Effect of Reynolds number in laminar flow through a sudden planar contraction

AIChE Journal ◽  
1985 ◽  
Vol 31 (10) ◽  
pp. 1736-1739 ◽  
Author(s):  
E. Mitsoulis ◽  
J. Vlachopoulos
Keyword(s):  
Reynolds Number ◽  
Laminar Flow ◽  
Flow Through ◽  
Planar Contraction

scholarly journals Heavy Oil Laminar Flow in Corrugated Ducts: A Numerical Study Using the Galerkin-Based Integral Method

Energies ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1363
Author(s):  
Valdecir Alves dos Santos Júnior ◽  
Severino Rodrigues de Farias Neto ◽  
Antonio Gilson Barbosa de Lima ◽  
Igor Fernandes Gomes ◽  
Israel Buriti Galvão ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Reynolds Number ◽  
Laminar Flow ◽  
Heavy Oil ◽  
Integral Method ◽  
Numerical Study ◽  
Temperature Dependent ◽  
Flow Through ◽  
Fanning Friction Factor ◽  
Cylindrical Duct

Fluid flow in pipes plays an important role in different areas of academia and industry. Due to the importance of this kind of flow, several studies have involved circular cylindrical pipes. This paper aims to study fully developed internal laminar flow through a corrugated cylindrical duct, using the Galerkin-based integral method. As an application, we present a study using heavy oil with a relative density of 0.9648 (14.6 °API) and temperature-dependent viscosities ranging from 1715 to 13000 cP. Results for different fluid dynamics parameters, such as the Fanning friction factor, Reynolds number, shear stress, and pressure gradient, are presented and analyzed based on the corrugation number established for each section and aspect ratio of the pipe.

Analysis of thermo-hydraulic and entropy generation characteristics for flow through ribbed-wavy channel

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Sumit Kumar Mehta ◽  
Sukumar Pati ◽  
Shahid Ahmed ◽  
Prangan Bhattacharyya ◽  
Jishnu Jyoti Bordoloi
Keyword(s):  
Reynolds Number ◽  
Laminar Flow ◽  
Entropy Generation ◽  
Relative Magnitude ◽  
Temperature Fields ◽  
Wavy Channel ◽  
Content Type ◽  
Flow Through ◽  
Numerical Solver ◽  
Wavy Channels

Purpose The purpose of this study is to analyze the thermal, hydraulic and entropy generation characteristics for laminar flow of water through a ribbed-wavy channel with the top wall as wavy and bottom wall as flat with ribs of three different geometries, namely, triangular, rectangular and semi-circular. Design/methodology/approach The finite element method-based numerical solver has been adopted to solve the governing transport equations. Findings A critical value of Reynolds number (Recri) is found beyond which, the average Nusselt number for the wavy or ribbed-wavy channel is more than that for a parallel plate channel and the value of Recri decreases with the increase in a number of ribs and for any given number of ribs, it is minimum for rectangular ribs. The performance factor (PF) sharply decreases with Reynolds number (Re) up to Re = 50 for all types of ribbed-wavy channels. For Re > 50, the change in PF with Re is gradual and decreases for all the ribbed cases and for the sinusoidal channel, it increases beyond Re = 100. The magnitude of PF strongly depends on the shape and number of ribs and Re. The relative magnitude of total entropy generation for different ribbed channels varies with Re and the number of ribs. Practical implications The findings of the present study are useful to design the economic heat exchanging devices. Originality/value The effects of shape and the number of ribs on the heat transfer performance and entropy generation have been investigated for the first time for the laminar flow regime. Also, the effects of shape and number of ribs on the flow and temperature fields and entropy generation have been investigated in detail.

Laminar flow through slots

1988 ◽  
Vol 190 ◽  
pp. 179-200 ◽  
Author(s):  
E. G. Tulapurkara ◽  
B. H. Lakshmana Gowda ◽  
N. Balachandran
Keyword(s):  
Reynolds Number ◽  
Laminar Flow ◽  
Flow Visualization ◽  
Vortex Shedding ◽  
Stokes Equations ◽  
Computer Code ◽  
Channel Height ◽  
Visualization Technique ◽  
Recirculating Flow ◽  
Flow Through

Laminar flow through slots is investigated using a flow-visualization technique and the numerical solution of the Navier-Stokes equations for steady flow. In the flow situation studied here, the fluid enters an upper channel blocked at the rear end and leaves through a lower channel blocked at the front end. The two channels are interconnected by one, two and three slots. The flow-visualization technique effectively brings out the various features of the flow through slot(s). The ratio of the slot width to the channel height w/h is varied between 0.5 to 4.0 and the Reynolds number Re, based on the velocity at the entry to the channel and the height of the channel, is varied between 300 and 2000. Both w/h and Re influence the flow in general and the extent of the regions of recirculating flow in particular. The Reynolds number at which the vortex shedding begins depends on w/h. Computations are carried out using the computer code 2/E/FIX of Pun & Spalding (1977). The computed flow patterns closely resemble the observed patterns at various Reynolds numbers investigated except around the Reynolds number where the vortex shedding begins.

