The Drag Coefficient and the Shape for a Single Bubble Rising in Non-Newtonian Fluids

2012 ◽  
Vol 134 (8) ◽  
Author(s):  
Shaobai Li ◽  
Youguang Ma ◽  
Shaokun Jiang ◽  
Taotao Fu ◽  
Chunying Zhu ◽  
...  
Keyword(s):  
Drag Coefficient ◽  
High Speed ◽  
Newtonian Fluids ◽  
Single Bubble ◽  
Dynamical Characteristic ◽  
Wide Range ◽  
Coefficient Corrélation ◽  
Deformed Bubble ◽  
Bubble Rising ◽  
Experimental Values

The dynamical characteristic of a single bubble rising in non-Newtonian fluid was investigated experimentally. The bubble aspect ratio and rising velocity were measured by high speed camera. The shape regimes for bubbles in non-Newtonian fluids was plotted by means of Reynolds number Re, Eötvös number Eo and Morton number Mo. The effects of bubble shape and liquid rheological property on the total bubble drag coefficient were studied. A new empirical drag coefficient correlation covering spherical bubble and deformed bubble was proposed, the predicted results shows good conformity to experimental values over a wide range of 0.05 < Re < 300.

Experimental Investigations of Single Bubble Rising in Static Newtonian Fluids as a Function of Temperature Using a Modified Drag Coefficient

2019 ◽  
Vol 29 (3) ◽  
pp. 2209-2226 ◽  
Author(s):  
Nannan Liu ◽  
Yong Yang ◽  
Jian Wang ◽  
Binshan Ju ◽  
Eric Thompson Brantson ◽  
...  
Keyword(s):  
Drag Coefficient ◽  
Newtonian Fluids ◽  
Single Bubble ◽  
Experimental Investigations ◽  
Bubble Rising

scholarly journals Mixing of complex fluids with coaxial mixers composed of two central impellers and an anchor

2021 ◽  
Author(s):  
Argang Kazemzadeh
Keyword(s):  
High Speed ◽  
Complex Fluids ◽  
Operating Conditions ◽  
Newtonian Fluids ◽  
Hydrodynamic Performance ◽  
Mixing Efficiency ◽  
Efficient System ◽  
Wide Range ◽  
Coaxial Mixers ◽  
Pseudoplastic Fluids

The coaxial mixers composed of a high-speed central impeller and a low-speed anchor have been recommended by the previous researchers for the mixing of highly viscous and non-Newtonian fluids. However, no study has been reported in the literature regarding the use of the coaxial mixing systems composed of two central impellers and an anchor in the agitation of complex fluids. Thus, the main objective of this study was to investigate the performance of coaxial mixers composed of two central impellers and an anchor in the agitation of the xanthan gum solution, which is a yield-pseudoplastic fluid, through electrical resistance tomography (ERT), the computational fluid dynamics (CFD), and design of experiments (DOE) combined with the response surface methodology (RSM). In the first stage of this study, the hydrodynamic performance of coaxial mixers, the single and double Scaba impellers in combination with an anchor impeller, was investigated in the mixing of yield-pseudoplastic fluids. Considering the mixing efficiency criteria, it was found that the double Scaba-anchor coaxial system was more efficient than the single Scaba-anchor coaxial mixer in the mixing of yield pseudoplastic fluids with regard to the mixing time and power drawn. In the second stage of this research project, the performances of three different coaxial mixers, namely, double Scaba-anchor coaxial (DSAC), double Rushton turbine-anchor coaxial (DRAC), and double pitched blade turbine-anchor coaxial (DPAC) mixers were assessed. It was found that the double Scaba-anchor coaxial (DSAC) mixer was more efficient system compared to the others at the same operating conditions. To evaluate the influence of the impeller spacing on the hydrodynamics of the double Scaba-anchor coaxial mixer, the lower impeller clearance and the spacing between two central impellers were changed within a wide range. The results demonstrated that a coaxial mixer with the impeller spacing of almost equal to the central impeller diameter was the most efficient configuration compared to the other cases. When the impeller spacing was varied, the merging flow and parallel flow patterns were observed. Finally, the hydrodynamic performances of different configurations of coaxial mixers composed of a wall scraping anchor impeller in combination with two different or identical central high-speed impellers were analyzed. The coaxial mixers utilized in this stage were the Scaba–Scaba-anchor (SSAC), Scaba-Rushton-anchor (SRAC), Rushton-Scaba-anchor (RSAC), Scaba-pitched blade-anchor (SPBAC), and pitched blade-Scaba-anchor (PBSAC). A new correlation was introduced for these complex configurations of the coaxial mixers by incorporating the Metzner-Otto constants (Ks) of the different types of the central impellers into the Reynolds number. The analysis of the collected data revealed that the Scaba-pitched blade-anchor coaxial (SPBAC) mixer was the most efficient mixing system in the mixing of the highly viscous non-Newtonian fluids.

