Simulation and Validation of

Piton Type Wave maker by CFD

Muniyandy ELANGOVAN and

Anant LAL

Indian Register of Shipping Mumbai

INDIA

• Simulate the Numerical Wave Tank• Generate the Regular Wave• Study Wave Damping• Validation

• Estimate - Ship Motion in Sea State by CFD• Hydrodynamics Forces• Wave Pattern

Performance of Ship

Passenger Comfort

Accurate estimation of forces for structural analysis

Achieve Required Speed

Needed Data

Ship Motion

Ship Design(Hull) Ship Construction

CFD - Analysis

Model Test

Hydrodynamic Forces

Resistance & Wave Pattern

Experiment Vs CFD Analysis

Towing Tankw/o Wave

Maker • Hydrodynamic Forces

• Exciting Forces• Ship Motions

SEAKEEPING ESTIMATIONS

Towing Tankwith Wave

Maker

* Piston Type* Flap Type* Plunger

Type

Wave Maker

PISTON TYPE WAVE MAKER

s End Wall

hw = heBeach

Tank Top

Piston

Wave Profile

Ap

Piston_displacement @ Ap sin (w t)

RANSE Solver Ansys CFX-11.0, based on Finite Volume Method (FVM) Multiphase (Water and Air) using VOF method Transient simulations Governing Equations: continuity, momentum, volume fraction and Turbulence model Boundary Conditions: Bottom, Beach slope and end wall as wall with no-slip condition

Flap

End wall

Beach

Tank Top

Side Wall

Bottom

3D view of Wave Tank

GRID AND TURBULANCE STUDY

Cases: Type: No. of Elements:

Case1 Coarse 5,115

Case2 Normal 9,246

Case3 Fine 15,921

hw = water heightt = Time periodAp = Piston Stroke LengthAp/t = constant velocity

Test cases:

hw (m)

t (s)

Ap/t (m/s)

Ap(m)

0.10.250.751.001.25

1.52.02.54.04.55.0

0.0625 0.100.150.20

Locations of Wave Elevation Measurement

Points Location (x in m)

P1 1

P2 2

P3 3

P4 4

P5 28

P6 30.5

P7 32

P8 33.5

2D Schematic view of Wave Tank

)1(cosh2

sinh

khw

khwkhwHS

S = stroke lengthH = wave height, hw = water height of the tank.K = Wave number S=2Af (Flap stroke length)

Relation between stroke length, water height and wave height is given by[8]

[8] Robert G. Dean and Robert A. Dalrymple

“Water wave mechanics, for Engineers and scientist”

BEACH ANALYSIS

s End Wall

Beach

Tank Top

Wave Profile

1:31:6 1:4.5

Max. damping for 1:3 slope

Wave elevation at Locations P1 and P4

BEACH ANALYSIS

Wave height and wave length are proportional to STROKE LENGTH

CFD => RESULTS and ANALYSIS

Dependency: STROKE LENGTH

CFD => RESULTS and ANALYSIS

Dependency: WATER HEIGHT

Wave height and wave length are proportional to WATER HEIGHT

CFD => RESULTS and ANALYSIS

Dependency: TIME PERIOD

CFD => RESULTS and ANALYSIS

Constant Velocity

WORKING PRINCIPLE SIMULATION

MESH MOVEMENT SIMULATION

VELOCITY PROFILE SIMULATION

WAVE PROFILE

CONCLUSIONS

Regular waves were generated using CFD technique Computed results are in good agreement with wave maker

theory Results can be used for establishing an experimental wave-

maker by knowing the limitations CFD simulations can effectively replace the experimental

Wave Tank

THANK YOU