Transcript Measurements & Instruments

OCEN 201
Introduction to Ocean &
Coastal Engineering
Instruments & Measurements
Jun Zhang
[email protected]
Measurements (Laboratory & Field)
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Laboratory Measurements:
Under well-controlled conditions or environments ,
they are easier to be conducted than the corresponding
Field Measurements.
They are cheaper and more “accurate”.
In view of coastal and ocean engineering, the sizes of
the models used in laboratory measurements are much
smaller than those of their prototypes. Hence, essential
similarity laws must be followed.
It is not likely to follow all essential similarity laws in
model tests, certain assumptions must be made.
Therefore, Laboratory Measurements cannot totally
replace the related Field Measurements.
• Field Measurements
1. They are difficult to be conducted because of
harsh environments (e.g. rough seas and high
wind speed in a hurricane).
2. They are usually very expensive and may not
be accurate.
3. It is necessary to conduct Field Measurements
in order to examine the validity of the
assumptions (such as the neglect of certain
similarity laws) made in the related Laboratory
Measurements.
• Similarity Laws (Chapter 9)
1. Geometric Similarity (model and prototype are
geometrically similar); that is, the corresponding
ratios of their dimensions are the same.
2. Kinematic Similarity
3. Dynamic Similarity. (matching non-dimensional
coeff. between model & prototype)
4. Important non-dimensional coefficients
- Reynolds # (viscous)**
- Froude # (gravity)**
- Euler #
(pressure)*
- Mach #
(compressibility or elasticity)
- Weber #
(surface tension)
Table 10-3 PP354 (old version pp267)
Measurements & Intstruments
1. Survey: water depth & beach contour (Lidar, sonar &
traditional survey instruments)
2. Force or pressure (strain gage, load cell & pressure
transducer)
3. Wave elevation (wave gage*, indirect measurements:
pressure transducer, velocimetry, LDV, ADV & PIV)
4. Velocity (LDV, ADV & PIV, electro-magnetic meter)
5. Accelerations: Accelerometer
Measurements & Intstruments
(continue)
5. Movement or deformation (optical tracking system,
PIV)
6. Wind velocity
7. Temperature
8. Salinity
9. Density
10. Sea Gilder
Wave Gage (Capacity* & Resistance)
Directional Wave Gages
Principles of Strain
Gages
Pressure
Transducers
For the information about LDV & PIV and Their
Applications
see the supplement materials
Facilities for Ocean & Coastal Related Lab M.
1. Wave Basins (Deepwater & Shallow water Basin:
OTRC wave Basin & Hayens Coastal Lab Basin)
-Directional wave generation
- Current generation (Nozzle type)
- Wind generation
2. Wave Flume (1-D wave Basin, CLAB 109,)
- Unidirectional wave generation
- Current generation
- Wind generation
Facilities for Ocean & Coastal Related Lab M.
3. Dredging loop (Hynes coastal lab)
- Current generation
- Towing Carriage
Description
Overview
• AUV / UUV
• Self-regulated
buoyancy
• Propelled by battery
power
• Propelled by ocean’s
thermal energy
• New technology!
History
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Preliminary designs (1986)
Test runs: Florida, New York (1991)
Result: the “Slocum” glider
Scripps / Woods Hole: “Spray”
APL-UW: “Seaglider”
Slocum “Thermal Glider” (2005)
Vehicle Control
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Driving force: lift provided by wings
Pitch/roll: internal weight shift
Onboard computers
Surface GPS fixes
Pressure sensors
Tilt sensors
Magnetic compasses
Slocum, Spray, and Seaglider
Webb Research “Slocum”
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Weight: 52 kg
Diameter: 21.3 cm
Length: 1.5 m
Speed: 40 cm/s
Depth: 4 – 200 m
Endurance: 30 days
Range: 1500 km
Alkaline batteries
Webb Research “Slocum”
Webb’s “Thermal Glider”
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Weight: 60 kg
Diameter: 21.3 cm
Length: 1.5 m
Speed: 40 cm/s
Depth: 4 – 2000 m
Endurance: 5 years!
Range: 40000 km
Environmental power
Webb’s “Thermal Glider”
Scripps/Woods Hole “Spray”
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Weight: 52 kg
Diameter: 20 cm
Length: 2 m
Speed: 25 cm/s
Depth: 1500 m
Endurance: 815 cycles
Range: 4700 km
Lithium cells
Scripps/Woods Hole “Spray”
APL-UW “Seaglider”
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Weight: 52 kg
Diameter: 30 cm
Length: 1.8 m
Speed: 25 cm/s
Depth: 1000 m
Endurance: 650 cycles
Range: 4600 km
Lithium cells
APL-UW “Seaglider”
Design
Early Field Trials
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Wakulla Springs, Florida
Straight flight, dives, turns
Navigation and data relays
Telemetry recorded
Maneuvering parameters
Instabilities found
Test Dive Profile
Design Solutions
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Increase glide speed
Decrease pitch/heading oscillations
Increase stall resistance
Revise autopilot algorithms
Swept wings
Antenna moved to nose
Test Results, Conclusions
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Glide slope ratio similar to Space Shuttle
Energy expended at bottom of dive cycle
Decrease dive cycles = less energy
How do we decrease cycles?
*Lower glide speeds*
Longer endurance
Greater range
Applications
Current Uses
• Slocum: shallow water, short range
• Spray/Seaglider: deeper, longer dives
• Take measurements
-temperature
-conductivity (salinity)
-currents
-chlorophyll fluorescence
-optical backscatter
Current Uses
• Seaglider:
-physical, chemical oceanography
-tactical oceanography
-underwater Reconnaissance
-communications gateway
-navigation aid
Dive Profile
Dive Profile
Spray: La Jolla 2001
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Underwater canyon, 3 km width
11 day mission
Maintained synthetic mooring
Plotted wave, current propagation
Monterey 2003
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10 Slocums and 5 Sprays
Sample 100 square-km area
Use networking to forecast conditions
Example of large-scale team usage
Monterey 2003
Spray: Gulf Stream 2004
• New England to Bermuda
• First crossing of the Gulf Stream
Seaglider: TASWEX-04
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Navy ASW exercise, East China Sea
Battlespace assessment
Tactical remote sensing
Mission successful
Future Uses
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ONR: Liberdade XRay
USN “PLUSNet” program
Largest glider
Hydrodynamic efficiency
Acoustics, electric field sensors
1-3 kt cruise, 1200-1500 km range
Liberdade XRay
Economics