Hydrodynamic Resistance of a Surfboard: An Analytical, Empirical, and Statistical Analysis
Kledzik, Andrew L.
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The objective of the present study defines a drag coefficient for a 9’0” surfboard. The hydrodynamic drag of a surfboard is derived from theory outlining the mathematical foundation used. Analytical solutions provide values for boundary layer thickness, momentum flux width, shear stress, drag force and the drag coefficient. This study also examines maximum velocities attainable from in-situ observations of surfers paddling in a controlled environment. The theoretical predictions are compared with experimental observations of surfboard resistance; while simultaneously validating instrumentation and methods of measurement. A number of problems are highlighted, ranging from mathematical problems on turbulent flow analysis to impacts on coastal processes and economic considerations. A review of the physical characteristics for ocean waves provides information on instrumentation deployed in the field. The methodology delivers a means for testing surfboard drag properties; and facilitates the pursuit of designing a more hydrodynamic surfboard. The results for the drag properties of a 9' 0" surfboard (average 𝐷𝑟𝑎𝑔 𝐹𝑜𝑟𝑐𝑒 = 311 Newtons, and velocity dependent average 𝐶𝐷 = 0.6 to 0.005 can be used for comparison against future surfboard drag experiments. Furthermore, identification of the resistive forces acting on a surfboard establishes a sound foundation for continued research of the more complicated aspects of the hydrodynamic characteristics of surfboard design. The experimental approach of the present study provides in-situ data for accelerations (𝐴𝑥 ≤ 3 𝑚/𝑠²), velocities (0 ≤ 𝑣 ≤ 3 𝑚/𝑠), Froude #’s (0.05 ≤ 𝐹𝑟 ≤ 0.6), and Reynolds #’s (1.0 ≤ 𝑅𝑒 ≤ 7.98 (x 10⁶)).