Fluid-Structure Interaction of Stirrers in Mixing Vessels: Part I — Development of the Mechanical Model Available to Purchase

Mixing stirrers are subject to severe damages when the rotational speed approaches the Eigenfrequency. Damping due to fluid-structure interaction between the mixing stirrer and the fluid in the vessel has major influence on the Eigenfrequency. Therefore coupled analysis of the flow field within a mixing vessel and the structural dynamic response of the stirrer should be conducted in order to evaluate vibrational amplitudes to guarantee life time safety for the stirrer. In some previous works at our institute CFD analysis of mixing stirrers has been carried out for both one-phase and two-phase flow. In this paper a simplified numerical model based on Newmark’s integration scheme is developed for the stirrer dynamics that is suitable to be implemented in the CFD code as a user subroutine. Results in terms of Eigenfrequencies are compared to results of analytical formulae and FEM results and show excellent agreement. In the second part of the paper the fully fluid-structure coupled analysis is presented (Part II).