Lighthouse Fever

I love lighthouses, and am borderline obsessed with them. I have lucky lighthouse socks (I’m wearing them today), I own books about them, and in high school I made a papier-mâché lighthouse lamp. I have spent hours in the rain trying to photograph them during storms. Furthermore, they are most often found in places where the sea is at its most violent, and from a technical perspective, most interesting.

Naturally, when a bright master’s student from our lab asked if I was interested in joining his thesis committee to research the impact of breaking waves on lighthouses, I could not help but say yes. My research on coral reefs focuses mainly on the complex ways in which waves change as they break across the reef. In many ways, this is a similar process to what happens when waves hit the rocky shoals that many lighthouses are built on. This makes for a compelling intersection between my professional interests and private obsessions!

I am extremely proud to announce that Jan van Gorsel has successfully defended his MSc thesis, “Numerical analysis of broken regular wave forces on a shoal-mounted cylinder“. I was extremely privileged to sit on his graduation committee and work with him for the past 9 months.

Simulation of a wave breaking on a rocky shoal and then colliding with a lighthouse, from Jan van Gorsel’s thesis. The blue represents air and the red water. It is really hard to predict something like this, because of the complex bouncing and splashing motion of the broken wave. Simulating this process is a bit like trying to predict the exact spatial distribution of spilled beer after a drunk guy stumbles and trips in a crowded pub. Sigh. Remember crowded pubs?

Jan applied an extremely complicated computational fluid dynamics (CFD) model called OpenFOAM. To make sure that the simulation was accurate, he validated it using data from a laboratory experiment. His results were pretty darn good, especially considering the complexity of the processes involved. I do a lot of numerical modelling in my own research, but I can unreservedly state that the one he used is vastly more complicated than the ones I rely on.

To capture the physics of every little water droplet that you can see in the above image, Jan’s model required incredibly high resoulution, and took weeks to run on high-powered computing clusters here in Delft and at Stanford University. His research is very valuable, because he was able to quantify precisely the rate at which the wave slams into a lighthouse and curls around it. This is important for being able to predict the force inflicted upon the structure.

Lighthouses form a vital part of marine infrastructure for safe navigation, and are also in many cases beautiful historical buildings. It is thus essential to quantify the forces acting on the structures in order to reinforce or rehabilitate them. With Jan’s work, hopefully we can keep their lights shining for many years to come.

In celebration of Jan’s big day, I would like to close by sharing my favourite lighthouses from around the world!

Nugget Point lighthouse, New Zealand (South Island)
Walton Lighthouse, Santa Cruz, California, US
Lighthouse Point, Santa Cruz, California, US
Phare Saint-Mathieu, Brittany, France
Phare du Four, Brittany, France. I waited about an hour in the pouring rain and howling wind trying to get a shot like this.
And lastly, my favourite lighthouse, in Texel, the Netherlands.

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