The results of a detailed experimental investigation of the near-wake (up to seven turbine diameters downstream) of a model horizontal axis tidal turbine (HATT) device in a large-scale recirculating water channel facility are reported. An Acoustic Doppler Velocimeter is used to provide detailed threedimensional mean and turbulent flow field information at five different depths across the full width of the channel downstream of the turbine, giving the most complete three-dimensional velocities and Reynolds normal and shear stress data set yet available. In addition the Reynolds-stress anisotropy tensor is used to illustrate the degree of anisotropy of the Reynolds stress within the turbine’s wake. These\ud
results reveal the strongly anisotropic nature of the near-wake turbulence suggesting isotropic turbulence models should not be used to model near-wake dynamics. Finally the power-law decay rates of the maximum normalised turbulent kinetic energy differ significantly from those found downstream of grids, meshes or perforated disks, suggesting that previous modelling approaches, which neglected swirl effects and modelled the turbine by absorption discs, may significantly over predict the turbulent kinetic energy decay rate of HATT wakes
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AbstractPurpose -To fabricate and characterise novel heat sinks manufactured by selective laser melting (SLM). The investigation explores features of SLM produced heat sinks that may be exploited to improve their heat transfer capability. Design/methodology/approach -The study was conducted on heat sinks manufactured from 316L stainless steel and aluminium 6061. The heat transfer devices' thermal and pressure drop performances were determined by experimental test. Findings -The research demonstrates the performance enhancements that can be realised by using novel heat sink designs, fabricated by SLM, over conventional pin fin arrays. aluminium 6061 is used with the process to illustrate the improvement in heat transfer provided by higher conductivity feedstock materials. Research limitations/implications -Although the manufacturing technique is still in the development stage and the heat transfer devices that have so far been manufactured should not be considered optimal, the potential for creative new designs and applications is clear. This study highlights the need to develop the SLM process parameters to allow the repeatable production of heat transfer devices from higher conductivity metals with controllable surface finishes. Originality/value -This paper outlines the design issues and performance of novel heat transfer devices fabricated using SLM. A new material, aluminium 6061, is introduced to the family of materials that can be processed with SLM and example heat sinks are tested.
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