(226f) Experimental Modelling of the Free Surface Shape in an Unbaffled Tank with a Newtonian Fluid

One of the most significant work on the prediction of the free surface shape in agitated tanks dates back to Nagata’s early contribution, over 40 years ago. Despite the usefulness of Nagata's findings, more work is required in order to predict the shape of free surfaces accurately, especially in industrial conditions. The aim of this work was to evaluate the applicability of two experimental methods for determining the free surface shape from the top of a tank. A Newtonian fluid of low viscosity was used to work in the turbulent flow regime. The first method relies on image processing and grey scales to determine both the shape and the depth of the vortex. The second one makes use of a laser beam to determine analogous information. The third method, used as a reference, is based on lateral observations of a transparent tank and on video recordings. To assess the performance of each method, we compare their accuracy and repeatability. Our results indicate that both methods (grey shades and laser beam) can provide reliable results for obtaining the shape and depth of the vortex. However, more variability was observed with the grey shades method. Additionally, the methods tested can provide quantitative measurements leading to the modelling of the shape of the vortex. The investigation methods presented herein will be helpful to determine vortex shapes and depths in industrial mixing conditions where transparent tanks and fluids are not used.