Tsunami Interaction with Nearshore Infrastructure Patrick Lynett

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1 Tsunami Interaction with Nearshore Infrastructure Patrick Lynett Sonny Astani Department of Civil Engineering University of Southern California

2 Tsunami Interaction with Nearshore Infrastructure: Outline Review tsunami generation and propagation modeling, focus on nearshore complexities Present recent observations of nearshore effects, and the motivation to develop simulation tools to predict some of the effects Apply the developed tool to look at the dynamic currents near coastal structures

3 Nature

4 Natur

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7 Nearshore Dynamics of Tsunamis Overarching theme of this research: Increase our understanding of nearshore tsunami evolution, such that we are better able to mitigate their effects and estimate the risk How well do we understand the physics? Is a tsunami like long wave (non-dispersive) or a wind wave (dispersive) Is a tsunami like a river flow (~steady) or like a breaking wind wave (unsteady)??? Well, it depends

8 Nearshore Dynamics of Tsunamis

9 Nearshore Dynamics of Tsunamis

10 Recent Events & Observations 2004 Indian Ocean Tsunami 9.3 Mag EQ ~10 minute rupture 30m+ runup near source 5m+ runup Sri Lanka, India, Thailand 3m+ runup Eastern Africa, Oman, Yemen 230,000 dead 1.7 million displaced

11 Recent Events & Observations East Coast, Sri Lanka

12 Recent Events & Observations

13 Recent Events & Observations Port Salalah, Oman 285-m container ship Maersk Mandraki From Okal et al., 2006 Broke moorings, was pulled out of the Port by a large eddy Drifted around the breakwater, nearly impacted the breakwater on the ocean side Drifted back across entrance, to the other side of the terminal, beached on a sand bar

14 Motivation: Recent Events & Observations Port Salalah, Oman From Okal et al., 2006

15 Recent Events & Observations Le Port, Réunion 196-m container ship MSC Uruguay From Okal et al., 2006 Broke all 12 of its hawsers, began drifting Drifted for 2 hours, striking & damaging gantry cranes Port crews re-secured moorings lines ~ 3 hours later, only to have them break again

16 50-m freighter Soavina III Recent Events & Observations From Okal et al., 2006 Broke its moorings, began drifting into interior harbor Impacted dock After ~ 3 hours of drifting, finally beached on nearby shore

17 Observations of Nearshore Tsunami Currents

18 Recent Events & Observations 2011 Japan Tsunami 9.0 Mag EQ 38 m max runup 15,500 dead ~$210B USD in losses ~$25B USD in insured losses

19 2011 Japan Tsunami 350 ports suffered some damage 18,000+ fishing boats out of operation Recent Events & Observations

20 Recent Events & Observations 2011 Japan Tsunami In Guam, two nuclear submarines (USS Houston and USS City of Corpus Christi) broke free of moorings

21 Recent Events & Observations 2011 Japan Tsunami In Guam, two nuclear submarines (USS Houston and USS City of Corpus Christi) broke free of moorings

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23 Nearshore Dynamics of Tsunamis Overarching theme of this work: Increase our understanding of nearshore tsunami evolution, such that we are better able to mitigate their effects and estimate the risk How well do we understand the physics? Traditional, accepted knowledge describes a tsunami as a long wave (nondispersive, ~ steady flow) Observations of tsunami in the past decade indicate that is not necessarily, or even likely, the case in the nearshore IF we want to be able to predict the dynamics of the flow Forces on structures Sediment transport Local current & energy amplifications We need a different approach, with better physics

24 Hydrodynamic Modeling Options Shallow water wave equations Depth-integrated, irrotational Vertically uniform horizontal velocity Standard equations used for tsunami Boussinesq equations Depth-integrated, irrotational Horizontal velocity varies in the vertical Dispersive Navier-Stokes equation models No leading order averaging (fully 3D) Use small-scale and/or small-time averaging to make simulations practical Breaking waves, wave-structure interaction, turbulence

25 Model Connections (N)LSW for oceanic propagation O(1 km) Boussinesq in refined nested grid for nearshore detail O(1-100m) N-S model with turbulence closure O(<1m) Couple/nest the models, parallelize the individual components, and then figure out how to balance the total load

