Meeting Abstract
Sharks in the hammerhead family (Sphyrnidae) can be recognized by their dorso-ventrally compressed and laterally expanded heads. Head width is highly variable within this family and the head width:body length ratio (HW:BL) decreases over evolutionary time. Additionally, there is a negative correlation between head width and pectoral fin area, suggesting that they may have complementary functions. Previous studies suggest that the pectoral fins, head or both play a role in lift generation, balancing forces on swimming sharks. Our goal is to determine how head morphology affects force generation in two hammerheads and one conventionally shaped shark. We collected CT-scan data from shark heads with varying morphology: blacknose (Carcharhinus acronotus – HW:BL = 15%), scalloped hammerhead (Sphyrna lewini – HW:BL = 26%), and bonnethead (Sphyrna tiburo – HW:BL = 18%). From the CT scans, we 3D printed models that were scaled to one-third of the original shark size. Models were placed in a water tunnel. We measured drag and lift coefficients for Reynolds numbers ranging from 2000 to 8000. Furthermore, we visualized the fluid-structure qualitatively through soap film set up and found a turbulent wake structure surrounded by unsteady laminar flow. To quantify the fluid-structure interaction, we applied Particle Image Velocimetry (PIV) . Quantifying the contribution of the hammerhead cephalofoil to generating lift may provide a better understanding of cephalofoil evolution and inspire biomimetic models.
