Mixing of Horizontally Injected High-Density Solution in Vertically Upward Low-Velocity Water Flow

Abstract

Basic experiments on the mixing of horizontally injected high-density calcium chloride water solution in vertically upward low-velocity water flow have been performed in a small-scale apparatus. Mixing patterns observed in the experiments have been classified into complete mixing and incomplete mixing, or complete entrainment and incomplete entrainment. In complete mixing, the injected high-density solution is completely mixed with or entrained into the vertically upward water flow. On the other hand, in incomplete mixing, the high-density solution is partly mixed with or entrained into the vertically upward water flow and partly falls down or stays there even in the upward water flow. Numerical calculations have been conducted by solving the continuity equation and the momentum equations for the total fluid together with the mass transfer equation for the solute, taking density change into account. The numerical calculations have predicted approximately the increase in mixing efficiency, which is defined as the fraction of the injected solute mass that actually leaves the test section, and the calculations also have estimated approximately the boundary flow rates between the complete and incomplete mixing processes observed in the experiments.