26 Modification of the Boussinesq-type Model to include Viscous-driven Vertical Structure Linear shear distribution e.g. Rodi (1980)

27 3D Turbulence Effects How can we approximate vertical turbulent fluctuations, or include that effect on the flow? Spatially filtered N-S equations Depth-average Stochastic BSM by Hinterberger, Frohlich, Rodi (2007)

28 Inclusion of Rotational & Turbulent Effects in Depth-Integrated Models Theory: Kim et al. (2009, Ocean Modelling); Kim & Lynett (2011, Physics of Fluids)

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30 Inclusion of Rotational & Turbulent Effects in Depth-Integrated Models Theory: Kim et al. (2009, Ocean Modelling); Kim & Lynett (2011, Physics of Fluids) O( 2 ) Dispersive Corrections O(1) Shallow Water terms O( ) Turbulent-Rotational Corrections O( ) Turbulent Mixing in Horizontal Plane. Eddy viscosity closed with Smagorinsky model O( ) Turbulent Mixing in Vertical Plane. Eddy viscosity closed with Elder s model O( ) Bottom Stress, closed with Mannings, Moody, etc. O( ) Depthaveraging stress terms, closed with BSM

31 Mixing by internal transverse shear instability u1 = 0.111m/s, u2 = 0.264m/s, Re = 5550 Experiment by Babarutsi and Chu (1998)

32 Mixing by topographical forcing

33 Applications: Tsunami Inundation of Coastal Infrastructure NSW Layers Boussinesq Layer

34 Applications: Tsunami Inundation of Coastal Infrastructure

35 Applications: Tsunami Inundation of Coastal Infrastructure

36 Harbor Studies 2004 Indian Ocean Tsunami Port Salalah, Oman

37 Harbor Studies 2004 Indian Ocean Tsunami Port Salalah, Oman Son et al. (2011, Ocean Modelling)

38 Harbor Studies

39 Harbor Studies

40 Harbor Studies Upwind differencing in low-order NLSW model leads to numerical diffusion= 2 2 u x u u 2 (1 Cr) with Cr ~ 0.5, u ~ 1-5m/s, x ~ 10m, m x num num ~ 10 x s Shear layers are numerically damped (eddies can t generate) Any generated eddies are quickly diffused

41 Applications: Turbulent, Tsunami-Induced Harbor Dynamics Numerical simulation results of the 2011 Japan tsunami, with a focus on the predictions in the Port of Oarai. Snapshots are from 188 minutes after the earthquake. Mid-Depth Vertical Vorticity (1/s) Fluid Speed at Ocean Surface (m/s)

42 Applications: Turbulent, Tsunami-Induced Harbor Dynamics

43 Applications: Turbulent, Tsunami-Induced Harbor Dynamics

44 Applications: Turbulent, Tsunami-Induced Harbor Dynamics

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46 Applications: Turbulent, Tsunami-Induced Harbor Dynamics Tsunami harbor effects include geometric amplification, resonance, large eddy creation Even when tsunami is small (~1 m), generated currents can be strong enough to break lines Turbulent structures, sensitive to precision of incident wave form, bathy/topo, etc. Deterministic approach?

47 Recent Events & Observations Tohoku

48 2D(V) RANS-1HD Boussinesq Coupling Sitanggang, K. and Lynett, P. (2009). "Multi-scale Simulation with a Hybrid Boussinesq-RANS Hydrodynamic Model." International Journal for Numerical Methods in Fluids

49 Detailed Wave-Structure Interaction Boussinesq Domain Interface Region RANS Domain Wave Direction Coastal Bridge Cross- section The parallel and hybrid models provided detailed simulations on a scale that would have been impossible without them movie

50 Detailed Wave-Structure Interaction Boussinesq Domain Interface Region RANS Domain Wave Direction Coastal Bridge Cross- section The parallel and hybrid models provided detailed simulations on a scale that would have been impossible without them movie

51 CONCLUSIONS Harbor Studies Open ocean propagation well understood, need additional effort to describe source mechanism as well as understanding nearshore complexity Localized flow features can create irregular and counter-intuitive patterns of flow damage potential Tsunami-structure interaction - additional research needed, particularly for large events