Numerical Analysis to Design a Hydraulic-Control Wave-Maker (HCW)

for the Study of Oceanographic Flows

Haeng Sik Ko1, Patrick J. Lynett1 1 Department of Civil and Environmental Engineering, University of Southern California, Los Angeles, CA

− Piston type (Flux limitation)

− Pump type (Pulsation problem)

− a/h=0.05 (left): a/h=0.3 (right) − Reflection coefficient: 4.76% (a/h=0.05) & 2.56% (a/h=0.3)

− a/h=0.05 (left): a/h=0.3 (right) − Reflection coefficient: 4.78% (a/h=0.05) & 2.10% (a/h=0.3)

2) Optimized baffle: a/h=0.01, kh=1

Absorbing wave reflection 2 − Extract horizontal velocity data any point − The data averaged and applied along outlet boundary − Using wave celerity, time shifting is computed

Absorbing wave reflection 1 − Extract horizontal velocity data near outlet boundary

(Experimentally this would be done in real time with ADV) − The data averaged and applied along outlet boundary

(Experimental radiation boundary condition)

3) Optimized baffle: a/h=0.05, kh=0.1

Sensitivity analysis − Baffle length, number

and position

4) Optimized baffle: a/h=0.05, kh=1

1) Optimized baffle: a/h=0.01, kh=0.1

Design of the optimized baffle − 10 baffles are located over wave amplitude range

of a/h=0.05 − Baffle length: 0.05m

2) Baffle number & position (a/h=0.05, kh=1) − To create various amplitude wave, lots of baffles should be

positioned

INTRODUCTION

Motivation − The lack of experimental studies with respect to complex

oceanographic flows: Nonlinear & multi-scale physics

− General wave-maker techniques (Dean & Dalrymple, 1991) have been used, based on dispersive & shallow water theory, linear to weakly nonlinear waves theory

Objective of HCW − Develop new experimental device to study multi-scale and

vertically-variable oceanographic flows − Design HCW by numerical analysis (OpenFOAM® )

1) Ability of wave generation and absorption: Compared to analytical solution 2) Optimized HCW:

Sensitivity analysis

METHODOLOGY

HCW system − Inlet and outlet boundaries: a set of vertical baffles − Each baffle connected to an individual pump − The controllable vertical distribution of flow − Horizontal particle velocities along water depth are averaged

over each baffle height − The averaged velocities are imposed at each baffle as inlet

condition

− Any arbitrary flow can be reasonably created

− Different sets of baffles can be connected to different reservoirs to create vertical density profiles

SENSITIVITY ANALYSIS

SENSITIVITY ANALYSIS RESULTS AND ANALYSES

1) Baffle length (a/h=0.05, kh=1, 3 inlet case)

− Baffle length ranges from 0.05 to 0.3

RESULTS AND ANALYSES

SUMMARY

− A new method of wave generation and absorption by using HCW is verified through numerical analysis.

− The optimized design of HCW is found through sensitivity analyses, such baffle length, number and position.

− Preliminary results using a small-scale physical model of a HCW will be presented.

REFERENCES

1. R. Dean, R. Dalrymple, (1991) Water Wave Mechanics for Engineers and Scientists, World Scientific.

FUTURE WORK