Experimental Investigations of Couette-Taylor-Poiseuille Flows Using the Electro-Diffusional Technique

2016 ◽  
Author(s):  
Emna Berrich ◽  
Fethi Aloui ◽  
Jack Legrand
Keyword(s):  
Mass Transfer ◽  
Shear Rate ◽  
Mass Transfer Rate ◽  
Axial Flow ◽  
Reynolds Numbers ◽  
Wall Shear Rate ◽  
Experimental Investigations ◽  
Local Mass ◽  
Local Mass Transfer ◽  
Wall Shear

Couette-Taylor-Poiseuille flow CTPF consists on the superposition of Couette-Taylor flow to an axial flow. The CTPF flow hydrodynamics studies remain rather qualitative or numerical or are restricted to relatively low Taylor and/or axial Reynolds numbers. For more comprehensive and control of CTPF, especially for relatively high Taylor numbers and high axial Reynolds numbers, we investigated experimentally CTF with and without an axial flow, using the electro-diffusion ED method. This technique requires the use of Electro-Diffusion ED probe which allows the determination of the local mass transfer rate from the Limiting Diffusion current measurement delivered by the ED probe while it is polarized by a polarization voltage. From the local mass transfer (the Sherwood number), we determined the wall shear rate using different approaches. The results illustrate that low axial flow can generate a stabilizing effect on the CT flow. The time-evolutions of the local mass transfer and the wall shear rate are periodic. These evolutions characterize the waviness or the stretching of the vortices. However, Taylor Wavy Vortex Flow TWVF is destabilized under the effect of relatively important axial flow. The time-evolutions of wall shear rate are no longer periodic. Indeed, Taylor vortices are overlapped or completely destructed.

Measurement of Local Mass Transfer and the Resulting Roughness in a Large Diameter S-Bend at High Reynolds Number

2016 ◽  
Vol 138 (6) ◽  
Author(s):  
D. Wang ◽  
D. Ewing ◽  
T. Le ◽  
C. Y. Ching
Keyword(s):  
Mass Transfer ◽  
Reynolds Number ◽  
Mass Transfer Rate ◽  
Large Diameter ◽  
Reynolds Numbers ◽  
High Mass ◽  
Local Mass ◽  
Roughness Elements ◽  
Local Mass Transfer ◽  
High Reynolds

The local mass transfer and the resulting roughness in a 203 mm diameter back-to-back bend arranged in an S-configuration were measured at a Reynolds number of 300,000. A dissolving wall method using gypsum dissolution to water at 40 °C was used, with a Schmidt number of 660. The topography of the unworn and worn inner surface was quantified using nondestructive X-ray computed tomography (CT) scans. The local mass transfer rate was obtained from the local change in radius over the flow time. Two regions of high mass transfer were present: (i) along the intrados of the first bend near the inlet and (ii) at the exit of the extrados of the first bend that extends to the intrados of the second bend. The latter was the region of highest mass transfer, and the scaling of the maximum Sherwood number with Reynolds number followed that developed for lower Reynolds numbers. The relative roughness distribution in the bend corresponded to the mass transfer distribution, with higher roughness in the higher mass transfer regions. The spacing of the roughness elements in the upstream pipe and in the two regions of high mass transfer was approximately the same; however, the spacing-to-height ratio was very different with values of 20, 10, and 6, respectively.

The Effect of Naturally Developing Roughness on the Mass Transfer in Pipes Under Different Reynolds Numbers

2017 ◽  
Vol 139 (10) ◽  
Author(s):  
D. Wang ◽  
D. Ewing ◽  
C. Y. Ching
Keyword(s):  
Mass Transfer ◽  
Reynolds Number ◽  
Initial Period ◽  
Reynolds Numbers ◽  
Multiple Time ◽  
Transfer Enhancement ◽  
Flow Loop ◽  
Local Mass ◽  
Mass Transfer Enhancement ◽  
Local Mass Transfer

The local mass transfer over dissolving surfaces was measured at pipe Reynolds number of 50,000, 100,000, and 200,000. Tests were run at multiple time periods for each Reynolds number using 203 mm diameter test sections that had gypsum linings dissolving to water in a closed flow loop at a Schmidt number of 1200. The local mass transfer was calculated from the decrease in thickness of the gypsum lining that was measured using X-ray-computed tomography (CT) scans. The range of Sherwood numbers for the developing roughness in the pipe was in good agreement with the previous studies. The mass transfer enhancement (Sh/Shs) was dependent on both the height (ep−v) and spacing (λstr) of the roughness scallops. For the developing roughness, two periods of mass transfer were present: (i) an initial period of rapid increase in enhancement when the density of scallops increases till the surface is spatially saturated with the scallops and (ii) a slower period of increase in enhancement beyond this point, where the streamwise spacing is approximately constant, and the roughness height grows more rapidly. The mass transfer enhancement was found to correlate well with the parameter (ep−v/λstr)0.2, with a weak dependence on Reynolds number.

scholarly journals Simultaneous measurements of thickness and local mass transfer rate on falling liquid films.

