Fluid Dynamics Summer School 

Charlie Suitters – c.c.suitters@pgr.reading.ac.uk 

Every year, Cambridge and École Polytechnique in Paris alternate hosting duties of the Fluid Dynamics of Sustainability and the Environment (FDSE) summer school. This ran for two weeks earlier in September, and like many other things took place online. After talking to previous attendees of the summer school, I went into the fortnight with excitement but also trepidation, as I had heard that it has an intense programme! Here is my experience of a thoroughly enjoyable couple of weeks. 

Structure 

The summer school brought together around 50 PhD students and a few postdocs from all over the world, from Japan to Europe to Arizona, and I have to admire the determination of those students who attended the school at unsociable times of the day! We all came from different backgrounds – some had a meteorological background like myself, but there were also oceanographers, fluid dynamicists, engineers and geographers to name but a few. It was great to hear from so many students who are passionate about their work in two brief ice-breaker sessions where we introduced ourselves to the group and I got to appreciate how wide-reaching the FDSE community is. 

Each day consisted of four 1-hour lectures – normally three ‘core’ subjects (fluid dynamics basics, atmospheric dynamics, climate, oceanography, etc.) and one guest lecturer per day (including our very own Sue Gray who gave us a whistle-stop tour of the mesoscale and extratropical cyclones). After this, there was the opportunity to split into breakout groups and speak to the day’s lecturers to ask them questions and spark discussions in small groups. On the final day, we also had a virtual tour of the various fluid dynamics labs that Cambridge has (there are a lot!) and a few of the students in the labs spoke about their work. 

Core Lectures 

Figure 1. Demonstration of a density current (blue) of salty water in a tank of less dense tap water. Taken from Jean-Marc Chomaz’s lecture

These lectures were given by very engaging specialists including Colm-Cille Caulfield, John Taylor, Alison Ming, Jerome Neufeld and Jean-Marc Chomaz; and provided the perfect opportunity to see lots of pretty videos about fluid flows (Fig. 1). Having done an undergraduate course in Meteorology, a lot of these gave me a refresher of things I should already know, but it was refreshing to see how other lecturers approach the same material. 

The most interesting core lectures to me were those regarding renewable energy, given by Riwal Plougonuen and Alex Stegner. Plougonuen lectured us on wind turbines, telling us how they worked and why they are designed like they are – did you know that actually the most efficient wind turbines have 2 blades, but the vast majority have three for better structural stability? On the other hand, Stegner spoke to us about hydroelectricity, and I learned that Norway produces nearly all of its electricity through hydropower. Other highlights from these core lectures include watching a video of a research hut being swamped by an avalanche (Nathalie Vriend, see video at the link here), and seeing Jerome Neufeld demonstrate ice flows using golden syrup (he likes his food!) 

Guest Lectures 

Figure 2. Flow patterns around a sash window with both slots open – the blue arrows showing incoming cold air and the red arrows showing warm flow to the outside. Taken from Megan Davies Wykes’ lecture.

For me, the guest lectures were the highlights of my time at the summer school. These lectures often explored things beyond my area of expertise, and demonstrated just how the fluid mechanics we had learned are highly applicable to many different areas of life. We had a lecture about building ventilation from Megan Davies Wykes, which made me realise that adequately ventilating a room is more than simply cracking open a window – you have to consider everything from the size of the room, outside wind speed, how many windows there are, and even the body heat from people inside the room. Davies Wykes’s passion about people using their sash windows correctly will always stick with me – turns out you need to open both the top and the bottom panes for the best ventilation (something she emphasised more than once!), see Fig. 2.  

Figure 3. Demonstration of how droplets and plumes of air from the mouth are kept closer to the body when wearing a mask (Bhagat et al. 2020).

Fittingly, we also had a lecture from Paul Linden about the transmission of Covid, and he demonstrated how effective masks are at preventing transmission using a great visualisation (Fig. 3). It was great to have topics such as these that are relevant in today’s world, and provided yet another real-world application of the fluid dynamics we had learned. 

Breakout Discussion Sessions 

Every afternoon, the day’s lecturers returned and invited us to ask them questions about their lectures, or just have an intelligent discussion about their area of expertise. Admittedly these sessions could get a little awkward when everyone was too tired to ask anything towards the end of the long two weeks, but these sessions were still incredibly useful. They provided us the means to speak to a professional in their field about their research, and allowed us time to network and ask them some challenging questions. 

Concluding Remarks 

Of course, over the course of the two weeks we learned so much more than what I described above, and yet again demonstrates the versatility of the field! The summer school as a whole was organised really well and the lecturers were engaging and genuinely interested in hearing about us and our projects. I would highly recommend attending this summer school next year to any PhD student – the scope of the school was so broad that I am sure there will be something for everyone in the programme, and fingers crossed it goes ahead in Paris next year! 

References 

Bhagat, R., Davies Wykes, M., Dalziel, S., & Linden, P. (2020). Effects of ventilation on the indoor spread of COVID-19. Journal of Fluid Mechanics, 903, F1. doi:10.1017/jfm.2020.720 

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