I have been involved in the creation of a European pre-standard for the validation of computational models used to predict the structural performance of engineering systems [see ‘Setting Standards‘ on January 24th, 2014]; so, an example of a two thousand year old standard in the National Palace Museum in Taipei particularly attracted my interest during a recent visit to Taiwan. A Jia-liang is a standard measure from the Xin Dynasty dated to between 9 and 24 CE. It is an early form of standard weights and measure issued by the Chinese emperor. The main cylinder contains a volume known as a ‘hu’; however, if you flip it over there is a small cylinder that contains a ‘dou’ which is one tenth of a ‘hu’. The object that looks like a handle on the right in the photograph is third cylinder that holds a ‘sheng’ which is one tenth of a ‘dou’ or one hundredth of a ‘hu’; and the handle on the left contains a ‘ge’ when it is as shown in the photograph and a ‘yue’ when the other way up. A ‘ge’ is tenth of ‘sheng’ and a ‘yeu’ is a twentieth. The Jia-liang was made of bronze with all of the information engraved on it and was used to measure grain across the Xin empire.
The harnessing of fusion energy has become something of a holy grail – sought after by many without much apparent progress. It is the energy process that ‘powers’ the stars and if we could reproduce it on earth in a controlled environment then it would offer almost unlimited energy with very low environmental costs. However, understanding the science is an enormous challenge and the engineering task to design, build and operate a fusion-fuelled power station is even greater. The engineering difficulties originate from the combination of two factors: the emergent behaviour present in the complex system and that it has never been done before. Engineering has achieved lots of firsts but usually through incremental development; however, with fusion energy it would appear that it will only work when all of the required conditions are present. In other words, incremental development is not viable and we need everything ready before flicking the switch. Not surprisingly, engineers are cautious about flicking switches when they are not sure what will happen. Yet, the potential benefits of getting it right are huge; so, we would really like to do it. Hence, the holy grail status: much sought after and offering infinite abundance.
Last week I joined the search, or at least offered guidance to those searching, by publishing an article in Royal Society Open Science on ‘An integrated digital framework for the design, build and operation of fusion power plants‘. Working with colleagues at the Culham Centre for Fusion Energy, Richard Taylor and I have taken our earlier work on an integrated nuclear digital environment for the nuclear energy using fission [see ‘Enabling or disruptive technology for nuclear engineering?‘ on january 28th, 2015] and combined it with the hierarchical pyramid of testing and simulation used in the aerospace industry [see ‘Hierarchical modelling in engineering and biology‘ on March 14th, 2018] to create a framework that can be used to guide the exploration of large design domains using computational models within a distributed and collaborative community of engineers and scientists. We hope it will shorten development times, reduce design and build costs, and improve credibility, operability, reliability and safety. It is a long list of potential benefits for a relatively simple idea in a relatively short paper (only 12 pages). Follow the link to find out more – it is an open access paper, so it’s free.
Patterson EA, Taylor RJ & Bankhead M, A framework for an integrated nuclear digital environment, Progress in Nuclear Energy, 87:97-103, 2016.
Patterson EA, Purdie S, Taylor RJ & Waldon C, An integrated digital framework for the design, build and operation of fusion power plants, Royal Society Open Science, 6(10):181847, 2019.
Most manufactured things break when you subject them to 90% strain; however Professor Xiaoyu Rayne Zheng of the Department of Mechanical Engineering at Virginia Tech has developed additively-manufactured metamaterials that completely recover from being deformed to this level. Strains are usually defined as the change in length divided by the original length and is limited in most engineering structures to less than 2%, which is the level at which steel experiences permanent deformation. Professor Zheng has developed a microstructure with a recurring architecture over seven orders of magnitude that allows an extraordinary level of elastic recovery; and then his team manufactures the material using microstereolithography. Stereolithography is a form of three-dimensional printing. Professor Zheng presented some of his research at the USAF research review that I attended last month [see ‘When an upgrade is downgrading‘ on August 21st, 2019 and ‘Coverts inspire adaptive wing design’ on September 11th, 2019]. He explained that, when these metamaterials are made out of a piezoelectric nanocomposite, they can be deployed as tactile sensors with directional sensitivity, or smart energy-absorbing materials.
Rayne Zheng and Aimy Wissa [‘Coverts inspire adaptive wing design’ on September 11th, 2019] both made Compelling Presentations [see post on March 21st, 2018] that captured my attention and imagination; and kept my phone in my pocket!
The picture is from https://www.raynexzheng.com/
For details of the additively-manufactured metamaterials see: Zheng, Xiaoyu, William Smith, Julie Jackson, Bryan Moran, Huachen Cui, Da Chen, Jianchao Ye et al. “Multiscale metallic metamaterials.” Nature materials 15, no. 10 (2016): 1100
For details of the piezoelectric metamaterials see: Cui, Huachen, Ryan Hensleigh, Desheng Yao, Deepam Maurya, Prashant Kumar, Min Gyu Kang, Shashank Priya, and Xiaoyu Rayne Zheng. “Three-dimensional printing of piezoelectric materials with designed anisotropy and directional response.” Nature materials 18, no. 3 (2019): 234
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.