Unstable Phenomenon of Flow in a Mixing Vessel with a Marine Propeller

Abstract

Unstable flow phenomena in a mixing vessel with a marine propeller were investigated experimentally using flow visualization and LDV techniques. It was found that the instantaneous bulk flow profiles were usually asymmetric with respect to the impeller shaft and they fluctuated in the large time scale. The circulation flow patterns in the space between two adjacent baffles were classified into quick-return flow (QR), full-circulation flow (FC) and intermediate-circulation flow (IC), which were replaced randomly one after another with time. Their lifetimes were widely distributed from about half a second to several minutes. Connected with the circulation flow patterns, the impeller stream was directed vertically downward or obliquely outward to the vessel wall and held a high level of angular momentum when pattern FC took place, while the impeller stream was directed obliquely inward to the impeller shaft with a low level of angular momentum when pattern QR took pace.