MapleSim Hydraulics Library from Modelon
Long Line Long line with laminar and turbulent flow
The LongLine component describes the dynamics of a long line with compressibility, inductance and frequency dependent viscosity. This model uses n elements for the line, therefore:
The oil in long lines is compressible, has a mass and a resistance. The model includes frequency dependent friction, compressibility and inductance. The dynamic response of long lines is a function of time and the spatial coordinate (that is, it is described by partial differential equations). For the library a lumped parameter model is used that breaks the whole line into n short elements. LongLine uses entrance and exit elements that have only half the length of the n1 middle elements, leading to an effective element length of 1 / n of the whole line length. The model is adequate if:
Variables used in the above equations

length of the Long Line component


speed of sound in fluid


highest frequency of interest



The steady state flow rate q is positive if oil enters the line at port_A; the pressure drop (port_A.p  port_B.p) is then positive.
The model is valid if the flow is laminar. There is no warning if this condition is not met. The Reynolds number is computed for the entrance and exit elements (in order to reduce the necessary computations).
Related Components
RigidLine

Losses of a rigid line as a function of Reynolds number




Equations




Variables


Name

Value

Units

Description

Modelica ID


[1]


Gas saturation pressure

p_sat


[2]


Local temperature

T


[3]


Density of oil

rho




Pressure at port A

summary_pA




Pressure at port B

summary_pB




Pressure drop

summary_dp




Flow rate flowing into port_A

summary_q


[4]


Hydraulic Power

summary_HP



[1]
[2]
[3]
[4]


Connections


Name

Description

Modelica ID


Layout of port where oil flows into an element (, means )

port_A


Hydraulic port where oil leaves the component (, means )

port_B



oil





Parameters



General Parameters


Name

Default

Units

Description

Modelica ID




Temperature offset from system temperature

dT_system




Total length of line

LineLength




Line diameter

diameter

constant properties



If true, properties are treated as constant over time

constantProperties


[1]


Bulk modulus (for nonelastic line)

beta0


[2]


Density of oil

rho0




Speed of sound in oil (for nonelastic line)

a0


[3]


Kinematic viscosity

nu0




Number of line segments

n

roughness



Roughness of pipe

roughness




Height difference, if positive then portA higher than portB

heightDiff

friction type

[4]


Type of flow model

frictionType

dynamic friction



If true, dynamic friction

dynFriction

steadystate init



If true, initialize in steady state

steadyStateInit



[1]
[2]
[3]
[4]


Constant Parameters


Name

Default

Units

Description

Modelica ID

elastic wall



If true, pipe properties affect speed of sound in oil

elasticWall


[1]


Line crosssection area

A




Length of one segment of line

ElementLength



[1]



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