Hydraulic Parameters Of Flow Research Articles

Reaeration Coefficient Estimate: New Parameter for Predictive Equations

The reaeration coefficient (K a) is an essential parameter to predict the dissolved-oxygen concentration in different aquatic ecosystems. The techniques applied to K a estimates require considerable efforts, since measuring this coefficient is a laborious and expensive task. Thus, the use of predictive equations wherein K a is found through hydraulic flow parameters is common. However, the available prediction equations lead to estimates often different from each other. A new predictive equation is addressed in the present study. The insertion of a dimensionless number resulting from the relation between the RMS (Root Mean Square) of the free-surface vertical velocity and the surface flow velocity is the great innovation of the study. The reaeration experiments and the surface vertical velocity mapping were performed in a circular hydraulic channel. The flow velocity varied from 0.25 to 0.64 m s−1, and depth varied from 0.09 to 0.15 m. The new equation led to more accurate results than the equations based on traditional hydraulic parameters such as the Reynolds and Froude numbers, mainly when it comes to K a values higher than 40 day−1. The sensitivity analysis has shown that the new dimensionless number is the most sensitive parameter of the herein proposed predictive equation and that the influence from the Reynolds and Froude numbers on K a weakens as turbulence gets more intense.

Response of soil detachment rate to the hydraulic parameters of concentrated flow on steep loessial slopes on the Loess Plateau of China

AbstractUsing hydraulic parameters is essential for describing soil detachment and developing physically based erosion prediction models. Many hydraulic parameters have been used, but the one that performs the best for describing soil detachment on steep slopes when the lateral expansion (widening) of rills is not limited has not been identified. An indoor concentrated flow scouring experiment was performed on steep loessial slopes to investigate soil detachment rates for different flow rates and slope gradients. The experiments were conducted on a slope‐adjustable plot (5 m length, 1 m width, 0.5 m depth). Sixteen combinations of 4 flow rates (10, 15, 20, and 25 L/min) and 4 slope gradients (17.6%, 26.8%, 36.4%, and 46.6%) were investigated. The individual and combined effects of slope gradient and flow hydraulic parameters on soil detachment rate were analysed. The results indicated that soil detachment rate increased with flow rate and slope gradient. Soil detachment rate varied linearly and exponentially with flow rate and slope gradient, respectively. Multivariate, nonlinear regression analysis indicated that flow depth exerted the greatest influence on the soil detachment rate, followed by unit discharge per unit width, slope gradient, and flow rate in this study. Shear stress and stream power could efficiently describe the soil detachment rate using a power equation. However, the unit stream power and unit energy of the water‐carrying section changed linearly with soil detachment rate. Stream power was an optimal hydraulic parameter for describing soil detachment. These findings improve our understanding of concentrated flow erosion on steep loessial slopes.

Pengaruh Sudut dan Jari-Jari Saluran Menikung terhadap Konsentrasi Aliran Sedimen Suspensi arah Transversal

The change in channel dimension has a great effect on the flow hydraulic parameters. Likewise, the angle and radius of the bend are not the same will also affect the concentration of suspended sediment flow. To determine the effect of angle and radius of the bend, the measurement of susupended sediment concentration was done at 4 (four) location in Mataram irrigation channel curve. The four locations describe 2 channels having relatively the same angle but having different radius, and 2 (two) channels having the same relative radius but having different angles. Measurement of suspended sediment concentration in tranversal direction is done some depth point used by opcon probe. The results of the research for different angle of bend shows that from the interance to the end of the channel bend so the trend of suspended sediment concentration value are decreases. After the end of the channel bend started there is no more the angle influenced, the trend value of suspended sediment concentration are constant. As for the different radius, the value of suspended sediment concentration is still relatively the same and there is no change significantly. This shows that the relation or influence between the length of the radius of the bend with the value of the suspended sediment concentration is not visible

Hydraulic parameters of flow bilaterally constrained by transverse floodplain dams in the region of its spreading

Hydraulic parameters of flow bilaterally constrained by transverse floodplain dams in the region of its spreading

MATHEMATICAL MODELLING OF MASS EXCHANGE PROCESSES BETWEEN FLOW AND ALLUVIAL SEDIMENTS

Objectives. The aim is to improve the mathematical model of the motion of channelfill deposits in terms of clarifying one of the main relationships on which the sediment flow rate depends: the frequency of pulsations of the vertical fluid velocity component with hydraulic flow parameters. Methods. The mathematical model is developed using probability theory and the theory of runs of random processes, taking into account the normal distribution of the horizontal and vertical components of the instantaneous flow velocities and the Rayleigh law of the distribution of their maxima. Results. As a result of the modelling, information was obtained concerning the volumes and areas of the zones of influence of increased turbidity on the aquatic bioresources of the Gizeldon River. The operation of the Gizeldon hydroelectric power station have led to the loss of zoobenthos habitats, the destruction of bottom biocenoses, the loss of food organisms of plankton and benthos, a decrease in the fodder base of fish and the direct death of the ichthyofauna. An assessment of the damage caused to aquatic bioresources from the operation of the Gizeldon hydroelectric power station was carried out. As a result, it was proved that the negative influence of the "turbidity loop" in the lower tail of the river, taking into account the critical values of suspended matter concentration in water will be traced for 3.7 km. The amount of damage to aquatic bioresources in physical terms is about 1.5 tons due to the destruction of the fodder base of fish and the deterioration of habitat conditions in the zone of increased turbidity. Conclusion. The results of mathematical modelling were tested on field data materials and used to calculate the turbidity of the Gizeldon River flow during the reconstruction of the Gizeldon hydroelectric power station. The results of the approbation of the mathematical model of the motion of channel-fill sediment are presented in order to identify the areas of increased turbidity during the assessment of the damage to the water resources of the Gizeldon River.

Mathematical Investigation of the Cavitation Phenomenon in the Nozzle with Partially Surface Wetting

Abstract Partially surface wetting has a great influence on friction losses in the fluid flow in both the pipeline system and the complex shape of hydraulic elements. In many hydraulic elements (valves, pump impellers), cavitation is generated, which significantly changes the hydraulic flow parameters, so the last part of the article is devoted to the mathematical solution of this phenomena and evaluates the impact of wall wetting on the size and shape of the cavitation area which appears in the nozzle and in small gaps at special conditions. If the cavitation appears e. g. near the wall of pipes, the blades of turbine or a pump, then it destroys the material surface. On the basis of this physical experiment (nozzle), a two-dimensional (2D) mathematical cavitation model of Schnerr-Sauer was made and calculated shape and size of the cavitation region was compared with the experiment. Later this verified model of cavitation was used for cavitation research flow with partial surface wetting. The pressure drop and the size of the cavitation area as it flows from partially surface wetting theory was tested depending on the adhesion coefficient.

Changes of the hydrodynamic conditions in the braided river

The paper focuses on the understanding of the basic hydrodynamic conditions along the braided gravel-bed river. The measuring cross-section was located in the Ochotnica River, where its braided channel development was observed. Investigations take place from 2003 up to 2014. Measurements were performed for selected characteristic points. The study focused mostly on the measurements of water velocities under different flow conditions, and next on finding basic hydraulic parameters of flow: shear velocity, shear stresses, Reynolds number, Froude number. In addition, the gravel material from the river bed was examined, in order to find sedimentological characteristics of it.

Hydraulics of subaqueous ash flows as deduced from their deposits: 2. Water entrainment, sedimentation, and deposition, with implications on pyroclastic density current deposit emplacement

Turbidity currents are the most common flows of water, and suspended and bed load sediment occurring in the relatively deep sea and lakes, and act as large systems of sediment distribution. Due to the turbid nature of the flow, they may impact subaqueous infrastructures, as well as ecosystems, during motion, so quantifying the turbidity degree is important to predict the current impact. A particular type of these currents is the so-called volcaniclastic turbidity currents or subaqueous ash flows, which are mostly composed of fine-grained volcanic particles, and are used here as synonymous (sensu hydraulic) with the meaning of secondary current.In this paper, a method to estimate the water entrainment (column condition model), as well as the sedimentation and deposition rates (conveyer model), in volcaniclastic turbidity currents is proposed, by starting from the physical features of the deposits or inverse procedure. Some criteria of sediment mechanics are used to approximate the flow hydraulic parameters needed to quantify the water entrainment, as well as the shear velocity in volcaniclastic turbidity currents.The deposits used as case study are the impressive, meters thick, well-sorted rhyolitic ash turbidites of Late Pliocene cropping out in Southern Italy, particularly in the Craco area, Matera. The water entrainment coefficient of the currents is calculated in a range of particle concentration and slope angle, whereas the slope angle giving the sedimentation rate is calculated in a range of flow shear velocity, which in turns gives the deposition rate.The results have a general validity for depositional turbidity currents laden with well-sorted sediment, and they show that the water entrainment is low for relatively dense, slow-moving, subcritical flows, but it increases as the Richardson number decreases for relatively dilute, fast, supercritical flows. Moreover, the sedimentation and deposition rates are high for relatively intense flows moving over gentle slopes, but they decrease for relatively weak flows moving over steep slopes. The deposit sedimentary structures thus infer sedimentation, and particularly depositional processes.Finally, the conveyer model is extended conceptually to pyroclastic density currents, when approximating, but not exclusively, the column condition model in the flow above the flow boundary zone.

