scholarly journals Stability of laminar flow in curved channels

1957 ◽  
Vol 2 (15) ◽  
pp. 305-310 ◽  
Author(s):  
Chia-Shun Yih ◽  
W. M. Sangster
Keyword(s):  
Laminar Flow ◽  
Curved Channels

Time-Dependent Laminar Flow in Curved Channels

1970 ◽  
Vol 37 (3) ◽  
pp. 838-843 ◽  
Author(s):  
R. J. Nunge
Keyword(s):  
Laminar Flow ◽  
Pressure Gradient ◽  
Constant Pressure ◽  
Time Dependent ◽  
Pressure Gradients ◽  
Straight Channel ◽  
Curvature Ratio ◽  
Curved Channels ◽  
Developing Flow ◽  
Time Required

The velocity distribution for time-dependent laminar flow in curved channels is derived. The analysis applies to flows with pressure gradients which are arbitrary functions of time. Numerical results are obtained for developing flow due to a constant pressure gradient. Developing flow in a straight channel is also discussed and it is found that the curvature ratio has only a small effect on the time required to reach the fully developed state.

scholarly journals Laminar flow around corners triggers the formation of biofilm streamers

2010 ◽  
Vol 7 (50) ◽  
pp. 1293-1299 ◽  
Author(s):  
Roberto Rusconi ◽  
Sigolene Lecuyer ◽  
Laura Guglielmini ◽  
Howard A. Stone
Keyword(s):  
Laminar Flow ◽  
Bacterial Biofilms ◽  
Middle Plane ◽  
Natural Ecosystems ◽  
Flow Cells ◽  
Curved Channels ◽  
Mutant Strains ◽  
Hydrodynamic Mechanism ◽  
Vortical Motion ◽  
Flow Experiments

Bacterial biofilms have an enormous impact on medicine, industry and ecology. These microbial communities are generally considered to adhere to surfaces or interfaces. Nevertheless, suspended filamentous biofilms, or streamers, are frequently observed in natural ecosystems where they play crucial roles by enhancing transport of nutrients and retention of suspended particles. Recent studies in streamside flumes and laboratory flow cells have hypothesized a link with a turbulent flow environment. However, the coupling between the hydrodynamics and complex biofilm structures remains poorly understood. Here, we report the formation of biofilm streamers suspended in the middle plane of curved microchannels under conditions of laminar flow. Experiments with different mutant strains allow us to identify a link between the accumulation of extracellular matrix and the development of these structures. Numerical simulations of the flow in curved channels highlight the presence of a secondary vortical motion in the proximity of the corners, which suggests an underlying hydrodynamic mechanism responsible for the formation of the streamers. Our findings should be relevant to the design of all liquid-carrying systems where biofilms are potentially present and provide new insights on the origins of microbial streamers in natural and industrial environments.

Experiments on laminar flow in curved channels of square section

1971 ◽  
Vol 48 (3) ◽  
pp. 417-422 ◽  
Author(s):  
J. A. Baylis
Keyword(s):  
Reynolds Number ◽  
Numerical Analysis ◽  
Laminar Flow ◽  
Friction Factor ◽  
Experimental Results ◽  
Radius Of Curvature ◽  
Dean Number ◽  
Rectangular Section ◽  
Curved Channels ◽  
Channel Dimension

Recently Cheng & Akiyama (1970) published a numerical analysis of laminar flow in curved channels of square and rectangular section. Experimental results are presented here for flow in curved channels of square section. The channels were toroidal in shape, and the flow was driven electromagnetically. Various ratios of the channel dimension d to the channel radius of curvature, R, were used to investigate the dependence of friction factor, f, on the Dean number K, and the Reynolds number, Re. For 5 × 102 < K < 7 × 104 the formula (fRe) = 1·51 K½ was found to fit all the results, although R/d was varied from 17·5 down to the low value of 1·75. At lower values of K the analysis of Cheng & Akiyama was approximately validated.

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