means that the flow rate is positive if it flows from A to B, and the pressure differential is determined as .
Fluid inertia is not taken into account.
The transition between laminar and turbulent regimes is assumed to be sharp and taking place exactly at Re=Recr.
Orifice passage area. The default value is 1e-4 m^2.
Semi-empirical parameter for orifice capacity characterization. Its value depends on the geometrical properties of the orifice, and usually is provided in textbooks or manufacturer data sheets. The default value is 0.7.
The maximum Reynolds number for laminar flow. The transition from laminar to turbulent regime is supposed to take place when the Reynolds number reaches this value. The value of the parameter depends on orifice geometrical profile, and the recommendations on the parameter value can be found in hydraulic textbooks. The default value is 12, which corresponds to a round orifice in thin material with sharp edges.
Parameters determined by the type of working fluid:
Fluid kinematic viscosity
The block has the following ports: