Manipulating the direction of spectral energy flux in a thin-layer flow*

Manipulating turbulent energy flux among different scales can be a formidable task because the energy at any scale is not localized in physical space and vice versa. The ability to control energy flux and, thus, redistribute it among different length scales can be beneficial in many processes, such as chemical reactors. Here, we report a theoretical framework to manipulate the direction of energy flux in multi-scale flows. The theoretical framework's efficacy was tested experimentally with moving grids in an electromagnetically driven thin-layer shear flow and numerically with blinking force monopoles in a linear shear flow. Our results indicate that a physical perturbation with a designed geometric alignment with the background flow can generate desired directions of net energy flux, which can be applied for a wide range of natural or engineering applications.