The double- to single-loop pattern transition in stirred vessels stemming from a change in the off-bottom clearance of a Rushton turbine has been investigated by laser doppler anemometry. Time-resolved data showed the transition occurring within a range of clearance values and allowed the distinction of three types of flow: the double-loop regime, the single-loop regime and an unstable one termed "transitional state". Experiments of up to 3-4 h duration showed that both the onset and the lifetimes of these types of flow were random; however, in the transitional state, the flow varied between the two circulation patterns in a periodic manner, with a frequency linearly related to the impeller rotational speed. The results have important implications for mixing process and vessel design as well as CFD predictions of the flows which are discussed.
|Autori:||GALLETTI C; BRUNAZZI E; YIANNESKIS M; PAGLIANTI A|
|Titolo:||Spectral and wavelet analysis of the flow pattern transition with impeller clearance variations in a stirred vessel|
|Anno del prodotto:||2003|
|Digital Object Identifier (DOI):||10.1016/S0009-2509(03)00230-6|
|Appare nelle tipologie:||1.1 Articolo in rivista|