Application of Dressler Theory to Weir Flow

1993 ◽  
Vol 60 (1) ◽  
pp. 163-166 ◽  
Author(s):  
Amruthur S. Ramamurthy ◽  
Ngoc-Diep Vo
Keyword(s):  
Experimental Data ◽  
Discharge Coefficient ◽  
Shallow Depth ◽  
Lower Range ◽  
Previous Experimental Data ◽  
Flow Past ◽  
Weir Flow ◽  
Total Head

The curvilinear flow past a circular-crested weir is analyzed with the help of Dressier equations. Specifically, the lower range of the depth over the weir crest is considered in the analysis, so that the shallow depth model could be adopted. The weir discharge coefficient is determined as a function of the total head of the approach flow and the crest radius. The weir discharge coefficient obtained on the basis of Dressier theory is verified with the help of present and previous experimental data.

Influence of Flow Characteristics on the Discharge Coefficient of a Multiperforated Wall

2005 ◽  
Author(s):  
Jean-Louis Champion ◽  
Pasquale Di Martino ◽  
Xavier Coron
Keyword(s):  
Experimental Data ◽  
Reynolds Number ◽  
General Expression ◽  
Discharge Coefficient ◽  
Flow Characteristics ◽  
Coolant Flow ◽  
Asymptotic Value ◽  
Rate Of Increase ◽  
Classical Correlations

The aim of this study is to determine the discharge coefficient of a multiperforated wall sample designed by AVIO, and more precisely to show the influence of each surrounding flow (inside holes, coolant and main flows). Results obtained are compared to correlations from literature. As previously observed, it is found that the discharge coefficient is strongly dependent on the Reynolds number relative to the hole flow (Reh). The influence of the coolant flow has been proved. The comparison with classical correlations shows many differences: i) on the expected asymptotic value ii) on the rate of increase for the lowest values of Reh. This influence is not taken into account by classical correlations deduced from experiments carried out without crossflow. Based on our experiments, we determined a general expression of Cd. Experimental data are fitted with a function of type Cd = A(1−exp(−B.Reh)), where A and B are expressed as functions of the Reynolds number (Re2) of the coolant flow.

Discharge coefficients for ogee weirs including the effects of a sloping upstream face

2020 ◽  
Vol 20 (4) ◽  
pp. 1493-1508 ◽  
Author(s):  
Farzin Salmasi ◽  
John Abraham
Keyword(s):  
Gene Expression ◽  
Experimental Data ◽  
Regression Analysis ◽  
Discharge Coefficient ◽  
Gene Expression Programming ◽  
Linear Interpolation ◽  
Performance Criteria ◽  
Upstream Face ◽  
Discharge Coefficients ◽  
Regression Techniques

Abstract Discharge coefficients (C0) for ogee weirs are essential factors for predicting the discharge-head relationship. The present study investigates three influences on the C0: effect of approach depth, weir upstream face slope, and the actual head, which may differ from the design head. This study uses experimental data with multiple non-linear regression techniques and Gene Expression Programming (GEP) models that are applied to introduce practical equations that can be used for design. Results show that the GEP method is superior to the regression analysis for predicting the discharge coefficient. Performance criteria for GEP are R2 = 0.995, RMSE = 0.021 and MAE = 0.015. Design examples are presented that show that the proposed GEP equation correlates well with the data and eliminates linear interpolation using existing graphs.

Discharge Coefficient for Venturi Flowmeter With Short Laying Length

1982 ◽  
Vol 104 (4) ◽  
pp. 463-467
Author(s):  
Masahiro Inoue
Keyword(s):  
Experimental Data ◽  
Potential Flow ◽  
Total Pressure ◽  
Discharge Coefficient ◽  
Empirical Equation ◽  
Static Pressure ◽  
Computational Technique ◽  
One Dimensional ◽  
Streamline Curvature ◽  
Venturi Flowmeter

This paper presents a method for predicting the discharge coeffcient for a venturi flowmeter with a short laying length where the static pressure is not uniform at the throat due to streamline curvature. The discharge coefficient is determined by combining potential flow calculations and one-dimensional viscous flow considerations. For the potential flow, an accurate computational technique proposed by the author is used to calculate the pressure at the throat tap by assuming that the total pressure is equal to the average one at the throat. The average total pressure is related to the inlet pressure by use of a generalized empirical equation based on one-dimensional considerations. Validity of the method is verified by comparison with published experimental data for short venturi flowmeters.

scholarly journals Overtopping breaching of river levees constructed with cohesive sediments

2016 ◽  
Vol 16 (7) ◽  
pp. 1541-1551 ◽  
Author(s):  
Hongyan Wei ◽  
Minghui Yu ◽  
Dangwei Wang ◽  
Yitian Li
Keyword(s):  
Soil Properties ◽  
Discharge Coefficient ◽  
Flow Model ◽  
Impinging Jet ◽  
Cohesive Sediments ◽  
Flow Shear ◽  
Flow Rates ◽  
Side Slope ◽  
Weir Flow ◽  
Headcut Retreat