1979 ◽  
Vol 12 (6) ◽  
pp. 483-485
Author(s):  
RYUZO ITO ◽  
KAORU TOMURA ◽  
MASAO YAMAMOTO ◽  
YUKIE OKADA ◽  
NOBUHIRO TSUBOI ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Transfer Rate ◽  
Mass Transfer Rate ◽  
Liquid Films ◽  
Local Mass ◽  
Simultaneous Measurements ◽  
Local Mass Transfer ◽  
Falling Liquid Films

scholarly journals Simulation of the nodal flow of mutant embryos with a small number of cilia: comparison of mechanosensing and vesicle transport hypotheses

2018 ◽  
Vol 5 (8) ◽  
pp. 180601 ◽  
Author(s):  
Toshihiro Omori ◽  
Katja Winter ◽  
Kyosuke Shinohara ◽  
Hiroshi Hamada ◽  
Takuji Ishikawa
Keyword(s):  
Shear Rate ◽  
Flow Direction ◽  
Research Field ◽  
Vesicle Transport ◽  
The Body ◽  
Wall Shear Rate ◽  
Experimental Investigations ◽  
Nodal Flow ◽  
Immotile Cilia ◽  
Wall Shear

Left–right (L-R) asymmetry in the body plan is determined by nodal flow in vertebrate embryos. Shinohara et al. (Shinohara K et al. 2012 Nat. Commun. 3 , 622 ( doi:10.1038/ncomms1624 )) used Dpcd and Rfx3 mutant mouse embryos and showed that only a few cilia were sufficient to achieve L-R asymmetry. However, the mechanism underlying the breaking of symmetry by such weak ciliary flow is unclear. Flow-mediated signals associated with the L-R asymmetric organogenesis have not been clarified, and two different hypotheses—vesicle transport and mechanosensing—are now debated in the research field of developmental biology. In this study, we developed a computational model of the node system reported by Shinohara et al. and examined the feasibilities of the two hypotheses with a small number of cilia. With the small number of rotating cilia, flow was induced locally and global strong flow was not observed in the node. Particles were then effectively transported only when they were close to the cilia, and particle transport was strongly dependent on the ciliary positions. Although the maximum wall shear rate was also influenced by ciliary position, the mean wall shear rate at the perinodal wall increased monotonically with the number of cilia. We also investigated the membrane tension of immotile cilia, which is relevant to the regulation of mechanotransduction. The results indicated that tension of about 0.1 μN m −1 was exerted at the base even when the fluid shear rate was applied at about 0.1 s −1 . The area of high tension was also localized at the upstream side, and negative tension appeared at the downstream side. Such localization may be useful to sense the flow direction at the periphery, as time-averaged anticlockwise circulation was induced in the node by rotation of a few cilia. Our numerical results support the mechanosensing hypothesis, and we expect that our study will stimulate further experimental investigations of mechanotransduction in the near future.

scholarly journals Mass transfer control of a backward-facing step flow by local forcing-effect of Reynolds number

2011 ◽  
Vol 15 (2) ◽  
pp. 367-378 ◽  
Author(s):  
Zouhaier Mehrez ◽  
Mourad Bouterra ◽  
Cafsi El ◽  
Ali Belghith ◽  
Quere Le
Keyword(s):  
Mass Transfer ◽  
Reynolds Number ◽  
Reynolds Numbers ◽  
Backward Facing Step ◽  
Local Mass ◽  
Eddy Simulation ◽  
Local Forcing ◽  
Large Eddy ◽  
Local Mass Transfer ◽  
Oscillating Jet

The control of fluid mechanics and mass transfer in separated and reattaching flow over a backward-facing step by a local forcing, is studied using Large Eddy Simulation (LES). To control the flow, the local forcing is realized by a sinusoidal oscillating jet at the step edge. The Reynolds number is varied in the range 10000 ? Re ? 50000 and the Schmidt number is fixed at 1. The found results show that the flow structure is modified and the local mass transfer is enhanced by the applied forcing. The observed changes depend on the Reynolds number and vary with the frequency and amplitude of the local forcing. For the all Reynolds numbers, the largest recirculation zone size reduction is obtained at the optimum forcing frequency St = 0.25. At this frequency the local mass transfer enhancement attains the maximum.

The Visualisation of Mass Transfer Rate Around a Sphere

1964 ◽  
Vol 68 (638) ◽  
pp. 137-139 ◽  
Author(s):  
K. Lee ◽  
H. Barrow ◽  
D. J. Ryley
Keyword(s):  
Mass Transfer ◽  
Transfer Rate ◽  
Large Scale ◽  
Mass Transfer Rate ◽  
Droplet Surface ◽  
Scale Model ◽  
Flow Visualisation ◽  
Local Mass ◽  
Large Scale Model ◽  
Local Mass Transfer

The purpose of this note is to report the results of an experimental investigation which was conducted to permit the local mass transfer rate around a sphere to be visualised. The present problem of mass transfer from a sphere had its origin in a study of the evaporation of a water droplet in a superheated steam atmosphere. Because of the small physical size of the droplet and the difficulty of measuring local mass transfer rates from the droplet surface, it was necessary to employ a large scale model to study local transfer rate around a sphere. It was considered that flow visualisation would afford at least a qualitative result of local mass transfer rate. In fluid mechanics studies, the flow visualisation techniques are well known. Such methods include the use of smoke filaments, tufts, or chemical coatings and so forth to provide information about the state of boundary layer over a solid surface, fluid particle paths and state of flow.

Sign in / Sign up

Export Citation Format

Share Document