Numerical investigation of the effects of combining sewer junction characteristics on the hydraulic parameters of flow in fully surcharged condition

AbstractIn this study, the effects of different parameters on flow structure and flow hydraulics for combining sewer junction consisting of manhole and lateral inflow were investigated numerically. For this purpose, the effects of dimension variations, main and lateral pipe slope, angle and the joint position of lateral pipe beside manhole, manhole geometry, and the outflow rate of manhole on flow structure and energy loss coefficients were investigated. Results show that the rate of energy loss decreases by heightening the installation position of lateral pipe beside manhole. In addition, it was shown that the slope variations of main and lateral pipes and outflow rate do not affect the rate of energy loss.

Characteristics of concentrated flow hydraulics for rangeland ecosystems: implications for hydrologic modeling

ABSTRACTConcentrated flow is often the dominant source of water erosion following disturbance on rangelands. Because of the lack of studies that explain the hydraulics of concentrated flow on rangelands, cropland‐based equations have typically been used for rangeland hydrology and erosion modeling, leading to less accurate predictions due to different soil and vegetation cover characteristics. This study investigates the hydraulics of concentrated flow using unconfined field experimental data over diverse rangeland landscapes within the Great Basin Region, United States. The results imply that the overall hydraulics of concentrated flow on rangelands differ significantly from those of cropland rills. Concentrated flow hydraulics on rangelands are largely controlled by the amount of cover or bare soil and hillslope angle. New predictive equations for concentrated flow velocity (R2 = 0·47), hydraulic friction (R2 = 0·52), and width (R2 = 0·4) representing a diverse set of rangeland environments were developed. The resulting equations are applicable across a wide span of ecological sites, soils, slopes, and vegetation and ground cover conditions and can be used by physically‐based rangeland hydrology and erosion models to estimate rangeland concentrated flow hydraulic parameters. Published in 2011. This article is a US Government work and is in the public domain in the USA.

Effect of Polyacrylamide Applications on Soil Hydraulic Characteristics and Sediment Yield of Sloping Land

The objective of this study is to determine how PAM applications to a fraction of the surface affect hydraulic parameters of flow, soil water infiltration and soil sediment yield during rainfall on steep sloping land. Five PAM application rates (PAMR) 0, 0.4, 0.7, 1.0 and 1.3 g kg-1 were used for 5 sloping plots in this study. As PAMR increased from 0 to 1.3 g kg-1 at the rainfall intensity (RI) of 1.58 mm min-1, the Froude numbers decreased from 34.7 to 9.1, the Reynolds numbers (Re) decreased from 568 to 305, and the Darcy–Weisbach coefficients increased from 0.0028 to 0.041. The total runoff values were 33.8, 35.9, 31.6, 25.6 and 18.1 mm when the PAMR were 0, 0.4, 0.7, 1.0 and 1.3 g kg-1, respectively. The cumulative sediment increased rapidly with the rainfall time. In conclusion, PAM applications to a fraction of soil surface can be effective at reducing the erosion of steep sloping land.

Modeling of water surface profile in subterranean channel by differential quadrature method (DQM)

This study, investigates the hydraulic of flow in a subterranean channel headspring. The continuity and momentum equations of flow in porous media considering real conditions were used and the basic equation of flow in a subterranean channel was resulted. This equation is very similar to the spatially varied flow with increasing discharge. An equation, defining the hydraulic parameters of a subterranean channel section was adopted. Then differential quadrature method (DQM), was applied to the equation of flow in subterranean channel, consequently the water surface profile was resulted. To illustrate the rightness of model, the hydraulic parameters of flow in the Gavgard branch of the Joopar Goharriz Qanat were measured and the water surface profile was determined. This water surface profile was compared to the water surface profile computed by the model, which are in good agreement.

