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ISSN Online: 2377-424X

ISBN Print: 978-1-56700-421-2

International Heat Transfer Conference 15
August, 10-15, 2014, Kyoto, Japan

Effect of Shark Skin Textures on Entropy Generation for Turbulent Channel Flow and Heat Transfer Problems

Get access (open in a dialog) DOI: 10.1615/IHTC15.ttr.008699
pages 9173-9187

Аннотация

Shark skin texture, as a biomimetic technology, can be adopted from dolphins and sharks in order to reduce the drag as well as change the heat transfer performance at the wall surface. In order to understand the mechanisms by which heat transfer and drag are affected when a wall is covered by a shark skin like texture the local entropy generation rate is determined and compared to that for a flow over smooth walls. The results are obtained from the direct numerical simulations (DNS) which solve the incompressible Navier-Stokes equations for the flowfield and the temperature equation for the forced convection. Based on the DNS solutions details of the turbulence close to the wall can be analyzed and leads to the conclusion that basically certain turbulent structures are lifted off the wall and get rearranged, a mechanism we call lift off and alignment (LOA). The distribution of (time averaged and instantaneous) entropy generation rates supports this interpretation, showing a reduction next to the wall and an increase further away. Numerical results show that, with appropriate riblet height and spacing, not only drag is reduced by this texture, but also the Nusselt number, thus increasing the thermal body protection. Wedge-shaped riblets lead to more drag and Nusselt number reduction than blade-shaped ones since less entropy is generated near the riblet tips.