Hydraulic Characteristics Of Flow Research Articles

Vegetative-hydraulic parameters generated by agricultural crops for laminar flows under a semi-arid environment of Pernambuco, Brazil

The structural parameters of vegetation have an important influence on the resistance imposed to shallow flow under the soil, being important in the control of floods, water erosion and sediment transport in the watersheds. Therefore, in order to obtain the hydraulic characteristics of overland flow, the variables of hydraulic resistance generated by the vegetation to surface flow, and the interrill erosion rates under semi-arid region led to the introduction of agricultural crops, through which shallow flows were generated on elephant grass (Pennisetum purpureum), corn (Zea mays sp.) and in a bare Entisol, placed in a toeslope landscape position. Results showed that the flow regime was slow, laminar and interrill erosion occurred (Re < 500 and Fr < 1). Nevertheless, the hydraulic characteristics of overland flow (Vm, h, q and log f) were probably affected by the proximity to the water table, a hypothesis supported by the obtained values for the infiltration. However, corn and principally elephant grass showed high hydraulic resistance to superficial flow and interrill erosion conferred by the highest ground coverage (lowest Ci = 0.198), by the effect of the sub-factors CiI, CiII and CiIII, and the lowest values of sediment concentration (CS), runoff coefficient (C), interrill detachment rate (Di), and soil loss (SL). Our results support the purpose of introducing agricultural crops in the Brazilian semi-arid region since increasing resistance to interrill erosion can be provided. Elephant grass is a more appropriate crop to be inserted under land management protocols in the semi-arid environment.

A numerical and experimental investigation of the effects of combination of spur dikes in series on a flow field

Spur dikes are used to protect river banks from erosion and also keep the main mitigation channel. Different additional structures such as “collar” and “protective spur dike” are used for reducing scouring around spur dikes. The combination of spur dike in series may be a new method to decrease scouring without using any additional structures. A computational fluid dynamic model was developed to investigate flow characteristics around triple combinational series with different shapes of spur dike (I (simple)-, L- and T-shaped). In order to verify the numerical model a (T L I) combinational series was experimented in the laboratory, and hydraulic characteristics of flow around them were measured. In this research, the numerical simulation based on optimum combination and control test is used in FLOW-3D software for analyses. In addition, several turbulence models (k–e, RNG and LES) have been applied to achieve the best numerical simulation. The results showed that the largest flow speed, pressure, shear stress and turbulent energy in the flat bed formed close to the location of maximum scour depth and erosion. Reduction in these features helps decrease scouring and erosion. The combination of spur dike in series is a method which achieves this goal. The (L T T) series is the most effective in reducing speed, shear stress, pressure and turbulent energy around spur dikes. Actually, different geometries of spur dike, when used together, have positive effect on reducing scouring. Finally, combination of spur dikes with protective spur dike compared with series without protect. The result showed that protective spur dike can decrease intensity of flow characteristics and scour depth.

Hydraulic and internal flow characteristics of swirling superheated hydrocarbon liquid jets

Hydraulic and internal flow characteristics of swirling superheated liquid jets of aviation fuel were investigated experimentally and numerically. Liquid hydrocarbon was heated to close to 573 K (300 °C) using an induction heater at an upstream pressure of up to 1.1 MPa and discharged to atmospheric downstream pressure conditions through a simplex pressure-swirl nozzle. Hydraulic characterization in terms of fuel temperature was carried out by introducing the discharge coefficient Cd, and the macroscopic internal flow characteristics were correlated with Reynolds number and cavitation numbers. As compared with the plain orifice injector configuration, with the pressure swirl injector the normalized Cd trend with respect to fuel injection temperature Tinj increases more with increasing Tinj until Tinj reaches the boiling point, and the resultant higher normalized Cd at the boiling point decreases faster as Tinj increases further above the boiling point. The CFD analysis of the swirling high temperature liquid jets shows that for cases of Tinj above the boiling point, the internal flow of the swirl injector becomes independent of the ambient (downstream) pressure. This implies that the swirl flow has reached the mass flow choking, or critical cavitation condition. Furthermore, the relatively scaled velocity and the normalized pressure P/Psat distributions of the swirl injector are found to converge to an almost identical shape when Tinj exceeds the boiling point, irrespective of ΔPs and Tinj. Distinct evidence of the choked cavitation of the swirling high temperature liquid jets is observed in the relationship between the mass flow rate and (Pinj − Psat)1/2, which shows that the mass flow choking of the swirling high temperature liquid jets is initiated as soon as the fuel injection temperature increases past the boiling point, and the effect of the choked cavitation represented by the decrease of the mass flow rate becomes stronger as Tinj increases further. Finally, the clear dependence of Cd on cavitation number suggests that cavitation dominates the Cd characteristics of the high temperature fuel injection for the swirl injector when Tinj increases past the boiling point, and, therefore, the degree of thermal cavitation of the swirling superheated liquid jets is nicely represented by the cavitation numbers.

