Construction and characterization of a large jet grid for the Twente Water Tunnel

A new jet grid has been developed for generating turbulence in the Twente Water Tunnel to facilitate experimental investigations into multiphase flows at high Taylor-Reynolds numbers. Our innovative system features 112 individually controllable jets pointing parallel to the main flow direction arranged in a square staggered grid. The jets fire with a nozzle exit velocity of around 10 m/s. The jet grid measures 45 by 45 centimeters, and boasts various advancements, such as the capability to independently control the mean flow and turbulence generation and a novel firing protocol, based on OpenSimplex noise. This type of gradient noise provides spatial and temporal coherence, allowing fine-tuning of turbulence downstream from the grid. We have experimentally investigated various jetting protocols using LDV and CTA measurements. We will present results of these validation measurements to demonstrate that the resulting turbulence is homogeneous and isotropic and to quantify the turbulence levels.