Reynolds number dependence of the drag coefficient for laminar flow through electrically-heated photoetched screens

1995 ◽  
Vol 18 (3) ◽  
pp. 206-209 ◽  
Author(s):  
J. R. Torczynski ◽  
T. J. O'Hern
Keyword(s):  
Reynolds Number ◽  
Laminar Flow ◽  
Drag Coefficient ◽  
Flow Through ◽  
Reynolds Number Dependence

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.

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 Slow flow through porous materials. (Effect of Reynolds number on drag coefficient).

1987 ◽  
Vol 30 (270) ◽  
pp. 1928-1934
Author(s):  
Toyofumi KATOH ◽  
Masanori KYO ◽  
Shin KAWAMATA ◽  
Nobunori OHSHIMA
Keyword(s):  
Reynolds Number ◽  
Drag Coefficient ◽  
Porous Materials ◽  
Slow Flow ◽  
Flow Through

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.

Effects of wavelength and amplitude of a wavy cylinder in cross-flow at low Reynolds numbers

2009 ◽  
Vol 620 ◽  
pp. 195-220 ◽  
Author(s):  
K. LAM ◽  
Y. F. LIN
Keyword(s):  
Reynolds Number ◽  
Laminar Flow ◽  
Circular Cylinder ◽  
Drag Coefficient ◽  
Shear Layer ◽  
Lift Coefficient ◽  
Three Dimensional ◽  
Spanwise Direction ◽  
Free Shear Layer ◽  
The Mean

Three-dimensional numerical simulations of laminar flow around a circular cylinder with sinusoidal variation of cross-section along the spanwise direction, named ‘wavy cylinder’, are performed. A series of wavy cylinders with different combinations of dimensionless wavelength (λ/Dm) and wave amplitude (a/Dm) are studied in detail at a Reynolds number of Re = U∞Dm/ν = 100, where U∞ is the free-stream velocity and Dm is the mean diameter of a wavy cylinder. The results of variation of mean drag coefficient and root mean square (r.m.s.) lift coefficient with dimensionless wavelength show that significant reduction of mean and fluctuating force coefficients occurs at optimal dimensionless wavelengths λ/Dm of around 2.5 and 6 respectively for the different amplitudes studied. Based on the variation of flow structures and force characteristics, the dimensionless wavelength from λ/Dm = 1 to λ/Dm = 10 is classified into three wavelength regimes corresponding to three types of wake structures. The wake structures at the near wake of different wavy cylinders are captured. For all wavy cylinders, the flow separation line varies along the spanwise direction. This leads to the development of a three-dimensional free shear layer with periodic repetition along the spanwise direction. The three-dimensional free shear layer of the wavy cylinder is larger and more stable than that of the circular cylinder, and in some cases the free shear layer even does not roll up into a mature vortex street behind the cylinder. As a result, the mean drag coefficients of some of the typical wavy cylinders are less than that of a corresponding circular cylinder with a maximum drag coefficient reduction up to 18%. The r.m.s. lift coefficients are greatly reduced to practically zero at optimal wavelengths. In the laminar flow regime (60 ≤ Re ≤ 150), the values of optimal wavelength are Reynolds number dependent.

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.

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