scholarly journals Mixing of complex fluids with coaxial mixers composed of two central impellers and an anchor

2021 ◽  
Author(s):  
Argang Kazemzadeh
Keyword(s):  
High Speed ◽  
Complex Fluids ◽  
Operating Conditions ◽  
Newtonian Fluids ◽  
Hydrodynamic Performance ◽  
Mixing Efficiency ◽  
Efficient System ◽  
Wide Range ◽  
Coaxial Mixers ◽  
Pseudoplastic Fluids

The coaxial mixers composed of a high-speed central impeller and a low-speed anchor have been recommended by the previous researchers for the mixing of highly viscous and non-Newtonian fluids. However, no study has been reported in the literature regarding the use of the coaxial mixing systems composed of two central impellers and an anchor in the agitation of complex fluids. Thus, the main objective of this study was to investigate the performance of coaxial mixers composed of two central impellers and an anchor in the agitation of the xanthan gum solution, which is a yield-pseudoplastic fluid, through electrical resistance tomography (ERT), the computational fluid dynamics (CFD), and design of experiments (DOE) combined with the response surface methodology (RSM). In the first stage of this study, the hydrodynamic performance of coaxial mixers, the single and double Scaba impellers in combination with an anchor impeller, was investigated in the mixing of yield-pseudoplastic fluids. Considering the mixing efficiency criteria, it was found that the double Scaba-anchor coaxial system was more efficient than the single Scaba-anchor coaxial mixer in the mixing of yield pseudoplastic fluids with regard to the mixing time and power drawn. In the second stage of this research project, the performances of three different coaxial mixers, namely, double Scaba-anchor coaxial (DSAC), double Rushton turbine-anchor coaxial (DRAC), and double pitched blade turbine-anchor coaxial (DPAC) mixers were assessed. It was found that the double Scaba-anchor coaxial (DSAC) mixer was more efficient system compared to the others at the same operating conditions. To evaluate the influence of the impeller spacing on the hydrodynamics of the double Scaba-anchor coaxial mixer, the lower impeller clearance and the spacing between two central impellers were changed within a wide range. The results demonstrated that a coaxial mixer with the impeller spacing of almost equal to the central impeller diameter was the most efficient configuration compared to the other cases. When the impeller spacing was varied, the merging flow and parallel flow patterns were observed. Finally, the hydrodynamic performances of different configurations of coaxial mixers composed of a wall scraping anchor impeller in combination with two different or identical central high-speed impellers were analyzed. The coaxial mixers utilized in this stage were the Scaba–Scaba-anchor (SSAC), Scaba-Rushton-anchor (SRAC), Rushton-Scaba-anchor (RSAC), Scaba-pitched blade-anchor (SPBAC), and pitched blade-Scaba-anchor (PBSAC). A new correlation was introduced for these complex configurations of the coaxial mixers by incorporating the Metzner-Otto constants (Ks) of the different types of the central impellers into the Reynolds number. The analysis of the collected data revealed that the Scaba-pitched blade-anchor coaxial (SPBAC) mixer was the most efficient mixing system in the mixing of the highly viscous non-Newtonian fluids.

