Hydraulic Characteristics Of Flow Research Articles

Hydraulic Characteristics of Unsteady Flow in Compound Channels with Wooded Zones on Flood Plains

Hydraulic characteristics of unsteady flows were investigated experimentally in compound channels with vegetated flood plains. Some noticeable differences between unsteady flow structure in compound channels with and without vegetation were revealed. The vegetation in the flood plains increases the unsteadiness of the main-channel velocity and its double peek property is changed by the effects of vegetation arrangement. During the rising stage, the velocity in the vegetation does not reach the value in the steady flow case so that the lateral velocity gradient and the turbulence intensity increase near the vegetation interface. Lastly, 1-D numerical calculation technique for unsteady flow with vegetation in flood plains was investigated.

Characterization of hydraulic flow patterns in facultative aerated lagoons

A tracer study was conducted in the winter at the Sainte Julie (Quebec, Canada) lagoon facilities to ascertain the hydraulic flow characteristics. The lagoon system is a continuous discharge type consisting of three facultative aerated lagoons and a maturation pond operating in series. The first three are provided with bottom air diflusers, the number of which decreases from the first to the third lagoon. C-diagrams indicate significant short-circuiting for all lagoons. Long tails in the C-diagrams of lagoons 1, 2, and 3 suggest the presence of stagnant or dead regions within them reducing the effective volume of the lagoons and hence the treatment efficiency that could otherwise be achieved. Values of the dispersion number, d, were 0.392, 0.452, 0.283, and 0.487 for lagoons 1, 2, 3, and 4, respectively. The jacknife statistical technique is used to assess the impact of influent flow variations on the dispersion number. Fluid flow pattern in the lagoons does not follow the simple “flow-through” behaviour. Rather, circulatory patterns are superposed on this as indicated by the multiple-peaked C-diagrams. Also, the Polprasert and Bhattarai model gives good prediction of the dispersion number for aerated lagoons.

The Removal of Reservoir Sediment

ABSTRACT Sedimentation of a reservoir created by a dam constructed on a natural watercourse is inevitable. A dam on a river changes the hydraulic characteristics of flow and the sediment—indicating a change in the transport capacity This article explains reservoir silting and assesses the economy of hydraulic resources and design of precise measures to maintain or improve this situation. Estimation of sediment yield is an extremely complicated problem. Reasonable results were obtained in Iran by applying the chasse flushing) method for Sefid Rud Dam. A 1,800 million m 3 reservoir had originally been created at the end of construction of the high dam in 1961. But sediments silted about 800 million m 3 of the reservoir capacity by 1981. During eight years of flushing operations, about 300 million m3 of sediments were removed from the reservoir through five bottom outlets at riverbed level. These outlets can be used for irrigation water intake when none of the five turbines with 165 m3 per second total installed capacity is operating. The outlets are almost evenly distributed along the base of the dam. The total discharge of these outlets at the reservoir normal water level (RNWL) is about 980 m3/s. Erosion plays a significant role in the amount of solids in runoff from the reservoir Measurement of erosion can be done in two ways: (I) metering of solid discharge, and (2) measurement of sedimentation in the reservoir Both procedures have been put into practice in the Sejid Rud Dam project.

Experimental Study on Hydraulic Characteristics of Flows in Embayments

Flows in embayments are investigated systematically using flow visialization technique and two-component electromagnetic velocimetry. Measured data show that the shape of embayment exerts considerable effect on the development of the vortices along the interface, hence velocity distribution in the embayment at low water depth. Under flood flow condition, flow becomes more complex due to the effect of vertical recirculation formed at the upstream end of the embayment and vegetation on the floodplain.

