dsd-int 2014 - symposium next generation hydro software (nghs) - verification of storm tide...

Watermotion.euHydrodyamics before Equations

The Help from Analytical SolutionsSolving the right equations right

Summing up

Storm Surges ValidationThe State-of-the-Play for D-Flow FM

watermotion.eu — waterbeweging.nl

Giordano Lipari

5.11.2014

watermotion.eu — waterbeweging.nl Storm Surges Validation for D-Flow FM: the State of the Play



Summing up

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As many approaches as facetsNever forget realityEquations from Physics, Solutions from Mathematics

Hydrodynamics on All Fours

Hydrodynamics calculation

analytical

numerical

contextknowledge

measurements

physics




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Words of CautionTrifle-worship, belief in answers, connectionism, black box mistake, methodolatry, dead-fishfallacy, Jehovah problem

bit.ly/7defects (publisher)bit.ly/find7defects (Google search)




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“Man is the measure of all things”Crosby Beach, UK. ’Another Place’ by Antony Gormley




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Physics and Computations

Equations from physics

I Trustworthy cause-effect relations

I Raison d’etre of equations

I Delft3D, D-Flow FMShallow-water (depth-averaged,long-wave) equations

I Water: Forces → Motion → Forces→ ...

I Validation of a choiceI Solving the right equations...I and/or choosing the right

interpretation?

Solutions from computationAnalytical solutions

I exact (absolute credibility)

I restrictive assumptions

I limited applicability

I results easy to interpret

Numerical solutions

I approximate (conditional credibility)

I flexible scope, wide applicability

I results harder to interpret

Verification of a procedure

I Are we solving the equations right?




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Building a modelThe message of the benchmarks

Space — Size — Contour — Forces — Response?How to build an exact and useful model

L

B

DD




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L

B

D

D




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L

B

DD




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Harbour of IJmuidenA look-alike




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Numerical models can be objectively testedBooks and journals




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Exact water-level and currents driven by the windOn a longitudinal transect (marked orange)




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Exact water-level and currents driven by the windSide view on the longitudinal cross section. Blue = water level. Green = velocity




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Solving the right equations rightComparison with close match of assumptions and settingsThe grid challengeTime-stepping

Solving the right equations rightTesting correctness in D-Flow FM

Hydrodynamics calculation

analytical

numerical

contextknowledge

measurements

physics




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Computational gridDelta Shell: observation points and cross sections




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Water-level history. Map viewW=25 m/s; h0 = 10m/s; λ = 10−3 m/s; ∆t = 5 s. Non linear terms turned offThe darker the shade, the deeper the water




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Water-level history. Downwind location (inundation)W=25 m/s; h0 = 10m/s; λ = 10−3 m/s; ∆t = 5 s. Non linear terms turned off.Blue line: D-Flow FM. Red line: exact solution

0.0 0.2 0.4 0.6 0.8 1.0t/T {T=21600.0 s}

0.0

0.5

1.0

1.5

2.0

e/E {E

=F0

*L/(g

H)=0.06

4 m}

History water level at x/L=5000.0/5000 [ST3d]




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Water-level history. Mid-basin locationW=25 m/s; h0 = 10m/s; λ = 10−3 m/s; ∆t = 5 s. Non-linear terms turned off.Blue line: D-Flow FM. Red line: exact solution

0.0 0.2 0.4 0.6 0.8 1.0t/T {T=21600.0 s}

−0.2

0.0

0.2

0.4

0.6

0.8

1.0

e/E

{E=

F0*L

/(gH)

=0.

064

m}





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Water-level history. First-quarter upwind locationW=25 m/s; h0 = 10m/s; λ = 10−3 m/s; ∆t = 5 s. Non-linear terms turned off.Blue line: D-Flow FM. Red line: exact solution

0.0 0.2 0.4 0.6 0.8 1.0t/T {T=21600.0 s}

−0.1

0.0

0.1

0.2

0.3

0.4

0.5

e/E

{E=

F0*L

/(gH)

=0.

064

m}





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Velocity history. Map viewW=25 m/s; h0 = 10m/s; λ = 10−3 m/s; ∆t = 5 s. Non linear terms turned offRed shades: net flow in. Blue shades: net flow out. White: zero net flow




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Velocity history. Upwind location (open boundary)W=25 m/s; h0 = 10m/s; λ = 10−3 m/s; ∆t = 5 s. Non-linear terms turned off.Green line: D-Flow FM. Red line: exact solution

0.0 0.2 0.4 0.6 0.8 1.0t/T {T=21600.0 s}

−1.0

−0.5

0.0

0.5

1.0

q/Q

{Q=

F0*L

/(gH)

^½

=0.

