The Estimation of Discharge in an Experimental Open Channel

2014 ◽  
Vol 905 ◽  
pp. 369-373
Author(s):  
Choo Tai Ho ◽  
Yoon Hyeon Cheol ◽  
Yun Gwan Seon ◽  
Noh Hyun Suk ◽  
Bae Chang Yeon
Keyword(s):  
Unsteady Flow ◽  
River Discharge ◽  
Open Channel ◽  
Flow Conditions ◽  
Mean Velocity ◽  
Velocity Equation ◽  
The Mean ◽  
Loop Form

The estimation of a river discharge by using a mean velocity equation is very convenient and rational. Nevertheless, a research on an equation calculating a mean velocity in a river was not entirely satisfactory after the development of Chezy and Mannings formulas which are uniform equations. In this paper, accordingly, the mean velocity in unsteady flow conditions which are shown loop form properties was estimated by using a new mean velocity formula derived from Chius 2-D velocity formula. The results showed that the proposed method was more accurate in estimating discharge, when compared with the conventional formulas.

Currentmeter Errors under Pulsating flow Conditions

1967 ◽  
Vol 9 (1) ◽  
pp. 45-54 ◽  
Author(s):  
P. Jepson
Keyword(s):  
Unsteady Flow ◽  
Theoretical Approach ◽  
Axial Flow ◽  
Pulsating Flow ◽  
Flow Conditions ◽  
Mean Velocity ◽  
Registration Errors ◽  
Flow Fluctuations ◽  
The Mean ◽  
Flow Pulsations

The paper deals with the effect of unsteady flow on the velocity registration of current-meters. In the first section of the paper, experiments are described which show that axial flow pulsations cause currentmeters to over-estimate and that flow fluctuations transverse to the mean velocity generally cause under-registration by amounts depending on the flow and meter parameters. From these tests general comments are made concerning the choice of metering station and to a lesser extent meter design. The second section is theoretical and deals with the effects of axially pulsating flows. It has been possible, using simple aerodynamic principles, to show how the meter design can be improved to minimize registration errors. The agreement between this theoretical approach and the registration errors obtained from experiment is fair.

scholarly journals Turbulent transport in the outer region of rough-wall open-channel flows: the contribution of large coherent shear stress structures (LC3S)

2007 ◽  
Vol 574 ◽  
pp. 465-493 ◽  
Author(s):  
D. HURTHER ◽  
U. LEMMIN ◽  
E. A. TERRAY
Keyword(s):  
Shear Stress ◽  
Open Channel ◽  
Outer Region ◽  
Threshold Level ◽  
Channel Flows ◽  
Intermediate Region ◽  
Flow Conditions ◽  
Open Channel Flows ◽  
The Mean ◽  
Bed Friction

Acoustic Doppler velocity profiler (ADVP) measurements of instantaneous three-dimensional velocity profiles over the entire turbulent boundary layer height, δ, of rough-bed open-channel flows at moderate Reynolds numbers show the presence of large scale coherent shear stress structures (called LC3S herein) in the zones of uniformly retarded streamwise momentum. LC3S events over streamwise distances of several boundary layer thicknesses dominate the mean shear dynamics. Polymodal histograms of short streamwise velocity samples confirm the subdivision of uniform streamwise momentum into three zones also observed by Adrian et al. (J. Fluid Mech., vol. 422, 2000, p. 1). The mean streamwise dimension of the zones varies between 1δ and 2.5δ. In the intermediate region (0.2<z/δ<0.75), the contribution of conditionally sampled u'w' events to the mean vertical turbulent kinetic energy (TKE) flux as a function of threshold level H is found to be generated by LC3S events above a critical threshold level Hmax for which the ascendant net momentum flux between LC3S of ejection and sweep types is maximal. The vertical profile of Hmax is nearly constant over the intermediate region, with a value of 5 independent of the flow conditions. Very good agreement is found for all flow conditions including the free-stream shear flows studied in Adrian et al. (2000). If normalized by the squared bed friction velocity, the ascendant net momentum flux containing 90% of the mean TKE flux is equal to 20% of the shear stress due to bed friction. In the intermediate region this value is nearly constant for all flow conditions investigated herein. It can be deduced that free-surface turbulence in open-channel flows originates from processes driven by LC3S, associated with the zonal organization of streamwise momentum. The good agreement with mean quadrant distribution results in the literature implies that LC3S identified in this study are common features in the outer region of shear flows.

Mean velocity and longitudinal dispersion of heavy particles in turbulent open-channel flow

1974 ◽  
Vol 65 (1) ◽  
pp. 11-28 ◽  
Author(s):  
B. Mutlu Sumer
Keyword(s):  
Open Channel ◽  
Dispersion Coefficient ◽  
Heavy Particle ◽  
Longitudinal Dispersion ◽  
Main Body ◽  
Longitudinal Dispersion Coefficient ◽  
Fall Velocity ◽  
Mean Velocity ◽  
Cross Sectional ◽  
The Mean

This paper deals with the motion of a heavy particle in a turbulent flow in an open channel with a smooth bottom. For the case when the particle stays in suspension in the main body of the flow almost all the time, (a) the probability density function of the projection on a cross-sectional plane of the particle position at any instant, and (b) the mean velocity and longitudinal dispersion coefficient of particles are determined analytically by employing the Eulerian formulation and applying the Aris moment transformations. It is found that the mean particle velocity decreases and the longitudinal dispersion coefficient of particles increases with the fall velocity.

