06/11/11

Water wave impacton rigid walls

BSc. R. Euser

Contents

● About Femto Egineering● Water wave impacts● Simulating water wave impacts

using Radioss SPH

About femto engineering

Company

About Software sales Consultancy

Engineering agency, offering both

consultancy and software for structural

analysis (>25 employees)

More than 12 years experience in CAEActive in BeNeLux

and Ukraine

Development of client specific software &

customization of Femap & Hyperworks

Partner of Siemens

Analysis software

Training

Support

FE-analysis

Product optimization

Certification

Outsourcing

Activities

Customers

Offshore projects

Water wave impacts

Applications

Offshore

Coastal

Piping

Automotive

About wave impacts

● Wave evolution● Surrounding structures● Wave pressure● Air bubbles (aeration)

Wave evolution

Breaking wave

Steepening wave

Stable wave

Crest

Trough

Crest

Air pocket

Trough

Trough

Crest

Surrounding structures

● Shape● Roughness● Stiffness

Wave pressure

P x=∫t before

t after

px , t d t

VelocityPressureVelocity

Wave Eye

Worst case

Pressure impulse

Air bubbles (aeration)

Positives:● Pressure

reduction● Damping

Negatives:● Longer impact

duration● Larger impact

areat = 0.0 ms t = 3.5 ms

“Evolution of the air cavity during a depressurized wave impact.”Lugni et al.

Simulating water wave impactsusing Radioss SPH

Contents

● Radioss CFD methods● Radioss SPH approach● SPH Simulations:

● 2D dam break correlation● 2D water wave impact on a rigid wall

● Conclusions

Radioss CFD methods

ALEArbitrary Lagrange Eulerian

SPHSmooth Particle Hydrodynamics

Radioss SPH approach

f xi =∑j

m j

jf x j W r ij , h

W r , h ={ 32h3 [ 23− rh

2

12 rh3] r≤h

14h32− rh

3

hr≤2h

Law Navier-Stokes Radioss SPH

Conservationof mass

Conservationof momentum

DiDt

=−i∑j

m j

juij∇W ij

D uiDt =−∑

jm j pi p ji j

ij∇W ijD uDt

=− 1 ∇ T

DDt =−∇ u

2D dam break correlation

Load case

3.55 m0.38 m

d

d 0

d 0=0.15md=0.018m

vgate=1.5m/s

0 0.1 0.2 0.3 0.4 0.5 0.6 0.70

0.5

1

1.5

2Gate velocity

t [s]

v [m

/s]

Radioss SPH model

30,225 particles

d particle=0.002m

Results

0.219 s 0.281 s 0.343 s

0.468 s0.406 s

=0.010

=0.010

0 1500300 600 900 1200

Pressure [Pa]

2D water wave impacton a rigid wall

Goal

Measure the effect of particle size on impact pressure

Load cases

Wave 1 Wave 2

0 2 4 6 8 10 12 14 16 18 20

-10

-5

0

5

10Acceleration vertical plate

t [s]

a [m

/s^2

]

0 2 4 6 8 10 12 14 16 18 20

-3-2-10123

Acceleration vertical plate

t [s]

a [m

/s^2

]

35 m

Sensors20x20 cm

Plate

15 m

15 m

Sensors20x20 cm

Plate

15 m

Models

Water particles

Detail A

Detail A

Model Particle size [m] Particle count

R1 0.2 3,750

R2 0.04 93,750

R3 0.02 375,000

Object Element type

Plate SPH

Rigid wall Shell

Water SPH

Sensors RBE2

Sensors

Impact measurement

P x=∫t before

t after

p x , t d tPressure impulse

P sensorz=∑T0

T1 F sensorhsensor d p

z ,TDTDiscretization

Load case T0 [s] T1 [s] DT [s]

Wave 1 11.1 11.7 0.001

Wave 2 8.1 8.4 0.001

Time interval

Results – Wave 1

0.0E+00 2.0E+04 4.0E+04 6.0E+04 8.0E+04 1.0E+050

2

4

6

8

10

12

14

Pressure Impulse

R1R2R3

PI [Pa s]

z [m

]

11.1 11.2 11.3 11.4 11.5 11.6 11.70.0E+00

2.0E+04

4.0E+04

6.0E+04

8.0E+04

1.0E+05

1.2E+05

1.4E+05

1.6E+05

Total Pressure

R1R2R3

t [s]

P [P

a]

t = 11.4 s t = 11.7 st = 11.1 s

R1

R2

R3

[m/s]

Results – Wave 2

0.0E+00 5.0E+04 1.0E+05 1.5E+05 2.0E+050

2

4

6

8

10

12

14

Pressure Impulse

R1R2R3

PI [Pa s]

z [m

]

8.1 8.15 8.2 8.25 8.3 8.35 8.40.0E+00

1.0E+05

2.0E+05

3.0E+05

4.0E+05

5.0E+05

6.0E+05

7.0E+05

Total Pressure

R1R2R3

t [s]

P [P

a]

R1

t = 8.1 s t = 8.3 s t = 8.4 s

R2

R3

[m/s]

Results discussion

● Fluid velocity● Fluid pressure● Total pressure (pressure peaks)● Pressure impulse

Conclusions

● Wave impacts:● Wave evolution● Surrounding structures● Impact pressure● Aeration

● Radioss SPH simulations:● 2D Dam Break correlation● 2D wave impacts

molslaan 1112611 rk delftT +31 (0) 15 285 05 80 F +31 (0) 15 285 05 81

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