Grid generated turbulence under the rigid boundary influence

Abstract

An experimental investigation was carried out to study the grid generated turbulence and rigid boundary interaction for different mesh size of grid. Quadrant analysis technique was adopted here to provided information on the turbulent bursting events contributing to the Reynolds shear stress at the near rigid boundary region. It was observed that, near the rigid boundary the contribution to the total shear stress due to the ejection and sweeping events changed significantly for larger mesh size. The relative dominance of these two events were found to contribute in a cyclic manner in the near bed region, whereas such phenomenon disappeared in the main flow region. The distribution of the time interval of the ejection and sweeping events were found to change with the change in mesh size of the grid. To characterize the behaviour of eddies, several turbulence scales such as the integral scale, the Kolmogorov microscale, and the Taylor length scales were determined and compared for different mesh size of grids under rigid boundary influence. Integral and Kolmogorov length scales for larger mesh size were less compared to smaller mesh size, which implied that the smaller mesh size reduced the turbulent kinetic energy dissipation at a rate faster than the larger mesh size.