Tag Archives: creativity

Coverts inspire adaptive wing design

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Earlier this summer, when we were walking the South West Coastal Path [see ‘The Salt Path‘ on August 14th, 2019], we frequently saw kestrels hovering above the path ahead of us.  It is an enthralling sight watching them use the air currents around the cliffs to soar, hang and dive for prey.  Their mastery of the air looks effortless.  What you cannot see from the ground is the complex motion of their wing feathers changing the shape and texture of their wing to optimise lift and drag.  The base of their flight feathers are covered by small flexible feathers called ‘coverts’ or ‘tectrix’, which in flight reduce drag by providing a smooth surface for airflow.  However, at low speed, such as when hovering or landing, the coverts lift up and the change the shape and texture of the wing to prevent aerodynamic stalling.  In other words, the coverts help the airflow to follow the contour of the wing, or to remain attached to the wing, and thus to generate lift.  Aircraft use wing flaps on their trailing edges to achieve the same effect, i.e. to generate sufficient lift at slow speeds, but birds use a more elegant and lighter solution: coverts.  Coverts are deployed passively to mitigate stalls in lower speed flight, as in the picture.  When I was in the US last month [see ‘When upgrading is downgrading‘ on August 21st, 2019], one of the research reports was by Professor Aimy Wissa of the Department of Mechanical Science & Engineering at the University of Illinois Urbana-Champaign, who is working on ‘Spatially distributed passively deployable structures for stall mitigation‘ in her Bio-inspired Adaptive Morphology laboratory.  She is exploring how flaps could be placed over the surface of aircraft wings to deploy in a similar way to a bird’s covert feathers and provide enhanced lift at low speeds.  This would be useful for drones and other unmanned air vehicles (UAVs) that need to manoeuvre in confined spaces, for instance in cityscapes.

I must admit that I had occasionally noticed the waves of fluttering small feathers across the back of a bird’s wing but, until I listened to Aimy’s presentation, I had not realised their purpose; perhaps that lack of insight is why I specialised in structural mechanics rather than fluid mechanics with the result that I was worrying about the fatigue life of the wing flaps during her talk.

 

The picture is from a video available at Kestrel Hovering and Hunting in Cornwall by Paul Dinning.

 

Taking a sketch instead of snapping a photo

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We are lucky to live in a house with a great view of Liverpool cathedral [see picture in ‘Two for one‘ on January 2nd, 2019].  Hundreds of tourists visit every day and take pictures of the cathedral with their smart phones.  A few even turn around and take a picture of our house!  It is a modern disease: capturing pictures of a spectacle without actually looking at it and then probably never looking at the photograph.  There is some small level of fulfilment in having taken the photograph; however, 120 years ago there were fewer tourists and they had no cameras.  Instead, when Charles Rennie MackIntosh visited Naples on April 8th, 1891, he admired the tower of the Church of Santa Maria del Carmine and ‘took a sketch’.  It must have taken him some time and concentrated effort.  The level of pleasure and fulfilment from taking a sketch must have been much greater than from our modern experience of snapping a photo.

Of course, there was no Liverpool Cathedral in 1891 and ten years later, Rennie Mackintosh was disappointed that his proposals for it were not selected from the 103 submitted.

Photograph taken on 17th August 2019 by the author at the Rennie Mackintosh Exhibition at the Walker Art Gallery, Liverpool.

Engineering correspondents needed

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Society’s perception  of scientists and engineers is not well-balanced; scientists tend to get the headlines when they make new discoveries while engineers are only in the headlines when things go wrong.  Even worse, when I was a student, the successes of the NASA’s space shuttle were usually reported as scientific achievements while its problems were engineering failures; when the whole programme was an enormous feat of engineering!  Perhaps this is because news organisations tend to have science correspondents and editors but no engineering correspondents.  When you search for engineering journalism jobs most of the results relate to roles associated with the technology of journalism; whereas a search for science journalism jobs results in dozens of vacancies for science writers, correspondents and editors.  The lack of engineering correspondents has been evident in the UK during the past week in reporting about the potential bursting of the dam at Toddbrock Reservoir and flooding of the town of Whaley Bridge in Derbyshire UK.  A 188 year old dam has been damaged by the turbulent flow of water over its spillway following unprecedented levels of rainfall (e.g. https://www.bbc.co.uk/news/uk-england-derbyshire-49222956). There is little discussion of the significant achievement of the Victorian engineers who designed and built a dam in the 1831 that has lasted 188 years or that climate change is causing shifts in weather patterns which have altered the design specifications for engineering infrastructure including dams, bridges and sea defences.  We need more journalists to write about engineering and preferable more journalists who have been educated as engineers particularly as society starts to face the potential existential threat caused by climate change and over-population.

For more on the nature of engineering, and its relationship to science, see ‘Making things happen‘ on September 26th, 2018; ‘Engineering is all about ingenuity‘ on September 14th, 2016 and ‘Life takes engineering‘ on April 22nd 2015.

And on the communication skills of engineers: ‘Poetasting engineers‘ on March 4th, 2015 and ‘Einstein and public engagement‘ on August 8th, 2018.

Meta-knowledge: knowledge about knowledge

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As engineers, we like to draw simple diagrams of the systems that we are attempting to analyse because most of us are pictorial problem-solvers and recording the key elements of a problem in a sketch helps us to identify the important issues and select an appropriate solution procedure [see ‘Meta-representational competence’ on May 13th, 2015].  Of course, these simple representations can be misleading if we omit parameters or features that dominate the behaviour of the system; so, there is considerable skill in idealising a system so that the analysis is tractable, i.e. can be solved.  Students find it especially difficult to acquire these skills [see ‘Learning problem-solving skills‘ on October 24th, 2018] and many appear to avoid drawing a meaningful sketch even when examinations marks are allocated to it [see ‘Depressed by exams‘ on January 31st, 2018].  Of course, in thermodynamics it is complicated by the entropy of the system being reduced when we omit parameters in order to idealise the system; because with fewer parameters to describe the system there are fewer microstates in which the system can exist and, hence according to Boltzmann, the entropy will be lower [see ‘Entropy on the brain‘ on November 29th, 2017].  Perhaps this is the inverse of realising that we understand less as we know more.  In other words, as our knowledge grows it reveals to us that there is more to know and understand than we can ever hope to comprehend [see ‘Expanding universe‘ on February 7th, 2018]. Is that the second law of thermodynamics at work again, creating more disorder to counter the small amount of order achieved in your brain?

Image: Sketch made during an example class