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Rotational Mechanical Converter (TL)

Interface between liquid and rotational mechanical subsystems


Thermal Liquid/Elements


The Rotational Mechanical Converter (TL) block represents the liquid side of a rotational mechanical interface. This interface converts liquid pressure into torque and vice versa. The output torque acts in a single direction, set using a Mechanical orientation parameter.

The rotational mechanical interface contains no hard stops. To include hard stops, use the Simscape™ Rotational Hard Stop block. A model of a rotational hydraulic actuator, for example, requires both blocks.

Port A is a thermal liquid conserving port corresponding to the converter inlet. Liquid pressure in the converter equals that at port A. Port Q is a thermal conserving port for modeling heat exchange between the converter liquid and the converter housing. Liquid temperature in the converter equals that at port Q.

The block models the dynamic evolution of temperature in the converter. The block can also model dynamic compressibility effects in the liquid. The following equations govern the dynamic behavior of liquid at the interface:


DConverter displacement
εMechanical orientation (1 for Positive, -1 for Negative)
τTorque the liquid exerts on the converter interface
VLiquid volume in the converter
vALiquid velocity into the converter at port A
ΩinterfaceInterface angular velocity (positive for converter expansion, negative for converter contraction)
pintLiquid pressure in the converter
TintLiquid temperature in the converter
Mass flow rate into the converter at port A
βintLiquid bulk modulus in the converter
αintLiquid coefficient of expansion in the converter
uintLiquid internal energy in the converter
ρintLiquid density in the converter
ϕA, ϕQThermal fluxes into the converter at ports A and Q

To view the block source code, at the MATLAB® command line enter:

edit <matlabroot>\toolbox\physmod\simscape\library\m\

Replace <matlabroot> with the output of the matlabroot command, and <converter> with the compressibility configuration mode:

  • rotational_converter_dynamic_compressibility for the code corresponding to fluid dynamic compressibility ‘On'

  • rotational_converter_steady_compressibility for the code corresponding to fluid dynamic compressibility ‘Off'

Assumptions and Limitations

  • Converter walls are not compliant. They cannot deform regardless of internal pressure and temperature.

  • The converter contains no mechanical hard stop.

Dialog Box and Parameters

Mechanical orientation

Select the relative orientation of the converter with respect to the thermal liquid system. The relative orientation determines the rotation direction associated with positive flow into the converter. That direction is positive if the mechanical orientation of the converter is positive. It is negative if the mechanical orientation of the converter is negative. The default setting is Positive.


Enter the displaced liquid volume corresponding to a unit rotation angle of the spinning converter interface. The default value is 1.2e-4 m^3/rad.

Initial angle

Enter the rotation angle between the spinning converter interface and the clamping structure at time zero. The default value is 0 rad.

Dead volume

Enter the liquid volume remaining in the converter at a zero rotation angle. The default value is 1e-5 m^3.

Fluid initial temperature

Enter the liquid temperature in the converter at time zero. The default value is 293.15 K.

Fluid dynamic compressibility

Select whether to include the effect of fluid dynamic compressibility on the transient response of the converter model. Selecting On exposes an additional parameter. The default setting is Off.

Fluid initial pressure

Enter the liquid pressure in the converter at time zero. This parameter is visible only if Fluid dynamic compressibility is On. The default value is 1 atm.


This block has four ports.

AThermal liquid conserving port
QThermal conserving port
RRotational mechanical conserving port associated with the moving interface
CRotational mechanical conserving port associated with the converter casing

See Also

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