Laboratory experiment and numerical verification in Surf and Swash Zone

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Laboratory experiment and numerical verification
in Surf and Swash Zone

• March 12, 2004
• Sungwon Shin

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Contents

• Introduction
• Basic Theory
• Experimental Conditions
• RBREAK2
• Comparison between data and model results
• Discussion and Future Works

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Wave Breaking Phenomena
Plunging Breaker, T 3 sec
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Basic Theory

• Logarithmic velocity for a rough bottom (Yaglom,
  1979)
• Bottom Stress (Cox et al, 1996)

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Experimental Conditions

• By Ashok Sukumaran (2000) in Texas AM
• Regular Wave Case (T 2s)
• D50 2.0 mm
• Beach slope 110, Plunging Breaker
• Water surface elevation and water particle
  velocity were measured by wave gage and LDV
• 35 m long by 0.90 m wide by 1.2 m high
  glass-walled wave flume equipped with a flap-type
  wave maker

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a
e
i
(cm)
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f at a 0.0085
f 0.004 0.012
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f at e 0.0069
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RBREAK2

• R(egg in Korean) BREAK 2 parts of egg
• By Kobayashi and Poff (1994)
• Modified one-dimensional time-domain model
• Depth-integrated equations for mass and
  x-momentum
• Finite difference scheme
• Spatial variation of bottom friction is available
• Can predict free surface oscillations in the surf
  and swash zones, energy dissipation due to wave
  breaking and bottom friction

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Compare data with model results

• Time series of free surface oscillation and
  horizontal velocity, and spectra.
• Cross-shore variation of mean water level
  considering setup (set down), wave height, energy
  dissipation rate due to wave breaking and bottom
  friction, and time-averaged horizontal velocity

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Wave Breaking
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Discussion

• Good agreement about most of wave characteristic
  quantities
• Lower frequency oscillation of model is somehow
  exaggerated in bore region compare to
  experimental data
• Difficulties to measure velocities (especially
  free stream velocity) and estimate friction
  factor in swash zone
• Will estimate energy dissipation due to wave
  breaking in the future

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2
1
0
-1
-2
0.5
1.0
1.5
0