Turbulence Characteristics in a Rough Open Channel Under Unsteady Flow Conditions

2021 ◽  
pp. 143-155
Author(s):  
Jnana Ranjan Khuntia ◽  
Kamalini Devi ◽  
Bhabani Shankar Das ◽  
Kishanjit Kumar Khatua
Keyword(s):  
Unsteady Flow ◽  
Open Channel ◽  
Flow Conditions ◽  
Turbulence Characteristics

PIV Study of Separated and Reattached Open Channel Flow Over Surface Mounted Blocks

2008 ◽  
Vol 130 (6) ◽  
Author(s):  
Martin Agelinchaab ◽  
Mark F. Tachie
Keyword(s):  
Boundary Layer ◽  
Shear Layer ◽  
Channel Flow ◽  
Open Channel ◽  
Open Channel Flow ◽  
Reynolds Stresses ◽  
Mean Flow ◽  
Mean Velocity ◽  
High Background ◽  
The Mean

A particle image velocimetry is used to study the mean and turbulent fields of separated and redeveloping flow over square, rectangular, and semicircular blocks fixed to the bottom wall of an open channel. The open channel flow is characterized by high background turbulence level, and the ratio of the upstream boundary layer thickness to block height is considerably higher than in prior experiments. The variation of the Reynolds stresses along the dividing streamlines is discussed within the context of vortex stretching, longitudinal strain rate, and wall damping. It appears that wall damping is a more dominant mechanism in the vicinity of reattachment. In the recirculation and reattachment regions, profiles of the mean velocity, turbulent quantities, and transport terms are used to document the salient features of block geometry on the flow. The flow characteristics in these regions strongly depend on block geometry. Downstream of reattachment, a new shear layer is formed, and the redevelopment of the shear layer toward the upstream open channel boundary layer is studied using the boundary layer parameters and Reynolds stresses. The results show that the mean flow rapidly redeveloped so that the Clauser parameter recovered to its upstream value at 90 step heights downstream of reattachment. However, the rate of development close to reattachment strongly depends on block geometry.

Improvement of Aerodynamic Performance of a Combustor Dump Diffuser Using Inclined Walls

2000 ◽  
Author(s):  
Shinji Honami ◽  
Eiichi Yamazaki ◽  
Takaaki Shizawa
Keyword(s):  
Pressure Loss ◽  
Total Pressure ◽  
Aerodynamic Performance ◽  
Total Pressure Loss ◽  
Flow Conditions ◽  
Mean Velocity ◽  
Cold Flow ◽  
Inlet Distortion ◽  
Flow Experiment ◽  
The Mean

The combustor diffuser with the deep flame dome in the recent engine results in the large total pressure loss. It is important to obtain both better aerodynamic performance by reduction of total pressure loss and reduced NOx in the exhaust from the combustor, regardless of the inlet flow conditions such as inlet distortion. Installation of an inclined wall within the combustor dump diffuser is suggested in order to improve the aerodynamic performance. A cold flow experiment using Pitot probe surveys in a model of a combustor diffuser shows that the inclined wall is effective in improvement of the total pressure loss, even if the velocity profile at the diffuser inlet is distorted. Furthermore, the flow rate distributions into the branched channels are also improved. The flow mechanism in the inclined wall configuration is clarified from the measurements of the mean velocity and turbulent Reynolds stress by a Laser Doppler Velocimetry (LDV) system.

Analytical model of the mean velocity distribution in an open channel with double-layered rigid vegetation

2014 ◽  
Vol 69 ◽  
pp. 106-113 ◽  
Author(s):  
Wenxin Huai ◽  
Weijie Wang ◽  
Yang Hu ◽  
Yuhong Zeng ◽  
Zhonghua Yang
Keyword(s):  
Velocity Distribution ◽  
Analytical Model ◽  
Open Channel ◽  
Mean Velocity ◽  
Rigid Vegetation ◽  
The Mean

Open channel flow recovery in the wake of a flat plate on rough beds

2011 ◽  
Vol 38 (6) ◽  
pp. 710-717
Author(s):  
F.N. Krampa ◽  
R. Balachandar
Keyword(s):  
Velocity Profile ◽  
Flat Plate ◽  
Open Channel ◽  
Outer Region ◽  
Wire Mesh ◽  
Mean Velocity ◽  
Upstream Condition ◽  
The Mean ◽  
Bed Roughness ◽  
Rough Beds

The flow recovery in the wake of a surface-mounted flat plate is investigated in an open channel. The plate with a thickness-to-chord ratio (t/c) of 0.12 is placed with the chord parallel to the flow. The characteristics of the mean velocity and higher-order statistics obtained along the wake axis upstream and downstream of the plate are discussed in the presence of bed roughness. Inner scaling of the mean velocity profile shows a depression in the outer region of the flow. The near-wall portion of the velocity profile in the plate wake region was found to recover faster to the upstream state. The profiles of the turbulent intensity in the plate wake deviate from the upstream profiles and recover gradually with downstream distance. The upstream turbulent intensities for the wire-mesh rough surface peak at farther wall normal locations compared to those of the sand grain and smooth surfaces. A similar roughness effect was observed at the downstream locations amidst the distorted flow, especially, in the intermediate and far wake regions. In the near- and intermediate-wake regions, both the velocity skewness and flatness factors data for the rough walls were higher compared to the data for the smooth surface. For all surfaces, even at the last measuring station (x = 200t) considered in the study, the skewness and flatness factors were found to be still recovering to the upstream condition.

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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