Experimental Study on Internal Structures of Ultra-Rapid Flow

On steep slope channel beds, It is well known that thin sheet flow has periodic Roll-Wave trains, but experimentally derived data is scant to this date. The hydraulic characteristics of Roll-Wave flow are experimentally reproduced and mean velocity, turbulence intensity, Reynolds stress and correlation coefficients of Reynolds stress are compared to corresponding Uniform flow data. In addition, a structural definition of Roll-Wave flow is attempted using instantaneously obtained values of main flow u, vertical flow v to the bed. The results indicate Rall-Wave flow's mean velocity is similar to Uniform flow's mean velocity, but differs in regard to turbulence pattern. It is hypothesized that velocity fluctuations and Reynolds stress are strongly influenced by water depth variance and Roll-Wave front.

Hydraulic Flow and Water Quality Characteristics in Rill Erosion

AbstractThe effects of interaction between water flow characteristics, soil sodicity, and water quality on the detachment of soil particles by flowing water was studied in the laboratory. Specific objectives of this study were to evaluate: (i) the use of flow shear stress and stream power for estimating soil detachment, (ii) the effect of low soil sodicity (exchangeable sodium percentage [ESP] <10) and water quality (deionized water [DW] and 0.005 M CaCl2 solution [TW]) on soil detachment, and (iii) the effect of negatively charged polyacrylamide (PAM) polymer on soil detachment. Detachment rates were measured in a small hydraulic fume. Several bed slopes and flow rates were studied. Detachment rate increased linearly with both shear stress and stream power of the flow. The rill erodibility of the Miami soil (fine‐loamy, mixed, mesic Typic Hapludalf) agreed well with field data. Water quality had no effect on rill erodibility for the soil tested when ESP < 3.0. Use of TW reduced the erodibility of soils with ESP 5 and 10 compared with DW. Surface treatment with PAM (0.05 g m−2) prevented soil detachment in flows with high shear stress. The formation of a surface soil layer with high cohesion and aggregate stability prevented soil detachment. Soil surface properties and not bulk soil properties determined soil detachment.

HYDRAULIC CHARACTERISTICS OF FLOW OVER DAM AND HYDRAULIC JUMP OF BINGHAM FLUID

HYDRAULIC CHARACTERISTICS OF FLOW OVER DAM AND HYDRAULIC JUMP OF BINGHAM FLUID

Hydraulic characteristics of two-layered tidal flows in the Hiji River

Hydraulic characteristics of two-layered tidal flows in the Hiji River

Hydraulic Characteristics of Flood Waves Passing Compound Channels

Hydraulic characteristics of unsteady flows were investigated experimentally when flood waves were passing through compound open channels. Some noticeable features of unsteady flow structure in compound channels were revealed which were significantly different from those in single rectangular channels. The unsteadiness of velocity becomes very large in main channels and the peak of velocity appears very earlier than in rectangular channels. Lateral shear stress increases in a rising stage at an interface region of main channel and flood plain. The bed shear stress exceeds the value of steady peak flow in the rising stage.

Soil Detachment by Shallow Flow at Low Slopes

Detachment of soil particles by shallow surface flow is influenced by soil cohesion, soil aggregate properties, and hydraulic flow characteristics. This study was conducted to evaluate relationships between soil detachment rates, soil aggregate size, soil tensile strength, flow shear stress, and flow stream power. Detachment rates were measured in a hydraulic flume on three aggregate size classes of two soils. Tensile strength and wet aggregate stability were measured to characterize each aggregate class. Flow depths ranged from 0.5 to 2.0 cm and slopes ranged from 0.5 to 2%. Detachment rates increased with both increasing flow depth and increasing bed slope. Multiple linear regression analyses indicated that the logarithm of detachment rate vs. flow depth, slope, and either mean weight diameter or tensile strength were good models (R² = 0.94 and 0.91, respectively) for predicting detachment rates. Detachment rate for a given soil material was not a function of either shear stress or streampower of the flow. The largest size class of aggregates were detached at a faster rate than the smaller two aggregate size classes.

