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# Single_Vessel

Fluid flow from an open, compliant vessel, driven only by the energy stored inthe compliant vesel wall.

Model number: 0218

 Run JSim model Applet: JSim Tutorial

## Description

```This model simulates current flow generated from the discharging
of a charged capacitor through a resistance element. It is
analogous in the fluid flow context to applying a pressure across
an open, compliant vessel that contains a volume of fluid and
then letting the fluid drain out driven only by the energy
stored in the compliant vessel wall. For example, a balloon is
filled with water with its outlet held closed which generates an
internal pressure, P. At a time, t=0, the outlet is allowed to open
and the time course for the balloon outflow can be recorded as a
function of time.

The simplest description of an elastic vessel under the influence
of time-varying pressure must have a resistance and compliance
element such as in this model. Here the simulation begins with
a given volume of fluid in the vessel and at time t=0 the outlet
of the vessel is opened and the compliant vessel drains. The flow,
F is a function of the difference in the current volume and the
volume at rest of the vessel as well as the compliance, C, of the
vessel and the resistance, R, to flow out of the vessel. The
change in vessel volume as a function of time is equal to the
flow out of the vessel, -F. External
pressure is assumed to be zero.

The model uses a constant compliance to create a linear
relationship between pressure and volume. In reality the
pressure-volume curves of flexible tubes are non-linear and
transmural pressure trends towards negative infinity as volume
goes to zero. However, there are linear portions of the P-V
curve which can be approximated using a constant compliance or
elastance value. A constant resistance that is independent of
vessel geometry is also used in this model. For laminar flow
through a cylindrical tube, resistance is dependent on fluid
viscosity, tube length and tube radius (Poiseiulle's Law);
however, resistance in this model remains independent of these
properties.

----------------------------------------------------------

REFERENCE EQUATIONS:
Eq. A)  Flow (mL/unit time) = change in volume / change in time
Basis: Definition of flow
Eq. B)  Compliance = Change in volume / Change in transmural pressure
Basis: Fluid analog of capacitance
Eq. C)  Pressure drop = Resistance * Flow
Basis: Fluid analog of Ohm's Law
Eq. D)  (Sum of flows entering junction = sum of flows leaving junction)
Basis: Kirchhoff Junction rule
Eq. E)  Pressure drop = (change in Flow/change in time)*Inertance
Basis: Fluid analog of inductance
---------------------------------------------------------

```

## Equations

The equations for this model may be viewed by running the JSIm model applet and clicking on the Source tab at the bottom left of JSim's Run Time graphical user interface. The equations are written in JSim's Mathematical Modeling Language (MML). See the Introduction to MML and the MML Reference Manual. Additional documentation for MML can be found by using the search option at the Physiome home page.

## References

Ohm GS. Die galvanische Kette, mathematisch bearbeitet, 1827

## Key Terms

Cardiovascular system, single, vessel, compliant wall, flow, Poiseiulle's Law, Hemodynamics