On the liquid boundary layer near the electrode surface during chlorine evolution

Abstract How microbubbles behave inside turbulent boundary layers are investigated experimentally. Water electrolysis is applied for generation of microbubbles in water, of which electrodes are flash mounted on the solid wall in the upstream section of the measurement area. Four kinds of solid surfaces are examined to compare the microbubble distribution. For a circular cylinder of the radius R = 22 mm at Re = 5,000, we found that microbubbles depart from the surface earlier than the liquid boundary layer. For an elliptic cylinder of the curvature radius of R = 60 mm and a hydrofoil of NACA0040, microbubble injection made the separation point move downstream in the range of 9,000 < Re < 90,000. To compare the effect with the cases of flat solid surfaces (R = infinity), we visualized three-dimensional distribution of microbubbles with color-coded volumetric illumination technique. The result has shown formation of microbubble clusters intermittently, which has Coulomb potential due to negative electric charge on bubble interfaces.

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Control of the liquid boundary layer in slide-valve converters and in laminar chokes of hydraulic drives

Russian Engineering Research ◽

10.3103/s1068798x09030071 ◽

2009 ◽

Vol 29 (3) ◽

pp. 249-250

Author(s):

I. V. Kholmogorov ◽

G. K. Khomyakov ◽

V. Ts. Vanchikov

Keyword(s):

Boundary Layer ◽

Slide Valve ◽

Liquid Boundary ◽

Liquid Boundary Layer

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Micro-structure of growth solid-liquid boundary layer of KTa1-xNbxO3 crystal

Acta Physica Sinica ◽

10.7498/aps.59.5085 ◽

2010 ◽

Vol 59 (7) ◽

pp. 5085

Author(s):

Zhang Qing-Li ◽

Yin Shao-Tang ◽

You Jing-Lin ◽

Wang Yuan-Yuan ◽

Zhou Wen-Ping ◽

...

Keyword(s):

Boundary Layer ◽

Micro Structure ◽

Liquid Boundary ◽

Solid Liquid ◽

Liquid Boundary Layer

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Biodegradation of lipids from olive oil mill wastewaters in a stationary basket bioreactor with immobilized Bacillus spp. cells – Influence of internal diffusion

Water Science & Technology ◽

10.2166/wst.2012.938 ◽

2012 ◽

Vol 65 (5) ◽

pp. 920-926 ◽

Cited By ~ 2

Author(s):

Dan Caşcaval ◽

Anca-Irina Galaction ◽

Marius Turnea ◽

Anca Marcela Lupăşteanu

Keyword(s):

Internal Diffusion ◽

Bacterial Cells ◽

Internal Mass ◽

Biodegradation Process ◽

Lipid Mass ◽

Bacillus Spp ◽

Liquid Boundary ◽

Mass Flows ◽

Mass Transfers ◽

Liquid Boundary Layer

The study is focused on the external and internal mass transfers of lipids during their biodegradation process in a bioreactor with stationary basket bed of immobilized Bacillus spp. cells. By means of the lipid mass balance for a single particle of biocatalyst, considering the kinetic model adapted for the immobilized bacterial cells, specific mathematical models have been developed to estimate their mass flows in the liquid boundary layer surrounding the particle and inside the particle. The values of mass flows are significantly influenced by the internal diffusion velocity of lipids and the rate of their consumption, but also by the position inside the basket bed. These influences accumulated led to the appearance of a biological inactive region near the particle centre, its magnitude varying from 1.3 to 49.4% of the overall volume of particles.

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A Two-Phase Boundary Layer and Its Drag-Reduction Characteristics

Journal of Applied Mechanics ◽

10.1115/1.3640562 ◽

1962 ◽

Vol 29 (2) ◽

pp. 408-414 ◽

Cited By ~ 3

Author(s):

E. M. Sparrow ◽

V. K. Jonsson ◽

E. R. G. Eckert

Keyword(s):

Boundary Layer ◽

Phase Boundary ◽

Liquid Flow ◽

Single Phase ◽

Free Stream ◽

Stream Velocity ◽

Two Phase ◽

Drag Forces ◽

Liquid Boundary ◽

Reduction Characteristics

Consideration is given to coexisting gas and liquid boundary layers which occur when a gas is injected at the surface of a flat plate into a free-stream liquid flow. It is postulated that the gas forms a continuous film over the plate surface. The problem can be formulated exactly within the framework of laminar boundary-layer theory. Solutions have been carried out for a range of values of blowing velocity and of a fluid property parameter (ρμ) L / (ρμ)g. It is demonstrated that the drag forces associated with the two-phase boundary layer are much smaller than those for the single-phase liquid flow. For example, for a blowing velocity which is 0.001 of the free-stream velocity and a gas Reynolds number of 105, the over-all drag calculation yields a value which is 0.0205 of the single-phase drag force. The effect of evaporation at the gas-liquid interface is analyzed and found to be small at temperatures which are not too close to saturation.

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Nitrification Kinetics and Simultaneous Removal of Biomass and Phosphorus in Rotating Biological Contactors

Water Science & Technology ◽

10.2166/wst.1990.0198 ◽

1990 ◽

Vol 22 (3-4) ◽

pp. 169-178 ◽

Cited By ~ 4

Author(s):

Yoshimasa Watanabe ◽

Chulhee Lee ◽

Makoto Koike ◽

Masayoshi Ishiguro

Keyword(s):

Molecular Diffusion ◽

Ammonia Concentration ◽

Simultaneous Removal ◽

Solids Concentration ◽

Nitrification Kinetics ◽

Liquid Boundary ◽

Bulk Substrate ◽

Rotating Biological Contactors ◽

Liquid Boundary Layer ◽

The Relationship

This paper presents some important aspects of the Rotating Biological Contactor. (1) Steady-state biofilm kinetics and its application to the design of an RBC aiming at nitrification : Using the proposed kinetics in which the flux of rate-limiting substrate is expressed as a function of the bulk substrate concentration, liquid boundary layer thickness, liquid film thickness, and molecular diffusion coefficient and intrinsic reaction rate of the substrate, the relationship between the bulk ammonia concentration and ammonia flux was predicted at various sizes and rotating speeds of disk. Experimental verification of the predicted results was also made. A new disk media, i.e., reticulated media with surface protrusions,was proposed to promote the external diffusion of soluble substrates to the biofilm, and to reduce the disk weight. (2) Simultaneous removal of the detached biomass and precipitated phosphorous in a two-storey RBC:A two-storey RBC, whose upper and lower parts function as the RBC trough and storage space of the detached biomass, was operated in a four-staged unit. Experimental investigation showed that the phosphorus precipitated by aluminium was adsorbed to the biofilm, and settled into the lower part as the detached biomass. The removal efficiency of the detached biomass was very high resulting in an effluent suspended solids concentration of about 10 ppm.

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