Identifying Flow Intervals by Pore Geometry and Petrophysics: Middle Trinity Aquifer (Lower Cretaceous Limestone)

A core from the Lower Cretaceous middle Trinity aquifer of southern Kendall County, Texas, was analyzed to compare its petrographic and petrophysical properties to its hydraulic flow characteristics. The analyses helped determine flow intervals in the core. Flow intervals are defined as vertical zones having similar geologic (depositional and diagenetic) history, petrophysical properties, and hydraulic conductivity characteristics. The information gathered from the study of a single core may be integrated with similar data from other cores or well logs to define 'flow units.' Methodology involved visual and image analysis examination of thin sections and epoxy pore casts of samples to evaluate pore geometry (pore size, pore throat size, pore interconnectivity, and pore throat size heterogeneity). Samples were thus grouped into pore-type families. Representative samples from each pore-type family were tested for air and brine permeability, porosity, and mercury injection capillary pressure. Pore throat size distributions obtained from the capillary pressure analyses were compared to the data derived from the pore casts and thin sections. Pore geometry evaluated correlated well with mercury capillary pressure data for the most permeable zone of the core. Geologically, this flow interval consists of a porous, medium-grained peloid grainstone that is characterized by large pores connectedmore » by large pore throats. Wherever present, such pore throat to pore body size ratios enhance flow through the rock. Correlation between pore geometry and capillary pressure data deteriorate in packstones with increasing micrite mud content and wackestones with increasing dolomitization. These lower correlations are due to decreasing pore throat size and increasing pore throat size heterogeneity in these rocks.« less

RHEOKINETICS EFFECT ON FLOW AND CONVECTIVE HEAT TRANSFER OF POLYMERIZING FLUIDS

A method is proposed for space-time separation and subsequent coincidence of the parameters for kinetic and convective stages of a process. It is implemented in a constant pressure device with independent thermostating thermal chemical (reservoir) and thermal hydraulic (channel) units. Based on the macrokinetic model, numerical calculations are made of thermal and kinetic characteristics of amine-curing-agent polymerization of epoxy resin. The viscosity of a partially cured composition is found as a function of temperature and conversion β. The technique is developed to calculate, to a one-dimensional approximation, integral hydraulic and thermal characteristics of nonisothermal pressure flow of partially cured fluid in the thermal entrance section of a tube. To evaluate its applicability, the two-dimensional problem on developing nonisothermal flow of thermo-sensitive fluid is considered to a boundary-layer approximation

Hydraulic Characteristics of Compound Channel Flows with Rough Floodplains

A series of experiments are performed to measure the mean velocity, turnbulence intensity and boundary shear stress distributions in compound channels with rough floodplains. Three different floodplain widths, main channel widths, and heights are used to understand the effects of varing channel geometry, size, the ratio of flow depth to the main channel depth and roughness elements. From these results the strong relation is observed between the mean velocity structure, turbulence structure and shear distribution. It is found, especially, that the roughness element on the floodplains strongly effects the flow structure in compound channel.

Consideration of meteorological factors when calculating large canals

The effect of meteorological factors on the dynamics of open-channel flows is taken into account, as a rule, when studying unsteady fluid flows [8–12]. In shallow-water equations (in particular, in the St. Venant equations), which are the most common mathematical model used for calculating open-channel unsteady flow, meteorlogical factors are included as conditions on the free surface (normal and shear stresses). The use of the indicated dynamic equations (of shallow water) makes it possible to obtain quite diverse information about the results of the effect of the atmosphere on the structure of the open-channel flow. The approach presented in this article, based on the equation of balance of mechanical energy and ultimately on the Bernoulli equation, does not permit obtaining such detailed information about the interaction of meteorological and hydraulic factors. It permits mainly obtaining simple estimates by means of which one can establish when the effect of meteorological factors on the hydraulic characteristics of flows in canals should be taken into consideration.

Hydraulic flow characteristics in the lignotuberous mallee Eucalyptus behriana F. Muell. in the field.