Determination of friction factor for corrugated drains

This paper describes two approaches for evaluating the resistance factor of corrugated drains. The first employs a monomial formula and is based on dimensional analysis while the second uses a physically based formula that incorporates the relationships among hydraulic parameters measured for a set of corrugated pipes. The latter depends on an evolutionary modelling technique that renders a superior description of the hydraulics of the tested corrugated pipes, outperforming the classical monomial formula for rough pipes. The formulae derived herein accurately reproduce experimental data and highlight the influence of dimensionless factors on roughness values. Three differently sized corrugated plastic pipes with slopes ranging between 3·5% and 17·5% were considered. The tests were directed at measuring open channel flow hydraulic parameters in order to ascertain the role of friction factors when wake interference occurs. This hydro dynamic phenomenon, observed in the tested pipes, is situated in the rough fully turbulent flow region of the Moody diagram. From a technical standpoint, wake interference is interesting because the abnormal turbulence experienced along the channel's wall-rough ness elements generates additional energy dissipation, entailing potentially significant implications for sewer networks installed on steep slopes.

Investigation of Flow Energy Dissipation over Different Stepped Spillways

In this study, to investigate energy dissipation of flow overstepped spillways of different step shapes, a physical wooden model has been built in the Shahid Bahonar University’s hydraulics lab. This model with 41.41° slope has 84 cm height and 21 steps. Each step has 4 cm height, 4.5 cm width and 30 cm length. Experiments have been carried out for different types of step shapes (plain steps, end sill steps with thickness of 1, 2, 3 and 4 cm and steps with a bottom adverse slope of 15, 26, 36 and 45°). Overall, 131 experiments were done, the hydraulic parameters of flow over the model were measured and the energy dissipation of flow was calculated. Results show that the energy dissipation of flow on end sill and inclined stepped spillways are more than the plain one, it is increased by increasing the thickness of end sill or the adverse slope size. Comparison of flow energy dissipation over end sills stepped spillway and inclined type show that the inclined type has been dissipated more energy than the equivalent end sill type. Also for stepping spillway of different step shapes, flow energy dissipation decreases with increasing the flow rate. It is concluded that for a large stepped spillway with high flow rate the inclined type spillway is more effective than the other forms.

Evaluating Hydraulic Parameters of Flow and Transport of a Nonreactive Solute in a River Regulated by a Chain of Hydropower Plants

A simple and efficient technique is proposed for use in combination with a known method for solving the Saint-Venant equation and the equation of advection–diffusion transport of a solute. This technique allows an overall calculation when there are several hydropower plant dams in a river channel. Practical calculations have been made for the upper reach of the Vuoksa River for the most realistic scenarios. The results of the calculations supplement the scarce field data on water level elevations, water flow, and mean flow velocities for quasi-steady-state conditions and for cases of water releases spreading downriver. The effect of water releases on the distribution of solute concentration along the river is assessed and the dependence of the pattern of a conventional pollutant spreading along the river channel after an impulse discharge on the coefficient of longitudinal dispersion is examined.

Risk assessment methodology for karst aquifers : (1) Estimating karst conduit-flow parameters

Quantitative ground-water tracing of conduit-dominated karst aquifers allows for reliable and practical interpretation of karst ground-water flow. Insights into the hydraulic geometry of the karst aquifer may be acquired that otherwise could not be obtained by such conventional methods as potentiometric-surface mapping and aquifer testing. Contamination of karst aquifers requires that a comprehensive tracer budget be performed so that karst conduit hydraulic-flow and geometric parameters be obtained. Acquisition of these parameters is necessary for estimating contaminant fate-and-transport. A FORTRAN computer program for estimating total tracer recovery from tracer-breakthrough curves is proposed as a standard method. Estimated hydraulic-flow parameters include mean residence time, mean flow velocity, longitudinal dispersivity, Peclet number, Reynolds number, and Froude number. Estimated geometric parameters include karst conduit sinuous distance, conduit volume, cross-sectional area, diameter, and hydraulic depth. These parameters may be used to (1) develop structural models of the aquifer, (2) improve aquifer resource management, (3) improve ground-water monitoring systems design, (4) improve aquifer remediation, and (5) assess contaminant fate-and-transport. A companion paper demonstrates the use of these hydraulic-flow and geometric parameters in a surface-water model for estimating contaminant fate-and-transport in a karst conduit. Two ground-water tracing studies demonstrate the utility of this program for reliable estimation of necessary karst conduit hydraulic-flow and geometric parameters.

