The Study Of The Effects Of Surface Roughness Of Loggerhead Sea Turtle Shell In Relation To Drag Coefficient

Chan, Alan Kah Poh (2008) The Study Of The Effects Of Surface Roughness Of Loggerhead Sea Turtle Shell In Relation To Drag Coefficient. Project Report. UTeM, Melaka, Malaysia. (Submitted)

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Abstract

The present investigation primarily studies the effect of surface roughness on the drag coefficient, Cd of a Loggerhead sea turtle carapace using a subsonic wind tunnel. The pressure coefficient, Cp distribution across the Loggerhead carapace was also investigated and is compared to the Cp trend of an airfoil in order to deduce the aerodynamics features of the Loggerhead carapace. One-to-five-scaled models are created based on the dimensions of a real Loggerhead Mle with simplification.Three roughness scales were employed to capture the Cd trend at increase Reynolds number, Re. As expected, the Cd leveled off with Re for all four models investigated.However, the Re where constant Cd begins varies with relative roughness of the carapace models. The results also show good correlation between the Cd and relative roughness. In addition, the wind tunnel results are able to capture the Cp trend of the carapace models where maximum Cd was achieved at an angle of attack of -30 ". Cp comparisons with an airfoil body both qualitatively classifies the upper surface of a Loggerhead carapace to be of stream-line-nature so long as its angle of attack is kept to a zero or negative-value (counter-clockwise direction) region from the horizontal axis, as analyzed from the Cp values at different angles of attack. This would trigger development in submergence vehicle research as spearheaded by a Japanese researcher, Konno (Konno A. et al. 2005)

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