scholarly journals Experimental analysis of the effect of bed-load movement on flow hydraulic characteristics

2021 ◽  
Author(s):  
Reza Estakhr ◽  
Ali Mahdavi Mazdeh ◽  
Mohammad Hossein Omid
Keyword(s):  
Friction Factor ◽  
Flow Resistance ◽  
Flow Characteristics ◽  
Shear Velocity ◽  
Bed Load ◽  
Mean Flow ◽  
Flow Friction ◽  
Rough Bed ◽  
Load Movement ◽  
Rough Beds

Abstract In this study, the effect of bed-load movement on mean flow characteristics was evaluated in two rigid rectangular flumes. The experiments consisted of creating flow conditions carrying sediments with mean diameters of D50 = 0.5, 0.6, and 2.84 mm over both smooth and rough beds. Various sediment concentrations were injected at the upstream end of the flume at non-deposit injection rates to study the effect of various concentrations on flow resistance. The effect of sediment movement on flow resistance was examined by comparing the results with those of clear water flows (without sediment injection on both smooth and rough beds). The results showed that the sediment transport in maximum injection rate may increase the friction factor up to 50 and 58 percent for smooth bed, and up to about 75 and 80 percent in rough bed with mean diameter of 0.5 and 0.6 mm. Besides, for D50 = 2.84 mm, the friction factor decreased in smooth bed and increased up to 50 percent in rough bed. In general, it can be concluded that bed-load transport can be increased by the flow friction factor. The results also showed that bed-loads may decrease the average velocity and increase shear velocity with extraction of momentum from the flow, which both of mentioned factors may increase the flow friction factor. Raising the bed-load concentration in the flow may increase the elevation of the friction factor, approaching a constant value after reaching to the aggregation threshold and generation of bed forms.

Effect of Bed-Load Movement on Flow Friction Factor

1998 ◽  
Vol 124 (2) ◽  
pp. 165-175 ◽  
Author(s):  
T. Song ◽  
Y. M. Chiew ◽  
C. O. Chin
Keyword(s):  
Friction Factor ◽  
Bed Load ◽  
Flow Friction ◽  
Load Movement

Effects of Bed Load Movement on Mean Flow Characteristics in Mobile Gravel Beds

2011 ◽  
Vol 25 (11) ◽  
pp. 2781-2795 ◽  
Author(s):  
Xianye Wang ◽  
Qingyuan Yang ◽  
Weizhen Lu ◽  
Xiekang Wang
Keyword(s):  
Flow Characteristics ◽  
Bed Load ◽  
Mean Flow ◽  
Gravel Beds ◽  
Load Movement

Flow Resistance Characteristics of a Specific Fuel RP-3 in Helical Tubes at Supercritical Pressure With Uniform Heat Flux

2017 ◽  
Author(s):  
Nan Zhang ◽  
Yanchen Fu ◽  
Haoran Huang ◽  
Jie Wen ◽  
Nigeer Te
Keyword(s):  
Heat Flux ◽  
Friction Factor ◽  
Mass Flux ◽  
Flow Resistance ◽  
Flow Characteristics ◽  
Supercritical Pressure ◽  
Uniform Heat Flux ◽  
Inlet Temperature ◽  
Uniform Heat ◽  
Helical Tubes

The flow resistance characteristics of aviation kerosene RP-3 in horizontal helical tubes at the supercritical pressure under heating condition are investigated. Both pressure drop and friction factor were examined under uniform heat flux of 50kW/m2−300kW/m2, mass flux from 786kg/m2s to 1375kg/m2s, and helical diameter from 20mm to 40mm. The influence of viscous factors on the resistance is analyzed to explore flow characteristics in a helical tube and provide a reference for the design of heat exchangers. Friction factor decreases with the increase of heat flux at low inlet temperatures 323K and 423K. It is explained that the viscosity changes more dramatically than the density. When the fluid inlet temperature is 523K and the fluid mean temperature Tb is close to pseudo-critical temperature, frictional flow resistance becomes significantly larger Tpc due to huge variations in thermal properties in the radical direction. The effect of centrifugal force makes the friction factor decline slowly. The friction factor goes up with the enlargement of mass flux when Tb>0.81Tpc. This phenomenon is caused by the larger radial velocity gradient under the large mass flux. Different helical diameters play the leading roles for the bending flow in the tubes.

