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Sungwon Shin

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02/2001: Surf zone void fraction & turbulence ... Laboratory Measurements of Void Fraction and Turbulence in the Bore Region of Surf Zone Waves. ... – PowerPoint PPT presentation

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Title: Sungwon Shin


1
Doctoral Preliminary Exam
  • Sungwon Shin
  • June 8th, 2004

2
Education Experience
  • BS Hanyang Univ., Korea, 1993. Oceanography
    (graduate cum laude)
  • MS Hanyang Univ., Korea, 1995. Physical
    Oceanography (Underwater Acoustics)
  • Navy officer, full time lecturer, department
    head of Oceanography at Korean Naval Academy,
    Korea, 1995-98
  • Ph.D. Texas AM Univ., 2000-02. Civil
    Engineering (Coastal Ocean Engr.)
  • Ph.D. Oregon State Univ., 2002-present. Civil
    Engineering (Coastal Ocean Engr.)

3
Course Work
4
Research Progress
  • Surf zone void fraction turbulence (2001-02)
  • Estimates of surf zone turbulence (2003)
  • Pile-supported breakwater project (2003)
  • Swash zone hydrodynamics (dissertation) (2003-05)

5
Research Time Line
  • 01/2000 Start of Ph.D. program TAMU
  • 11/2000 Doctoral qualifying exam (written
    oral)
  • 02/2001 Surf zone void fraction turbulence
  • 12/2001 Surf zone void fraction turbulence
    paper submitted
  • 01/2002 Data analysis of swash zone hydrodynamics
  • 08/2002 Transfer to OSU
  • 05/2003 Doctoral program meeting
  • 07/2003 Estimates of surf zone turbulence
  • 09/2003 Pile-supported breakwater project
  • 02/2004 Pile-supported breakwater papers
    submitted (2)
  • 03/2004 Numerical modeling of swash zone
  • 03/2005 Expected date of graduation

6
1. Surf Zone Void Fraction Turbulence Brown
bag seminar (03/2004)
  • Objective
  • Understand air entrainment and turbulence by wave
    breaking in the surf zone
  • Measurements
  • u (LDV), ? (wave gage), air bubbles (VFM)
  • First simultaneous meas.above trough level
  • Analysis
  • su2, no. of drop-outs by bubbles, void fraction

Experimental setup (TAMU, 2001)
7
1. Surf Zone Void Fraction Turbulence Brown
bag seminar (03/2004)
  • Conclusions
  • Horizontal turbulent intensity increases rapidly
    above TL
  • Peak ensemble-averaged void fraction ranges from
    15 to 20.
  • Turbulent intensity void fraction higher for
    spilling breakers than for plunging above TL
  • Possible future work
  • Transition region
  • Large-scale
  • Measure bubble velocity
  • Publication
  • Cox, D.T., and Shin, S. (2003). "Laboratory
    Measurements of Void Fraction and Turbulence in
    the Bore Region of Surf Zone Waves.'' J.
    Engineering Mechanics, 129(10), p 1197-1205.

8
2. Estimates of Surf Zone Turbulence C. Scott,
D. Cox, S. Shin, and N. Clayton
  • Objectives
  • Compare four methods to separate turbulent and
    wave-induced motions
  • Quantify scaling effects between small- and
    large-scale laboratory experiments on wave
    breaking turbulence
  • Compare average turbulence levels for regular and
    irregular waves
  • Contribution
  • Experimental setup and data collection
  • ICCE 04 Abstract (accepted)
  • Scott, C.P., Cox, D.T., Shin, S., and Clayton, N.
    (2004). Estimates of Surf Zone Turbulence in a
    Large-Scale Laboratory Flume. Submitted to Proc.
    29th Int. Conf. on Coast. Engrg.