On Bubble Rising in Countercurrent Flow

2012 ◽  
Vol 10 (1) ◽  
Author(s):  
Marek Vecer ◽  
Pavel Lestinsky ◽  
Kamil Wichterle ◽  
Marek Ruzicka
Keyword(s):  
Surface Tension ◽  
Aspect Ratio ◽  
High Speed ◽  
Single Bubble ◽  
Viscous Liquids ◽  
Suitable Parameter ◽  
Theoretical Predictions ◽  
Bubble Rising ◽  
Bubble Rising Velocity ◽  
Eotvos Number

A single bubble of typical volume 20 mm³ ≤ VB ≤ 400 mm³ was placed in downward conically diverging flow of low and moderate viscous liquids (aqueous solutions of glycerine and of electrolytes (NaCl, Na3PO4, MgSO4), and butanol). Experiments were performed over a range of Reynolds number 60≤Re≤2200, Weber number 1≤We≤14, Tadaki number 1≤Ta≤10, Eötvös number 1≤Eo≤22, and bubble aspect ratio 0.4≤b/a≤0.9. The bubble shape, bubble position and motion were investigated by direct observation of two plane projection of bubble by high speed camera. Typical sampling frequency was 150 fps. Relatively long records, (approximately 9000 frames per one bubble observation) allow us to get relevant statistics of treated data. Bubble aspect ratio has been determined from both projection planes. Dimensionless front area of observed bubble has been introduced as suitable parameter for correlation with Eötvös number. Model of static bubble and classical Wellek correlation were employed as asymptotes. Bubble rising velocity has been determined and tested for each single bubble with respect to liquid properties. Velocity data are plotted within the frame given by several theoretical predictions for pure and contaminated liquids. Dimensional analysis is used considering viscosity and surface tension effect. New simple correlation of bubble rising velocity separating the effects of viscosity and surface tension is presented.

Drag Coefficient Prediction of a Single Bubble Rising in Liquids

2018 ◽  
Vol 57 (15) ◽  
pp. 5385-5393 ◽  
Author(s):  
Xiaokang Yan ◽  
Kaixin Zheng ◽  
Yan Jia ◽  
Zhenyong Miao ◽  
Lijun Wang ◽  
...  
Keyword(s):  
Drag Coefficient ◽  
Single Bubble ◽  
Bubble Rising

Drag coefficient fluctuation prediction of a single bubble rising in water

2017 ◽  
Vol 316 ◽  
pp. 553-562 ◽  
Author(s):  
Xiaokang Yan ◽  
Yan Jia ◽  
Lijun Wang ◽  
Yijun Cao
Keyword(s):  
Drag Coefficient ◽  
Single Bubble ◽  
Bubble Rising

Temperature Effects on Single Bubble Collapse and Induced Impulsive Pressure

1988 ◽  
Vol 110 (2) ◽  
pp. 194-199 ◽  
Author(s):  
A. Shima ◽  
Y. Tomita ◽  
T. Ohno
Keyword(s):  
Water Temperature ◽  
Temperature Effect ◽  
High Speed ◽  
Solid Wall ◽  
Saturated Vapor ◽  
Single Bubble ◽  
Bubble Collapse ◽  
Cavitation Damage ◽  
Wide Range ◽  
Impulsive Pressure

In relation to the temperature effect in cavitation damage, the collapse of a single bubble in water over a wide range of temperatures was experimentally studied. A spark-induced bubble was observed by using a high speed camera and the impulsive pressure caused by the bubble collapse was measured by means of a pressure transducer. As water temperature increases, the motion of a bubble tends to weaken owing to the increase in saturated vapor pressure of water, and the surface configuration of a bubble becomes highly irregular because of thermal instability. The impulsive pressure depends not only on the bubble size and its distance from a solid wall but also on the water temperature. When the water temperature approaches the boiling point of water, the impulsive pressure abruptly decreases with increasing water temperature. The evidence obtained seems to be associated with the known temperature effect on cavitation damage at high water temperature.

Sign in / Sign up

Export Citation Format

Share Document