Protecting coastal structures from high-impact waves

Vivek Francis loves a good swim. And, whenever in the water, he pays careful attention to the tiniest of ripples. After all, this research scholar with the IITB-Monash Research Academy is pursuing a project titled, ‘Wave Impact on Protective Coastal Structures’.

Wave action on coastal structures (source: http://www.panoramio.com/photo/48851473)

“Increasing storm surges and tsunamis have led to a need for stronger coastal protective structures like breakwaters, sea walls, and groynes,” explains Vivek. “Protective structures should ideally withstand different wave types across a wide range of conditions. This includes varying speeds, angles of incidence, and height. Most importantly, tsunami- and wind-driven storm waves are vastly different and require different design strategies.” Studies to understand the effectiveness of protective coastal structures have so far been either purely experimental, or, more recently, purely numerical, with limited scope for validation. “With recent advances in numerical modelling techniques and increased computational power, however, one is now able to perform 3D numerical simulations that accurately replicate the experimental setup, and provide a sound basis to validate such problems,” says Vivek. His objectives are three-fold — to obtain good experimental validation data for the impact of waves on coastal protective structures, to develop a Smoothed Particle Hydrodynamics (SPH) model to simulate such impacts, and to validate the simulations of the experimental tests to establish their accuracy. When a wave moves from deep water to shallow water regions, its crest becomes higher, the curvature of its profile increases, and the trough becomes flatter. “Therefore, in shallow water regions, small amplitude (linear) wave theory cannot be used. A more accurate depiction of the wave climate is provided by nonlinear finite amplitude wave theories, two of which are the cnoidal wave theory and the solitary wave theory,” says Vivek. “A porous barrier is a barrier against the movement of one type of object that does not pose a barrier to the movement of another type. Although the hydrodynamic characteristics of porous barriers under the influence of small amplitude waves have been researched in great detail, their hydrodynamic characteristics when under the action of nonlinear shallow water waves have not been investigated.” And this is where he is hoping to make a difference.

Experimental setup in the Ocean Engineering Lab at IIT Bombay

Prof Murali Sastry, CEO of the Academy, sees immense scope in this area of research. “Vivek’s work can lead to multiple benefits. When a wind-generated ocean wave reaches a breakwater structure, it will be partly or totally reflected, depending on the permeability of the structure. Strong wave reflections would make the maneuvering of vessels in the vicinity of these structures quite difficult. Thus a proper understanding of wave-structure interaction phenomena could be of immense value to the offshore industry as well,” he says. “Today’s research challenges require a multi-disciplinary approach. And the way in which the IITB-Monash Research Academy has been set up makes it possible for such multi-disciplinary investigations to be carried out. I am convinced that the Academy will create significant science, societal, and industry impact in the future.” The IITB-Monash Research Academy is a Joint Venture between IIT Bombay and Monash University, Australia. Opened in 2008, it operates a graduate research programme located in Mumbai that aims to enhance research collaborations between Australia and India. Students like Vivek study for a dually-badged PhD from both institutions, and spend time during their research in both India and Australia. Whether with life or research, Vivek’s philosophy is simple: When you are not able to stop the waves, learn to ride them.

Research scholar: Vivek Francis, IITB-Monash Research Academy

Project title: Wave Impact on Protective Coastal Structures

Supervisors: Prof Balaji Ramakrishnan, Prof Murray Rudman, Prof Mahesh Prakash

Contact details: vivek.francis@monash.edu

This story was written by Mr Krishna Warrier based on inputs from the research student, his supervisors and IITB-Monash Research Academy. Copyright IITB-Monash Research Academy.