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Orifice

Fixed orifice

 

Description

Optional Volumes

Equations

Variables

Connections

Parameters

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 VA  and VB 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=pApB=π8ρνqCd2AcsπAcs16q4π2Acs2ν4+Cr414

q=qAqVA=qB+qVB

qVA={dVfAdtuseVolumeA0otherwiseqVB={dVfBdtuseVolumeB0otherwise

VfA=VA1+pAKVfB=VB1+pBK

Variables

Name

Units

Description

Modelica ID

p

Pa

Pressure drop from A to B

p

pX

Pa

Pressure at port X

pX

q

m3s

Flow rate from A to B

q

qVX

m3s

Flow rate into port X's optional volume

qVX

VfX

m3

Effective volume at port X

VfX

Connections

Name

Description

Modelica ID

portA

Upstream hydraulic port

portA

portB

Downstream hydraulic port

portB

Parameters

General Parameters

Name

Default

Units

Description

Modelica ID

A

1·10−6

m2

Area of opening

A

Cd

710

 

Flow-discharge coefficient

Cd

Cr

12

 

Reynolds number at critical flow

ReCr

Volume Parameters

Name

Default

Units

Description

Modelica ID

Use volume A

false

 

When true a hydraulic volume chamber is added to portA

useVolumeA

VA

1·10−6

m3

Volume of chamber A

Va

Use volume B

false

 

When true a hydraulic volume chamber is added to portB

useVolumeB

VB

1·10−6

m3

Volume of chamber B

Vb

For more information see Port Volumes.

See Also

Hydraulics Library

Restrictions