Propagation of Disturbance in Fluid Lines

1967 ◽  
Vol 89 (2) ◽  
pp. 415-422 ◽  
Author(s):  
J. S. Ansari ◽  
R. Oldenburger
Keyword(s):  
Coefficient Of Friction ◽  
Pressure Pulse ◽  
Viscous Fluids ◽  
Viscous Effects ◽  
Mean Velocity ◽  
The Coefficient Of Friction ◽  
The Mean

The purpose of this paper is to investigate the phenomena of the decay and dispersion of a disturbance pulse as it travels in a fluid along a pipe. A disturbance has associated with it deviations in the mean velocity and pressure. The disturbance pulse, therefore, may be considered as a velocity or a pressure pulse. By decay we mean here a decrease in the intensity, and by dispersion an increase in the width of the pulse with time. In an ideal nonviscous fluid contained in a rigid pipe, decay and dispersion do not occur, but are observed in the viscous fluids. A reflection of the pulse from a closed free end of the pipe also causes decay and dispersion. It is observed that for sufficiently low values of the coefficient of friction the viscous effects may be approximated by a pure decay without dispersion.

Effect of Upstream Flow Processes on Hydrodynamic Development in a Duct

1977 ◽  
Vol 99 (3) ◽  
pp. 556-560 ◽  
Author(s):  
E. M. Sparrow ◽  
C. E. Anderson
Keyword(s):  
Reynolds Number ◽  
Reynolds Numbers ◽  
Center Line ◽  
Viscous Effects ◽  
Mean Velocity ◽  
Inertia Effects ◽  
Reynolds Number Flow ◽  
Compact Size ◽  
Number Flow ◽  
The Mean

Consideration is given to the developing laminar flow in a parallel plate channel, with the fluid being drawn from a large upstream space. The flow fields upstream and downstream of the channel inlet were solved simultaneously. A finite-difference technique was employed which was facilitated by a coordinate transformation that telescoped the broadly extended flow domain into a more compact size. For the solutions, the Reynolds number was assigned values from 1 to 1000, covering the range from viscous-dominated flows to those where both viscous and inertia effects are relevant. Streamline maps indicate that whereas a low Reynolds number flow glides smoothly into the channel, a high Reynolds number flow has to turn sharply to enter the channel, with the result that the sharply turning fluid tends to overshoot at first and then readjust. A significant amount of upstream predevelopment occurs at low and intermediate Reynolds numbers. Thus, for example, at Re = 1 and 100, the center-line velocities at inlet are, respectively, 1.37 and 1.13 times the mean velocity (the fully developed center-line velocity is 1.5 times the mean). The upstream pressure drop, measured in terms of the velocity head, is substantially increased by viscous effects at low and intermediate Reynolds numbers.

The Design of a Linear “Out of Phase” Vibratory Conveyor

1973 ◽  
Vol 95 (1) ◽  
pp. 42-47 ◽  
Author(s):  
R. E. Schofield ◽  
M. Yousuf
Keyword(s):  
Phase Angle ◽  
Coefficient Of Friction ◽  
Experimental Investigations ◽  
Phase Effect ◽  
Theoretical Predictions ◽  
The Coefficient Of Friction ◽  
Drive Belt ◽  
The Mean ◽  
Vibratory Conveyor ◽  
Normal Track

This paper describes the development of a linear “out-of-phase” vibratory conveyor. The “out-of-phase” effect is achieved by controlling the components of motion normal to and parallel to the track independently. This is done by mounting the trough on sets of double “U” shear rubber mountings. From Fig. 1(a) it can be seen that these mountings allow motion in any direction in the plane of the rubber while substantially constraining motion perpendicular to that plane. Excitation of the trough is by two hydraulic pumps the phase angle between which is controlled by a positive drive belt. Experimental investigations into the behavior of single parts were carried out and results comparable to the theoretical predictions for “out-of-phase” were obtained. Substantial increases in the mean conveying velocity of single parts can be achieved without erratic part movement because it is possible with this system to use high values of normal track acceleration An/g combined with low vibration angles. Increases in mean conveying velocity of as much as 270 percent are obtained, depending on the coefficient of friction and vibration angles.

