Measurement and Prediction of Rough Wall Effects on Friction Factor—Uniform Roughness Results

1988 ◽  
Vol 110 (4) ◽  
pp. 385-391 ◽  
Author(s):  
W. F. Scaggs ◽  
R. P. Taylor ◽  
H. W. Coleman
Keyword(s):  
Friction Factor ◽  
Roughness Element ◽  
Discrete Element ◽  
Turbulent Pipe Flow ◽  
Number Range ◽  
Flow Friction ◽  
Friction Factors ◽  
Roughness Model ◽  
Factor Data ◽  
Good Agreement

The results of an experimental investigation of the effects of surface roughness on turbulent pipe flow friction factors are presented and compared with predictions from a previously published discrete element roughness model. Friction factor data were acquired over a pipe Reynolds number range from 10,000 to 600,000 for nine different uniformly rough surfaces. These surfaces covered a range of roughness element sizes, spacings and shapes. Predictions from the discrete element roughness model were in very good agreement with the data.

A Review of Explicit Friction Factor Equations

1985 ◽  
Vol 107 (2) ◽  
pp. 280-283 ◽  
Author(s):  
D. J. Zigrang ◽  
N. D. Sylvester
Keyword(s):  
Friction Factor ◽  
Pipe Flow ◽  
Turbulent Pipe Flow ◽  
Explicit Equation ◽  
Flow Friction ◽  
Friction Factors ◽  
High Degree ◽  
Very High

A review of the explicit friction factor equations developed to replace the Colebrook equation is presented. Explicit friction factor equations are developed which yield a very high degree of precision compared to the Colebrook equation. A new explicit equation, which offers a reasonable compromise between complexity and accuracy, is presented and recommended for the calculation of all turbulent pipe flow friction factors for all roughness ratios and Reynold’s numbers.

Experimental Measurements and Computations of Heat Transfer and Flow Friction Factor in a Staggered Pin Fin Array

2001 ◽  
Author(s):  
Forrest E. Ames ◽  
Christopher S. Solberg ◽  
Michael D. Goman ◽  
Daniel J. Curtis ◽  
Bradley T. Steinbrecker
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Friction Factor ◽  
Experimental Measurements ◽  
Wall Region ◽  
Number Range ◽  
Flow Friction ◽  
Pin Fin ◽  
Factor Data ◽  
Pin Fin Array

Abstract This paper presents experimental measurements and CFD calculations for heat transfer and flow friction factor in a staggered pin fin array. The heat transfer and flow friction factor data are taken in a constant temperature facility and are acquired over a Reynolds number range of 1500 to 31,000. The array is comprised of eight rows of pins spaced at 2.5 diameters in the streamwise and spanwise directions with a pin height of two diameters. The heat transfer data are presented in terms of both average array data and row resolved data. The data accurately match the recent pin fin correlation of Chyu et at. [1] and extend its range to lower Reynolds numbers. The flow friction factor data accurately match the low and high Reynolds number data of Metzger et al. [2]. The steady state computations for a 2D and 3D representation of the geometry are performed and compared with archival correlations and the present data. The calculations are performed using a general purpose commercial solver (FLUENT 5.3 [3]) and apply the realizable k-ε model of Shih et al. [4] along with a two layer model which solves the k equation in the near wall region. Generally, the calculations perform relatively well with the 2D calculations matching the literature correlations slightly better than the 3D calculations.

scholarly journals New explicit correlations for turbulent flow friction factor

2017 ◽  
Author(s):  
Dejan Brkić
Keyword(s):  
Turbulent Flow ◽  
Friction Factor ◽  
Pipe Flow ◽  
Single Phase ◽  
Turbulent Pipe Flow ◽  
Pipe Surface ◽  
Flow Friction ◽  
Total Absence ◽  
Friction Factors ◽  
Transient Zone

Two new correlations of single-phase friction factor for turbulent pipe flow are shown in this paper. These two formulas are actually explicit approximations of iterative Colebrook's relation for calculation of flow friction factor. Calculated friction factors are valid for whole turbulent flow including hydraulically smooth and rough pipes with special attention on transient zone of turbulence between them. Hydraulically smooth regime of turbulence does not occur only in total absence of roughness of inner pipe surface, but also, four new relations for this theoretical regime are presented. Some recent formulas for turbulent flow friction calculation are also commented.