Dynamics and Control of Liquid Level in Annular Conical Tank Process: Modelling and Experimental Validation

Objectives: The present work has been carried out to prove the superiority of IMC based PID control strategy over the conventional PID, based on simulation studies and experimental validation on an annular conical tank liquid level nonlinear process. Methods/Statistical Analysis: First principles based Mathematical Model of an annular conical tank liquid level nonlinear process has been developed based on the mass balances and outlet flow hydraulic characteristics. Linearization of the nonlinear model at a specific steady-state operating point led to the theoretical development of state-space and standard first order transfer function models. Open loop and closed loop experimental studies on a computer controlled physical setup were performed to identify the parameters of a FOPDT Model with variable gain and time constant. IMC based PID controller was designed and compared to the conventional PID controller. Findings: The variation in process parameters was attributed to two factors: (a) the variation in annular cross sectional area of the conical tank at different levels, and (b) the variation in outlet flow resistance. The IMC based PID controller has been shown to exhibit superior performance in terms of quantitative performance indices such as ISE, IAE, ITAE, rise time, settling time and percentage overshoot, at four different steady-states. Application/Improvements: Study of Modelling of annular conical tank process and a systematic methodology of process system identification from experimental setup have been reported. The advantages of IMC based PID controller design over the conventional PID tuning method has been experimentally verified. Keywords: Annular Flow Conical tank process, FOPDT model, System Identification, PID controller tuning, IMC based PID.

Numerical investigation of fluid flow and heat transfer of nanofluids in microchannel with longitudinal fins

Thermal and hydraulic characteristics of laminar nanofluid flow in square microchannel with longitudinal inner fins are numerically investigated. The external walls of microchannel are heated at constant heat flux and four rectangular fins are fixed on the internal walls. Four different types of nanofluid are used as working fluids which are SiO2, Al2O3, CuO and ZnO dispersed in pure water base fluid. Different volume fractions of 1-2 and different nanoparticle diameters of 30-60 nm are employed. The results show that the SiO2 nanofluid has the highest heat transfer rate among all of four tested nanofluids. The increase in nanoparticle volume fraction and the decrease in the nanoparticle diameter would increase the Nusselt number value. The friction factor does not change significantly by using nanofluid with different volume fractions and different nanoparticle diameters. Moreover, the results indicate that nanofluid can enhance the performance of microchannel with longitudinal fins. © 2018 Ain Shams University

Three-dimensional multiphase CFD modeling of thermal–hydraulic characteristics of nanofluid flow in helical microchannels

Forced convection heat transfer of two different types of water-based nanofluids (Al2O3, TiO2) was investigated numerically. In this numerical investigation, mixture two-phase model was considered and the governing equations were discretized based on the finite element method. The developed model agrees well with the experimental data for the two straight and helical microchannel tubes. The presented model covers the helical microchannel with different axial pitches and curvature ratios. The obtained results showed that geometrical parameters (curvature ratio and axial pitch) with a combination of nanofluid types and concentration have impressive effects on thermal performance and pressure drop. The results revealed that the Nu number was about 14% higher compared to pure water for the helical-containing Al2O3 nanofluids. Moreover, addition of both nanoparticles had negligible effect on friction factor in helical microchannel. The optimum operating conditions which are most economical from an industrial point of view were evaluated using the effectiveness parameter (η).

