## Hydraulic orifice definition

- @HYDRAULIC_ORIFICE_DEFINITION {
- @HYDRAULIC_ORIFICE_NAME {HydOrfcName} {
- @HYDRAULIC_DEVICE_MODEL_NAME {HydModl}
- @HYDRAULIC_CHAMBER_NAME {HydChmb0Name, HydChmb1Name}
- @FUNCTION_1D_NAME {Fun1DName}
- @ORIFICE_AREA {A
_{orf}} - @ORIFICE_DISCHARGE_COEFFICIENT {C
_{d}} - @ORIFICE_ENTRANCE_PRESSURE {p
_{Ent}} - @ORIFICE_CIRCUIT_PRESSURE {p
_{Cir}} - @COMMENTS {CommentText}
- }
- }

### Introduction

Figure 1. Configuration of the hydraulic orifice.

The **hydraulic orifice**, shown in fig. 1, allows the flow of hydraulic fluid through an orifice of sectional area * A_{orf}* and is associated with hydraulic device model,

**. The orifice is connected to two hydraulic chambers,**

*HydModl***and**

*HydChmb0Name***, respectively, with pressures**

*HydChmb1Name**and*

**p**_{0}*, respectively. A pressure differential,*

**p**_{1}*, will drive a flow rate*

**Δp = p**_{0}- p_{1}*across the orifice; the positive direction of this flow, indicated on the figure, is from*

**Q**_{orf}**to**

*HydChmb0Name***.**

*HydChmb1Name*Pressures * p_{0}* and

*are, in general, the pressures in chambers*

**p**_{1}**and**

*HydChmb0Name***, respectively. For the linear hydraulic actuator, the orifice connects a chamber to an oil supply that can be at the entrance pressure**

*HydChmb1Name**or at the circuit pressure*

**p**_{Ent}*.. In such case,*

**p**_{Cir}*.*

**HydChmb0Name = NULL**The description and formulation of the hydraulic orifice and elements describes the relationships among these variables.

### Computation of the orifice flow

The flow through the orifice, * Q_{orf}*, is related to the pressure drop,

*, across the orifice and can be computed in two alternative manners.*

**Δp**-
If the orifice area,
, and the orifice dischage coefficient,**A**_{orf}, are defined an empirical formula is used:**C**_{d}where**Q**_{orf}= A_{orf}C_{d}√(2|Δp|/ρ) sign(Δp),is the orifice throttling area and ρ the mass density of the hydraulic fluid. For turbulent flow conditions, the theoretical value of the discharge coefficient is**A**_{orf}. The term**C**_{d}= 0.611enforces the sign convention.**sign(Δp)** -
If 1D function,
, is defined, the flow through the orifice is computed as*Fun1DName*, where a 1D function,**Q**_{orf}= F(|Δp|) sign(Δp), defines the relationship between the flow and the pressure drop across the orifice through a Chebyshev expansion. 1D function,**F = F(|Δp|)**, must be defined of the type HYDRAULIC_ORIFICE. Typically, the flow-pressure drop relationship is determined experimentally and a Chebyshev approximation is used to fit the data. The empirical formula above corresponds to*Fun1DName*.**F(|Δp|) = A**_{orf}C_{d}√(2|Δp|/ρ)

### NOTES

- It is possible to attach comments to the definition of the object; these comments have no effect on its definition.

### Sensors

Sensors can be defined to extract information about hydraulic orifices. The following * SensorType* specifications are allowed for hydraulic orifices:

*. (*

**ORIFICE_DATA***Default value:*

*).*

**ORIFICE_DATA**No * u value* and

*are accepted for the hydraulic device.*

**v value**