Simscape Reference

Constant Area Pneumatic Orifice (ISO 6358)
• Cv coefficient (USCU) — Provide value for the flow coefficient specified in
US units. This value is internally converted by the block into an equivalent value
for the orifice effective area.
• Kv coefficient (SI) — Provide value for the flow coefficient specified in SI
units. This value is internally converted by the block into an equivalent value for
the orifice effective area.
Sonic conductance
Specify the sonic conductance of the orifice, that is, the ratio between the mass
flow rate and the product of upstream pressure and the mass density at standard
conditions when the flow is choked. This value depends on the geometrical properties
of the orifice, and usually is provided in textbooks or manufacturer data sheets. The
default value is 1.6 l/s/bar. This parameter appears in the dialog box if Orifice is
specified with parameter is set to Sonic conductance.
Effective area
Specify the orifice cross-sectional area. The default value is 1e-5 m^2. This
parameter appears in the dialog box if Orifice is specified with parameter is set to
Effective area.
Cv coefficient
Specify the value for the flow coefficient in US units. The default value is 0.6. This
parameter appears in the dialog box if Orifice is specified with parameter is set to
Cv coefficient (USCU).
Kv coefficient
Specify the value for the flow coefficient in SI units. The default value is 8.5. This
parameter appears in the dialog box if Orifice is specified with parameter is set to
Kv coefficient (SI).
Critical pressure ratio
Specify the critical pressure ratio, that is, the ratio between the downstream pressure
and the upstream pressure at which the gas velocity achieves sonic speed. The
default value is 0.528.
Pressure ratio at laminar flow
Specify the ratio between the downstream pressure and the upstream pressure at
laminar flow. This value can be in the range between 0.995 and 0.999. The default
value is 0.999.
Reference temperature
1-41