The Turbulent Flow in the Close-Up Region of Fractal Grids

Turbulence generated by fractal square grids differs substantially from all other documented turbulent flows. Previous experiments indicated that the turbulence intensity reaches its maximum at a position proportional to the length and thickness of the largest bar in the grid [2]. The goal of this work was to investigate the evolution of the flow behind grids with different smallest scales. Hot wire measurements were conducted close to the grid in two different wind tunnels using three different fractal grids. It was found that the positions of the flatness peak and turbulence intensity peak change by altering the numbers of iterations and the blockage ratio respectively. Furthermore, it was shown that this result is invariant to the investigated different boundary conditions.