9
3. Pile-Supported Breakwater Project PI K.D.
Suh. Seoul National Univ.
  • Objectives
  • Test effectiveness of pile-supported breakwater
  • Validate numerical model with experimental results
  • Publications
  • Suh, K.D., Shin, S., and Cox, D.T. "Hydrodynamic
    Characteristics of Pile-Supported Vertical Wall
    Breakwaters. 1. Regular Waves." JWPCOE,
    (Submitted 02/04).
  • Suh, K.D., Shin, S., and Cox, D.T. "Hydrodynamic
    Characteristics of Pile-Supported Vertical Wall
    Breakwaters. 2. Irregular Waves." JWPCOE,
    (Submitted 02/04).

10
3. Pile-Supported Breakwater Project PI K.D.
Suh. Seoul National Univ.
  • Measurements (Shin)
  • Regular and random wave cases
  • Incident, reflected and transmitted waves
  • Wave runup on the structure
  • Force on the structure
  • Velocity behind the piles
  • Numerical simulation
  • Eigenfunction expansion method (Suh)
  • Model run and comparison (Shin)

11
4. Swash Zone Hydrodynamics Dissertation Topic
  • Objectives
  • Obtain complete data set of swash zone
    measurements
  • Extract turbulent quantities
  • Validate numerical models in swash zone
  • Experiment
  • A. Sukumaran (2000, TAMU)
  • Turbulence analysis
  • Transport Eq. for TKE
  • Bottom stress using law of wall
  • Model comparisons

12
Details of Swash Zone Hydrodynamics
13
Research Objective
  • What is the relative importance of wave breaking
    turbulence and bottom boundary layer turbulence?

Region IV Swash Zone
Region I Wave Shoaling
Region III Inner Surf Zone
Region II Wave Breaking
High turbulence above trough Weaker
interaction with bottom
Wave height envelope
?
Strong turbulence by wave breaking invades
boundary layer Air entrainment
14
Phase dependence
t/T p
t/T p/2
Maximum runup
Bore-generated turbulence dominant
t/T 3p/2
t/T 2p
Interaction of rundown with next wave
BBL-generated turbulence dominant
15
Swash Hydrodynamics Literature Review
16
(40 references and still adding)
17
Swash Hydrodynamics Literature Review
  • Field measurements
  • Holland et al (2001) PIV, Horizontal velocity
    fields
  • Puleo et al (2000) SSC is high in uprush and low
    in downrush
  • Raubeheimer et al (2002) Infragravity wave
    contributes to velocity variance and
    asymmetry (observation and prediction)
  • Lab. Experiments
  • Cowen, Sou, Liu, et al (2003) PIV (very small
    scale, no bubbles)
  • Petti and Longo (2001) LDV, u-component only
  • Bore-generated turbulence is dominant in uprush
  • Bottom stress-generated turbulence is dominant
    in downrush

18
Swash Hydrodynamics Literature Review
  • Numerical modeling
  • Kobayashi and Poff (1994) RBREAK2 (NLSWE Lab
    and field)
  • Wei, Kirby et al (1995) FUNWAVE (Boussinesq
    Surf zone)
  • Lin and Liu (1998) and Bradford (2000) RANS
    model (Surf zone)
  • Christensen (1990, 2001) LES model (Surf zone)

Emerat and Christensen (2000), Proc. ICCE
19
Swash Zone Hydrodynamics Approach
  • Laboratory data analysis
  • Analyze 2-D velocity measurement from BBL to
    crest
  • Separate turbulent velocity from organized motion
  • Calculate TKE, Reynolds stress, friction
    velocity, and friction factor
  • Estimate energy dissipation due to wave breaking
    and friction
  • Numerical modeling
  • RBREAK2, FUNWAVE, COBRAS, YNU (LES)
  • Compare hydrodynamic quantities from data with
    numerical results
  • Quantify each models performance in the swash
    zone

20
Experimental Setup A. Sukumaran (TAMU M.Sc.,
2000)
  • Regular Wave Case (T 2s), Plunging Breaker
  • D50 2.0 mm (Fixed)
  • Composite slope 135 110
  • Glass-walled wave flume 35 m long, 0.90 m wide,
    1.2 m high

21
Data Analysis
  • Procedure
  • Data acquisition
  • Separate from u (ensemble average)
  • Data analysis
  • TKE from wave breaking
  • Bottom friction in boundary layer

