Tsunami coastal impact The use of VOF-URANS methods with examples

Richard MARCER

TANDEM – tsunami school, Bordeaux, 28/04/16 2 Richard.marcer@principia.fr

Coastal impact : physics to simulate

EOLE CFD : a 3D Navier-Stokes code

Focus on the VOF free surface method

Examples of validations on academic tsunami test-cases

Content

3 TANDEM – tsunami school, Bordeaux, 28/04/16

Richard.marcer@principia.fr

Complex physics to simulate 3D Breaking x Two-phase flow with possible complex interface x Entrapped air bubbles x Emulsion (mixing of water and bubbles) x Turbulence

Flooding x Friction on bottom, roughness

Fluid / structure interactions x Hydrodynamic loads on structures x Possible collapse of the structures x Debris moving in the flow

Coastal impact of a tsunami

4 TANDEM – tsunami school, Bordeaux, 28/04/16

Richard.marcer@principia.fr

EOLE CFD code developed by PRINCIPIA

Navier-Stokes multi-phase flows

Structured curvilinear multi-block meshes Pseudo-compressibility method Dual time stepping Second order finite volume VOF free surface method

Implicit (no CFL constraint) 2 methods x Eulerian (“mass” conservation equation) x Lagrangian

Turbulence: 2-equations models (k-H, k-Z, SST) Coupling fluid / structure (rigid body)

Example of VOF-URANS CODE

5 TANDEM – tsunami school, Bordeaux, 28/04/16

Richard.marcer@principia.fr

System of Navier-Stokes equations

Flux terms

External force

Contravariant velocity components (curvilinear meshes)

EOLE CFD code

6 TANDEM – tsunami school, Bordeaux, 28/04/16

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Richard.marcer@principia.fr

Two-phase flow with separated phases (interface) Each cell of the mesh is characterized by the volume fraction of the phase 1 with respect to phase 2 (discrete function F)

F=1 : phase 1 (liquid) F=0 : phase 2 (air) 0<F<1 : cells containing an interface phase 1 / phase 2 Position of the interface determined from the computation of the normal

VOF interface model - concept

7 TANDEM – tsunami school, Bordeaux, 28/04/16

Richard.marcer@principia.fr

𝛻F

Eulerian : conservation equation of the VOF function (F) Fluxes computation based on a “simplified” representation of the interface slope in each cell Example:

Lagrangian (SLVOF) Based on more realistic

representation of the slope

Interface advection

8 TANDEM – tsunami school, Bordeaux, 28/04/16

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U = grid velocity W&

= interface velocity 𝑈

Richard.marcer@principia.fr

Horizontal Free surface

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VOF model algorithm

9 TANDEM – tsunami school, Bordeaux, 28/04/16

F(tn)

Interface advection

F(tn+1)

Eulerian Lagrangian or

Time iteration

water: F(tn)=1

air: F(tn)=0

interface water / air 0<F(tn)<1

Richard.marcer@principia.fr

Solitary wave breaking on a slope

• Solitary wave on a 2D vertical reef

Russel’s wave generator

• Wedge sliding down a 3D slope

Dam break with structure impact

• Impact of a tsunami on a urban area

Examples of CFD validations on Tsunami academic cases

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TANDEM – tsunami school, Bordeaux, 28/04/16

Richard.marcer@principia.fr

Slope 1/15 Solitary wave Wave amplitude = 0.45 h (h=depth of the channel) Visualizations of free surface at different instants of the breaking

Breaking of a tsunami wave on a constant slope

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Li and Raichlen, 1998

TANDEM – tsunami school, Bordeaux, 28/04/16

Richard.marcer@principia.fr

Simulation with EOLE Plunging wave Splash-up

Breaking of a tsunami wave on a constant slope

12 TANDEM – tsunami school, Bordeaux, 28/04/16

Richard.marcer@principia.fr

Comparison with the code EOLENS (Principia / IMATH) Unstructured meshes Free surface : color function (not VOF) Adaptative mesh Compression interface model (possible)

Breaking of a tsunami wave on a constant slope

13 TANDEM – tsunami school, Bordeaux, 28/04/16

Richard.marcer@principia.fr

Emerged reef (initially ) Propagation, run-up, overtopping, bore and reflection

Solitary wave A/h0 = 0.3 (with h0=2.5m)

