scholarly journals Overtopping breaching of river levees constructed with cohesive sediments

2016 ◽  
Author(s):  
H. Y. Wei ◽  
M. H. Yu ◽  
D. W. Wang ◽  
Y. T. Li
Keyword(s):  
Soil Properties ◽  
Discharge Coefficient ◽  
Flow Model ◽  
Cohesive Sediments ◽  
Flow Shear ◽  
Flow Rates ◽  
Side Slope ◽  
Weir Flow ◽  
Scour Hole ◽  
Headcut Retreat

Abstract. Experiments were conducted in a bend flume to study the overtopping breaching process and the corresponding overflow rate of river levees constructed with cohesive sediments. The river and land regions were separated by the constructed levee model 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. Mechanism such as scour-hole erosion, 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, the levee breaching flow rates were simulated by a depth averaged 2-D flow model. The calculated overflow rates can be 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.

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.

Pressure Drop, Air Entrainment and Moments of the Axial Velocity in the Laminar-Turbulent Transition Jet Flow in Domestic Gas Injectors

2021 ◽  
Author(s):  
William Alexander Carrillo Ibañez ◽  
Márcio Demétrio ◽  
Amir Oliveira ◽  
Fernando Pereira
Keyword(s):  
Reynolds Number ◽  
Pressure Drop ◽  
Axial Velocity ◽  
Energy Flow ◽  
Discharge Coefficient ◽  
Mixing Layer ◽  
Air Entrainment ◽  
Flow Rates ◽  
Free Jet ◽  
Internal Mixing

Abstract This works aims at characterizing the flow in the outlet of three gas injectors used in atmospheric burners and developing correlations for the discharge coefficient, air entrainment, momentum and energy flow rates. These devices have millimeter sized orifices, a cup-like region at the injector outlet and the flow occurs in the transition from the laminar to the fully turbulent regimes. The pressure drop was measured and correlated as a function of the orifice Reynolds number for the three injectors. The correlations are able to predict the discharge coefficient within ± 5% deviation from the measurements in the range 90 < Re < 4400. The axial velocity and turbulent intensity were measured at the outlet of the injectors using a hot-wire anemometer at the orifice Reynolds number of 3060, which is typical of the applications. The measurements were compared to CFD solutions using the gamma - Re-theta RANS transition model in the STAR-CCM+ commercial package. The results indicate the strong influence of the shape of the outlet cup-like region of the injectors in the development of an internal mixing layer and the external mixing layer in the free jet. The momentum and energy flow rates for the injector model with the largest cup are reduced to 50% and 21%, respectively, of the simplest gas injector. However, the gas jet in this injector carries 28% of the stoichiometric air before leaving the cup. These aspects must be taken into account in the preliminary design of atmospheric burners.

A Shock-Tube Technique to Determine Steady-Flow Losses of Orifices and Other Duct Elements

1960 ◽  
Vol 82 (1) ◽  
pp. 195-200 ◽  
Author(s):  
George Rudinger
Keyword(s):  
Shock Tube ◽  
Steady Flow ◽  
Discharge Coefficient ◽  
Initial Conditions ◽  
Test Element ◽  
Pressure Measurements ◽  
Flow Data ◽  
Flow Rates ◽  
Flow Losses ◽  
Good Agreement

It is shown that a simple shock tube is capable of producing appreciable steady-flow rates through a short duct element, such as an orifice, a valve, or a screen. The flow upstream and downstream of the test element and, therefore, also the losses caused by the test element, can be calculated from known initial conditions in the shock tube and pressure measurements at one point upstream of the element. Experiments to determine the discharge coefficient of a sharp-edged orifice are described as an illustration of the method. The results are in good agreement with available steady-flow data.

Demonstration of Fluidic Throat Skewing for Thrust Vectoring in Structurally Fixed Nozzles

2001 ◽  
Vol 123 (3) ◽  
pp. 502-507 ◽  
Author(s):  
P. J. Yagle ◽  
D. N. Miller ◽  
K. B. Ginn ◽  
J. W. Hamstra
Keyword(s):  
Conceptual Development ◽  
Discharge Coefficient ◽  
Companion Paper ◽  
Nozzle Throat ◽  
Thrust Coefficient ◽  
Thrust Vectoring ◽  
Flow Rates ◽  
Critical Design ◽  
Design Variables ◽  
Nozzle Pressure

The experimental demonstration of a fluidic, multiaxis thrust vectoring (MATV) scheme is presented for a structurally fixed, afterburning nozzle referred to as the conformal fluidic nozzle (CFN). This concept for jet flow control features symmetric injection around the nozzle throat to provide throttling for jet area control, and asymmetric injection to subsonically skew the sonic plane for jet vectoring. The conceptual development of the CFN was presented in a companion paper (Miller et al. [1]). In that study, critical design variables were shown to be the flap length and expansion area ratio of the nozzle, and the location, angle, and distribution of injected flow. Measures of merit were vectoring capability, gross thrust coefficient, and discharge coefficient. A demonstration of MATV was conducted on a 20 percent scale CFN test article across a range of nozzle pressure ratios (NPR), injector flow rates, and flow distributions. Both yaw and pitch vector angles of greater than 8 deg were obtained at NPR of 5.5. Yaw vector angles greater than 10 deg were achieved at lower NPR. Values of thrust coefficient for the CFN generally exceeded published measurements of shock-based vectoring methods. In terms of vectoring effectiveness (ratio of vector angle to percent injected flow), fluidic throat skewing was found to be comparable to shock-based vectoring methods.