Numerical investigation of heat transfer and friction characteristics for turbulent flow in various corrugated tubes

Thermal and hydraulic characteristics of turbulent water flow in a transverse corrugated tube with various corrugation direction (inward/outward) and corrugation shape (triangle, curve, rectangle, and trapezoid) are numerically investigated. The axisymmetric model of corrugated tubes with 10 mm inner diameter was investigated by changing the geometrical parameters for Reynolds number ranging from 5000 to 61,000 and constant heat flux boundary condition. Structured, nonuniform grid system is applied. Momentum, continuity, and energy equations were treated by means of a finite volume method using the SIMPLE scheme with the k–ε turbulence model and enhanced wall treatment. The results reveal that corrugation direction and corrugation shape have perceptible effects upon the heat transfer in the form of Nusselt number ( Nu) and pressure drop in the form of friction factor (ƒ). The average Nu for (inward) trapezoidal, rectangular, curved, and triangular corrugation shapes are 52.61%, 50.12%, 47.82%, and 44.96%, respectively, higher than the smooth tube. The average Nu for (outward) trapezoidal, curved, triangular, and rectangular corrugation shapes are 48.31%, 45.72%, 41.23%, and 40.94%, respectively, which are higher than a smooth tube. The results reveal that both inward/outward curved and triangular roughness shape have the superior performance evaluation criterion than rectangular and trapezoidal. Turbulence kinetic energy contour shows the increase in heat transfer performance for all corrugated tubes compared with a smooth tube. Inward corrugated tube provides the highest turbulence kinetic energy along the tube length and, consequently, the highest heat transfer. In addition, inward corrugated tubes provide the highest values and homogeneity of the velocity distribution along the core of tubes.

Effect of fertilization and sediment flow hydraulic characteristics on emitter clogging in muddy water drip fertigation system†

AbstractIn a drip fertigation system using the Yellow River, suspended solids in the water serve as a bridge between physical flocculation and chemical adsorption. They impact the emitter clogging process and flow turbulence properties. Therefore, a laboratory test was conducted with artificial muddy water drip fertigation (MWF) to investigate the anti‐clogging performance of emitters. Four types of fertilizer (i.e. [CO (NH2)2], Ca (H2PO4)2·H2O, K2SO4 and [CO (NH2)2] + KH2PO4 + KNO3) were applied at 0.5, 1, 2 and 3% concentrations respectively. The results showed that the relative discharge of emitters (Dra) remained in a fluctuation balance phase, and at 0.5% concentration with MWF, there was a decrease of 5, 11.1, 8.8 and 4.9%. For fertigation concentrations between 1 and 2%, the fluctuation balance phase significantly reduced, and the Dra began a linear decrease of 12.5, 42.2, 37.6 and 5.1%. At a fertilizer concentration increase of 3%, the Dra improved relatively with urea and P fertilizer drip irrigation but slightly declined with K and compound fertilizer. The particle size distribution of flocs ranked from broad to narrow as follows: P fertilizer &gt; K fertilizer &gt; urea &gt; compound fertilizer. Urea showed a viscosity‐reducing effect on muddy water (MW). Conversely, K fertilizer exhibited the greatest viscosity‐increasing effect, followed by P fertilizer, while compound fertilizer exhibited the least viscosity‐increasing effect. The filter criteria of the drip irrigation system can be suitably reduced for drip fertigation with urea in the Yellow River irrigation area. © 2018 John Wiley &amp; Sons, Ltd.

Thermal hydraulic characteristics of turbulent single-phase flow in an enhanced tube using louvered strip insert with various slant angles

Effect of slant angle (α) of louvered strip insert on single-phase forced convection heat transfer and friction factor of internal flow was investigated experimentally. The parameter of slant angles (α) 15°, 20° and 25° was examined at the Reynolds number (Re) of 5300–17,500. The plain tube was also performed for comparison. The results show that the louvered strip insert provided the increases in heat transfer and friction factor up to 77.02% and 3.35 times above the plain tube. The results also indicate that heat transfer and friction factor increased with increasing slant angle. The highest slant angle yielded the highest thermal performance factor in the value of 1.12. Empirical correlations were also developed for Nusselt number and friction factor based on experimental data.

