Effect of Wetting on Friction Factors for Turbulent Flow of Mercury in Annuli

1976 ◽  
Vol 98 (1) ◽  
pp. 113-116 ◽  
Author(s):  
O. E. Dwyer ◽  
P. J. Hlavac ◽  
B. G. Nimmo
Keyword(s):  
Reynolds Number ◽  
Turbulent Flow ◽  
Friction Factor ◽  
Maximum Velocity ◽  
Outer Wall ◽  
Limited Range ◽  
Friction Factors ◽  
Fully Developed Turbulent Flow

Friction factors were determined for fully developed turbulent flow of mercury in smooth concentric annuli under conditions where either both walls were unwetted, or both were wetted, or the inner wall was wetted and the outer one unwetted. Three radius ratios (r2/r1) were used, i.e., 2.09, 2.78, and 4.00. Unwetted walls gave the lowest friction factors, which were practically independent of the r2/r1 ratio over the limited range tested. The factors were 10 ± 1 percent higher than the commonly accepted values for smooth pipes (at the same Reynolds number). The highest friction factors were obtained with the inner wall wetted and the outer wall unwetted, and the greater the r2/r1 ratio the greater was the effect. For example, at r2/r1 = 4.00, the friction factors were 9.9% greater than for the situation when both walls were unwetted. The wetting conditions affected the location of the radius of maximum velocity (rm); and it was found that the nearer rm approached r2, the higher was the friction factor.

Numerical and Experimental Analysis of Turbulent Flow in Corrugated Pipes

2010 ◽  
Vol 132 (7) ◽  
Author(s):  
Henrique Stel ◽  
Rigoberto E. M. Morales ◽  
Admilson T. Franco ◽  
Silvio L. M. Junqueira ◽  
Raul H. Erthal ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Pressure Drop ◽  
Turbulent Flow ◽  
Friction Factor ◽  
Turbulence Models ◽  
Reynolds Numbers ◽  
Velocity Magnitude ◽  
Geometric Configurations ◽  
Corrugated Surfaces ◽  
Friction Factors

This article describes a numerical and experimental investigation of turbulent flow in pipes with periodic “d-type” corrugations. Four geometric configurations of d-type corrugated surfaces with different groove heights and lengths are evaluated, and calculations for Reynolds numbers ranging from 5000 to 100,000 are performed. The numerical analysis is carried out using computational fluid dynamics, and two turbulence models are considered: the two-equation, low-Reynolds-number Chen–Kim k-ε turbulence model, for which several flow properties such as friction factor, Reynolds stress, and turbulence kinetic energy are computed, and the algebraic LVEL model, used only to compute the friction factors and a velocity magnitude profile for comparison. An experimental loop is designed to perform pressure-drop measurements of turbulent water flow in corrugated pipes for the different geometric configurations. Pressure-drop values are correlated with the friction factor to validate the numerical results. These show that, in general, the magnitudes of all the flow quantities analyzed increase near the corrugated wall and that this increase tends to be more significant for higher Reynolds numbers as well as for larger grooves. According to previous studies, these results may be related to enhanced momentum transfer between the groove and core flow as the Reynolds number and groove length increase. Numerical friction factors for both the Chen–Kim k-ε and LVEL turbulence models show good agreement with the experimental measurements.

Turbulent flow in smooth concentric annuli with small radius ratios

1974 ◽  
Vol 64 (2) ◽  
pp. 263-288 ◽  
Author(s):  
K. Rehme
Keyword(s):  
Reynolds Number ◽  
Shear Stress ◽  
Turbulent Flow ◽  
Strong Influence ◽  
Maximum Velocity ◽  
Small Radius ◽  
Stress Distributions ◽  
Number Range ◽  
Fully Developed Turbulent Flow ◽  
Flow Through

Fully developed turbulent flow through three concentric annuli was investigated experimentally for a Reynolds-number rangeRe= 2 × 104−2 × 105. Measurements were made of the pressure drop, the positions of zero shear stress and maximum velocity, and the velocity distribution in annuli of radius ratios α = 0.02, 0.04 and 0.1, respectively. The results for the key problem in the flow through annuli, the position of zero shear stress, showed that this position is not coincident with the position of maximum velocity. Furthermore, the investigation showed the strong influence of spacers on the velocity and shear-stress distributions. The numerous theoretical and experimental results in the literature which are based on the coincidence of the positions of zero shear stress and maximum velocity are not in agreement with reality.

