Tag Archives: aerospace

Fake facts & untrustworthy predictions

I need to confess to writing a misleading post some months ago entitled ‘In Einstein’s footprints?‘ on February 27th 2019, in which I promoted our 4th workshop on the ‘Validation of Computational Mechanics Models‘ that we held last month at Guild Hall of Carpenters [Zunfthaus zur Zimmerleuten] in Zurich.  I implied that speakers at the workshop would be stepping in Einstein’s footprints when they presented their research at the workshop, because Einstein presented a paper at the same venue in 1910.  However, as our host in Zurich revealed in his introductory remarks , the Guild Hall was gutted by fire in 2007 and so we were meeting in a fake, or replica, which was so good that most of us had not realised.  This was quite appropriate because a theme of the workshop was enhancing the credibility of computer models that are used to replicate the real-world.  We discussed the issues surrounding the trustworthiness of models in a wide range of fields including aerospace engineering, biomechanics, nuclear power and toxicology.  Many of the presentations are available on the website of the EU project MOTIVATE which organised and sponsored the workshop as part of its dissemination programme.  While we did not solve any problems, we did broaden people’s understanding of the issues associated with trustworthiness of predictions and identified the need to develop common approaches to support regulatory decisions across a range of industrial sectors – that’s probably the theme for our 5th workshop!

The MOTIVATE project has received funding from the Clean Sky 2 Joint Undertaking under the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 754660 and the Swiss State Secretariat for Education, Research and Innovation under contract number 17.00064.

The opinions expressed in this blog post reflect only the author’s view and the Clean Sky 2 Joint Undertaking is not responsible for any use that may be made of the information it contains.

Image: https://www.tagesanzeiger.ch/Zunfthaus-Zur-Zimmerleuten-Wiederaufbauprojekt-steht/story/30815219

 

Same problems in a different language

I spent a lot of time on trains last week.  I left Liverpool on Tuesday evening for Bristol and spent Wednesday at Airbus in Filton discussing the implementation of the technologies being developed in the EU Clean Sky 2 projects MOTIVATE and DIMES.  On Wednesday evening I travelled to Bracknell and on Thursday gave a seminar at Syngenta on model credibility in predictive toxicology before heading home to Liverpool.  But, on Friday I was on the train again, to Manchester this time, to listen to a group of my PhD students presenting their projects to their peers in our new Centre for Doctoral Training called Growing skills for Reliable Economic Energy from Nuclear, or GREEN.  The common thread, besides the train journeys, is the Fidelity And Credibility of Testing and Simulation (FACTS).  My research group is working on how we demonstrate the fidelity of predictions from models, how we establish trust in both predictions from computational models and measurements from experiments that are often also ‘models’ of the real world.  The issues are similar whether we are considering the structural performance of aircraft [as on Wednesday], the impact of agro-chemicals [as on Thursday], or the performance of fusion energy and the impact of a geological disposal site [as on Friday] (see ‘Hierarchical modelling in engineering and biology‘ on March 14th, 2018) .  The scientific and technical communities associated with each application talk a different language, in the sense that they use different technical jargon and acronyms; and they are surprised and interested to discover that similar problems are being tackled by communities that they rarely think about or encounter.

Coverts inspire adaptive wing design

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.

 

When an upgrade is downgrading

I had slightly surreal time last week.  I visited the USA to attend a review of a research programme sponsored by the US Government and reported on two of our research projects.  When I arrived in the USA on Monday evening, I went to collect my rental car and was told that I had been upgraded to a pick-up truck because the rental company did not have left any of the compact cars that had been booked for me.  I gingerly manoeuvred the massive vehicle, a Toyota Tacoma, out of the parking garage and on to the freeway.  I should admit to having owned a large SUV when we lived in the USA and so driving along the freeway was not a totally new experience, except that the white bonnet in front of me seemed huge.

The following morning, I drove to the location of the review and strategically selected a parking space with empty spaces all around it so that I could drive through into the space and avoid needing to reverse the behemoth.  As I was walking across the parking lot, someone accosted me and said: ‘Nice truck, how do you like it?’  Embarrassed at driving such an environmental-unfriendly vehicle, I responded that it was a rental car that I just picked up.  To which he replied that the best protection against my Tacoma, was his Tacoma. And, that it was his dream car.  Then, I noticed that he had parked his black one alongside mine.

Our children learnt to drive in our ancient Ford Explorer and loved it.  We all knew that it was wrong to drive something that consumed fuel so voraciously even if it did get us effortlessly through the most horrendous winter storms.  However, we have left all that behind and now either use public transport or drive cars that achieve 60 mpg or more on good days. But here I was being admitted to a club that worshipped their pick-up trucks.

We walked together into the review which was held in a small lecture theatre equipped with comfortable armchairs, which was just as well because we sat there from 8.30 to 4.30 for two days listening to half-hour presentations with only short breaks.  We were presented with some stunning research based on brilliant innovative thinking, such as materials that can undergo 90% deformation and fully recover their shape and how the rippling motion of covert feathers on a bird’s wings could help us design more efficient aeroplanes.  More on that in later posts.  Of course, there were some less good presentations that had many us reaching for our mobile phones to catch up on the endless flow of email [see: ‘Compelling Presentations‘ on March 21st, 2018).  At the end of each day, we dispersed to different hotels scattered across town in our rental cars.  On Thursday, I drove back to the airport and topped up the fuel tank before returning my truck.  I worked out that it had achieved only 19 mpg (US) or 23 mpg (UK), despite my gentle driving – that’s almost three times the consumption of my own car!  On the plane home I started reading ‘Overstory‘ by Richard Powers, a novel about our relationship to trees and the damage we are doing to the environment on which trees, and us, are dependent.