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FSI-Example: Artery
Flow/ Oscillometric Blood pressure measurement
Often FSI
problems are transient and in many cases a rather complex interaction of
underlying physics occurs. A typical situation where these complex interactions
take place is the blood flow in arteries. Here, the pulse wave velocity plays an
important role not only as a medical indicator (e.g. for early detections of
vascular diseases), the pulse wave velocity also effects the physics of the flow
motion essentially. In rigid tubes with undeformable walls the wave speed is
given by the compressibility of the fluid and therefore a physical property of
the fluid only. Liquids like water behave almost incompressible and the
wavespeed reaches approximately 1300 m/s in the case of water.
The artery wall
is relatively soft, so the stiffness of the system is not given by the
compressibility of the fluid but by the stiffness of the deformable wall: In
this case the pulse wave velocity is significantly reduced to 4-10 m/s,
depending of local properties of the artery wall.
In numerical FSI
analysis, special solving methods have to be used for problems like this.
In the first
step of the simulation the pulse wave velocity (PWV) is verified in a three
dimensional model. In the second step the oscillometric blood pressure
measurement is discussed: An external pressure cuff causes high deformations of
the vessel. The pressure wave induces different oscillations used in conjunction
with the actual cuff pressure to estimate the blood pressure.
Details see:
Heck U. "Transient Fluid Structure Interaction", Nafems Seminar "Simulation of
Coupled Flow phenomena (Multified FSI)" May 2006, Conference Procedures, ISBN
1-874376-11-5 |
