Detached eddy simulation of the liquid mixing in stirred tanks

In the present work, the detached eddy simulation (DES) model was used to gain an insight into the liquid-phase mixing processes in stirred tanks agitated by centrically and eccentrically located four pitched-blade turbine. The impeller rotation was modeled using the sliding mesh (SM) method. Based on the time variation of the scalar concentration, the mixing patterns and mixing time were analyzed and compared with the published planar laser induced fluorescence (PLIF) experimental data (Hu YY, Liu Z, Yang JC, Cheng Y. Liquid mixing in eccentric stirred tank. CIESC J 2010; 61(10): 2517–22). Results show that the combination of DES model and SM method can characterize the transient mixing state in stirred tanks and can provide a detailed spatial and temporal evolution of the scalar concentration. The concentration recorded at several locations inside the domain revealed different mixing patterns under concentric and eccentric agitation configurations. The differences in mixing time at different monitoring points were small under eccentric agitations, which exhibit better mixing performance than the concentric agitation. Overall, the predicted mixing time compared well, on average within 20%, with the results obtained by the PLIF technique. The agreement shows that DES is a reliable tool to investigate the unsteady mixing characteristics in stirred tanks.

► The first application of DES model in the mixing process simulation in stirred tanks.
► DES model can predict the mixing characteristics in stirred tanks with high accuracy.
► DES model can produce good predictions as the PLIF experimental results.
► DES model can be used as a CFD tool in predicting the mixing process in stirred tanks.