introduction to cavitation. why study cavitation? has been an important topic in engineering...
TRANSCRIPT
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 BiophysicsFrom 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
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
2
vo
U2
1pp
Water Tunnels
US Navy Large Cavitation Channel3m X 3mTest Section
10 Stories High
SAFL Water Tunnel0.19m X 0.19 m Test Section
1 Story High
Propeller Cavitation
Japan
PIV Imaging, Italy
The NetherlandsComparison of measurementswith numerical simulations,USA
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
Tip Vortex Cavitation
Observation of Singing Vortex
Pressure Slowly Decreasing
Slow Motion, 4500 fps
Supercavitating Vehicles
A joint venture between SAFLand AEM
AEM: Stability and ControlSAFL: Physics of Ventilated Flows
Sponsored by ONR
Ventilated Flow Studies-Supercavitation
The FutureWe are always
looking for new applications
For Further Information: http://www.safl.umn.edu