Laminar, Transitional and Turbulent Friction Factors for Gas Flows in Smooth and Rough Microtubes

2008 ◽  
Author(s):  
Marco Lorenzini ◽  
Gian Luca Morini ◽  
Sandro Salvigni
Keyword(s):  
Reynolds Number ◽  
Friction Factor ◽  
Turbulent Regime ◽  
Turbulent Friction ◽  
Compressibility Effect ◽  
Flow Acceleration ◽  
Friction Factors ◽  
Macro Scale ◽  
Fully Developed Turbulent Flow ◽  
Microscale Transport

Theoretical and experimental works on microscale transport phenomena have been carried out in the past decade in the attempt to analyse possible new effects and to assess the influence of scaling on the classical correlations which are used in macro-scale heat and fluid flow, following the need to supply engineers with reliable correlations to be used in the design of micro-scale devices. These results were sometimes in mutual contrast, as is the case for the determination of the friction factor, which has been found to be lower, higher or comparable to that for macroscopic channels, depending on the researchers. In this work the compressible flow of nitrogen inside circular microchannels from 26 μm to 508 μm in diameter and with different surface roughness (<1%) is investigated for the whole range of flow conditions: laminar, transitional and turbulence. Over 5000 experimental data have been collected and analysed. The data confirmed that in the laminar regime the agreement with the conventional theory is very good in terms of friction factors both for rough and smooth microtubes. For the smaller microchannels (<100 μm) when Re is greater than 1300 the friction factor tends to deviate from the Poiseuille law because the flow acceleration due to compressibility effect gains in importance. The transitional regime was found to start no earlier than at values of the Reynolds number around 1800–2000. Both smooth and sudden changes in the flow regime have been found, as reported for conventional tubes. Fully developed turbulent flow was attained with both smooth and rough tubes, and the results for smooth tubes seem to confirm Blasius’s relation, while for rough tubes the Colebrook’s correlation is found to be only partially in agreement with the experimental friction factors. In the turbulent regime the dependence of the friction factor on the Reynolds number is less pronounced for microtubes with respect to the prediction of the Colebrook’s correlation and the friction factor tends only to depend on the microtube relative roughness.

An Analysis of Heat Transfer for Fully Developed Turbulent Flow in Concentric Annuli

1968 ◽  
Vol 90 (1) ◽  
pp. 43-50 ◽  
Author(s):  
N. W. Wilson ◽  
J. O. Medwell
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Turbulent Flow ◽  
Velocity Distribution ◽  
Maximum Velocity ◽  
Dimensionless Form ◽  
Temperature Distributions ◽  
Wide Range ◽  
Fully Developed Turbulent Flow ◽  
Heat And Momentum Transfer

The heat and momentum transfer analogy is employed to analyze the heat transfer phenomena for turbulent flow in concentric annuli. A modification of the velocity distribution due to Van Driest is assumed and equations in dimensionless form are developed to predict: (a) the position of maximum velocity in the annulus; (b) the friction factor-Reynolds number relationship, and (c) temperature distributions and heat transfer relations over a wide range of Reynolds number and Prandtl modulus.

Investigation of Fully Developed Turbulent Flow in a Straight Duct With Large Eddy Simulation

1994 ◽  
Vol 116 (4) ◽  
pp. 677-684 ◽  
Author(s):  
M. D. Su ◽  
R. Friedrich
Keyword(s):  
Reynolds Number ◽  
Large Eddy Simulation ◽  
Turbulent Flow ◽  
Secondary Flow ◽  
Initial Conditions ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Fully Developed Turbulent Flow ◽  
High Reynolds ◽  
Straight Duct

Large eddy simulations have been performed in straight ducts with square cross section at a global Reynolds number of 49,000 in order to predict the complicated mean and instantaneous flow involving turbulence-driven secondary motion. Isotropic grid systems were used with spatial resolutions of 256 * 642. The secondary flow not only turned out to develop extremely slowly from its initial conditions but also to require fairly high resolution. The obtained statistical results are compared with measurements. These results show that the large eddy simulation (LES) is a powerful approach to simulate the complex turbulence flow with high Reynolds number. Streaklines of fluid particles in the duct show the secondary flow clearly. The database obtained with LES is used to examine a statistical turbulence model and describe the turbulent vortex structure in the fully developed turbulent flow in a straight duct.

