From bore-soliton-splash to a new wave-to-wire wave-energy model

We explore extreme nonlinear water-wave amplification in a contraction or, analogously, wave amplification in crossing seas. The latter case can lead to extreme or rogue-wave formation at sea. First, amplification of a solitary-water-wave compound running into a contraction is disseminated experimentally in a wave tank. Maximum amplification in our bore–soliton–splash observed is circa tenfold. Subsequently, we summarise some nonlinear and numerical modelling approaches, validated for amplifying, contracting waves. These amplification phenomena observed have led us to develop a novel wave-energy device with wave amplification in a contraction used to enhance wave-activated buoy motion and magnetically induced energy generation. An experimental proof-of-principle shows that our wave-energy device works. Most importantly, we develop a novel wave-to-wire mathematical model of the combined wave hydrodynamics, wave-activated buoy motion and electric power generation by magnetic induction, from first principles, satisfying one grand variational principle in its conservative limit. Wave and buoy dynamics are coupled via a Lagrange multiplier, which boundary value at the waterline is in a subtle way solved explicitly by imposing incompressibility in a weak sense. Dissipative features, such as electrical wire resistance and nonlinear LED loads, are added a posteriori. New is also the intricate and compatible finite-element space–time discretisation of the linearised dynamics, guaranteeing numerical stability and the correct energy transfer between the three subsystems. Preliminary simulations of our simplified and linearised wave-energy model are encouraging and involve a first study of the resonant behaviour and parameter dependence of the device

Analytical and computational modelling for wave energy systems:the example of oscillating wave surge converters

This is an Open Access Article. It is published by Springer under the Creative Commons Attribution 4.0 International Licence (CC BY). Full details of this licence are available at: http://creativecommons.org/licenses/by/4.0/The development of new wave energy converters has shed light on a number of unanswered questions in fluid mechanics, but has also identified a number of new issues of importance for their future deployment. The main concerns relevant to the practical use of wave energy converters are sustainabiliy, survivability, and maintainability. And of course, it is also necessary to maximize the capture per unit area of the structure as well as to minimize the cost. In this review, we consider some of the questions related to the topics of sustainability, survivability, and maintenance access, with respect to sea conditions, for generic wave energy converters with an emphasis on the oscillating wave surge converter (OWSC). New analytical models that have been developed are a topic of particular discussion. It is also shown how existing numerical models have been pushed to their limits to provide answers to open questions relating to the operation and characteristics of wave energy converters

Comparison of a percutaneous device and the bougie-assisted surgical technique for emergency cricothyrotomy: an experimental study on a porcine model performed by air ambulance anaesthesiologists

Background A large number of techniques and devices for cricothyroidotomy have been developed. In this study, the Portex™ Cricothyroidotomy Kit (PCK, Smiths Medical Ltd, Hythe, UK) was compared with the bougie assisted emergency surgical cricothyrotomy technique (BACT). Methods Twenty air ambulance anaesthesiologists performed emergency cricothyrotomy on a cadaveric porcine airway model using both PCK and BACT. Baseline performance and performance after the intensive training package were recorded. Success rate, time to secured airway and tracheal damage were the primary endpoints, and confidence rating was a secondary endpoint. Results During baseline testing, success rates for PCK and BACT were 60% and 95%, respectively. Tracheal injury rate with PCK was 60% while no such injury was found in BACT. A lecture was given and skills were trained until the participants were able to perform five consecutive successful procedures with both techniques. In the post-training test, all participants were successful with either technique. The mean time to successful insertion was reduced by 15.7 seconds (from 36.3 seconds to 20.6 seconds, p< 0.001) for PCK and by 7.8 seconds (from 44.9 seconds to 37.1 seconds, p=0.021) for BACT. In the post-training scenario, securing the airway with PCK was significantly faster than with BACT (p<0.001). Post-training tracheal laceration occurred in six (30%) of the PCK procedures and in none of the BACT procedures (p=0.028). The self-evaluated confidence level was measured both pre- and post-training using a confidence scale with 10 indicating maximum amount of confidence. The median values increased from 4 to 8 for PCK and from 6.5 to 9.5 for BACT. All participants reported that BACT was their preferred technique. Conclusions Testing the base-line PCK skills of prehospital anaesthesiologists revealed low confidence, sub-optimal performance and a very high failure rate. The BACT technique demonstrated a significantly higher success rate and no tracheal damage. In spite of PCK being a significantly faster technique in the post-training test, the anaesthesiologists still reported a higher confidence in BACT. Limitations of the cadaveric porcine airway may have influenced this study because the airway did not challenge the clinicians with realistic tissue bleeding

Combining in-situ simulation and live HEMS mission facilitator observation: a flexible learning concept

Background Continuous medical education is essential in Helicopter Emergency Medical Services (HEMS). In-situ simulation training makes it possible to train in a familiar environment. The use of a dedicated facilitator is essential; however, when an in-situ simulation training session is interrupted by a live mission, the efforts invested in the training are left unfulfilled. This study aims to evaluate if HEMS mission observation and debriefing by the simulation facilitator is a feasible alternative to mission-interrupted simulation training, and how this alternative to simulation training is perceived by both facilitators and HEMS crew members. Methods Facilitator observation during live missions and post-mission debriefing was offered as an alternative to mission-interrupted simulation training over a one-year period at three HEMS bases. Immediate feedback was requested from crews and facilitators after each observed live mission on a predefined questionnaire. At the end of the study period, semi-structured interviews were performed with a sample of HEMS crew members and facilitators to further explore the experience with the concept. Numerical data about the sessions were recorded continuously. Results A total of 78 training sessions were attempted, with 46 (59%) of the simulations conducted as planned. Of the remaining, 23 (29%) were not started because the crew had other duties (fatigued crew or crew called for a mission where observation was inappropriate/impossible), and 9 (12%) training sessions were converted to observed live missions. In total, 43 (55%), 16 (21%) and 19 (24%) attempts to facilitate simulation training were undertaken on the three bases, respectively. The facilitators considered mission observation more challenging than simulation. The interviews identified local know-how, clinical skills, and excellent communication skills as important prerequisites for the facilitators to conduct live mission observation successfully. Participating crews and facilitators found simulation both valuable and needed. Being observed was initially perceived as unpleasant but later regarded as a helpful way of learning. Conclusion Live mission observation and debriefing seems a feasible and well-received alternative to an in-situ simulation program in HEMS to maximise invested resources and maintain the learning outcome. Furthermore, additional training of simulation facilitators to handle the context of live mission observation may further improve the learning output