631

m²/s

}

History depth-averaged velocity at x/L=0.0/5000 [ST3d]




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Velocity history. Mid-basin locationW=25 m/s; h0 = 10m/s; λ = 10−3 m/s; ∆t = 5 s. Non-linear terms turned off.Green line: D-Flow FM. Green line: exact solution

0.0 0.2 0.4 0.6 0.8 1.0t/T {T=21600.0 s}

−0.6

−0.4

−0.2

0.0

0.2

0.4

0.6

q/Q

{Q=

F0*L

/(gH)

^½

=0.

631

m²/s

}





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Velocity history. Third-quarter downwind locationW=25 m/s; h0 = 10m/s; λ = 10−3 m/s; ∆t = 5 s. Non-linear terms turned off.Blue line: D-Flow FM. Red line: exact solution

0.0 0.2 0.4 0.6 0.8 1.0t/T {T=21600.0 s}

−0.3

−0.2

−0.1

0.0

0.1

0.2

0.3

q/Q

{Q=

F0*L

/(gH)

^½

=0.

631

m²/s

}





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Introducing a bit of challengeA meander-like grid (but there’s no meander). Skewed grid and flow.




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Water-level history. Mid-basin locationSkewed flow and grid ... Non-linear terms turned-off.Blue line: D-Flow FM. Red line: exact solution

0.0 0.2 0.4 0.6 0.8 1.0t/T {T=21600.0 s}

−0.2

0.0

0.2

0.4

0.6

0.8

1.0

1.2

e/E

{E=

F0*L

/(gH)

=0.

064

m}

History water level at x/L=2500.0/5000 [ST3h]




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Velocity history. Mid-basin locationSkewed flow and grid ... Non-linear terms turned-off.Green line: D-Flow FM. Red line: exact solution

0.0 0.2 0.4 0.6 0.8 1.0t/T {T=21600.0 s}

−0.6

−0.4

−0.2

0.0

0.2

0.4

0.6

q/Q

{Q=

F0*L

/(gH)

^½

=0.

631

m²/s

}

History depth-averaged velocity at x/L=2500.0/5000 [ST3h]




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Time-step sensitivityIncreasing the time step from a sound 5 s to 30 s




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Water-level history. Mid-basin locationTime-step sensitivity. W=25 m/s; h0 = 10m/s; λ = 10−3 m/s; ∆t = 30 s.Blue line: D-Flow FM. Red line: exact solution

0.0 0.2 0.4 0.6 0.8 1.0t/T {T=21600.0 s}

−0.2

0.0

0.2

0.4

0.6

0.8

1.0

e/E

{E=

F0*L

/(gH)

=0.

064

m}

History water level at x/L=2500.0/5000 [ST3g]




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Velocity history. Mid-basin locationTime-step sensitivity. W=25 m/s; h0 = 10m/s; λ = 10−3 m/s; ∆t = 30 s.Green line: D-Flow FM. Red line: exact solution

0.0 0.2 0.4 0.6 0.8 1.0t/T {T=21600.0 s}

−0.6

−0.4

−0.2

0.0

0.2

0.4

0.6

q/Q

{Q=

F0*L

/(gH)

^½

=0.

631

m²/s

}

History depth-averaged velocity at x/L=2500.0/5000 [ST3g]




Summing up

State of the Play: Hop Jump Spring

I Solving the right equations Solving the equations right

I Analytical solutions Exact credibility at the cost of limited scope

I Numerical methods All options can be guaged against a reference

I Storm surges Unsteady long waves. The more accurate the better

I D-Flow FM simulates the velocity and water level oscillations well

I Source code can be made compliant to benchmarks (transparency)

I Follow good modelling practices to avoid inaccuracy (expectedly)

I Now Leveraging more information from the current test case

I Soon Comparison with Delft3D

I Then Test cases for similar wind-driven flows




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Thanks and Credits

Deltares staff (they did dare to share!):Arthur van Dam, Edward Melger, Herman Kernkamp, Sander vander PijlFlickr contributors: Beverley Goodwin, Chris Saxman, Terry Kerney

PNG/Tikz community for graphics templates




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Thanks for your attentionHope this has been been useful

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dsd-int 2014 - symposium next generation hydro software (nghs) - verification of storm tide...

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