Turbulent Flow in a Microchannel With Surface Patterned Microribs Oriented Parallel to the Flow Direction

2007 ◽  
Author(s):  
K. Jeffs ◽  
D. Maynes ◽  
B. W. Webb
Keyword(s):  
Reynolds Number ◽  
Laminar Flow ◽  
Turbulent Flow ◽  
Friction Factor ◽  
Solid Wall ◽  
Flow Direction ◽  
Flowing Liquid ◽  
Free Region ◽  
Flow Through ◽  
Oriented Parallel

Due to the increase of application in a number of emerging technologies, a growing amount of research has focused on the reduction of drag in microfluidic transport. A novel approach reported in the recent literature is to fabricate micro-ribs and cavities in the channel wall that are then treated with a hydrophobic coating. Such surfaces have been termed super- or ultrahydrophobic and the contact area between the flowing liquid and the solid wall is greatly reduced. Previous numerical studies have focused primarily on the laminar flow through such channels with reductions in the flow resistance as large as 87% being predicted and observed. There has been little work however, that has explored the physics and the potential drag reduction associated with turbulent flow through microchannels with ultrahydrophobic walls. This paper reports the results of a numerical investigation of the turbulent flow in a parallel plate microchannel with ultrahydrophobic walls. In this study microribs and cavities are oriented parallel to the flow direction. The channel walls are modeled in an idealized fashion, with the shape of the liquid-vapor meniscus approximated as flat. A k-ω turbulence modeling scheme is implemented for closure to the turbulent RANS equations. Results are presented for the friction factor Reynolds number product as a function of relevant governing dimensionless parameters. The Reynolds number was varied from 2,000 to 10,000. Results show, as with the laminar flow case, that as the shear-free region increases the friction factor-Reynolds number product decreases. The observed reduction, however, was found to be significantly greater under turbulent flow conditions than for the laminar flow scenarios.

Laminar Flow Heat Transfer and Pressure Drop in a Circular Tube Having Wire-Coil and Helical Screw-Tape Inserts

2013 ◽  
Vol 135 (2) ◽  
Author(s):  
Pratap Kumar Rout ◽  
Sujoy Kumar Saha
Keyword(s):  
Reynolds Number ◽  
Nusselt Number ◽  
Laminar Flow ◽  
Friction Factor ◽  
Circular Tube ◽  
Inertia Force ◽  
Large Reynolds Number ◽  
Nusselt Numbers ◽  
Wire Coil ◽  
Flow Through

The experimental friction factor and Nusselt number data for laminar flow through a circular duct having wire-coil and helical screw-tape inserts have been presented. Peripherally and axially local temperatures on the duct outside wall have been measured. The temperature drop across the duct wall has been calculated to obtain the duct inside wall temperatures. Peripherally averaged and axially local temperatures have been used to get axially local Nusselt numbers. These axially local Nusselt numbers have been averaged over the whole length of the duct to get the mean Nusselt number. Predictive friction factor and Nusselt number correlations developed by log-regression analysis have also been presented. Nusselt number correlation takes care of the thermal development length represented by the Graetz number, swirl and inertia force due to forced convection at large Reynolds number, buoyancy force due to natural convection at low Reynolds number represented by Rayleigh number and the geometrical parameters of wire-coil and helical screw-tape inserts. The thermohydraulic performance has been evaluated. The helical screw-tape inserts in combination with wire-coil inserts perform better than the individual enhancement technique acting alone for laminar flow through a circular tube up to a certain value of fin parameter.

Steady Laminar Fluid Flow Through Variable Constrictions in Vascular Tube

1994 ◽  
Vol 116 (1) ◽  
pp. 66-71 ◽  
Author(s):  
T. S. Lee
Keyword(s):  
Reynolds Number ◽  
Fluid Flow ◽  
Laminar Flow ◽  
Recirculation Zone ◽  
Flow Fields ◽  
Laminar Fluid Flow ◽  
Spacing Ratio ◽  
Flow Through ◽  
Steady Laminar

Steady laminar flow fields in the neighborhoods of two consecutive constrictions in a vascular tube were studied for approaching Reynolds number Re in the range of 5 to 200. The upstream stenosis was set at a dimensionless diameter constriction c1 of 0.5 while the downstream stenoses were allowed to vary from c2 = 0.2 to 0.6. The proximity of the constrictions was determined by the spacing ratio of S/D = 1, 2, 3, and ∞. When c2 > c1, a recirculation zone filled the valley between the two constrictions with little changes to the separation and reattachment points as Re was further increased. For c2 < c1 and when Re was increased, the recirculating eddy formed downstream of the first constriction tended to spread beyond the region of the second constriction. This resulted in negative wall vorticity peak occurring in the region of the second constriction for smaller S/D at high Re.

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