Turbulence enhancement with a fan array wind generator using geometrically textured actuation and particle swarm optimization

Fan array wind generators (FAWG) are designed to generate a rich set of turbulent flows reminiscent of those found in natural environments. In this study, we experimentally investigate a square FAWG consisting of 10 × 10 individually controllable fans with 4 cm width and a maximum velocity of 17 m/s. The goal is to maximize the turbulence intensity in the test region. Two approaches for fan operation are investigated: first, geometric texturing of the duty cycle distribution, and second, maximization of the turbulence intensity at selected hot-wire sensors with particle-swarm optimization (PSO). We find that geometric texturing, specifically a checkerboard pattern of active fans, yields a nearly uniform turbulence field driven by jet interactions with turbulence levels around 0.14. However, particle swarm optimization doubles this local turbulence level yielding 0.28 at the chosen sensor locations but sacrifices performance elsewhere. A physical analysis reveals that particle swarm location places the sensors in the shear-layer between active and inactive regions while geometric texturing exploits the large fluctuation at the end of the potential core of the active patches. This region marks the maximum achievable turbulence level. The proposed physical interpretation of texture-based turbulence enhancement is corroborated with a square 40 × 40 fan array wind generator (Guinness World Record 2025) with a width of 3.25 m. Texture-based turbulence control opens a promising avenue to simultaneously command the mean velocity profile and the turbulence level field of a sufficiently large fan array wind generator.