towards an understanding of form drag at three tree...
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Towards an understanding of form drag at Three Tree Point
Sally Warner, Parker MacCreadyUniversity of Washington
Jim Moum, Jonathan Nash, Uwe StöberOregon State University
September 22, 2010 IMSPO, Seattle, WA
Form drag and mixing
U0
Form dragpressure
large form drag
small form drag
blunt body
streamlined body
Form drag and mixing
U0
Form dragpressure
Tidalenergyconversion
Form drag causes:
- internal wave generation
- eddy generation
- local mixing and dissipation
Motivation for this study
Seattle
Tacoma
Edwards et al., 2004
Puget Sound, WA
PointThree Tree
Previous work
McCabe et al., 2006
> Measured the internal form drag
> Measured the external form drag
Our goal> Measure the total form drag with bottom pressure sensors
Cruise at TTP in Dec. 2009
Seattle
Tacoma
Puget Sound, WA
PointThree Tree
Pressure sensors (PPODs) at Three Tree Point (TTP)
PPODs
-200 -100 0 100 [m]
-122.41 -122.39 -122.37 -122.35
47.48
47.47
47.46
47.45
47.44
47.43
47.42
PPOD pressure signalsRaw PPOD data [psi]
12/03 12/04 12/05 12/06 12/07 12/08 12/09 12/1050
100
150
200
250
300
350
GMT 2009
psi
TTP01TTPANTTP02TTP03TTP04TTP05TTP06TTP07TTP08TTPASTTP09TTPHS
-200 -100 0 100 [m]
-122.41 -122.39 -122.37 -122.35
47.48
47.47
47.46
47.45
47.44
47.43
47.42
350
300
250
200
150
100
12/03 12/05 12/07 12/09
12/03 12/04 12/05 12/06 12/07 12/08 12/09 12/10−0.05
−0.04
−0.03
−0.02
−0.01
0
0.01
0.02
0.03
0.04
0.05
GMT 2009
m
Residual pressure signalOffset plot of pressure [m of SSH]
-200 -100 0 100 [m]
-122.41 -122.39 -122.37 -122.35
47.48
47.47
47.46
47.45
47.44
47.43
47.42
12/03 12/05 12/07 12/09
0.05
0.04
0.03
0.02
0.01
0
-0.01
-0.02
-0.03
-0.04
-0.05
−2
−1
0
1
2
N/m
12/05 12/06 12/07 12/08 12/09 12/10−500
0500
100015002000
GMT 2009
W/m
Residual dragResidual pressures
Residual form drag and wave drag
}
W/m
N/m
x 104
}
}1 cmof SSH
N
S
Tidal conversion rate per unit width
−250
−200
−150
−100
−50
m
−3000 −2000 −1000 0 1000 2000 3000−0.4
−0.2
0
0.2
0.4
m/m
meters from tip of TTP
topographicheight
topographicslope
N
N
S
S
}}
}
Running mean: ~300 W/m times width: ~0.7 MW
ROMS model of TTP
http://faculty.washington.edu/dsuth/MoSSea/
Modeling the Salish SeaDavid Sutherland
Domain for TTP model
ROMS model of TTPsurface vorticity [1/s]
TTP
Bottom pressure sensors can be used to measure form drag on topography in the ocean.
A numerical model will help to quantify the total form drag and understand the physical processes that play a role in energy conversion at Three Tree Point.
Conclusions / future work>
>
Thank you
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