14 wave gauges

Solitary wave on a 2D reef

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[Roeber, 2012]

0.14m 2.5 m

TANDEM – tsunami school, Bordeaux, 28/04/16

Richard.marcer@principia.fr

Solitary wave on a 2D reef

15 TANDEM – tsunami school, Bordeaux, 28/04/16

Richard.marcer@principia.fr

Movies

Solitary wave on a 2D reef

16 TANDEM – tsunami school, Bordeaux, 28/04/16

Richard.marcer@principia.fr

Solitary wave on a 2D reef

17 TANDEM – tsunami school, Bordeaux, 28/04/16

Richard.marcer@principia.fr

Example of comparison with Boussinesq codes (dedicated paper on progress)

Time series of wave elevation in WG9 (breaking)

WG9

Boussinesq

Navier-Stokes

Tsunami generation due to the falling into water of a rigid body (massive cliff, ice body)

Rectangular block x 38.2 Kg, 0.4m tall, 0.3m long x T=0: just below the free surface

Depth D (= 0.288m, 0.210m, 0.116m) Monitoring x Wave elevation at 1.2m x Values of H and B (issued from video measurements)

Russel’s wave generator

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[Monaghan and Kos, 1999] TANDEM – tsunami school, Bordeaux, 28/04/16

Richard.marcer@principia.fr

Coupling fluid / structure (rigid body) : free motion in vertical

Movie

Russel’s wave generator - simulation

19 TANDEM – tsunami school, Bordeaux, 28/04/16

Richard.marcer@principia.fr

Russel’s wave generator

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H

B

TANDEM – tsunami school, Bordeaux, 28/04/16

Richard.marcer@principia.fr

Elevation at x=1.2m

Wave elevation at X=1.2 Parameters B and H

x=1.2m

Velocity versus vertical position

Russel’s wave generator

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Curve to be read from right to left with increasing time

TANDEM – tsunami school, Bordeaux, 28/04/16

Richard.marcer@principia.fr

Entry of the block Block approaching the bottom

Tsunami generation due to submarine landslide ½ slope beach Monotoring

Wave elavation Run-up

Wedge sliding down on a slope

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[Liu et al., 2005]

TANDEM – tsunami school, Bordeaux, 28/04/16

Richard.marcer@principia.fr

y

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Coupling fluid / structure (rigid body) : imposed motion Movie

Wedge sliding down on a slope - simulation

23 TANDEM – tsunami school, Bordeaux, 28/04/16

Richard.marcer@principia.fr

Wedge sliding down on a slope

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gauge 2

runup 3

gauge 1

runup 2

TANDEM – tsunami school, Bordeaux, 28/04/16

Comparisons elevation / runup

Experiments EOLE

Richard.marcer@principia.fr

Physical model 1/50 scale of real city of Seaside (Oregon) H=0.2m (2.1m depth offshore) More than 30 wave elevation / velocity gauges

Tsunami on a coastal urban area

25 TANDEM – tsunami school, Bordeaux, 28/04/16

Richard.marcer@principia.fr

[Park et al., 2013]

Numerical model Multi-block mesh: 9M cells All buildings included Initial solitary wave

Tsunami on a coastal urban area - simulation

26 TANDEM – tsunami school, Bordeaux, 28/04/16

Richard.marcer@principia.fr

Movies

Tsunami on a coastal urban area

27 TANDEM – tsunami school, Bordeaux, 28/04/16

Richard.marcer@principia.fr

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Tsunami on a coastal urban area Experiment EOLE CFD

TANDEM – tsunami school, Bordeaux, 28/04/16

Richard.marcer@principia.fr

Elevation on gauges A

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A1

A6 A9

A2

EOLE CFD experience

TANDEM – tsunami school, Bordeaux, 28/04/16

Richard.marcer@principia.fr

Elevation on gauges C

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C3

C9

C5

EOLE CFD experience

TANDEM – tsunami school, Bordeaux, 28/04/16

Richard.marcer@principia.fr

Velocity gauges

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A6

C9

B6

EOLE CFD experience

TANDEM – tsunami school, Bordeaux, 28/04/16

Richard.marcer@principia.fr

Remerciements Camille Journeau (Ingénieur à Principia) Kevin Pons (doctorant à Principia)

Merci pour votre attention !

33 TANDEM – tsunami school, Bordeaux, 28/04/16

Richard.marcer@principia.fr