Abstract. Experiments were conducted in a bend flume to study the overtopping breaching process and the corresponding overflow rates of river levees constructed with cohesive sediments. The river and land regions were separated by the constructed levee in the bend flume. Results showed that the levee breaching process can be subdivided into a slope erosion stage, a headcut retreat stage and a breach widening stage. Mechanisms such as flow shear erosion, impinging jet erosion, side slope erosion and cantilever collapse were discovered in the breaching process. The erosion characteristics were determined by both flow and soil properties. Finally, a depth-averaged 2-D flow model was used to simulate the levee breaching flow rates, which is well expressed by the broad-crested weir flow formula. The deduced discharge coefficient was smaller than that of common broad-crested rectangular weirs because of the shape and roughness of the breach.

Cavitation Effect on the Discharge Coefficient of the Sharp-Edged Orifice Plate

1960 ◽  
Vol 82 (1) ◽  
pp. 1-6 ◽  
Author(s):  
F. Numachi ◽  
M. Yamabe ◽  
R. O¯ba
Keyword(s):  
Experimental Data ◽  
Discharge Coefficient ◽  
Cavitation Number ◽  
Orifice Plate ◽  
Cavitation Effect

The object of this paper is to investigate the effects of cavitation on the discharge coefficient of sharp-edged orifice plates with reference to various degrees of cavitation as defined by a cavitation number. The experimental data described in this paper substantiate the fact that cavitation can exist to a minimum cavitation number of 0.2 without introducing errors in the orifice discharge coefficient in excess of the normal expected accuracy. In addition to this, it was found that the use of air-inhalation to suppress the vibration and noise from the cavitation had no effect on the discharge coefficient.

Prediction of Aeroacoustic Resonance in Cavities of Hole-Pattern Stator Seals

2010 ◽  
Author(s):  
David N. Liliedahl ◽  
Forrest L. Carpenter ◽  
Paul G. A. Cizmas
Keyword(s):  
Experimental Data ◽  
Flow Instability ◽  
Numerical Results ◽  
Navier Stokes ◽  
Empirical Constant ◽  
Freestream Velocity ◽  
Flow Solver ◽  
Eddy Simulation ◽  
Flow Past ◽  
Acoustic Instabilities

A Reynolds-averaged Navier-Stokes (RANS) solver developed in-house was used to simulate grazing channel flow past single and multiple cavities. The objective of this investigation was to predict fluid instabilities in hole-pattern stator seals. The numerical results generated with the RANS solver showed good agreement with those obtained using a commercial Large Eddy Simulation (LES) code. In addition, the numerical results agreed well with experimental data. Rossiter’s formula, a popular semi-empirical model used to predict frequencies of hole-tone acoustic instabilities caused by grazing fluid flow past open cavities, was modified using the RANS solver results to allow for its application to channel flows. This was done by modifying the empirical constant κ, the ratio of vortex velocity and the freestream velocity. The dominant frequencies predicted using the Rossiter’s formula with the new κ value matched well the experimental data for hole-pattern stator seals. The RANS solver accurately captured the salient features of the flow/acoustic interaction and predicted well the dominant acoustic frequencies measured in an experimental investigation. The flow solver also provided detailed physical insight into the cavity flow instability mechanism.

Multishock Compactions of Powder Media Influenced by Elastic Waves in Punch and Plug

1991 ◽  
Vol 113 (4) ◽  
pp. 372-381
Author(s):  
Yukio Sano ◽  
Koji Tokushima ◽  
Kiyohiro Miyagi
Keyword(s):  
Experimental Data ◽  
Elastic Waves ◽  
Critical Length ◽  
Wall Friction ◽  
Initial Powder ◽  
Green Density ◽  
Previous Experimental Data ◽  
Powder Medium ◽  
Theoretical Predictions ◽  
The Mean

The previous theoretical predictions of the compaction of a copper powder medium, based on the assumption that the punch and plug were both a rigid body, did not satisfactorily agree with the experimental results obtained for short initial powder lengths and long plug lengths. This type of compaction amounts to cases when the plug length exceeds the second critical length which will be described below. Shock waves in a powder medium and elastic waves in the elastic punch and plug, schematically shown in space coordinate-time diagrams, suggest that the elastic wave in the plug is the probable cause of the inconsistency between the theoretical and experimental data of the previous investigation. In fact, the diagrams indicate that the shock wave transmitted in the medium across the medium-plug interface exerts an effect on the compaction process when the plug length does not exceed what is termed the first critical length. In cases when the effect of die wall friction is neglected, the mean green density-initial powder length relation of the copper medium is obtained from a theoretical approximation based on energy of the medium for the compaction with the sum of the initial powder length and the plug length being constant. This relation indicates that the effect of elasticity of the plug is large as the plug length becomes large. The second critical plug length at which the effect of elasticity becomes balanced with the effect of die wall friction is established by this relation and by the previously computed density-length relation with the effect of die wall friction taken into account. More specifically, these two relations provide a relation involving the first and second critical-plug lengths. The relation inferred as such agrees qualitatively with the previous experimental data in the examined region of the initial powder length. This qualitative agreement suggests that if the effects of elasticity and die wall friction are considered, a satisfactory theoretical and experimental agreement could be obtained. Therefore, the mean green density-initial powder length relation is computed taking into account both the effects. The computed relation agrees quantitatively with the previous experimental data even for short initial powder lengths and long plug lengths.

