Calculation of Friction Coefficients for Noncircular Channels

2004 ◽  
Vol 126 (6) ◽  
pp. 1033-1038 ◽  
Author(s):  
S. He ◽  
J. A. Gotts
Keyword(s):  
Hydraulic Resistance ◽  
Turbulent Flows ◽  
Shape Factor ◽  
Arbitrary Shape ◽  
Characteristic Length ◽  
New Method ◽  
Circular Pipe ◽  
Friction Coefficients ◽  
Flow Channels ◽  
Good Agreement

This paper presents a method for estimating a hydraulic resistance multiplier to enable approximate values of friction coefficients to be calculated for turbulent flows in noncircular channels of arbitrary shape using correlations developed for the circular pipe. Unlike most other methods, no preknowledge on the flow channels, such as the laminar shape factor or characteristic length, is required. Good agreement between predictions using the new method and experiments was achieved.

Development of an Instantaneous Velocity-Vector-Profile Method Using Conventional Ultrasonic Transducers

2021 ◽  
Author(s):  
Dongik Yoon ◽  
Hyun Jin Park ◽  
Tomonori Ihara
Keyword(s):  
Velocity Vector ◽  
Ultrasound Velocity ◽  
Ultrasonic Transducers ◽  
New Method ◽  
Ultrasound Transducers ◽  
Accuracy And Precision ◽  
Conventional Ultrasound ◽  
Measurable Distance ◽  
Profile Technique ◽  
Good Agreement

Abstract The velocity vector profile technique based on an ultrasound pulsed Doppler method can enrich the information of a flow field, however, it has shown a low availability because a new design of special transducers is required for each measurement case. This study proposes a new method of profiling the velocity vectors using conventional ultrasound transducers that are widely supplied to UVP (Ultrasound velocity profile) users. We constructed a configuration of the transducers to minimize the uncertainty of the detection points at the receivers, and a measurable distance was theoretically determined by the configuration. Two feasibility tests were carried out. One was a test for the assessment of the measurable distance, which agreed well with the theoretical distance. The other was the evaluation of the measurement of two-dimensional velocity vectors by the new method and it was performed in a towing tank facility without the velocity fluctuation. From the evaluation, it was confirmed that the measured vectors showed good agreement to the reference values, and their accuracy and precision were competitive compared to previous studies. The developed method was applied to two unsteady flows for demonstrations. The results clarified that the proposed method guarantees high availability and accuracy for the velocity vector profiles.

Measurement and Prediction of the Effects of Nonuniform Surface Roughness on Turbulent Flow Friction Coefficients

1988 ◽  
Vol 110 (4) ◽  
pp. 380-384 ◽  
Author(s):  
R. P. Taylor ◽  
W. F. Scaggs ◽  
H. W. Coleman
Keyword(s):  
Turbulent Flows ◽  
Rough Surfaces ◽  
Reynolds Numbers ◽  
Base Diameter ◽  
Friction Coefficients ◽  
Friction Factors ◽  
Random Rough Surfaces ◽  
The Status ◽  
Uniform Array ◽  
Prediction Approach

The status of prediction methods for friction coefficients in turbulent flows over nonuniform or random rough surfaces is reviewed. Experimental data for friction factors in fully developed pipe flows with Reynolds numbers between 10,000 and 600,000 are presented for two nonuniform rough surfaces. One surface was roughened with a mixture of cones and hemispheres which had the same height and base diameter and were arranged in a uniform array. The other surface was roughened with a mixture of two sizes of cones and two sizes of hemispheres. These data are compared with predictions made using the previously published discrete element prediction approach of Taylor, Coleman, and Hodge. The agreement between the data and the predictions is excellent.

A new method for the determination of shape factor and particle density

1985 ◽  
Vol 30 (3) ◽  
pp. 155-158 ◽  
Author(s):  
Joaquim Casal ◽  
Antoni Lucas ◽  
Josep Arnaldos
Keyword(s):  
Shape Factor ◽  
Particle Density ◽  
New Method

Oblique Penetration of a Circular Pipe Target by a Prefabricated Fragment

2019 ◽  
Vol 19 (10) ◽  
pp. 1950119
Author(s):  
Yajun Wang ◽  
Weibing Li ◽  
Guili Zhu ◽  
Wenbin Li
Keyword(s):  
Initial Velocity ◽  
Critical Angle ◽  
Circular Pipe ◽  
Entry Angle ◽  
Failure Characteristics ◽  
Finite Element Software ◽  
Direction Angle ◽  
The Relationship ◽  
Penetration Velocity ◽  
Good Agreement

