Numerical simulation of laminar-turbulent transition on a dolphin using the γ-Reθ model

Summary. The γ-Reθ-model, a two equation, correlation-based transition model using local variables, has been employed to predict the extension of the laminar regions on a stiff geometry of the common dolphin (delphinus delphis) moving in the Reynolds regime of 5.5·10 5 to 10 7. Mesh independence was gained for a domain resolution of approximately 30 million cells in an unstructured polyhedral mesh with a prismatic wall region (y + ≈ 1). The final results conclude with very limited laminar regions and thus a mainly turbulent flow around the body of a dolphin travelling at the usual speed of 3 m/s and a resulting drag coefficient of CD ≈ 0.004 referring to the wetted surface area of A = 1.571 m 2. Consequently the potential for active laminarisation due to the anisotropic structure of the dolphin skin is well established and is estimated to be as high as 20 % with respect to drag force reduction.