Characterization of the reacting laminar flow in a cylindrical cavity with a rotating endwall using numerical simulations and a combined PIV/PLIF technique

In this paper we analyse, numerically and experimentally, the laminar reactive flow in a cylindrical cavity with a rotating end wall. A basic solution is initially in the cavity and an acid solution is introduced at very low velocity through the center of the stationary endwall when the flow in the cavity is at the steady state. The effect of the different flow structures obtained at different Reynolds numbers on the irreversible fast acid-base neutralization is measured with a simultaneous Particle Image Velocimetry (PIV) and Planar Laser Induced Fluorescence (PLIF) technique and simulated numerically with a finite volume code. The observed flow structure, the recirculation bubbles in the vortex breakdown regions as well as the numerical velocity profiles are in agreement with the measurements and with previous studies. The range of measured concentrations is limited to regions where the molar fraction of the base (xB) is larger than 0.57. The comparison between the experimental and numerical contours of concentration of base solution at Re = 1000 and 1500 are in general agreement. At larger Reynolds numbers (Re = 1700, 2000 and 2300), the experimental and numerical contours of concentration of base solution inside the vortex breakdown bubbles differ because of the relatively large concentration of product (i.e. xB < 0.57) in these regions, which is predicted by the numerical simulations. The effects of small lateral displacements of the axis of rotation with respect to the axis of the cylindrical cavity on the flow and the chemical reaction are analyzed. It has been found that for the fast irreversible reaction considered the small displacements do not increase significantly the reaction rate but improve the mixing of the product of the reaction.