For the oblique penetration of a circular pipe target by a prefabricated fragment, the finite element software LS-DYNA was used to build a computational model for the circular pipe considering the penetration by a cylindrical fragment from different directions. The failure characteristics of the pipe were acquired and the critical penetration velocity was calculated. The relationship between the initial velocity and critical angle of ricochet was found. The experiment was then conducted to verify the results obtained, indicating that the simulation results are in good agreement with the experimental ones. It was shown that the main critical failure pattern of a circular pipe is shear perforation or a penetrating crack. The critical penetration velocity is positively correlated with the direction angle [Formula: see text] and entry angle [Formula: see text]. For entry angles greater than 30∘, the critical penetration velocity increases with an increase in the direction angle, and this effect is stronger for higher direction angles. The critical angle of ricochet is positively correlated with the initial velocity of the fragment. The critical angle of ricochet tends to approach a constant of 60∘ as the initial velocity of the fragment increases.

A New Method to Assess Ductility of CFT Box Columns with Binding Bars under Axial Compression

2012 ◽  
Vol 446-449 ◽  
pp. 78-81 ◽  
Author(s):  
Yue Ling Long ◽  
Jian Cai
Keyword(s):  
Experimental Data ◽  
Axial Compression ◽  
Material Properties ◽  
New Method ◽  
Box Columns ◽  
Good Agreement

A new method based on material properties instead of experimental data was proposed to assess the ductility of concrete-filled steel box columns with binding bars and those without binding bars. Comparison between ductility coefficients based on experimental data and the calculated values by the proposed method shows good agreement.

Evaluation of polydispersity index Mw/Mn by quasielastic light scattering

1987 ◽  
Vol 52 (5) ◽  
pp. 1235-1245 ◽  
Author(s):  
Petr Štěpánek ◽  
Zdeněk Tuzar ◽  
Čestmír Koňák
Keyword(s):  
Molecular Weight ◽  
Light Scattering ◽  
Decay Time ◽  
Sampling Time ◽  
Polydispersity Index ◽  
New Method ◽  
Molecular Weights ◽  
Quasielastic Light Scattering ◽  
Good Agreement

The response of quasielastic light scattering to the polydispersity of scattering objects has been investigated. A new method of the polydispersity index determination has been suggested, suitable for the range 1.02 ⪬ Mw/Mn ⪬ 2.0 and consisting in the measurement of the dependence of the apparent decay time on the correlator sampling time. The polydispersity index can be determined by comparing these dependences with the theoretical ones obtained using correlation curves simulated for various values of the polydispersity index, assuming lognormal and Schulz-Zimm distributions of molecular weights. The test measurements on polystyrene standards having molecular weights in the range 9 103 – 20.6 106 give polydispersity index values Mw/Mn that are in a good agreement with those given by the manufacturer. The polydispersity index for polystyrene having the molecular weight Mw = 20.6 106 thus determined was Mw/Mn = 1.35.

A New Method for Measuring Thermal Contact Conductance: Experimental Technique and Results

2008 ◽  
Author(s):  
Simon Woodland ◽  
Andrew D. Crocombe ◽  
John W. Chew ◽  
Stephen J. Mills
Keyword(s):  
Thermal Contact ◽  
New Method ◽  
Thermal Contact Conductance ◽  
Metal Working ◽  
Loading History ◽  
Test Rig ◽  
Contact Conductance ◽  
Pressure Surface ◽  
Surface Flatness ◽  
Good Agreement

Thermal contact conductance (TCC) is used to characterise heat transfer across interfaces in contact. It is important in thermal modelling of turbomachinery components and finds many other applications in the aerospace, microelectronic, automotive and metal working industries. A new method for measuring TCC is described and demonstrated. A test rig is formed from an instrumented split tube with washers in-between and loading applied in controlled conditions. The experimental method and data analysis is described, and the effect on thermal contact conductance of parameters such as contact pressure, surface roughness, surface flatness and loading history is investigated. The results of these tests are compared to those in the available literature and good agreement of trends is found. However, the tests conducted to measure the effect of load cycling on TCC have found that the TCC continues to increase beyond 20 or so load cycles, contrary to some results in the literature.

A Continuous Prediction Method for Fully Developed Laminar, Transitional, and Turbulent Flows in Pipes

1975 ◽  
Vol 42 (1) ◽  
pp. 51-54 ◽  
Author(s):  
N. W. Wilson ◽  
R. S. Azad
Keyword(s):  
Turbulent Flows ◽  
Flow Characteristics ◽  
Prediction Method ◽  
Reynolds Numbers ◽  
Mean Flow ◽  
Number Range ◽  
Circular Pipes ◽  
The Mean ◽  
Single Set ◽  
Good Agreement

A single set of equations is developed to predict the mean flow characteristics in long circular pipes operating at laminar, transitional, and turbulent Reynolds numbers. Generally good agreement is obtained with available data in the Reynolds number range 100 < Re < 500,000.

Sign in / Sign up

Export Citation Format

Share Document