Optimizing turbulent flow in an octagonal tank driven by synthetic jet arrays

We investigate turbulent flow in the octagonal tank stirred by four-quadrant planar jet arrays. The zero-net-mass flux jets are individually controlled by the Sunbathing algorithm in which the On / Off times are selected from two Gaussian distributions with different means but the same coefficient of variation. In order to create the optimal turbulent flow, a large volume of homogeneous isotropic turbulence with negligible mean flow, we vary the experimental conditions including jet-array configuration (jet-to-jet distance and the number of jets in horizontal and vertical direction), with or without screens in front of arrays, and the algorithmic parameters (mean On / Off time ratio and period of a single On-Off cycle). The quantitative measurement is performed by two-dimensional particle image velocimetry (PIV). The merit of the octagonal tank is to allow orthogonal field-of-views to be aligned without additional optics, such as a liquid-filled prism used for the stereoscopic PIV in the box-shaped tank. Velocity statistics, two-point correlations, energy spectra, and turbulence metrics are acquired from the velocity data and applied to compare the performance of the experimental conditions.