THE LAMINAR AND TURBULENT-FLOW PATTERN OF A PITCHED BLADE TURBINE

The flow field generated by the pitched-blade turbine in both laminar and turbulent operation has been investigated using laser Doppler velo cimetry (LDV) and digital particle image velocimetry (DPIV) experiment al techniques. This data has been used to critically evaluate the perf ormance of computational fluid mixing (CFM) tools. It has been found t hat current CFM software can accurately predict the laminar flow behav iour of the pitched-blade impeller if the proper velocity boundary con ditions are provided around the entire periphery of the impeller. In t urbulent operation, CFM simulations predict some of the features of th e flow field, but dramatically underpredict the total energy dissipati on rate in the vessel. They are not currently capable of describing th e large-scale instabilities in the flow detected by DPIV.