OES modelling workshop

The OES Annex V workshop on Computational Modeling and Analysis of Marine Energy Converters (25-26 Nov 2013) was organised by Roger Bagbey (Cardinal, USA) and Bob Thresher (NREL, USA), and hosted by Henry Jeffrey (The University of Edinburgh, Scotland UK).

Launching the boat

Skagen is a small town at the northern tip of Denmark, at the meeting of the North and Baltic Seas. There was a group of artists living here around the turn of the nineteenth century. A favourite subject was the local folk who worked the sea. One of the Skagen painters, Michael Ancher, painted the fisherman and lifeboat man, Lars Kruse. Kruse had earned a medal for saving many lives, but this was revoked upon discovery that in his youth he had done some illegal beach-combing. Ancher championed his cause, and did several paintings depicting the harsh and heroic lives of the lifeboat men [Chief lifeboatman Lars Kruse, The drowned fisherman, Fishermen launching a rowing boat]. Kruse's medal was eventually reinstated.

Apache to the rescue

The announcement of an American competition for an open source hydrodynamic solver posed a conundrum for a French research laboratory with their own in-house hydrodynamic code. The LHEEA lab at École Centrale de Nantes (ECN) had been thinking of open-sourcing their code Nemoh for some time. Submitting Nemoh to NREL's OpenWARP competition would make it available to a wide audience, but this would come at a cost: ECN would effectively loose authorship of the code. It was decided to make Nemoh open source first, and then to submit it to OpenWARP.

This idea posed a couple of problems for NREL. Firstly, with Nemoh open source, any old cowboy could submit Nemoh as an entry to OpenWARP. Secondly, the type of open source licence that ECN had planned to attach to Nemoh was problematic.

Battle of the BEMs

2014 looks set to being a good year for open access code for marine renewables. Three projects are due to go online this year: WEC-Sim, OPEN-WARP, and Nemoh. The last two are Boundary Element Method (BEM) codes: if one of these turns out to the long-awaited open source equivalent to the excellent but prohibitively expensive WAMIT, this could be a real boost to marine renewables. The availability of free code for modelling WECs will considerably reduce the cost, complexity and effort associated with development at early technology readiness levels. So please spread the word:

Do you have any dusty unloved code that has slipped down the back of the couch? Time to stop sitting on it! Check out the OPEN-WARP competition.

What makes a WEC concept 'good'?

The topic of innovation in the design of WECs has been a bit of a recurring theme for me lately. It has cropped up in the form of an innovation competition for WECs, new concepts aired at this year's All Energy Opportunities conference, and in Weber's paper on the Performance/Readiness Matrix. All this leads to a conundrum that has been puzzling me for some time now:

“How can you tell if a particular WEC concept is any good?”

Serious about research?

Having a bad day? Remind yourself of the true meaning of 'research'. 

The tube map dynamic model

The London tube map is a strange and wonderful thing. Compared to most maps, it is not information dense. Yet it contains exactly enough information to allow passengers to easily navigate a complex system of interchanges. Compared to most maps, it is not geometrically similar. The one criteria that usually determines the usefulness of a map has been flouted: indeed a geometrically similar tube map would be more difficult to follow, and hence less useful.

The London tube map is an example of how the measure of a model's quality and information content depends on its purpose. There is no one model that is the best choice in all contexts. It is also a useful reminder that a model is distinct from the concept it represents.

Why not use wavemakers?

"If you are trying to make a good wavemaker, why not use wavemakers?"

If we take the statement 'a good wave absorber is a good wave maker' to its logical conclusion, then why not consider the wavemakers in our wave tanks? Most tanks for simulating deep water waves have a series of bottom-hinged flaps, mounted on the edge of the tank.