Thermal and hydraulic characteristics of turbulent nanofluids flow in trapezoidal-corrugated channel: Symmetry and zigzag shaped

Thermal and hydraulic characteristics of turbulent nanofluids flow in a trapezoidal-corrugated channel are numerically investigated by implementing the finite volume method to solve the governing equations. The adiabatic condition for the straight walls, constant heat flux for the corrugated walls, and two configurations of trapezoidal channel symmetry and zigzag shape were examined. The performance of a trapezoidal-corrugated channel with four different kinds of nanofluids ( ZnO, Al2O3, CuO, and SiO2), with four various nanoparticle volume fractions of 2%, 4%, 6% and 8% using water as base fluid is thoroughly analyzed and discussed. The nanoparticles diameter, another parameter is taken into consideration, varied from 20 to 80 nm. Results show that the symmetry profile of trapezoidal-corrugated channel has a great effect on the thermal performance compared with a straight profile and zigzag profile. The Nusselt number dropped as the nanoparticle diameter grew; however, it grew as the nanoparticle volume fraction and Reynolds number dropped. The best improvement in heat transfer among the nanofluids types was by SiO2-water. The present investigation uncovers that these trapezoidal symmetry-corrugated channels have favorable circumstances by utilizing nanofluids and in this manner fill in as a promising contender for incorporation in more compact heat exchanger devices.

Refined dependences of power-law form for calculation of hydraulic resistance and velocity distribution

To solve the engineering problems of hydraulic engineering, water supply and sanitation, prevent emergency situations at hydraulic structures, regulate channel processes, efficient ecological monitoring of water bodies, and develop measures that exclude crisis ecological situations, more and more accurate estimates are required for the hydraulic characteristics of water flows. Inaccurate assumptions and approximate methods of integration can lead to significant errors that significantly affect the results of predicting flooding of riverine areas; this requires further refinement of the calculation methods. Until now, theoretical and experimental substantiations of the basic propositions of the theory of turbulence, hydraulic resistances, channel processes cannot be considered sufficiently complete. The compositions of problems associated with flows in wide channels, problems of turbulence, ax symmetric flows in smooth and rough pipes, are of scientific and practical interest. The article investigates the dependencies for the calculation of kinematic and dynamic flow characteristics in deformed and undeformable boundaries. New formulas are given for a refined description of the distribution of flow velocities and hydraulic resistance of turbulent flows in pipes and channels. Based on the known fundamental research, the calculation-theoretical methods are refined. The results obtained for flows in non-deformable channels can be useful for estimating not only flow in pipes, but also river flows in hard, undeformable boundaries and with minor channel deformations (in channels and rivers). For the first time, the analysis made it possible to obtain power-law approximations of the resistance laws for smooth and rough tubes and to establish the actual relationship between the exponents in the velocity profile and the law of resistance.

Effects of farmland vegetation row direction on overland flow hydraulic characteristics

Abstract Soil erosion of farmland is a major issue faced by the agricultural industry. Control of water-induced erosion can be improved through the simulation of different configurations of vegetation row direction to analyze the effects of farmland vegetation row directions RD on the hydraulic characteristics of flow. The farmland vegetation row directions were simulated and the anisotropic influence of the farmland vegetation row direction on flow hydraulic characteristics was experimentally analyzed. Three groups of farmland vegetation row directions with angles θ of 15°, 45°, and 90° with respect to the flow direction FD were configured. Experimental results show that different angles caused variation in hydraulic parameters velocity V, Reynolds number Re, Froude number Fr, and Darcy–Weisbach friction factor λ along the directions of flow. The rates of change of λ, Re, and Fr were analyzed statistically, where θ was increased every 10°; the average rate of decrease of λ was 5.2% and the average rates of increase of Re and Fr were 2.2% and 3.4%, respectively. These results indicate that the vegetation distribution pattern on farmland has an anisotropic influence on the hydraulic characteristics of flow. This investigation provides valuable references for the optimization of farmland vegetation distribution and soil erosion control.

Numerical evaluation on thermal–hydraulic characteristics of dilute heat-dissipating nanofluids flow in microchannels

The present work deals with numerical investigations on heat transfer characteristics and friction factor of aqueous CuO nanofluids flow in a set of four microchannels connected in parallel under laminar regime. For each single phase, volume of fluid, mixture and Eulerian models, a particular computer code is developed to carefully simulate this problem. The three-dimensional steady-state governing equations are solved through finite volume method. The primary aim of this study is to comparatively distinguish the most appropriate and accurate model for numerical studies of nanofluids in microchannels. The results are compared with one another and the data obtained from an experimental work. Regarding the results, an acceptable consistency is observed for all models with the experimental data. The current study truly demonstrates that applying single-phase model to simulate and evaluate the laminar flow of CuO–water nanofluid inside microchannels with uniform wall temperature is more modest, precise and reliable compared with two-phase models.