Energetics of sediment‐laden streamflows

The present approach, which considers a diluted sediment suspension as a perturbation to a clear‐water flow, permits a direct comparison of the energetics of turbulent sediment‐laden and clear‐water open‐channel flows of constant slope and depth. On the basis of the Boussinesq approximation to the momentum equations for the flow with sediment in suspension and the Navier‐Stokes equations for the clear‐water flow, a depth‐averaged equation for the change in turbulence energy dissipation rate and an equation for the flow energy budget are obtained. From the analysis of these equations it becomes clear that the presence of the suspension affects the distribution of energy in the flow; also, the turbulence kinetic energy can increase, decrease, or remain the same depending on the sediment loading conditions, and its rate of dissipation can increase, decrease, or remain the same depending on the magnitude of the flow hydraulic parameters relative to that of the loading conditions. These findings provide additional insight into the energetics of these complex flows, agree qualitatively with experimental data, and complement available models.

Transient modelling of water-table variation in a floodplain wetland, Narborough Bog, Leicestershire

This paper describes the application of a transient three-dimensional groundwater model to simulate water flux through a floodplain wetland, Narborough Bog, in Central England. The results of a programme of water-table monitoring are summarised to indicate the extent of water-table fluctuation, and experiments to determine hydraulic flow parameters are detailed. Hydraulic conductivities of deposits are highly variable; observations were in the range 1.16 × 10 −3–4.63 × 10 −2 cm s −1 for herbaceous peat, 1.16 10 −4 cm s −1 for wood peat, and 9.14 × 10 −6–3.36 × 10 −8 cm s −1 for silty clay. A three-layer groundwater model of the wetland is developed using MODFLOW from these initial values, and with stratigraphic data obtained by hand augering. The model is calibrated using data for two periods of recharge from precipitation by adjusting specific yield and vertical hydraulic conductivity within prescribed limits. The accuracy of the model is then assessed by comparing daily model predictions of water-table response to potential evapotranspiration at specific monitoring points. Model, results demonstrate the importance of variation in hydraulic characteristics with depth in wetlands, thus emphasizing the dependence of water-table response upon water-table position, and preceding moisture conditions. The resulting water-table configuration reflects the balance between horizontal and lateral water flow through the wetland, and its relationship to river stage. The success of the stratigraphic representation is considered and its general applicability evaluated. Finally, the use of the calibrated model for local hydrological management is considered, and the effects on the wetland water budget of varying river stage by specified amounts are examined.

Isotope hydrology investigations in large refuse lysimeters

With the aim of studying the hydraulic behaviour and isotopic effects in refuse dumps, measurements of the 18O and 2H content of rainwater infiltrating into large cylindrical refuse lysimeters (1.5–4 m height with diameter of about 5 m), installed by the Technical University of Brunswick, Germany, were performed. The 11 lysimeters were filled with household refuse and sewage sludge under different conditions (aerobic/anaerobic, compaction, layering). The long-term hydraulic parameters of flow through the lysimeters (transit time, apparent dispersivity, volume of total water) were estimated with a specially adapted black-box model, which used isotopic content curves of rainwater and infiltrated water sampled at different depths in the lysimeters. The transit times of rainwater through the lysimeters (3–6 years) and the mean flow velocities deduced from them (0.4–1 m year −1), correspond to values in the unsaturated zone of sandy aquifers. The dispersivities are in the range of 0.1–1 cm. A special attempt was made to follow individual heavy rain events and estimate the travel times and portions of rainwater percolating swiftly through the lysimeter. It was found that up to 40% of those precipitation events drains off directly, i.e. within a few weeks. However, as it remains only a short time in the lysimeter, this water should not be greatly affected by the lysimeter filling. In addition, by evaluating the δ 2H-δ 18O relationship of the water samples from the different lysimeter sampling points, it was possible to differentiate, on a preliminary basis, isotopic effects caused by evaporation and biochemical reactions.

Problems of the hydrodynamics and Deposition in Estuaries and River Mouths

1. The methods developed for predicting the change of the coast due to a change of the hydrologic regime of the river and shore are based on different mathematical approaches, the most hopeful of which are the phenomenological theories of the transformation of the coastal area in the region of river mouths. 2. Noteworthy in the area of full-scale investigations are the recently conducted, technically complicated observations to determine the effect of tides and waves on the character of transformation of the river mouth and its filling with deposited river sediments. Of interest are the new instruments for studying the hydraulic flow parameters and characteristics of sediment, for example, the instrument of the Wallingford hydraulic research station. 3. Characteristic for the third group of reports is the fact that the majority of investigators validly concentrate on a study of the physical mechanism of sediment transport in rivers and estuaries and not just the collection of quantitative data. It is especially necessary to emphasize the use of modern measurement instruments: lasers, signal-averaging devices, and digital computers.