scholarly journals Experimental Study of Flow Characteristics in A Rectangular Gravel Bed Channel

2021 ◽  
Vol 873 (1) ◽  
pp. 012047
Author(s):  
Robby Yussac Tallar ◽  
Dea Teodora Ferninda ◽  
Efferiki ◽  
Prabu Mandvi Hafiz Anjar Suhendar ◽  
Frankie Pandapotan Purba
Keyword(s):  
Experimental Study ◽  
Flow Velocity ◽  
Friction Factor ◽  
Flow Resistance ◽  
Open Channel ◽  
Rectangular Channel ◽  
Flow Characteristics ◽  
Flume Experiments ◽  
Sediment Bed ◽  
Set Up

Abstract In an open channel flow, the characteristics of flow resistance are greatly affected by the roughness of the base and the walls of the channel. The existence of an object or other material, including gravel, also influenced the resistance of flow, therefore the purpose of this study is to examine the flow characteristics (flow velocity and flow resistance) in gravel open channel by using experimental study. A laboratory study to explore the effect of channel bed in terms of roughness of types of sediment on the hydraulics flow in 8 m length x 40 cm width a rectangular channel is presented. The study consists of an extensive set of rectangular flume experiments for flows with certain slope and sediment bed. The study was using the Before After Control Impact (BACI) method by set up five different scenarios. The results show that the lowest flow velocity (v=0.3041 m/sec) was occurred in the scenario 3 (50%sand and 50% gravel). Based on the Manning’ coefficient (n), it was also found that at the 100% discharge flow condition, the highest value of friction factor (f=0.0780) within 5 scenarios was scenario 3 with the sediment consisted of 50%sand and 50%gravel. Whereas the value of the lowest friction factor(f=0.0652) was scenario 1 with the sediment only gravel within. It concluded that the results gave the lower value of Manning’ coefficient (n) compared to the table of Manning’s coefficient (f= 0.04) for the channel with gravel base condition.

scholarly journals Rill flow resistance law under sediment transport

2021 ◽  
Author(s):  
Costanza Di Stefano ◽  
Alessio Nicosia ◽  
Vincenzo Palmeri ◽  
Vincenzo Pampalone ◽  
Vito Ferro
Keyword(s):  
Sediment Transport ◽  
Flow Velocity ◽  
Friction Factor ◽  
Flow Resistance ◽  
Fixed Bed ◽  
Accurate Estimate ◽  
Mean Flow ◽  
Mobile Bed ◽  
Resistance Equation ◽  
Rill Flow

Abstract Purpose In this paper, a deduced flow resistance equation for open-channel flow was tested using measurements carried out in mobile bed rills with sediment-laden flows and fixed bed rills. The main aims were to (i) assess the effect of sediment transport on rill flow resistance, and (ii) test the slope-flow velocity relationship in fixed bed rills. Methods The following analysis was developed: (i) a relationship between the Γ function of the velocity profile, the rill slope and the Froude number was calibrated using measurements carried out on fixed bed rills; (ii) the component of Darcy-Weisbach friction factor due to sediment transport was deduced using the corresponding measurements carried out on mobile bed rills (grain resistance and sediment transport) and the values estimated by flow resistance equation (grain resistance) for fixed bed rills in the same slope and hydraulic conditions; (iii) the Γ function relationship was calibrated using measurements carried out on mobile bed rills and the data of Jiang et al. (2018). Results This analysis demonstrated that the effect of sediment transport on rill flow resistance law is appreciable only for 7.7% of the examined cases and that the theoretical approach allows for an accurate estimate of the Darcy-Weisbach friction factor. Furthermore, for both fixed and mobile beds, the mean flow velocity was independent of channel slope, as suggested by Govers (1992) for mobile bed rills. Conclusions The investigation highlighted that the effect of sediment transport on rill flow resistance is almost negligible for most of the cases and that the experimental procedure for fixing rills caused the unexpected slope independence of flow velocity.

