EXPERIMENTAL SCANNING FOR SIMPLIFYING THE MODEL OF A STIRRED-TANK FLOW

Velocity measurements by two-component laser Doppler velocimetry (LDV) and laser sheet visualizations were used to analyze the 3D turbulent flow field in a stirred tank, for the purpose of reducing the intricac y of the hydrodynamics to more simple models. We first deal with the m ean flow field measured, and the instantaneous visualized patterns, to appreciate the deviation from steadiness and predict the dispersion o f particles from the mean motion alone. The study then focuses on the discharge flow from the agitator (Rushton turbine). The jet at the exi t from the turbine is modeled in mean values. The flow instability as shown experimentally indicates that the Reynolds number plays no part in this phenomenon. A study based on dynamical system theory, consider ing a frequency modulation of the flow, shows the possibility of descr ibing rather simply the deterministic component in the velocity fluctu ation due to the blades.