The lignotuberous mallee Eucalyptus behriana F. Muell, had much lower predawn leaf water potentials (not higher than - 1.2MPa) than other eucalypts (as high as - 0.2MPa), even after extended rain. This led to the expectation that the lignotuber of E. behriana might have specific hydraulic characteristics. Keeping the soil around partially defoliated mallces for several days underwater did not raise the water status above the maximum leaf water potential observed under natural conditions. Digging a plant out and placing its roots in water after removal of the soil rapidly increased the water status to a level consistant with other eucalypts. This indicated that the major impedance to water uptake was a component of the soil rather than in the roots or in the lignotuber. Some of the individual mallces had only two major stems or branches. One stem or branch was kept covered throughout the experiments to prevent transpiration. The other stem was subjected to a variety of different conditions in order to modify water loss from it. The transpiring branch affected the water status of the non-transpiring plant parts. Hydraulic resistances in the shoot and root/lignotuber were determined from differences in the leaf water potential of covered and uncovered branches, at high water flow rates through the plant. Resistances in branches, including the liquid phase component of the leaf, were significantly larger than in root or lignotuber. The total plant hydraulic resistance of E. behriana was similar to that of other eucalypts, such as E. pauciflora Sieb. ex Spreng. or E. delegatensis R. T. Bak., even though its growth form was different and its natural leaf water potentials were much lower. An osmotic adjustment at the leaf level was observed in the mallee, keeping its bulk leaf turgor in the same range as compared to the other eucalypt species.

A new approach for determining permeability characteristics of rock using slug testing techniques

A new technique of determining hydraulic flow characteristics of rock in the laboratory is presented. The technique is a laboratory simulation of a well known in situ ‘slug’ testing method where aquifer parameters are determined by the removal of water slug in a test borehole. The time taken for the water level in the borehole to return to its original rest level, is observed. The results are treated using an analytical technique, first developed by Theis [1]. The laboratory technique involves a test on a very small scale, with a slow rate of rise of water in a drill hole. The laboratory equipment and test procedure are described together with the advantages and limitations of the system. The technique offers an inexpensive, simple and effective method for determining the permeability of standard core samples, whilst keeping the amount of sample preparation to a minimum. The technique offers a potential for testing of most rock types under a variety of loading conditions.

Hydraulic Transport of Copper Tailings

An experimental study was conducted to define the flow hydraulic characteristics and to establish the feasibility of transporting slurries of the El Teniente Copper mine.

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.

Fluid dynamic effects on Apollo engine pressure spikes.

Apollo Service Propulsion System Block II firings exhibited an average spontaneous pressure spike (pop) rate a factor of 5 or more greater than Block I. The incidence of combustion instability also increased. The present study was undertaken to determine if the source of the pops was related to the hydraulic flow characteristics of the injector, or to the gasdynamic environment within the chamber. A mechanism for the occurrence of pops was hypothesized: zones of unreacted propellants may exist as a result of the injector pattern design; if these zones are suddenly mixed, a pop may result. To verify this theory, experimental studies were conducted to evaluate the hydraulic characteristics of the injector elements, and the existence of unreacted zones of propellant. By these studies, the existence of the potential for pops was verified. The injector was modified by counterboring certain orifices to prevent hydraulic flip. These modifications resulted in reduction in the pop rate by two orders of magnitude.

Hydraulic and micromorphological properties of stream channel sediments

In the arid and semiarid regions of the southwestern United States, a large portion of the natural water recharge is through channel beds and alluvial deposits in river basins. Water transmission in these beds varies with time, location, depth and extent of alluvium, and hydraulic characteristics of flows, sediment loads, and morphology of the channels. An alluvial profile in an ephemeral stream channel was found to have layers with relatively high clay and silt accumulation. Samples from a pit in the channel were subjected to a micromorphological examination using thin sections. Clay and silt were found to have accumulated on sand and gravel particles and around aggregates. In the laboratory, samples of alluvium material were dispersed. The clay and silt fractions were collected, dried, and then mixed again with the washed material. The hydraulic conductivity of the mixed material was 30% less than that for the nondispersed sample. These results are attributed to the orderly arrangement of clay and silt on the surfaces and between the larger sand and gravel particles of the nondispersed samples. (Key words: Sediment; porous medium; infiltration; permeability)