Studies on the Flow Patterns of Liquids in a Cylindrical Mixing Vessel, Over a Wide Range of Reynolds Number

Abstract

The flow patterns of liquids agitated in a cylindrical mixing vessel without baffles were measured by a photographic method, ranging from laminar to so-called transitional flow. The authors are now able to discuss the flow pattern of the liquid and the discharge performance of the impellers over a wide range of Reynolds number, combined with the previous results published for the turbulent flow range. Some of the experimental results are shown in Figs. 6, 7, 8 and 10. The authors discovered the following results on the velocity distribution of the liquid : In the range of very small Reynolds number, the liquid velocity is considerably high only in the neighbourhood of the impeller and decreases abruptly with the distance from the impeller. On the other hand, in the range of high Reynolds number, secondary circulation flow occurs as shown in Fig. 9 and also the flow becomes turbulent, so that the liquid attains considerable velocity even at a distance from the impeller by the transmission of momentum, and the velocity distribution is considerably unified throughout the vessel. Concerning the discharge flow from the tip of the impeller blades which causes the secondary circulation, the non-dimensional quantities, Nq₁, and Nᴘ/Nq₁, are defined, as in the previous report. These values were calculated and the characteristic curves of discharge performance were obtained for various types of impellers (refer to Table 1), as shown in Fig. 12. Furthermore, the relations between flow pattern, discharge performance and power consumption (Nᴘ-Rₑ relation) were discussed.