scholarly journals Effects of bed-load movement on flow resistance over bed forms

Sadhana ◽  
2010 ◽  
Vol 35 (6) ◽  
pp. 681-691 ◽  
Author(s):  
Mohammad Hossein Omid ◽  
Masoud Karbasi ◽  
Javad Farhoudi
Keyword(s):  
Flow Resistance ◽  
Bed Load ◽  
Bed Forms ◽  
Load Movement

Broadband liner impedance eduction for multimodal acoustic propagation in the presence of a mean flow

2016 ◽  
Vol 11 (2) ◽  
pp. 150-155
Author(s):  
R. Troian ◽  
D. Dragna ◽  
C. Bailly ◽  
M.-A. Galland
Keyword(s):  
Numerical Model ◽  
Flow Characteristics ◽  
Acoustic Propagation ◽  
Rational Fraction ◽  
Physical Parameters ◽  
Mean Flow ◽  
Linearized Euler Equations ◽  
Grazing Flow ◽  
Propagation Medium ◽  
Difference Time

Modeling of acoustic propagation in a duct with absorbing treatment is considered. The surface impedance of the treatment is sought in the form of a rational fraction. The numerical model is based on a resolution of the linearized Euler equations by finite difference time domain for the calculation of the acoustic propagation under a grazing flow. Sensitivity analysis of the considered numerical model is performed. The uncertainty of the physical parameters is taken into account to determine the most influential input parameters. The robustness of the solution vis-a-vis changes of the flow characteristics and the propagation medium is studied.

scholarly journals Experimental study on the mean flow characteristics of a supersonic multiple jet configuration

2021 ◽  
Vol 108 ◽  
pp. 106377
Author(s):  
Mohammed Faheem ◽  
Aqib Khan ◽  
Rakesh Kumar ◽  
Sher Afghan Khan ◽  
Waqar Asrar ◽  
...  
Keyword(s):  
Experimental Study ◽  
Flow Characteristics ◽  
Mean Flow ◽  
The Mean

scholarly journals Numerical Study of Heat Transfer Intensification in a Circular Tube Using a Thin, Radiation-Absorbing Insert. Part 1: Thermo-Hydraulic Characteristics

Energies ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4596
Author(s):  
Piotr Bogusław Jasiński
Keyword(s):  
Heat Transfer ◽  
Flow Resistance ◽  
Numerical Study ◽  
Flow Characteristics ◽  
Cylindrical Tube ◽  
Radiation Absorption ◽  
Fluid Temperature ◽  
Gas Temperature ◽  
Insert Size ◽  
Channel Diameter

The presented paper, which is the first of two parts, shows the results of numerical investigations of a heat exchanger channel in the form of a cylindrical tube with a thin insert. The insert, placed concentrically in the pipe, uses the phenomenon of thermal radiation absorption to intensify the heat transfer between the pipe wall and the gas. Eight geometric configurations of the insert size were numerically investigated using CFD software, varying its diameter from 20% to 90% of the pipe diameter and obtaining the thermal-flow characteristics for each case. The tests were conducted for a range of numbers Re = 5000–100,000 and a constant temperature difference between the channel wall and the average gas temperature of ∆T = 100 °C. The results show that the highest increase in the Nu number was observed for the inserts with diameters of 0.3 and 0.4 of the channel diameter, while the highest flow resistance was noted for the inserts with diameters of 0.6–0.7 of the channel diameter. The f/fs(Re) and Nu/Nus(Re) ratios are shown on graphs indicating how much the flow resistance and heat transfer increased compared to the pipe without an insert. Two methods of calculating the Nu number are also presented and analysed. In the first one, the average fluid temperature of the entire pipe volume was used to calculate the Nu number, and in the second, only the average fluid temperature of the annular portion formed by the insert was used. The second one gives much larger Nu/Nus ratio values, reaching up to 8–9 for small Re numbers.

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