Tag Archives: water

Storm in a computer

Decorative painting of a stormy seascapeAs part of my undergraduate course on thermodynamics [see ‘Change in focus’ on October 5th, 2022) and in my MOOC on Thermodynamics in Everyday Life [See ‘Engaging learners on-line‘ on May 25th, 2016], I used to ask students to read Chapter 1 ‘The Storm in the Computer’ from Philosophy and Simulation: The Emergence of Synthetic Reason by Manuel Delanda.  It is a mind-stretching read and I recommended that students read it at least twice in order to appreciate its messages.  To support their learning, I provided them with a précis of the chapter that is reproduced below in a slightly modified form.

At the start of the chapter, the simplest emergent properties, such as the temperature and pressure of a body of water in a container, are discussed [see ‘Emergent properties’ on September 16th, 2015].  These properties are described as emergent because they are not the property of a single component of the system, that is individual water molecules but are features of the system as a whole.  They arise from an objective averaging process for the billions of molecules of water in the container.  The discussion is extended to two bodies of water, one hot and one cold brought into contact within one another.  An average temperature will emerge with a redistribution of molecules to create a less ordered state.  The spontaneous flow of energy, as temperature differences cancel themselves, is identified as an important driver or capability, especially when the hot body is continually refreshed by a fire, for instance.  Engineers harness energy gradients or differences and the resultant energy flow to do useful work, for instance in turbines.

However, Delanda does not deviate to discuss how engineers exploit energy gradients.  Instead he identifies the spontaneous flow of molecules, as they self-organise across an energy gradient, as the driver of circulatory flows in the oceans and atmosphere, known as convection cells.  Five to eight convections cells can merge in the atmosphere to form a thunderstorm.  In thunderstorms, when the rising water vapour becomes rain, the phase transition from vapour to liquid releases latent heat or energy that helps sustain the storm system.  At the same time, gradients in electrical charge between the upper and lower sections of the storm generate lightening.

Delanda highlights that emergent properties can be established by elucidating the mechanisms that produce them at one scale and these emergent properties can become the components of a phenomenon at a much larger scale.  This allows scientists and engineers to construct models that take for granted the existence of emergent properties at one scale to explain behaviour at another, which is called ‘mechanism-independence’.  For example, it is unnecessary to model molecular movement to predict heat transfer.  These ideas allow simulations to replicate behaviour at the system level without the need for high-fidelity representations at all scales.  The art of modelling is the ability to decide what changes do, and what changes do not, make a difference, i.e., what to include and exclude.

Source:

Manuel Delanda Philosophy and Simulation: The Emergence of Synthetic Reason, Continuum, London, 2011.

Image: Painting by Sarah Evans owned by the author.

Floods: an everyday example

floodingI wrote this post before going to the concert at the Philharmonic Hall which inspired the post on February 5th [Rhapsody in Blue].  So, this post is not quite as timely as planned originally but it is still raining frequently here and the Somerset levels remain flooded.

Since before Christmas news bulletins in the US and UK have been dominated by reports of extreme weather events.  Earlier this month the sea on the south coast of the England swept away a substantial length of the main railway line between London and the South-West of the country.  Large areas of the south of the UK have been flooded by storms that rolled across the Atlantic having first caused disruption in North America.  There seems to be plenty of everyday evidence from these events that our climate is changing and this appears to have been confirmed by the Chief Scientist at the UK Metrological Office.

The Intergovernmental Panel on Climate Change has stated ‘Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia.  The atmosphere and oceans have warmed, the amounts of snow and ice diminished, sea level has risen, and the concentrations of greenhouse gases have increased.’  They go on to say ‘It is extremely likely that human influence has been the dominant cause of the observed warming since the mid-twentieth century’.  Despite these assertions, our governments have been unable to make significant progress towards limiting global warming to 2 degrees Celsius compared to pre-industrial levels.  The delegations from most of the developed countries walked out of talks at the Warsaw climate conference last November, followed by representatives from the Green groups and NGOs the next day.  As a consequence, Kofi Annan [Climate crisis: Who will act? in International NYT  November 25, 2013] has called for a global grass-roots movement to tackle climate change and its consequences.  We need to act as individuals whenever we can to reduce global warming and mitigate its impact both directly in our personal and professional lives and indirectly by lobbying our political and industrial/commercial leaders.

In the UK, politicians and the media are beginning to talk about the need for engineers to protect us against flooding and some engineers are responding by highlighting that the cost will be very high and that if climate change continues then we will have consider abandoning some areas.

At a simpler level, those us working in the classroom can use the flooded roads and overwhelmed drainage systems to create topical, and perhaps increasingly everyday, examples focused on flow in drainage ditches, gutters etc., as in the lesson plan below.

5EplanNoF10_open_channel_flow

See also the Everyday Examples page on this blog for more lesson plans and more background on Everyday Examples.

Water, water, everywhere

Wood engraving illustration of the Ancient Mariner by Gustave Dore

Wood engraving illustration of the Ancient Mariner by Gustave Dore

Water, water, every where,
And all the boards did shrink;
Water, water, every where,
Nor any drop to drink.

These lines are from the Rime of the Ancient Mariner by Samuel Taylor Coleridge published in 1798.  They were brought to my mind when I was looking at the data in the GIO report on ‘Water’ that I mentioned in my post entitled ‘Closed system: water’ [17th July, 2013].

The quantity of water used to produce some everyday familiar items is staggering, for instance 140 liters to make one cup of coffee [growing the beans, harvesting, transporting and processing them], or 1,300 litres for a kilogram of wheat resulting in 40 litres per slice of bread but that is tiny compared to 1800 litres for a 4oz beef burger.  You might be reading this in a part of the world that is constantly, or at least frequently, deluged with rain and so be thinking that none of this matters, except that much of what you consumes probably comes from a part of the world where water is less readily available and massive civil engineering projects are required to ensure an adequate supply, which have enormous ecological consequences.

And that pair of jeans you are probably wearing, well, they required 10,855 litres of water!

Click to access ibm_gio_water_report.pdf