Transcript Cavitation in Biophysics

Introduction to Cavitation
Why Study Cavitation?
 Has been an important topic in engineering
science for well over 100 years. Any device
handling liquids is subject to cavitation.
 Can adversely affect the performance of
turbomachinery, the thrust of propulsion
systems and the accuracy of fluid meters.
 Noise, vibration and erosion occur in many
applications
Why Study Cavitation?
 Important in applications such as ultrasonic
cleaning, homogenization of milk, enhanced
chemical processes through coagulation,
formation of suspensions and degassing of
liquids.
 Cavitation can be used to increase heat and
mass transfer in liquids, to promote
crystallization and to enhance various
sonochemical reactions such as
polymerization and polymer degradation.
Why Study Cavitation?
 Biomedical applications include the
removal of kidney stones and
automated drug delivery to patients.
 Important new applications in the
pollution control area are of interest.
 Plays a role in biomechanics,
geomorphology and other topics in
physics.
Cavitation in Biophysics
From SCIENCE VOL 289 22 SEPTEMBER 2000
Spillway Damage Due to a
Horseshoe Vortex
Vortex Damage in a
Hydroturbine
Geomorphology
See Movie
Cavitation Can Occur in the Flow or
Adjacent to a Boundary
On the surface of a Hydrofoil
Jet Flow
Fundamentals

The fundamental parameter in describing the physics
of the process is the cavitation index, defined by
po  pv

1
U 2
2

We can think of i as a performance boundary such
that
 > i no cavitation effects
 < i cavitation effects such as performance
degradation, noise, and vibration
Water Tunnels
SAFL Water Tunnel
0.19m X 0.19 m Test Section
1 Story High
US Navy Large Cavitation Channel
3m X 3mTest Section
10 Stories High
Propeller Cavitation
Japan
The Netherlands
PIV Imaging, Italy
Comparison of measurements
with numerical simulations,USA
Tip Vortex Cavitation
Wind tunnel and water tunnel simulations are used to study this
problem experimentally. Experiments are supplemented with numerical
simulations. Example shown is a NACA 662-415 section with elliptic
planform.
Wind tunnel
Water tunnel
Observation of Singing Vortex
Slow Motion, 4500 fps
Pressure Slowly Decreasing
Supercavitating Vehicles
A joint venture between SAFL
and AEM
AEM: Stability and Control
SAFL: Physics of Ventilated
Flows
Sponsored by ONR
Ventilated Flow StudiesSupercavitation
The Future
We are always
looking for new applications
For Further Information:
http://www.safl.umn.edu