On the Use of the Preston Tube in Concentric Annuli

1967 ◽  
Vol 71 (673) ◽  
pp. 47-49 ◽  
Author(s):  
Alan Quarmby
Keyword(s):  
Reynolds Number ◽  
Turbulent Flow ◽  
Skin Friction ◽  
Radius Ratio ◽  
Experimental Results ◽  
Core Tube ◽  
Reasonable Range ◽  
Fully Developed Turbulent Flow ◽  
Good Agreement

Experimental results are presented of the measurement of skin friction in fully developed turbulent flow in concentric annuli using Preston tubes situated on the inner and outer annular surfaces. Both Preston's calibration and Patel's calibration were used to evaluate the results. It was found that the latter gave excellent results. Several radius ratios were investigated with a reasonable range of the annulus Reynolds number. The good agreement was not affected by radius ratio or smallness of core tube within the range of these parameters investigated here.

A New Low-Reynolds-Number k-ε Model for Turbulent Flow Over Smooth and Rough Surfaces

1996 ◽  
Vol 118 (2) ◽  
pp. 255-259 ◽  
Author(s):  
Hanzhong Zhang ◽  
Mohammad Faghri ◽  
Frank M. White
Keyword(s):  
Reynolds Number ◽  
Turbulent Flow ◽  
Dissipation Rate ◽  
Rough Surfaces ◽  
Low Reynolds Number ◽  
Friction Factors ◽  
Log Law ◽  
Low Reynolds ◽  
Flow Experiments ◽  
Grain Roughness

A new low-Reynolds-number k-ε model is proposed to simulate turbulent flow over smooth and rough surfaces by including the equivalent sand-grain roughness height into the model functions. The simulation of various flow experiments shows that the model can predict the log-law velocity profile and other properties such as friction factors, turbulent kinetic energy and dissipation rate for both smooth and rough surfaces.

Frictional Pressure Drop in Micro-Channel

2004 ◽  
Author(s):  
Yasuo Koizumi ◽  
Hiroyasu Ohtake ◽  
Hiroki Takahashi ◽  
Yoshiaki Ohno
Keyword(s):  
Reynolds Number ◽  
Pressure Drop ◽  
Friction Factor ◽  
Frictional Pressure Drop ◽  
Turbulent Transition ◽  
Friction Factors ◽  
Turbulent Flow Regime ◽  
Form Pressure ◽  
Laminar And Turbulent Flow ◽  
Flow Through

The friction characteristics of water in a sub-millimeter scale channel were investigated experimentally. The friction factors and the critical Reynolds number were measured using water flow through circular tubes with diameters of 0.5, 0.25 and 0.17 mm. The experimental results show that the measured friction factor for water agreed well with the conventional Poiseuille (λ = 64/Re) and Blasius (λ = 0.316 Re−0.25) equations in laminar and turbulent flow regime; the laminar-turbulent transition Reynolds number was approximately 2300 for diameter 0.5 mm. For diameter 0.25 mm, the friction factor evaluated by the form pressure drop also agreed well with the Poiseuille equation. For diameter 0.17 mm, the measured total friction factor was close to the Poiseuille prediction.

scholarly journals Experimental and theoretical studies of dissolution roughness

1974 ◽  
Vol 65 (4) ◽  
pp. 735-751 ◽  
Author(s):  
Paul N. Blumberg ◽  
Rane L. Curl
Keyword(s):  
Mass Transfer ◽  
Reynolds Number ◽  
Turbulent Flow ◽  
Friction Factor ◽  
Flow Structure ◽  
Friction Velocity ◽  
Theoretical Studies ◽  
Average Mass ◽  
Characteristic Wavelength ◽  
Experimental And Theoretical Studies

Periodic dissolution patterns that result from the interaction of a soluble surface and an adjacent turbulent flow have been investigated experimentally and theoretically. They occur at a Reynolds number based on a characteristic wavelength and friction velocity of about 2200. Experimental results for the stable geometry, propagation, mass-transfer distribution, average mass-transfer correlation and friction factor are presented. An interpretation based upon the repetitive transitional nature of the flow structure is advanced to explain aspects of the origin and behaviour of this type of roughness.

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