Gravity waves over a non-uniform flow

1969 ◽  
Vol 39 (4) ◽  
pp. 817-829 ◽  
Author(s):  
H. G. M. Velthuizen ◽  
L. Van Wijngaarden
Keyword(s):  
Velocity Distribution ◽  
Gravity Waves ◽  
Propagation Velocity ◽  
Fluid Velocity ◽  
Wall Layer ◽  
Mean Flow ◽  
Viscous Effects ◽  
Critical Height ◽  
Mean Velocity ◽  
The Mean

This paper is concerned with the propagation of small amplitude gravity waves over a flow with non-uniform velocity distribution. For such a flow Burns derived a relation for the velocity of propagation in terms of the velocity distribution of the mean flow. This result is derived here in another way and some of its implications are discussed. It is shown that one of these is hardly acceptable physically. Burns's result holds only when a real value of the propagation velocity is assumed; the mentioned difficulties vanish if complex values are allowed for, implying damping or growth of the waves. Viscous effects which are the cause of damping or growth are important in the wall layer near the bottom and also at the critical depth, which is present when the wave speed is between zero and the fluid velocity at the free surface.In § 2 the basic equations for the present problem are given. In § 3 exchange of momentum and energy between wave and primary flow is discussed. This is analogous to what happens at the critical height in a wind flow over wind-driven gravity waves. In § 4 the viscous effects at the bottom are included in the analysis and the complex equation for the propagation velocity is derived. Finally in § 5 illustrations of the theory are given for long waves over running flow and for the flow along a ship advancing in a wavy sea. In these examples a negative curvature of the mean velocity profile is shown to have a stabilizing effect.

scholarly journals Characterization of the Effect of Moisture on Tribology of Titanium Rubbed Against Different Pin Materials

2020 ◽  
pp. 1-10
Author(s):  
Bodhi R. Manu ◽  
Adam M. Schroeder ◽  
Ahalapitiya H. Jayatissa
Keyword(s):  
Friction Coefficient ◽  
Relative Humidity ◽  
Coefficient Of Friction ◽  
Water Film ◽  
Interfacial Surface ◽  
The Coefficient Of Friction ◽  
The Mean ◽  
Machine Parts ◽  
Pin On Disk

Tribology investigations were conducted to understand the effect of humidity and water adsorption at the interfacial surface on the friction coefficient of titanium. Pin-on-disk tribometer tests were conducted at different levels of humidity ranging from 0% to 71% RH using aluminum and steel pins on a titanium plate. The variation of the mean coefficient of friction was plotted as a function of relative humidity. The friction coefficient slightly decreased when the relative humidity was increased from 0% to 10% RH. However, it increased with a further increase in humidity. The maximum friction coefficients were observed at 55% and 65% RH for steel and aluminum, respectively. The thickness of the wear tracks also showed the same trend as the friction coefficient. Under high humidity conditions, water vapor can condense on the surface of the moving machine parts. To understand the influence of this water film, a pin-on-disk test was carried out on a sample where a thin film of water masks metal surfaces from contact. Although the coefficient of friction was similar for both the aluminum and steel pins’ interaction with titanium (~0.36), the wear tracks were not formed for steel pin/titanium interaction even though this experiment was conducted for more cycles.