Turbulence intensity
Shear velocity
22
Wave Breaking TKE(Approximate local equilibrium)
  • Transport equation of turbulent kinetic energy
    (ASCE,1988)

23
Wave Breaking TKE(Approximate local equilibrium)
  • Dimensionless variables (Cox et al, 1994)

(s ratio between the horizontal and vertical
length scale)
Local equilibrium
Local equilibrium
24
Calibration of Cd Cl
into
Substitute
Estimate Cl
(By least square method using
)
25
Estimation DB
DB Energy dissipation due to wave breaking
Cox et al, 1994
26
TKE in the Surf Zone
Dissipation
Production
Cox et al., ICCE 1994
27
TKE in the Swash
Old
New
Dissipation
Production
k (su2sw2) / 2
suw
Almost nothing reported in literature
Using Cl
Du / Dz
28
Boundary Layer Processes(Bottom Friction)
  • Logarithmic velocity for a rough bottom (Yaglom,
    1979)
  • Bottom Stress (Cox et al, 1996)

(Grant and Madsen, 1979)
  • Energy dissipation due to bottom friction

29
Bottom Shear Stress
30
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32
Experimental Analysis Summary
  • Whats been done?
  • Separate u, w and compute TKE, su2, and suw
  • Estimate bottom friction factor and its energy
    dissipation
  • Whats left to do?
  • Estimate Cl Cd
  • Estimate dissipation due to wave breaking

33
Numerical Comparison
  • Motivation
  • Varying degrees of wave model complexity
  • Most numerical models are focused on surf zone
  • Very few models validated in swash zone
  • Energy dissipation is uncertain
  • Skewness/Asymmetry
  • Bottom boundary layer dynamics
  • Sediment transport in swash will depend on these
    details.

34
Numerical models for comparison
35
Model Output and Data Availability
36
RBREAK2
  • Kobayasi Poff, 1994
  • Nonlinear shallow water equation (NLSWE)
  • 1-D depth averaged time domain model
  • Hrms, ?, and setup were compared with the swash
    data from SUPERTANK Lab. Data Collection Project
    (1992)
  • Estimates energy dissipation due to wave breaking
    and bottom friction

37
RBREAK2 vs Swash Data
? Exp. Data x RBREAK2
38
RBREAK2 Preliminary Results
? Exp. Data - RBREAK2
39
FUNWAVE
  • Kirby, Wei, Chen, et al (1998)
  • Fully nonlinear Boussinesq equation
  • Eddy viscosity type wave breaking (through the
    momentum correction surface roller model)
  • Bottom friction by quadratic law (law of the wall)

Run of Demo Case
40
COBRAS
  • Lin Liu (1998)
  • Reynolds averaged Navier-Stokes equation
  • k-e model for turbulence
  • VOF method (Hirt Nichols, 1981) for free surface

Lin and Liu (1998), J. Fluid Mechanics
41
COBRAS Preliminary Result
? COBRAS x Exp. data
42
COBRAS Preliminary Result
- COBRAS x Exp. data
43
YNU (LES)
  • Okayasu (Yokohama National Univ.)
  • Large eddy simulation
  • Subgrid scale model (SGS model) for smaller scale
    turbulence
  • Density function method for free surface

Example of LES from Christensen (2001), Coastal
Engrg.
44
YNU (LES) Preliminary Results
Three waves takes approximately 6 hrs on 2 GHz PC.
45
Numerical Comparison Summary
  • Whats been done?
  • Preliminary runs for all models
  • Calculated dissipation due to bottom friction
    (RBREAK2)
  • Calculated free surface and instantaneous
    velocity (YNU)
  • Whats left to do?
  • Run models for experimental conditions
  • Quantify each models performance in the swash
    zone

46
Dissemination of Results
  • Journal Paper 1
  • Data analysis and comparison of wave breaking and
    bottom friction
  • To be submitted to J.Marine Geology. (Special
    issue on swash dynamics J. Puleo, Ed.)
  • Journal Paper 2
  • Comparison of numerical models
  • To be submitted to Coastal Engineering
  • Conference Presentation
  • AGU Fall meeting SF, 2004

47
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