Understanding freak waves

Sep 27, 2011
Understanding freak waves

(PhysOrg.com) -- Rogue waves, once considered nothing more than a sailor’s myth, are more predictable than ever thanks to new research from the oceanography team at Swinburne University of Technology.

Dr Alessandro Toffoli, who lectures in water, port engineering and oceanography, has shown that rogue waves – or ‘’, as they are often referred to in the media – are more likely to occur when a wave formation enters a current travelling in the opposite direction.

Rogue waves are giant waves that can occur without warning, often towering two or three times higher than other waves around it. Recently a 26.5 metre rogue wave – about the size of a 10-storey building – was detected in a 10-metre sea.

Toffoli, who collaborated on the paper, Triggering rogue waves in opposing currents, with Dr Miguel Onorato and Dr Davide Proment from the Università degli Studi di Torino in Italy, found that when a stable group of waves enters an ocean current, it can trigger an instability process that causes one wave in the group to rapidly increase in size.

For a rogue wave to occur, Toffoli said a number of conditions must be met. The direction of the waves and direction of the current, the velocity of both, and the change in velocity of the current field, are all factors contributing to the formation of a rogue wave.

As an example, Toffoli said a wave system travelling from the Southern Ocean to the east coast of Australia had the potential to form a rogue wave as it entered the south-travelling East Australian Current (EAC). A swell with a period of about 12 seconds interacting with the EAC may increase its height by up to 60 per cent, while storm waves can increase by up to 100 per cent.

Rogue waves often occur far out to sea and are similar to wind-generated waves - they are hundreds of metres long and can be tens of metres high - and are therefore very steep. They are different to tsunamis, which are generated by earthquakes and are hundreds of kilometres long in the open ocean, and are not steep.

Rogue waves were thought to be a myth until recently, when off-shore platforms and satellite tracking confirmed their existence.

“Ten, 20 years ago, mariners would say a ship was sunk by a rogue wave and no one would believe it,” Toffoli said.

“Lately there has been advancement in the field. We understand that rogue waves can occur, and now we are beginning to understand why they occur.”

Toffoli said his research could be used to improve forecasting rogue waves, which could help the offshore and shipping industries.

“The work we’ve done is very much theoretical, in principle it can be applied in off-shore engineering, for example. As we’re predicting rogue waves, that has safety implications for marine operations, but it can also help design practices, to properly account for the wave-load on structures.”

The research could also improve navigational software, which could suggest alternative routes for ships based on the likelihood of a rogue wave occurring.

Toffoli said his research can also be applied to other fields of physics, such as nonlinear optics, where the instability of wave packets is important.

Toffoli’s paper has been accepted for publication in the prestigious Physical Review Letters. (see hdl.handle.net/1959.3/203690)

Explore further: The unifying framework of symmetry reveals properties of a broad range of physical systems

Provided by Swinburne University of Technology

5 /5 (3 votes)
add to favorites email to friend print save as pdf

Related Stories

Making monster waves

Oct 19, 2009

Rogue waves -- giant waves that spring up suddenly and tower over the seas around them—have inspired physicists to look for an analogue in light. These high-intensity pulses can cross large distances without ...

Rogue wave recreated in laboratory tank

May 24, 2011

(PhysOrg.com) -- A team of researchers have used a mathematical equation to create a so called "rogue" wave; the giant kind that appear out of nowhere in the open ocean to topple ships and drown their crews. ...

CSIRO researchers create giant waves -- virtually

Dec 03, 2009

(PhysOrg.com) -- CSIRO scientists have created 'rogue waves' more than 20 metres high and smashed them into virtual oil and gas production platforms to compare different mooring designs.

New research sheds light on freak wave hot spots

Aug 05, 2009

Stories of ships mysteriously sent to watery graves by sudden, giant waves have long puzzled scientists and sailors. New research by San Francisco State professor Tim Janssen suggests that changes in water depth and currents, ...

On the crest of a freak wave

Jun 15, 2011

It was on 1 January 1995 that a wave over 25 metres high was recorded at the Draupner platform in the North Sea off the coast of Norway.

Recommended for you

Single laser stops molecular tumbling motion instantly

1 hour ago

In the quantum world, making the simple atom behave is one thing, but making the more complex molecule behave is another story. Now Northwestern University scientists have figured out an elegant way to stop a molecule from ...

What time is it in the universe?

Aug 29, 2014

Flavor Flav knows what time it is. At least he does for Flavor Flav. Even with all his moving and accelerating, with the planet, the solar system, getting on planes, taking elevators, and perhaps even some ...

Watching the structure of glass under pressure

Aug 28, 2014

Glass has many applications that call for different properties, such as resistance to thermal shock or to chemically harsh environments. Glassmakers commonly use additives such as boron oxide to tweak these ...

User comments : 0