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Jet Pump

(To be removed) Jet liquid-liquid pump

The Hydraulics (Isothermal) library will be removed in a future release. Use the Isothermal Liquid library instead. (since R2020a)

For more information on updating your models, see Upgrading Hydraulic Models to Use Isothermal Liquid Blocks.

  • Jet Pump block

Simscape / Fluids / Hydraulics (Isothermal) / Pumps and Motors


The Jet Pump block represents a jet liquid-liquid pump consisting of a nozzle, throat, and diffuser, as shown in this illustration.

Jet Pump schematic diagram

The model is based on these equations, described in [1]:







q1Primary flow rate pumped through the nozzle
q2Secondary flow rate
qdOutput flow rate
p1Pressure at the nozzle inlet
p2Pressure at the secondary flow rate inlet
p0Pressure at the throat inlet
pdPressure at the pump outlet
AnNozzle area
AthThroat area
aDiffuser area ratio, Ath / Ad
AdDiffuser outlet area
KnNozzle hydraulic loss coefficient
KenThroat entry hydraulic loss coefficient
KthThroat hydraulic loss coefficient
KdiDiffuser hydraulic loss coefficient
ρFluid density

Equation 1 describes the nozzle, Equation 2 describes the throat entry, and Equation 3 describes the combination of the throat and the diffuser. The equations correspond to a standard configuration of the pump, where all the longitudinal dimensions conform to established, empirically determined values. For more details, see [1].

The pump parameters are closely related to each other, and the methodology described in [1] is recommended to determine their initial values.


To set the priority and initial target values for the block variables prior to simulation, use the Initial Targets section in the block dialog box or Property Inspector. For more information, see Set Priority and Initial Target for Block Variables.

Nominal values provide a way to specify the expected magnitude of a variable in a model. Using system scaling based on nominal values increases the simulation robustness. Nominal values can come from different sources, one of which is the Nominal Values section in the block dialog box or Property Inspector. For more information, see Modify Nominal Values for a Block Variable.

Assumptions and Limitations

  • The model is based on the one-dimensional theory.

  • The primary and secondary flows enter the mixing throat with uniform velocity distribution, and the mixed flow leaves the diffuser with uniform velocity distribution.

  • The fluid in the primary and secondary flows is the same.

  • The fluid is assumed to be incompressible and containing no gas.



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Hydraulic conserving port associated with the nozzle entry. The nozzle is the primary flow entry.

Hydraulic conserving port associated with the pump suction. The pump suction is the secondary flow entry.

Hydraulic conserving port associated with the pump outlet.

Internal hydraulic conserving port associated with the throat entry section of the pump. This port is not visible on the block icon. You can view the variables associated with the port by logging the simulation data. For more information, see Data Logging.


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Cross-sectional area of the nozzle.

Cross-sectional area of the throat. The throat area is usually two to four times larger than the nozzle area.

Ratio between the inlet and outlet diffuser areas. For a standard pump with a 5°–7° included-angle diffuser, the ratio is close to 0.2.

Hydraulic friction loss coefficient in the nozzle.

Hydraulic friction loss coefficient in the throat entry.

Hydraulic friction loss coefficient in the throat.

Hydraulic friction loss coefficient in the diffuser.


[1] I.J. Karassic, J.P. Messina, P. Cooper, C.C. Heald, Pump Handbook, Fourth edition, McGraw-Hill, NY, 2008

Extended Capabilities

C/C++ Code Generation
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Version History

Introduced in R2010b

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