Abstract
Biological processes for wastewater treatment rely heavily on hydrodynamics, particularly mixing, for the removal of predominantly organic contaminants using microorganisms. The productivity of microorganisms and their life demands low shear flows especially laminar flows. Envisaging this objective, in the present work, the concept of laminar jet reactors is introduced. Lab scale experimental and numerical investigations have been carried out to study mixing characteristics and flow patterns in such a reactor. Experimentation has been conducted by visually observing the dispersion of the dye to determine the mixing time. Single phase Computational Fluid Dynamics (CFD) simulations have been employed for understanding the flow patterns and mixing time over a wide range of parameters namely Reynolds number (Re) in the range 581 = Re = 4000, and two discrete inlet heights from top to the radius, expressed as the normalized ratio (0.77 and 2.31). An optimum Re of 1000 gave the lowest mixing time for two specific jet inlet positions. A good agreement was observed between experiments and simulation predictions in mixing time with a deviation of 13-20%. Further, qualitative flow patterns in terms of velocity vectors from CFD simulations have also been presented.
