Oscillating grid Turbulence: The influence of Reynolds number and forcing

Direct numerical simulations are performed to study turbulence generated by oscillating grids, modeled by a localized body forcing. The flow exhibits three distinct regions: (i) a homogeneous turbulent core, (ii) a transport-dominated zone with algebraic decay, and (iii) an interfacial layer where the turbulent kinetic energy decreases exponentially. Velocity spectra in the core region develop a Kolmogorov-like inertial subrange, confirming the establishment of fully developed turbulence. The results show persistent anisotropy, with grid-normal velocity fluctuations exceeding parallel components across all Reynolds numbers, in contrast to classical freely decaying turbulence. The energy decay exponents depend on the geometry and forcing of the grid and agree with the broad scatter reported in experimental studies. These findings indicate that oscillating-grid turbulence is reproducible but non-universal, providing a controlled configuration for the study of entrainment, mixing, and scalar transport.