ENHANCEMENT OF TURBULENT MIXING BY EMBEDDED LONGITUDINAL VORTICITY: A NUMERICAL STUDY AND EXPERIMENTAL COMPARISON
PROCEEDINGS OF THE ASME FLUIDS ENGINEERING DIVISION SUMMER CONFERENCE
1, PTS A AND B
This work concerns the characterization of turbulent flow underlying the mixing phenomenon in a static mixer-reactor HEV (high-efficiency vortex). An experimental test section made of a cylindrical tube equipped with seven rows of vortex generators was designed and constructed for this purpose. Each row has four vortex generators fixed symmetrically on the tube wall. This new type of mixer generates coherent structures in the form of longitudinal counter-rotative vortices. The resulting flow enhances radial mass transfer and thus facilitates the dispersion and mixing of the particles. The energy cost of this mixer is 1000 times less than that of other mixers for a given interface area [1, 2]. The aim of this work is to study numerically and experimentally the turbulence structure of the flow generated by the mixer, in particular the more energetic structures present in the base flow. Numerical simulations of the velocity distribution and turbulence levels inside the static mixer were conducted for various turbulence models by using the commercial mesh-generator code Gambit coupled with the CFD package Fluent. Attention was focused on the evolution and distribution of the rate of turbulent kinetic energy dissipation as the underlying mechanism for turbulent mixing. Experiments were carried out on the test section in a flow loop by using LDA. Mean and turbulent quantities were measured and numerical results were compared with experimental results. This study provides a basis for understanding the physical mechanisms in the mixing and homogenising of the flow and therefore the efficiency of the mixer.