An Investigation Into the Performance of Two ISA Metering Nozzles of Finite and Zero Area Ratio

1965 ◽  
Vol 87 (2) ◽  
pp. 525-529 ◽  
Author(s):  
S. Soundranayagam
Keyword(s):  
Reynolds Number ◽  
Potential Flow ◽  
Discharge Coefficient ◽  
Flow Model ◽  
Reynolds Numbers ◽  
Area Ratio ◽  
Flow Through

The flow through two ISA nozzles of area ratio zero and 0.4 was investigated to determine the nature of the flow and its variation with Reynolds number. Separation occurs within the nozzle of zero area ratio, the size of the bubble increasing with decreasing Reynolds number. The predicted discharge coefficient based on a simplified flow model agrees with experiment for large Reynolds numbers. Upstream influences affect the performance of the nozzle of area ratio 0.4. The flows through the two nozzles are not comparable, and potential-flow results cannot be used to explain flow in venturis and nozzles in pipes. The discharge-coefficient curve for area ratio 0.4 shows a distinct hump when based on the head differential measured as for venturis, but no hump when based on the head differential across the corner taps.

Calibration of a Small Venturimeter for Wet Steam at Low Reynolds Number

1969 ◽  
Vol 184 (3) ◽  
pp. 151-153
Author(s):  
M. D. Bennett ◽  
K. Martin
Keyword(s):  
Reynolds Number ◽  
Discharge Coefficient ◽  
Thrust Bearing ◽  
Area Ratio ◽  
Low Flow ◽  
Wet Steam ◽  
Steam Quality ◽  
Design Data ◽  
Flow Rates ◽  
Machined Parts

A device was required to measure the flow rate of steam through a small thrust bearing over the range 0–1·5 kg/h at pressures varying from 4·5 to 10 bar abs. and for steam quality varying from 0·75 dry to 100°C superheat. The ranges appeared to be outside those of existing instruments and not covered by existing design data for differential pressure devices; nor could the authors find any published work on the metering of wet steam at these low flow rates. Accordingly a 12·7-mm diameter venturimeter having an area ratio of 0·25 was made from stainless steel and has been calibrated for wet steam using a compounded differential U-tube manometer. The manometer and associated equipment is extremely simple and cheap to construct, and consists entirely of easily machined parts and standard pipe fittings. The results indicate that the discharge coefficient is very low and approximately a linear function of Reynolds number over the range tested.

scholarly journals Water flow model for the Harrier Basin, Kurdistan of Iraq

2013 ◽  
Vol 32 (2) ◽  
Author(s):  
Azad J. Sharif ◽  
Ziyad R. Elias ◽  
Mohummed F. Omar
Keyword(s):  
Land Use ◽  
Water Flow ◽  
Loss Rate ◽  
Flow Model ◽  
Forest Land ◽  
Flow Rates ◽  
Factors Affecting ◽  
Number Of Factors ◽  
Hydrologic Module ◽  
Simulated Flow

AbstractSharif A.J., Elias Z.R., Omar M.F.: Water flow model for the Harrier basin, Kurdistan of Iraq. Ekologia (Bratislava), Vol. 32, No. 2, p. 242-247, 2013.The study includes computer topographic and morphologic simulation of water flow produced using a watershed modelling system that uses hydrologic and physical data from the study area. The DEM module, TIN module, Map module and Hydrologic module were used in this study. A land use data, a soil data and rainfall data were used to produce a curve that illustrates quantity of water flow versus time of water flow across the Harrier basin. The calculated water loss rate can be attributed to a number of factors such as joints, faults, bedding and land use (agriculture and forest). Land use and soil characteristics are both important factors affecting water flow rates. The climate in the Harrier basin is semi-arid. Simulated flow data indicate that the top flow rate is 32 m3/s and that water can reach to the basin outlet in 3 hours and 10 minutes.

scholarly journals A revised Tesla Turbine concept for 2-phase applications

2021 ◽  
Vol 238 ◽  
pp. 10006
Author(s):  
L. Talluri ◽  
P. Niknam ◽  
A. Copeta ◽  
M. Amato ◽  
P. Iora ◽  
...  
Keyword(s):  
Shear Stress ◽  
Flow Model ◽  
Preliminary Design ◽  
Labyrinth Seals ◽  
Two Phase ◽  
Flow Rates ◽  
Real Fluid ◽  
New Concepts ◽  
Torque Transmission ◽  
Original Concept

The Tesla turbine is an original expander working on the principle of torque transmission by wall shear stress. The principle – demonstrated for air expanders at lab scale has some attractive features when applied to two-phase expanders: it is suitable for handling limited flow rates (as is the case for machines in the range from 500W to 5 kW), it can be developed to a reasonable size (rotor of 0.1 to 0.25 m diameters), with acceptable rotational speeds (which range from 500 to 10000 rpm). The original concept was revisited, designing it for two-phase operation and considering not only the rotor configuration but the whole machine. The flow model was developed using complete real fluid assumptions including several new concepts such as bladed channels for the stator, labyrinth seals, and a rotating diffuser. Preliminary design sketches are presented, and results discussed and evaluated.

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