Biologging devices are used ubiquitously across vertebrate taxa in studies of movement and behavioural ecology to record data from organisms without the need for direct observation. Despite the dramatic increase in the sophistication of this technology, progress in reducing the impact of these devices to animals is less obvious, notwithstanding the implications for animal welfare. Existing guidelines focus on tag weight (e.g. the ‘5% rule'), ignoring aero/hydrodynamic forces in aerial and aquatic organisms, which can be considerable. Designing tags to minimize such impact for animals moving in fluid environments is not trivial, as the impact depends on the position of the tag on the animal, as well as its shape and dimensions. We demonstrate the capabilities of computational fluid dynamics (CFD) modelling to optimize the design and positioning of biologgers on marine animals, using the grey seal (Halichoerus grypus) as a model species. Specifically, we investigate the effects of (a) tag form, (b) tag size, and (c) tag position and quantify the impact under frontal hydrodynamic forces, as encountered by seals swimming at sea. By comparing a conventional versus a streamlined tag, we show that the former can induce up to 22% larger drag for a swimming seal; to match the drag of the streamlined tag, the conventional tag would have to be reduced in size by 50%. For the conventional tag, the drag induced can differ by up to 11% depending on the position along the seal's body, whereas for the streamlined tag this difference amounts to only 5%. We conclude by showing how the CFD simulation approach can be used to optimize tag design to reduce drag for aerial and aquatic species, including issues such as the impact of lateral currents (unexplored until now). We also provide a step‐by‐step guide to facilitate the implementation of CFD in biologging tag design.

The BLOODHOUND SSC project was publicly announced in October 2008, with a primary engineering objective of designing, constructing and running a vehicle capable of achieving a speed of 1000 mph on land. The aerodynamic design of this vehicle is to be accomplished using computational simulation only and this paper describes the development and application of the approach adopted. The computational model employs a cell vertex finite volume algorithm for the solution of compressible viscous flow problems on unstructured hybrid meshes. A one equation turbulence model is adopted and the solution of the steady flow equations is obtained by explicit relaxation. For the combination of high Mach number, complex geometry and complex boundary conditions, involving rotating surfaces and a rolling ground, a consistent HLLC numerical flux function is adopted to ensure a stable procedure. To illustrate the impact of the approach upon the final configuration, a number of simulations undertaken to aid the aerodynamic design are described.

In this paper, an alternative approach to the traditional continuum analysis of flow problems is presented. The traditional methods, that have been popular with the CFD community in recent times, include potential flow, Euler and Navier-Stokes solvers. The method presented here involves solving the governing equation of the molecular gas dynamics that underlies the macroscopic behaviour described by the macroscopic governing equations. The equation solved is the Boltzmann kinetic equation in its simplified collisionless and BGK forms. The algorithm used is a discontinuous Taylor-Galerkin type and it is applied to the 2D problems of a highly rarefied gas expanding into a vacuum, flow over a vertical plate, rarefied hypersonic flow over a double ellipse, and subsonic and transonic flow over an aerofoil. The benefit of this type of solver is that it is not restricted to continuum regime (low Knudsen number) problems. However, it is a computationally expensive technique.

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.

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