Performance analysis of vertical axis water turbines under single-phase water and two-phase open channel flow conditions

2021 ◽  
Vol 238 ◽  
pp. 109769
Author(s):  
Kan Liu ◽  
Meilin Yu ◽  
Weidong Zhu
Keyword(s):  
Performance Analysis ◽  
Channel Flow ◽  
Single Phase ◽  
Open Channel ◽  
Open Channel Flow ◽  
Vertical Axis ◽  
Flow Conditions ◽  
Two Phase ◽  
Phase Water ◽  
Water Turbines

scholarly journals Free-surface flows with near-critical flow conditions

1996 ◽  
Vol 23 (6) ◽  
pp. 1272-1284 ◽  
Author(s):  
H. Chanson
Keyword(s):  
Free Surface ◽  
Channel Flow ◽  
Open Channel ◽  
Flow Instability ◽  
Open Channel Flow ◽  
Surface Characteristics ◽  
Free Surface Flows ◽  
Critical Flow ◽  
Flow Conditions ◽  
Weir Flow

Open channel flow situations with near-critical flow conditions are often characterized by the development of free-surface instabilities (i.e., undulations). The paper develops a review of several near-critical flow situations. Experimental results are compared with ideal-fluid flow calculations. The analysis is completed by a series of new experiments. The results indicate that, for Froude numbers slightly above unity, the free-surface characteristics are very similar. However, with increasing Froude numbers, distinctive flow patterns develop. Key words: open channel flow, critical flow conditions, free-surface undulations, flow instability, undular surge, undular broad-crested weir flow, culvert flow.

An experimental investigation of microplastic transport in fluvial systems

2020 ◽  
Author(s):  
Jan-Pascal Boos ◽  
Benjamin-Silas Gilfedder ◽  
Hassan Elagami ◽  
Sven Frei
Keyword(s):  
Porous Media ◽  
Channel Flow ◽  
Open Channel ◽  
Treatment Plant ◽  
Open Channel Flow ◽  
Agricultural Runoff ◽  
Hydrodynamic Flow ◽  
Waste Water Treatment Plant ◽  
Flow Conditions ◽  
Fluvial Systems

<p>Although a major part of marine microplastic (MP) pollution originates from rivers and streams, the mechanistic behavior of MP in fluvial systems is only poorly understood. MP enter fluvial systems from e.g. waste water treatment plant (WWTP) effluents, sewer overflows during heavy rain events, agricultural runoff, aerial input/atmospheric fallout, road runoff or via fragmentation of plastic litter. As part of this project we want to investigate the hydrodynamic transport mechanisms that control the behavior and re-distribution of MP in open channel flow and the streambed sediments. Hydrodynamic conditions in open channel flow are represented in an experimental flume environment.  Different porous media materials (e.g. aqua beads, glass beads and sand) are used in the flume experiments to shape typical bed form structures such as riffle-pool sequences, ripples and dunes. The aim of this experimental setup is to create hydrodynamic flow conditions such as hydraulic jumps, low and high flow velocity environments for which the transport and sedimentation behavior of MP can be investigated under realistic conditions. Hydrodynamic flow conditions in the flume are characterized using a Laser-Doppler-Anemometry (LDA) and Particle Image Velocimetry (PIV). Detection and tracking of fluorescent MP-particles in open channel flow and in porous media will be achieved with a fluorescence-camera-system.</p>

Turbulence Structure Modification and Drag Reduction by Microbubble Injections in a Boundary Layer Channel Flow

2008 ◽  
Vol 130 (11) ◽  
Author(s):  
C. C. Gutiérrez-Torres ◽  
Y. A. Hassan ◽  
J. A. Jimenez-Bernal
Keyword(s):  
Boundary Layer ◽  
Drag Reduction ◽  
Channel Flow ◽  
Single Phase ◽  
Pure Water ◽  
Channel Height ◽  
Turbulence Structure ◽  
Two Phase ◽  
Flow Measurements ◽  
Phase Water

Turbulent boundary layer modification in a channel flow using injection of microbubbles as a means to achieve drag reduction was studied. The physical mechanism of this phenomenon is not yet fully understood. To obtain some information related to this phenomenon, single-phase (pure water) flow and two-phase (water and microbubbles) channel flow measurements are taken. The void fraction conditions were varied while maintaining a Reynolds number of 5128 based on the half channel height. The study indicates that the presence of microbubbles within the boundary layer modifies the turbulence structure such that variations in time and space turbulent scales are observed, as well as ejection and sweep phenomena.

scholarly journals A Study on the Friction Factor and Reynolds Number Relationship for Flow in Smooth and Rough Channels

Water ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 1714
Author(s):  
Yeon-Moon Choo ◽  
Jong-Gu Kim ◽  
Sang-Ho Park
Keyword(s):  
Friction Coefficient ◽  
Channel Flow ◽  
Open Channel ◽  
Flow Characteristics ◽  
Open Channel Flow ◽  
Shear Velocity ◽  
Estimation Methods ◽  
Flow Conditions ◽  
Key Factors ◽  
Mean Velocity

The shear velocity and friction coefficient for representing the resistance of flow are key factors to determine the flow characteristics of the open-channel flow. Various studies have been conducted in the open-channel flow, but many controversies remain over the form of equation and estimation methods. This is because the equations developed based on theory have not fully interpreted the friction characteristics in an open-channel flow. In this paper, a friction coefficient equation is proposed by using the entropy concept. The proposed equation is determined under the rectangular, the trapezoid, the parabolic round-bottomed triangle, and the parabolic-bottomed triangle open-channel flow conditions. To evaluate the proposed equation, the estimated results are compared with measured data in both the smooth and rough flow conditions. The evaluation results showed that R (correlation coefficient) is found to be above 0.96 in most cases, and the discrepancy ratio analysis results are very close to zero. The advantage of the developed equation is that the energy slope terms are not included, because the determination of the exact value is the most difficult in the open-channel flow. The developed equation uses only the mean velocity and entropy M to estimate the friction loss coefficient, which can be used for maximizing the design efficiency.

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