ABSTRACT

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This study is concerned with liquid flow induced by a disk which rotates steadily around its axis and touches the free surface of liquid contained in a cylindrical vessel. It is a simplified model of the flow in the inlet part of a vertical cooling crystallizer where a rotary distributor of inflowing solution is situated above the free surface of solution contained in the crystalliser. Numerical simulations of flow phenomena were conducted and the simulation results were interpreted assuming an analogy with Kármán's theoretical equations. In a cylindrical coordinate system, the components of flow velocity were identified as functions of distance from the surface of the rotating disk. The experimental setup was developed to measure velocity fields, using digital particle velocimetry and optical flow. Conclusions concerning the influence of disc rotation on liquid velocity fields were presented and the experimental results were found to confirm the results of numerical simulation. On the basis of simulation data, an approximation function was determined to describe the relationship between the circumferential component of flow velocity and the distance from the disk.

In the paper the formation of bubble chains over two nozzles has been experimentally investigated and modelled. Bubbles were generated from twin brass nozzles (with the inner diameter equal to 1 mm) to distilled water. The appearance and disappearance of alterative bubble departures have been investigated. It has been found that during disappearance of alternative bubble departures bubbles depart from nozzle outlets simultaneously. The PIV method was used to reconstruct the liquid velocity field around the bubble chains. The results of experiment were comparing with results of numerical simulation in which the Level Set method has been used. The PIV method show that during the alternate bubble departures the range of the velocity field formed by the bubble chain is smaller than in case when bubbles depart in non-alternative way. In this case the bubbles velocity above the nozzles outlet is greater in comparison with bubble velocity during the simultaneously bubble departures. The numerical simulations show that in alternative bubble departures bubble just after its departure is attracted to the common bubble chain. The hydrodynamic interactions between departing bubbles lead to uniform distribution of bubbles in bubble chain.

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