Abstract
We attempted to generate homogeneous turbulence of high intensity and large scale using a multi-fan wind tunnel. Input signals composed of multiple sinusoidal waves of constant amplitude were fed to each fan with quasi-random phases (“random-phase method”). This method produced approximately homogeneous and isotropic turbulence within a short distance. Although a pulsating component survived for the random-phase method using a single sinusoidal wave, it disappeared when multiple sinusoidal waves were applied. The initially provided rectangular spectrum rapidly changed its form as turbulence convected downstream, and asymptoted to a well-known broader spectrum with a few decades of inertial subrange of slope close to -5/3. The traditional method of generating approximately isotropic turbulence is by means of a grid, for which turbulence Reynolds number Reλ is low, typically in the range 50 to 150. The present method achieved a turbulence-Reynolds number of 753 for the largest amplitude of the input signals. The turbulence characteristics were compared with those of previous studies using active tubulence generation, such as a Makita-style active grid.