The effects of vegetation distribution pattern on overland flow

AbstractSoil erosion is a major environmental problem. Vegetation, on the other hand, plays an important role in controlling soil erosion. The goal of the study is to examine the effects of the distribution pattern of vegetation on water flow. The vegetation parameters involved included the direction of plant rows, plant stem diameter and row spacing. To study how vegetation affects the flow of water on slopes, flume simulation experiments were conducted using three different plant row directions, three different plant diameters and three row spacing. Experimental slope is fixed, slope ratio of 1.0%. The hydraulic characteristics of the slope under the three vegetation distribution patterns are explored. The results showed that the pattern of vegetation distribution significantly affected the resistance of vegetation to water flow and pattern on this slope. When the angle (θ) between plant row and water flow directions decreased, the plant diameter (d) increased, or the row spacing (a × a) decreased, the Darcy–Weisbach resistance coefficient (f) for water flow became larger. Simultaneously, the Reynolds and Froude numbers (Re and Fr) both became smaller. In experimental procedure condition, the change rate of f, Re and Fr were analysed by linear regression, the θ decreased every 10°, the average increase rate of f was 6.6%, the average decrease rate of Re and Fr were 2.0 and 3.0%. The d increased every 0.001 m, the average increase rate of f was 41.6%, the average decrease rate of Re and Fr were 11.2 and 12.2%. The a × a decreased every 0.01 m, the average increase rate of f was 45.2%, the average decrease rate of Re and Fr were 11.7 and 10.7%. The flow depth h increased every 0.01 m, the average increase rate of f and Re were 13.6 and 25.2%, and the average decrease rate of Fr was 10.4%. The experimental procedure results will be valuable for not only revealing the hydraulic characteristics of flow over vegetation land, but also the optimisation of the distribution of vegetation on a slope.

Flow regimes at grid drop-type dissipators caused by changes in tail-water depth

ABSTRACTA comprehensive set of experiments was performed on grid drop-type dissipators in a rectangular open channel. The study aims to examine the adjustment and boundaries of different flow regimes as well as the variation of flow hydraulic characteristics downstream of a grid drop-type dissipator, caused by the gradual alteration of the tail-water depth. Considering an upstream subcritical flow approaching the grid drop-type dissipator, the tail-water depths were gradually changed until they exceeded the height of the vertical drop leading to a submerged flow condition. The flow regimes and hydraulic characteristics of the flow downstream of the drop were precisely inspected using flow visualization techniques. Results indicated that two key flow regimes, namely “bubble impinging jet flow regime” and “surface flow regime”, arise because of the changes made in the tail-water depth. Accordingly, empirical equations were derived for estimating the boundaries of flow regimes as well as the hydraulic characteristics of flow downstream of the grid drop-type dissipators.

On hydraulic analysis of the main parameters of longitudinalcirculating flow

Recently in practice of engineering hydraulic structures spillways with a longitudinal-circulating flow are applied. The distinguished properties of longitudinal-circulating flows are a unique example of compatibility of flow type with technological purpose of a spillway structure. The hydraulic characteristics of flow (throughput capacity, velocity distribution, pressure distribution, cavitation analysis, etc.) are determined on the basis of the calculation methods developed in the above studies, namely for: longitudinal flow using the known standard calculation methods [1]; longitudinal-circulating flow interacting with solid boundaries of spillway [1-4]; longitudinal-circulating flow in the form of a swirling stream in the aquatic environment or in the air [2; 3]; the flow arising from the interaction of unidirectional longitudinal-circulating flows [4; 5]; the flow arising from the interaction of oppositely swirling coaxial flows [3]. In this paper, the authors consider the longitudinal-circulating flow of viscous incompressible fluid in a closed channel and in a jet using a velocity wurf linking the three components of velocity U , V and W .