scholarly journals Simulation Analysis of Combined Flow over and under Semi-Cylindrical Structure

2019 ◽  
Vol 27 (2) ◽  
pp. 39-49
Author(s):  
Shaker Abdulatif Jalil
Keyword(s):  
Separation Zone ◽  
Simulation Analysis ◽  
Cylindrical Shape ◽  
Flow Profile ◽  
Combined Flow ◽  
Weir Flow ◽  
Total Head ◽  
Measured Flow ◽  
Discharge Simulation ◽  
Different Diameters

Combined flow over and under structure may solve the problem of the deposit of suspension materials in channels. Semi-cylindrical shape reduces the curvature of streamlines which reflected on its performance. To study how this shape performs, experimental and simulation has been done. The laboratory models were of four different diameters and four different gate openings. The same physical structures have been modeled in commercial software, FLOW-3D®, by employing RNG k- ε turbulence model. The verification has been based on measured flow profile and discharge. Simulation outputs indicate that a separation zone located at a distance from the structure became farther when the diameter and gate opening decreases, also the separation portions and their thickness are related to the incoming discharge.  The location height of separation zone tends to be lower when there is an increase in flow discharge and it is located at half the total depth when two flow portions are equal. The weir flow in this system shows a better performance than traditional weir by at least 33%, while the gate out flow is less than free flow of the same total head by 70% to 90%. Within the limitation of this work, two mathematical models for predicting discharge coefficient have been proposed for the weir and gate respectively, moreover a model for predicting relative discharge of weir to gate, and one mathematical model for the dimensionless total discharge.

scholarly journals Laminar flow past the bottom with obstacles – a suspension approximation

2015 ◽  
Vol 63 (3) ◽  
pp. 685-695
Author(s):  
R. Wojnar ◽  
W. Bielski
Keyword(s):  
Experimental Data ◽  
Spatial Distribution ◽  
Fluid Flow ◽  
Laminar Flow ◽  
Gravity Force ◽  
Fluid Viscosity ◽  
Suspension Concentration ◽  
Flow Past ◽  
Flow Through

Abstract From Albert Einstein’s study (1905) it is known that suspension introduced to a fluid modifies its viscosity. We propose to describe the influence of obstacles on the Stokesian flow as a such modification. Hence, we treat the fluid flow through small obstacles as a flow with suspension. The flow is developing past the plane bottom under the gravity force. The spatial distribution of suspension concentration is treated as given, and is regarded as an approximation of different obstacles which modify the fluid flow and change its viscosity. The different densities of suspension are considered, beginning of small suspension concentration until 40%. The influence of suspension concentration on fluid viscosity is analyzed, and Brinkman’s formula as fitting best to experimental data is applied.

scholarly journals A Study of Isothermal Flow Past a Confined Bluff Body

1990 ◽  
Author(s):  
M. K. Y. Lai ◽  
M. V. D’Souza ◽  
I. G. Campbell ◽  
G. J. Smallwood ◽  
D. R. Snelling
Keyword(s):  
Experimental Data ◽  
Bluff Body ◽  
Laser Sheet ◽  
Velocity Ratio ◽  
Co2 Concentration ◽  
Gas Analysis ◽  
Isothermal Flow ◽  
Numerical Predictions ◽  
Flow Past ◽  
Radial Profiles

The paper describes a preliminary assessment of a TEACH-based mathematical model, known as TURCOM, for isothermal flow past a confined bluff-body. The assessment is based on comparisons of numerical predictions with the experimental data. Laser Doppler Velocimetry (LDV) and gas analysis were used to measure radial profiles of axial velocity and CO2 concentration. Laser sheet illumination was employed to study the gross features of the flow. Depending on the jet velocity ratio, two or three recirculation zones and two well-defined stagnation points along the centerline were predicted. Agreement between the predictions and experimental data were reasonably good, but the axial location of the fuel stagnation point was under-estimated when compared with the LDV data. Flow visualization indicated vortex shedding off the edges of the bluff body, an unsteady flow phenomenon that neither TURCOM prediction nor LDV measurements could identify.

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