Experimental Investigation of aluminum doping crumb rubber/epoxy composite in reciprocating motion

2015 ◽  
Vol 3 ◽  
pp. 1
Author(s):  
Goutam Chandra Karar ◽  
Nipu Modak
Keyword(s):  
Experimental Investigation ◽  
Coefficient Of Friction ◽  
Epoxy Composite ◽  
Normal Load ◽  
Crumb Rubber ◽  
The Other ◽  
Reciprocating Motion ◽  
Molding Process ◽  
Friction Tester ◽  
The Coefficient Of Friction

The experimental investigation of reciprocating motion between the aluminum doped crumb rubber /epoxy composite and the steel ball has been carried out under Reciprocating Friction Tester, TR-282 to study the wear and coefficient of frictions using different normal loads (0.4Kg, 0.7Kgand1Kg), differentfrequencies (10Hz, 25Hz and 40Hz).The wear is a function of normal load, reciprocating frequency, reciprocating duration and the composition of the material. The percentage of aluminum presents in the composite changesbut the other components remain the same.The four types of composites are fabricated by compression molding process having 0%, 10%, 20% and 30% Al. The effect of different parameters such as normal load, reciprocating frequency and percentage of aluminum has been studied. It is observed that the wear and coefficient of friction is influenced by the parameters. The tendency of wear goes on decreasing with the increase of normal load and it is minimum for a composite having 10%aluminum at a normal load of 0.7Kg and then goes on increasing at higher loads for all types of composite due to the adhesive nature of the composite. The coefficient of friction goes on decreasing with increasing normal loads due to the formation of thin film as an effect of heat generation with normal load.

The flow of liquid in a stream from the standard turbine impeller

1979 ◽  
Vol 44 (3) ◽  
pp. 700-710 ◽  
Author(s):  
Ivan Fořt ◽  
Hans-Otto Möckel ◽  
Jan Drbohlav ◽  
Miroslav Hrach
Keyword(s):  
Reynolds Number ◽  
Kinematic Viscosity ◽  
Momentum Flux ◽  
Relative Size ◽  
Mean Velocity ◽  
Axial Profile ◽  
The Mean ◽  
Hot Film ◽  
Turbine Impeller

Profiles of the mean velocity have been analyzed in the stream streaking from the region of rotating standard six-blade disc turbine impeller. The profiles were obtained experimentally using a hot film thermoanemometer probe. The results of the analysis is the determination of the effect of relative size of the impeller and vessel and the kinematic viscosity of the charge on three parameters of the axial profile of the mean velocity in the examined stream. No significant change of the parameter of width of the examined stream and the momentum flux in the stream has been found in the range of parameters d/D ##m <0.25; 0.50> and the Reynolds number for mixing ReM ##m <2.90 . 101; 1 . 105>. However, a significant influence has been found of ReM (at negligible effect of d/D) on the size of the hypothetical source of motion - the radius of the tangential cylindrical jet - a. The proposed phenomenological model of the turbulent stream in region of turbine impeller has been found adequate for values of ReM exceeding 1.0 . 103.

scholarly journals Tribological Aspects, Optimization and Analysis of Cu-B-CrC Composites Fabricated by Powder Metallurgy

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4217
Author(s):  
Üsame Ali Usca ◽  
Mahir Uzun ◽  
Mustafa Kuntoğlu ◽  
Serhat Şap ◽  
Khaled Giasin ◽  
...  
Keyword(s):  
Weight Loss ◽  
Wear Rate ◽  
Coefficient Of Friction ◽  
Applied Load ◽  
Practical Significance ◽  
Tribological Characteristics ◽  
M 10 ◽  
Wide Range ◽  
The Coefficient Of Friction ◽  
Four Levels

