When a body is submerged into a moving fluid, a wake forms. The nature of the wake can affect the body's aerodynamics, structural integrity and the generated noise. Over the last 60 years, axisymmetric wakes have been generated using axisymmetric bodies, such as disks, spheres and bodies of revolution, and key parameters such as the drag coefficient, shedding frequency and similarity and scaling of the wake width and velocity deficit have been documented and verified by numerous experimental and numerical studies. However, asymmetric fractal plates have recently been used to generate axisymmetric wakes. These multiscale wake generators provide a new way to investigate turbulent wakes by exciting several scales and weakening the vortex shedding phenomena. The aim of this video is to illustrate some key characteristics of fractal-generated wakes by mean of comparisons between Direct Numerical Simulation visualisations and wind-tunnel measurements. See Non equilibrium scalings of turbulent wakes M. Obligado, T. Dairay, and J. C. Vassilicos Phys. Rev. Fluids 1, 044409 and Dairay T. & Vassilicos J.C. Direct numerical simulation of a turbulent wake: the non-equilibrium dissipation law, Int. J. of Heat and Fluid Flow, 62(A), 68-74 for more details. Credits: Thibault Dairay, Martin Obligado and Christos Vassilicos.
Vortical structures generated in the wake of two in-line wind turbines with an incoming velocity of 10 m/s. The simulation was performed on ARCHER using the high-order finite-difference flow framework Winc3d/Incompact3d. The wind turbines are modelled using an actuator line model. Credits: Georgios Deskos