LAUSR

Abstract Contrary to existing knowledge, the flow field showed a hysteresis effect when the rotational speed varied. The speed up operation in hysteresis range generates a semi-radial flow field, whereas the slow down operation causes an axial flow filed. Therefore, two stable flow fields can be formed at the same rotational speed and which one prevails depends on the flow history. The flow fields were measured using PIV and UVP, to explore the hysteresis range of four different xanthan gum solutions. The hysteresis range shifts toward higher rotational speed with increasing concentrations. The Reynolds number was failed to characterize the flow within hysteresis range but can be used for rotational speeds exceeding hysteresis range. The aim of this work was to introduce this phenomenon and to provide the first comparison between the two flow patterns and the fundamental for further researches dealing with the hysteresis effect in flow fields.