Tribological properties of engineering components are a key issue due to their effect on the operational performance factors such as wear, surface characteristics, service life and in situ behavior. Thus, for better component quality, process parameters have major importance, especially for metal matrix composites (MMCs), which are a special class of materials used in a wide range of engineering applications including but not limited to structural, automotive and aeronautics. This paper deals with the tribological behavior of Cu-B-CrC composites (Cu-main matrix, B-CrC-reinforcement by 0, 2.5, 5 and 7.5 wt.%). The tribological characteristics investigated in this study are the coefficient of friction, wear rate and weight loss. For this purpose, four levels of sliding distance (1000, 1500, 2000 and 2500 m) and four levels of applied load (10, 15, 20 and 25 N) were used. In addition, two levels of sliding velocity (1 and 1.5 m/s), two levels of sintering time (1 and 2 h) and two sintering temperatures (1000 and 1050 °C) were used. Taguchi’s L16 orthogonal array was used to statistically analyze the aforementioned input parameters and to determine their best levels which give the desired values for the analyzed tribological characteristics. The results were analyzed by statistical analysis, optimization and 3D surface plots. Accordingly, it was determined that the most effective factor for wear rate, weight loss and friction coefficients is the contribution rate. According to signal-to-noise ratios, optimum solutions can be sorted as: the highest levels of parameters except for applied load and reinforcement ratio (2500 m, 10 N, 1.5 m/s, 2 h, 1050 °C and 0 wt.%) for wear rate, certain levels of all parameters (1000 m, 10 N, 1.5 m/s, 2 h, 1050 °C and 2.5 wt.%) for weight loss and 1000 m, 15 N, 1 m/s, 1 h, 1000 °C and 0 wt.% for the coefficient of friction. The comprehensive analysis of findings has practical significance and provides valuable information for a composite material from the production phase to the actual working conditions.

scholarly journals The mean velocity of posterior cerebral artery and basilar artery in Parkinson's disease with sleep disorders

2021 ◽  
Vol 4 ◽  
pp. 100207
Author(s):  
Muhammad Iqbal Basri ◽  
Ida Farida ◽  
Yudy Goysal ◽  
Jumraini Tammasse ◽  
Muhammad Akbar
Keyword(s):  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Sleep Disorders ◽  
Cerebral Artery ◽  
Basilar Artery ◽  
Posterior Cerebral Artery ◽  
Mean Velocity ◽  
The Mean

scholarly journals Influence of Beam Power on Young’s Modulus and Friction Coefficient of Ti–Ta Alloys Formed by Electron-Beam Surface Alloying

Metals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1246
Author(s):  
Stefan Valkov ◽  
Dimitar Dechev ◽  
Nikolay Ivanov ◽  
Ruslan Bezdushnyi ◽  
Maria Ormanova ◽  
...  
Keyword(s):  
Electron Beam ◽  
Young’S Modulus ◽  
Coefficient Of Friction ◽  
Young's Modulus ◽  
Beam Power ◽  
Surface Alloying ◽  
Surface Alloys ◽  
X Ray ◽  
The Coefficient Of Friction ◽  
Beam Surface

In this study, we present the results of Young’s modulus and coefficient of friction (COF) of Ti–Ta surface alloys formed by electron-beam surface alloying by a scanning electron beam. Ta films were deposited on the top of Ti substrates, and the specimens were then electron-beam surface alloyed, where the beam power was varied from 750 to 1750 W. The structure of the samples was characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD). Young’s modulus was studied by a nanoindentation test. The coefficient of friction was studied by a micromechanical wear experiment. It was found that at 750 W, the Ta film remained undissolved on the top of the Ti, and no alloyed zone was observed. By an increase in the beam power to 1250 and 1750 W, a distinguished alloyed zone is formed, where it is much thicker in the case of 1750 W. The structure of the obtained surface alloys is in the form of double-phase α’and β. In both surface alloys formed by a beam power of 1250 and 1750 W, respectively, Young’s modulus decreases about two times due to different reasons: in the case of alloying by 1250 W, the observed drop is attributed to the larger amount of the β phase, while at 1750 W is it due to the weaker binding forces between the atoms. The results obtained for the COF show that the formation of the Ti–Ta surface alloy on the top of Ti substrate leads to a decrease in the coefficient of friction, where the effect is more pronounced in the case of the formation of Ti–Ta surface alloys by a beam power of 1250 W.

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