TRACING CHEMICAL PLUMES IN TURBULENT WATERS

1
TRACING CHEMICAL PLUMES IN TURBULENT WATERS

• Jiri Janata, Hiroshi Ishida, Timo Kikas
• School of Chemistry and Biochemistry
• Georgia Institute of Technology
• Atlanta, GA 30332-0400, USA

ACKNOWLEDGMENTS GEORGIA INST. OF TECHNOLOGY D.
WEBSTER TOKYO INST. OF TECHNOLOGY T.
MORIIZUMI FUNDING (1998-2000) DARPA
Project Number N00014-98-1-077
2
How to make the best use of signals from sensor
array?
Outline Where is the information in the
plume? Data acquisition Correlation
analysis - theory - bandwidth - experiments
Conclusions
3
0.7 mm cylinder 2.54 cm downstream from the
nozzle f (St).U/d 1.2 Hz
4
Simulated Microelectrode Sensor Array
50 cm from the source on the centerline. Spacing
between sensors is 1 cm.
ARRAY CAN DETECT FLOW VELOCITY
5
WHERE IS THE OTHER INFORMATION?

• TIME-VARYING SIGNAL HAS TWO PARTS, THE MEAN VALUE
  AND THE FLUCTUATING PART
• S (t) S s (t)
• HYPOTHESIS THE INFORMATION IS IN THE FLUCTUATING
  PART OF THE SIGNAL

6
VIRTUAL PLUME SET-UP
7
CORRELATION ANALYSIS
Time series of channel 1
Time series of channel 2
Auto-power spectrum density of channel 1
Auto-power spectrum density of channel 2
Cross-power spectrum density of channels 1 and 2
Coherence spectrum
8
FREQUENCY CONTENT OF THE PLUME
9
FLUIDIC BANDWITH
10
TWO-FREQUENCY MODULATION
11
COHERENCE PEAK ASSIGNMENTS
12
(No Transcript)
13
AQUATIC ANIMALS---
Do they use the frequency mode of information
acquisition?
14
Conclusions
Information about source location appears to
be frequency encoded in 0 5Hz bandwidth
Coherence was found to be sensitive to -
Orientation of the sensor array, - Spacing
between the sensors. - Edge of the plume. -
Distance from the source Coherence in
frequency-modulated plume shows peak at the
modulation frequency given by the size and shape
of the source Coherence is not sensitive to
flow or dilution, Encoding in multiple
frequencies is possible Blue crabs are very
smart!
15
Thank You!