Reservoir (IL)

R2026b

Isothermal liquid reservoir at constant or time-varying pressure

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Reservoir (IL) block

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Libraries:
Simscape / Foundation Library / Isothermal Liquid / Elements

Description

The Reservoir (IL) block represents an infinite reservoir of isothermal liquid. Use this block to set the boundary condition in an isothermal liquid network. The liquid in the reservoir can be at a constant pressure, either atmospheric or specified by a block parameter. You can also control the pressure inside the reservoir by using the physical signal input port P. Port A, an isothermal liquid conserving port, represents the reservoir inlet.

The block icon changes depending on the values of the Provide input signal for pressure and Pressure specification parameters.

Reservoir Type	Pressure Specification	Block Icon
Constant — Provide input signal for pressure is off	Atmospheric pressure
	Specified pressure
Controlled — Provide input signal for pressure is on

Assumptions and Limitations

• The volume of liquid inside the reservoir is assumed infinite. Therefore, the flow is assumed quasi-steady.

• There is no flow resistance between port A and the reservoir interior.

Examples

Hydraulic Actuator with Analog Position Controller

How the Foundation library can be used to model systems that span electrical, mechanical and isothermal liquid domains. In the model, a hydraulic system implemented in the isothermal liquid domain controls the mechanical load position in response to a voltage reference demand. If the reference demand is zero, then the hydraulic actuator (and load) displacement is zero, and if the reference is +5 volts, then the displacement is 100 mm.

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Ports

Input

P — Pressure control signal, Pa

physical signal

Physical signal port that provides the reservoir pressure control signal. The signal saturates when its value drops below the minimum valid pressure specified by the Isothermal Liquid Properties (IL) block connected to the circuit.

Dependencies

To enable this port, select Provide input signal for pressure.

Programmatic Use

Port: P

Conserving

A — Reservoir inlet

isothermal liquid

Isothermal liquid conserving port associated with the reservoir inlet.

Programmatic Use

Port: A

Parameters

Provide input signal for pressure — Method to specify pressure

off (default) | on

Method to use to specify the pressure in the reservoir. If you clear this check box, the block models pressure based on the value of the Reservoir pressure parameter or atmospheric pressure. The reservoir pressure remains constant during simulation. If you select this check box, the block models pressure based on the value of the signal at port P, which can vary during simulation.

Programmatic Use

Parameter:	pressure_input
Values:	"true" | "false"

Pressure specification — Specification method for constant reservoir pressure

Atmospheric pressure (default) | Specified pressure

Specification method for the reservoir pressure:

• Atmospheric pressure — Use the atmospheric pressure specified by the Isothermal Liquid Properties (IL) block connected to the circuit.

• Specified pressure — Specify a value by using the Reservoir pressure parameter.

Dependencies

To enable this parameter, clear the Provide input signal for pressure check box.

Programmatic Use

Parameter:	pressure_spec
Values:	"foundation.enum.pressure_spec.atmospheric" | "foundation.enum.pressure_spec.specified"

Reservoir pressure — Pressure in reservoir

0.101325 MPa (default) | positive scalar

Desired pressure in the reservoir. This pressure remains constant during simulation. The specified pressure cannot be greater than the atmospheric pressure specified by the Isothermal Liquid Properties (IL) block connected to the circuit.

Dependencies

To enable this parameter, clear the Provide input signal for pressure check box and set Pressure specification to Specified pressure.

Programmatic Use

Parameter: reservoir_pressure

Programmatic Use: Add Block

To add the block programmatically, use the add_block function with one of these library block paths as the source.

"fl_lib/Isothermal Liquid/Elements/Reservoir (IL)"

Example: add_block("fl_lib/Isothermal Liquid/Elements/Reservoir (IL)","myModel/myBlock",MakeNameUnique="on")

For information about programmatic access to individual block parameters, see the Programmatic Use section of parameter descriptions on this page.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Version History

Introduced in R2020a

R2026b: Shortened parameter name

To improve consistency with other fluid domains, the Reservoir pressure specification parameter name has been shortened to Pressure specification. This change has no effect on block functionality.

R2026a: Use consistent options for reservoirs across fluid domains

To improve consistency with other fluid domains, the Reservoir type parameter, with values Constant or Controlled, has been replaced with the Provide input signal for pressure check box and the block icon for the controlled reservoir updated. The block functionality is unchanged.