The regularities of resistance and flow in pipes and wide channels

The data of hydraulic characteristics of flow are required to be more accurate to increase reliability and accident-free work of water conducting systems and hydraulic structures. One of the problems in hydraulic calculations is the determination of friction loss that is associated with the distribution of velocities over the cross section of the flow. The article presents a comparative analysis of the regularities of velocity distribution based on the logarithmic velocity profile and hydraulic resistance in pipes and open channels. It is revealed that the Karman parameter is associated with the second turbulence constant and depend on the hydraulic resistance coefficient. The research showed that the behavior of the second turbulence constant in the velocity profile is determined mainly by the Karman parameter. The attached illustrations picture the dependence of logarithmic velocity profile parameters based on different values of the hydraulic resistance coefficient. The results of the calculations were compared to the experimental-based Nikuradze formulas for smooth and rough pipes.

Shape optimization of bi-directional flow passage components based on a genetic algorithm and computational fluid dynamics

ABSTRACTThe inlet/outlet is an important part of a water conveyance system in a pumped storage power station (PSPS). Its hydraulic characteristics are directly related to the operation and economic benefit of the PSPS. Frequent changes between inflow and outflow operations pose significant challenges in the design of the inlet/outlet diffusion segment shape. In this study, an effective optimization method, including three-dimensional parametric modelling, computational fluid dynamics and a genetic algorithm, is introduced and coupled to the design of the diffusion segment shape. The hydraulic characteristics of bi-directional flow, including the head loss, velocity uneven distribution and uneven discharge distribution, are selected as the objective function in the optimization method. Using this method, the recommended shape of the inlet/outlet is studied and its hydraulic characteristics are discussed. The results indicate that the optimized inlet/outlet has better performance.

Relationships of the hydraulic flow characteristics with the transport of soil organic carbon and sediment loss in the Loess Plateau

Erosive power is characterized by the hydraulic forces of moving water and determines the water transport capacity of soil organic carbon (SOC) and sediment. Understanding the relationships of hydraulic flow characteristics (flow velocity and depth, shear stress and stream power) with the transport of sediments and SOC will improve the understanding of the transport mechanism of sediment and SOC, which in turn will improve SOC prediction. To address this issue, two loess soils (one silt loam and one silty clay) were selected, and 32 simulated rainfall experiments were conducted in a 1m by 5m soil pan at a varying slopes (10°, 15°, 20°, and 25°) and two rainfall intensities (90mmh−1 and 120mmh−1). The results showed that the flow velocities had significant positive linear relationships with the SOC concentrations (P<0.001) under the rainfall intensity of 90mmh−1 and that the flow velocities also had close relationships with the suspension transport of clay particles in the fine-textured soil and the rolling transport of light large aggregates in the coarse-textured soil. Under the rainfall intensity of 120mmh−1, the runoff depth was positively correlated with the SOC concentrations due to the suspension transport of the clay particles and was negatively correlated with the sediment concentration. The slope had a greater effect on the sediment and SOC loss of the coarse-textured soil than those of the fine-textured soil. Additionally, the stream power was a better descriptor of the sediment loss in the loess soils than shear stress. Overall, both the soil texture and rainfall intensity changed the relationships of the hydraulic flow characteristics with the sediment and SOC loss. Finally, the results of our study will provide important knowledge for improving or building hydraulic-based SOC and sediment loss models.

Effects of simulated submerged and rigid vegetation and grain roughness on hydraulic resistance to simulated overland flow

Better understanding of the role of vegetation and soil on hydraulic resistance of overland flow requires quantitative partition of their interaction. In this paper, a total of 144 hydraulic flume experiments were carried out to investigate the hydraulic characteristics of overland flow. Results show that hydraulic resistance is negatively correlated with Reynolds number on non-simulated vegetated slopes, while positively on vegetated slopes. The law of composite resistance agrees with the dominant resistance, depending on simulated vegetation stem, surface roughness, and discharge. Surface roughness has greater influence on overland flow resistance than vegetation stem when unit discharge is lower than the low-limited critical discharge, while vegetation has a more obvious influence when unit discharge is higher than the upper-limited critical discharge. Combined effects of simulated vegetation and surface roughness are unequal to the sum of the individual effects through t-test, implying the limitation of using linear superposition principle in calculating overland flow resistances under combined effect of roughness elements.