Flow in Rotating Straight Pipes of Circular Cross Section

1971 ◽  
Vol 93 (3) ◽  
pp. 383-394 ◽  
Author(s):  
H. Ito¯ ◽  
K. Nanbu
Keyword(s):  
Friction Factor ◽  
Cross Section ◽  
Circular Cross Section ◽  
Constant Angular Velocity ◽  
Smooth Wall ◽  
Good Qualitative Agreement ◽  
Fully Developed Flow ◽  
Number Range ◽  
Friction Factors ◽  
Laminar And Turbulent Flow

The friction factor for fully developed flow in smooth wall straight pipes of circular cross section rotating at a constant angular velocity about an axis perpendicular to its own has been measured in the Reynolds number range from 20 to 60,000. Empirical equations for friction factors for small values of RΩ/R were presented for both laminar and turbulent flow. In the case of laminar flow, an approximate analysis based on the assumption that the flow consists of a frictionless central core surrounded by a boundary layer was presented. The results were in good qualitative agreement with experimental results in regard to the friction factor, velocity distribution in the plane of symmetry and pressure distribution along the circumferential wall of the pipe.

scholarly journals Friction-Factor Data for Flat-Plate Tests of Smooth and Honeycomb Surfaces

1992 ◽  
Vol 114 (4) ◽  
pp. 722-729 ◽  
Author(s):  
T. W. Ha ◽  
Dara W. Childs
Keyword(s):  
Flat Plate ◽  
Friction Factor ◽  
Smooth Surface ◽  
Factor Model ◽  
Test Apparatus ◽  
Cell Width ◽  
Plate Test ◽  
Friction Factors ◽  
Line Flow ◽  
Factor Data

Friction-factors for honeycomb surfaces are measured with a flat plate tester. The flat plate test apparatus is described and a method is discussed for determining the friction-factor experimentally. The friction-factor model is developed for the flat plate test based on the Fanno Line Flow. The comparisons of the friction-factor are plotted for smooth surface and twelve-honeycomb surfaces with three-clearances, 6.9 bar to 17.9 bar range of inlet pressure, and 5,000 to 130,000 range of the Reynolds number. The optimum geometries for the maximum friction-factor are found as a function of cell width to cell depth and clearance to cell width ratios.

scholarly journals Discussion of “Accurate and Efficient Explicit Approximations of the Colebrook Flow Friction Equation Based on the Wright ω-Function” by Dejan Brkić and Pavel Praks, Mathematics 2019, 7, 34; doi:10.3390/math7010034

Mathematics ◽  
2020 ◽  
Vol 8 (5) ◽  
pp. 793
Author(s):  
Majid Niazkar
Keyword(s):  
Friction Factor ◽  
Evaluation Criteria ◽  
Standard Approach ◽  
Accuracy Evaluation ◽  
Engineering Applications ◽  
Flow Friction ◽  
Friction Factors ◽  
One Step

Estimating the Darcy–Weisbach friction factor is crucial to various engineering applications. Although the literature has accepted the Colebrook–White formula as a standard approach for this prediction, its implicit structure brings about an active field of research seeking for alternatives more suitable in practice. This study mainly attempts to increase the precision of two explicit equations proposed by Brkić and Praks. The results obviously demonstrate that the modified relations outperformed the original ones from nine out of 10 accuracy evaluation criteria. Finally, one of the improved equations estimates closer friction factors to those obtained by the Colebrook–White formula among 18 one-step explicit equations available in the literature based on three of the considered criteria.

An Experimental Investigation of Gaseous Flow Characteristics in Microchannels

2004 ◽  
Author(s):  
G. H. Tang ◽  
Y. L. He
Keyword(s):  
Experimental Investigation ◽  
Flow Characteristics ◽  
Fused Silica ◽  
Helium Flow ◽  
Gaseous Flow ◽  
Compressibility Effect ◽  
Circular Tubes ◽  
Flow Friction ◽  
Friction Factors ◽  
Good Agreement

Gaseous flow characteristics in fused silica microtubes and square microchannels are studied experimentally. The existing works in the literature on experimental gaseous flow are analyzed. The data in fused silica micro circular tubes with diameters ranging from 50 μm to 201 μm and the data in fused silica micro square channels with hydraulic diameter ranging from 52 μm to 100 μm show that the flow friction factors are in good agreement with the theoretical prediction for conventional tubes and no distinguishable deviation is observed. The transition Reynolds number is around 2000 and a slight early transition from laminar to turbulent is observed due to the compressibility effect. For the helium flow in fused silica microtubes with inner diameters ranging from 10 μm to 20 μm, the decrease in friction factor is observed. In addition, factors including roughness, compressibility and rarefaction that may have significant effects on flow characteristics in microchannels are discussed.

