A little surprised to see the term “parametric rolling” in a non-maritime context.
Also, the leading cause of lost containers is parametric rolling in following seas.
I wonder if the re-routing boxships around the Cape vs Red Sea will have any effect on losses ?
parametric rolling pretty much only happens when they are going slow,.
I would guess due to the extra miles they will be going faster?
I’d guess it’d be easy to throw a few boxes off while running full speed in a big quartering sea.
go faster than the waves?
Do different oceans have different wave speeds?
In water whose depth is large compared to the wavelength, the wave speed expression contains two terms, one for gravity effects and one for surface tension effects. The wave speed is given by:
where g is the gravitational field strength, γ is the surface tension, ρ is the density of the water, and λ the wavelength. As this equation makes clear (wave speed depends on wavelength), water is a dispersive medium.
For short wavelength (ripples), the second term predominates, and the speed is approximately
In deep water, the surface tension, γ, is too small to matter. The density, ρ , does not appear because if it increases, the force acting and the mass to be moved both increase by the same factor, with no net effect on the response time of water ahead of a wave front.
The speed of waves in shallow water can be given by v shallow≈√SQR gh (assuming λ >> h and A << h , where A is the wave amplitude, and h is simply the depth of the water).
above explains re waves speed and on routes via Cape google " rougue waves of Aghulhas current. " and weather conditions required for steep freak waves creation.
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No, ship slower than the waves, the speed of big swell can run 20 or 30 kts.
Wow not seen that before
Only remember the Atlantic which was about 12-15kts, Europe to Caribbean
Rough rule of thumb, wave speed a little more than half wind speed.
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From the link in post in the OP
Based on scientific analyses, studies, and desktop as well as real-life measurements, the project aims to develop specific, actionable and effective recommendations to increase container safety. Initial results have shown that parametric rolling in following seas is especially hazardous for container vessels, a phenomenon that is not well known and can develop unexpectedly with severe consequences.
Re parametric rolling:
Introduction-to-Parametric-Rolling-Motion-ver-A4-presentation.pdf (nautinst.org)
Re Cape route and local dangers there : Rogue waves are often associated with sites where ordinary waves encounter ocean currents and eddies. The strength of the current concentrates the wave energy, forming larger waves – Lehner compares it to an optical lens, concentrating energy in a small area. This is especially true in the case of the notoriously dangerous Agulhas current off the east coast of South Africa. Source : the european space agency
With an increased traffic of megacontainer vsl via Cape , there may be more encounters with such waves but one must wait for the winter season .
If such short but high and steep monsters can break a ships neck , then surely such energy may be distructive to container lashing systems causing stacks to collapse due to impact. So lets wait for winter season there and see what happens.
The advise to mariners in NP pilot books was to hug the shore as much as possible what I did on a tiny 1700 teu ship in conditions, which were conducive for the creation of such waves , meaning very strong wind against the flow of the current.
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Back in the day in an early generation of container ship we stowed most of our containers below deck leading to a high freeboard compared to modern container vessels. Our trade between Europe and Australia and New Zealand was via both Capes at a service speed of 24 knots.
On route to Cape Horn the aft mooring deck 11 meters above the waterline was out of bounds as seas swept through it. I would expect to see an increase in containers lost given the comparatively low freeboard of modern container ships, particularly those under 11,000 TEU.
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Is this likely to effect insurance ?