Ben Evans

Nano-particle drag prediction at low Reynolds number using a direct Boltzmann–BGK solution approach

Abstract This paper outlines a novel approach for solution of the Boltzmann–BGK equation describing molecular gas dynamics applied to the challenging problem of drag prediction of a 2D circular nano-particle at transitional Knudsen number (0.0214) and low Reynolds number (0.25–2.0). The numerical scheme utilises a discontinuous-Galerkin finite element discretisation for the physical space representing the problem particle geometry and a high order discretisation for molecular velocity space describing the molecular distribution function. The paper shows that this method produces drag predictions that are aligned well with the range of drag predictions for this problem generated from the alternative numerical approaches of molecular dynamics codes and a modified continuum scheme. It also demonstrates the sensitivity of flow-field solutions and therefore drag predictions to the wall absorption parameter used to construct the solid wall boundary condition used in the solver algorithm. The results from this work has applications in fields ranging from diagnostics and therapeutics in medicine to the fields of semiconductors and xerographics.

Characterisation of an under-cured epoxy adhesive for use on the riv-bonded Bloodhound SSC lower chassis

Bloodhound SSC is a vehicle that aims to raise the World Land Speed Record to over 1000 mile/h in Hakskeen Pan, South Africa. Its lower chassis is a riv-bonded fabrication made using steel sheet for skins and aluminium alloy machinings for bulkheads. Fasteners alone were enough to satisfy the lower chassis structural requirements; however, Redux 312/5 epoxy adhesive was used to increase the stiffness of the structure and limit potential corrosion due to water and soil ingress. The use of dissimilar metals in the chassis could lead to panel buckling during elevated cure temperatures, meaning a low adhesive cure temperature of 80–90 ℃ was required to minimise this risk. As the cure pressure for the lower chassis adhesive was achieved using only rivets, the variation of cure pressure was experimentally investigated and found to be within the manufacturer’s recommendations for large sections of the lower chassis. Tensile testing indicated the chassis could be cured at 80 ℃ instead of the optimum 121 ℃, without significant loss of mechanical strength. A thermal characterisation of the adhesive was conducted using dynamic mechanical analysis and differential scanning calorimetry. A variety of cure profiles was investigated and resulted in a cure profile that maximised the glass transition temperature (Tg). An increase in cure duration to 8 h was recommended, which resulted in an increase in Tg by 15–24 ℃ to 83–92 ℃.

Solid particle erosion protection for the BLOODHOUND SSC front wheel arches

BLOODHOUND SSC is a World Land Speed Record Vehicle designed to travel at speeds of up to 1050 mph (469 m·s−1), with the lower chassis and suspension extremely close to the ground. The shockwave from the nose of the car is expected to fluidise the desert surface of the track in Hakskeen Pan, South Africa. Sacrificial materials must be added to the exterior of the car to limit erosive wear. An open loop gas blast erosion rig was used to test materials at velocities predicted by computational fluid dynamics in the front wheel arches, an area highlighted by the BLOODHOUND SSC engineers as requiring extensive protection. Tests of potential erosion protection materials were performed at 15° and 90° Impact angle using alumina as a substitute for Hakskeen Pan soil. Testing resulted in the use of a 2-mm thick Kevlar 49 laminate and 1.2 mm thick titanium Ti 15 V-3Cr-3Sn-3Al sheet for the wheel arch liner, with titanium Ti 6Al-4V used for the wheel arch lip. The erodent mass flow rate for the application was an unknown variable during testing; the test rig used a specific erodent mass flow rate of approximately 300 kg·m−2·s−1. Depending on in-service erosion rates, the titanium liner may be replaced with either a more durable liner made from Stellite 6B or a less dense liner made from aluminium Al 6082-T6.

Simulating the aerodynamic characteristics of the Land Speed Record vehicle BLOODHOUND SSC

This paper describes the application of a parallel finite-volume compressible Navier–Stokes computational fluid dynamics solver to the complex aerodynamic problem of a land-based supersonic vehicle, BLOODHOUND SSC. This is a complex aerodynamic problem because of the supersonic rolling ground, the rotating wheels and the shock waves in close proximity to the ground. The computational fluid dynamics system is used to develop a mature vehicle design from the initial concept stage, and the major aerodynamic design changes are identified. The paper’s focus, however, is on the predicted aerodynamic behaviour of the finalised (frozen) design which is currently being manufactured. The paper presents a summary of the data bank of predicted aerodynamic behaviours that will be used as the benchmark for vehicle testing and computational fluid dynamics validation throughout 2015 and 2016 in an attempt to achieve a Land Speed Record of 1000 mile/h (approximately Mach 1.3). The computational fluid dynamics predictions indicate that the current design has a benign lift distribution across the whole Mach range of interest and a sufficiently low drag coefficient to achieve this objective. It also indicates that the fin is sized appropriately to achieve the static margin requirements for directional stability. The paper concludes by presenting the impact of feeding the detailed computational fluid dynamics predictions into the overall vehicle performance model together with recommendations for further computational fluid dynamics study.

Enhancing Undergraduate Teaching and Feedback using Social Media - an Engineering Case Study

Abstract For large modules taught within the College of Engineering at Swansea University such as the level 1 module Scientific and Engineering Skills (EG168) or the Engineering Analysis (EG189/190) mathematics courses, it is a considerable challenge for the lecturer(s) to develop a meaningful relationship with students. Lecture cohorts on these modules are large (250 + students) and examples are delivered through smaller classes (~50 students) and laboratory sessions delivered by supplementary lecturers and/or postdoctoral researchers. This inevitably leads to a lack of continuity and meaningful engagement with regards to students’ contact with the lecturer. It also places a significant pressure on ‘office hours’ and email. It is common in student module feedback that the generic theory on these courses is not linked closely enough to discipline-specific engineering examples. Often this is due to wide range of disciplines studying the course (the EG168 module is taken by all level 1 engineering students and sports science students). This paper details a project aimed at tackling these problems by establishing an online community, using the social networking facility Twitter to connect students to the lecturer, who was able to drip feed examples to students in the form of online video ‘mini lectures’ posted and discussed via Twitter. It will be argued that this not only allowed an enhanced sense of affinity and belonging within the module cohort, but also improved real time feedback for the lecturer who was able to adjust future lecture content based on the feedback being received via Twitter. This technique was initially trialled on the EG168 Scientific and Engineering Skills module: a very large module (550 students) taken by students in the first term of their degree at Swansea University. It has more recently been adopted by other lecturers within the College on a range of modules. One of the aims within the EG168 module in recent deliveries has been to try and tailor examples to specific engineering disciplines whilst delivering generic content to the whole cohort through large lectures. It will be shown that delivery of online multimedia discipline-specific examples to students via the web (posted and discussed using Twitter) was a significant factor that helped achieve this.

Scale Adaptive Simulations over a Supersonic Car

In this study, the unsteady Reynolds-averaged Navier-Stokes equations are employed together with the Menter SST-SAS turbulence model in compressible flows. Numerical simulations over a supersonic car, the BLOODHOUND SSC (http://www.bloodhoundssc.swan.ac.uk/), are shown and discussed with Mach numbers up to 1.3.