Test Results for Liquid “Damper” Seals Using a Round-Hole Roughness Pattern for the Stators

1999 ◽  
Vol 121 (1) ◽  
pp. 42-49 ◽  
Author(s):  
Dara W. Childs ◽  
Patrice Fayolle
Keyword(s):  
Friction Factor ◽  
Round Hole ◽  
Test Results ◽  
Partial Explanation ◽  
Rotordynamic Coefficients ◽  
Stiffness Coefficients ◽  
Friction Factors ◽  
Direct Stiffness ◽  
Factor Data ◽  
Pressure Driven Flow

Test results are reviewed for two annular liquid seals (L = 34.9 mm; D = 76.5 mm) at two clearances (.1 and .12 mm). The seal stators use hole-pattern-roughened stators that are identical except for hole depths of .28 and 2.0 mm. Tests are conducted at three speeds out to 24,600 rpm and three pressures out to 68 bars. Test data consist of leakage rates and rotordynamic coefficients at centered and eccentric positions with static eccentricity ratios out to 0.5. Test results are consistent with expectations in regard to the reduction of cross-coupled stiffness coefficients due to stator roughness. However, the measured direct stiffness coefficients were unexpectedly low. A partial explanation for these results is provided by measured friction factor data which show an increase in the friction factors for pressure-driven flow with an increase in clearance. A prediction model for rotordynamic coefficients, incorporating the friction-factor data, predicted a substantial loss in direct stiffness but could not explain the very low (or negative) values that were measured. The model did explain the measured drop in cross coupled stiffness (k) and provides an alternative explanation to observed reductions in k values; specifically, an increase in the friction factor with increasing clearance causes a reduction in k irrespective of any parallel reduction in the average circumferential velocity.

An Experimental and Analytical Investigation of Friction Factors for Fully Developed Flow in Internally Finned Triangular Ducts

1986 ◽  
Vol 108 (3) ◽  
pp. 507-512 ◽  
Author(s):  
H. Chegini ◽  
S. K. Chaturvedi
Keyword(s):  
Reynolds Number ◽  
Friction Factor ◽  
Reynolds Numbers ◽  
Analytical Investigation ◽  
Momentum Equation ◽  
Fully Developed Flow ◽  
Finite Difference Technique ◽  
Friction Factors ◽  
Experimental Values ◽  
Good Agreement

Friction factors for fully developed flow in triangular ducts with fins of various height and width are investigated for Reynolds numbers ranging from 150 to 90,000. Two triangular ducts having apex angles of 60 and 38.8 deg are studied. Results are presented in the form of standard plots of friction factor as a function of Reynolds number. Friction factor values for the smooth triangular duct cases are in good agreement with the existing results. For the finned-duct cases, the fully developed axial velocity profiles in laminar flow are determined by solving the x-momentum equation iteratively by the Gauss–Seidel finite-difference technique. The theoretically determined friction factors for these cases are in good agreement with the experimental values of friction factors based on pressure drop measurements.

Hydrodynamic Characteristics of Crossflow over MEMS-Based Pillars

2011 ◽  
Vol 133 (8) ◽  
Author(s):  
Ali Koşar ◽  
Brandon Schneider ◽  
Yoav Peles
Keyword(s):  
Friction Factor ◽  
Hydrodynamic Characteristics ◽  
Flow Conditions ◽  
Pin Fin ◽  
Aspect Ratios ◽  
Friction Factors ◽  
Wide Range ◽  
Hydrodynamic Processes ◽  
Factor Data ◽  
Key Parameter

A parametric study was performed to reveal the hydrodynamic processes controlling crossflow over MEMS-based micro pin fin devices. Pressure drop experiments were conducted and used to obtain friction factors on a wide range of micro pin fin devices for various flow conditions and geometrical configurations, including pin fin height-to-diameter aspect ratios, spacings, and shapes. The acquired data suggests that the device geometry is the key parameter dictating friction factor trends and magnitude along with the Reynolds number. Additionally, friction factor data has shown that correlations based on experimental results performed on conventional scale tube bundles do not accurately predict the trends under working conditions pertaining to microfluidic systems.

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