Hydraulic Engineering Problems Research Articles

Revised Friction Groups for Evaluating Hydraulic Parameters: Pressure Drop, Flow, and Diameter Estimation

Suitable friction groups are provided for solving three typical hydraulic problems. While the friction group based on viscous forces is used for calculating the pressure drop or head loss in pipes and open channels, commonly referred to as the Type 1 problem in hydraulic engineering, additional friction groups with similar behaviors are introduced for calculating steady flow discharge as the Type 2 problem and, for estimating hydraulic diameter as the Type 3 problem. Contrary to the viscous friction group, the traditional Darcy–Weisbach friction factor demonstrates a negative correlation with the Reynolds number. This results in curves that slope downward from small to large Reynolds numbers on the well-known Moody chart. In contrast, the friction group used here, based on viscous forces, establishes a more appropriate relationship. In this case, the friction and Reynolds number are positively correlated, meaning that both increase or decrease simultaneously. Here, rearranged diagrams for all three mentioned problems show similar behaviors. This paper compares the Moody diagram with the diagram for the viscous force friction group. The turbulent parts of both diagrams are based on the Colebrook equation, with the newly reformulated version using the viscous force friction group. As the Colebrook equation is implicit with respect to friction, requiring an iterative solution, an explicit solution using the Lambert W-function for the reformulated version is offered. Examples are provided for both pipes and open channel flow.

Refined implicit characterization of engineering geology with uncertainties: a divide-and-conquer tactic-based approach

In engineering geology, a reasonable assessment of the spatial distribution of uncertainty in a region is vital in guiding research, saving money, and shortening the period. However, the traditional modeling process requires a lot of manual interaction, and the uncertainty of the geological model cannot be accurately quantified and utilized. This paper proposes a novel implicit geological modeling and uncertainty analysis approach based on the triangular prism blocks, which is divided into data point acquisition, ensemble model with divide-and-conquer tactic (EMDCT), uncertainty analysis, and post-processing. By employing machine learning algorithms, the EMDCT gives superior results for implicit modeling. The sensitivity analysis of the prediction results is further evaluated via information entropy. According to the distribution of uncertainty, supplementary boreholes are selected as additional knowledge to retrain the local components of the model to enhance their performances. The implicit modeling method is applied to real hydraulic engineering problems by employing the EMDCT, and the proposed model has obvious advantages in the implicit geological characterization. The overall accuracy in the working area with sparse boreholes reaches 0.922, which is 0.013 higher than the traditional method. By evaluating the distribution of uncertainty, an accuracy of 0.962 can be achieved, which is equivalent to reducing 10 boreholes.

Simulation of submerged granular flows by development of a two-phase incompressible explicit mesh-free method

The interaction between fluid and sediment particles is widely involved in hydraulic engineering problems. In the current study, an explicit incompressible mesh-free method in the framework of the Moving Particle Semi-implicit (MPS) method is proposed to simulate the interaction between the two phases in submerged conditions. The proposed method solves two sets of the continuity and momentum equations, respectively, for the fluid phase and the sediment phase according to the mixture theory. In the method, the pressure and velocity fields are explicitly calculated for the sediment phase with the solid concentration obtained from the mixture theory, in which a rheology model is used to account for the viscosity and shear stress. The governing equations for the fluid are solved using the predictor–corrector time-splitting scheme and the resulting Poisson equation for pressure is calculated using an explicit scheme. In each loop, the discretized points move according to the velocity of the fluid in the mesh-free Lagrangian approach. The proposed method is used to simulate the submerged granular flows including submerged granular column collapse, submerged granular sliding on slopes, and erodible dam-break flow. In the simulations, the parameters of particle distance and collision distance in the numerical method are investigated. It is found that the flow characteristics in the granular flows are reflected by the proposed method and the simulated free surface and water–sediment interface profiles are in good agreement with experimental observations.

Numerical Study of Flow Downstream a Step with a Cylinder Part 1: Validation of the Numerical Simulations

The backward-facing step flow (BFSF) is a classical problem in fluid mechanics, hydraulic engineering, and environmental hydraulics. The nature of this flow, consisting of separation and reattachment, makes it a problem worthy of investigation. In this study, divided into two parts, the effect of a cylinder placed downstream of the step on the 2D flow structure was investigated. In Part 1, the classical 2D BFSF was validated by using OpenFOAM. The BFSF characteristics (reattachment, recirculation zone, velocity profile, skin friction coefficient, and pressure coefficient) were validated for a step-height Reynolds number in the range from 75 to 9000, covering both laminar and turbulent flow. The numerical results at different Reynolds numbers of laminar flow and four RANS turbulence models (standard k-ε, RNG k-ε, standard k-ω, and SST k-ω) were found to be in good agreement with the literature data. In laminar flow, the average error between the numerical results and experimental data for velocity profiles and reattachment lengths and the skin friction coefficient were lower than 8.1, 18, and 20%, respectively. In turbulent flow, the standard k-ε was the most accurate model in predicting pressure coefficients, skin friction coefficient, and reattachment length with an average error lower than 20.5, 17.5, and 6%, respectively. In Part 2, the effect on the 2D flow structure of a cylinder placed at different horizontal and vertical locations downstream of the step was investigated.

ABOUT THE IMPROVEMENT AND NEW DESIGNS OF HYDROCYCLONE-TYPE APPARATUSES

One of the main problems of hydraulic engineering is the improvement and creation of qualitatively new water intake devices of pumping stations and irrigation machines that increase the ecology of the environment. A variety of types of irrigation pump pumps and irrigation units require a comprehensive solution to many issues. Firstly, irrigation machines should receive purified irrigated water, and secondly, the pumps should undergo minimal wear. The most well-known methods of phase separation - sediment deposition by gravity and filtering do not always meet the demands of practice and do not meet the necessary requirements: small size, compactness of the device, a high degree of separation, and the ability to collect and purify water positionally and in a stationary state or directly when the irrigation unit moves. These problems can be successfully solved by applying the effect of centrifugal phase separation during the rotational movement of two and three phase liquids in hydrocyclone-type apparatuses. Due to the simplicity of design, ease of layout in various technological systems (devices), they have found wide application in the national economy.

Numerical solutions to unsteady filtration problems in hydraulic engineering

Introduction. The authors consider a solution to the unsteady filtration problem, arising in the clay core of a high earth-and-rockfill dam. Towards this end, the authors use the case of the dam at Nurek hydroelectric power plant. The authors provide a review of studies and calculation methods applied to unsteady filtration problems. Plaxis 2D software is used to develop a numerical solution to the filtration problem arising in the clay core of an earth-and-rockfill dam. The authors have solved the problem of its saturation with water in the process of the reservoir filling and operation. A 30-year operation period was considered.
 Materials and methods. The finite element method (FEM) and Plaxis 2D software package were applied to study the unsteady filtration mode using the case of the clay core of Nurek, a high earth-and-rockfill dam. Nowadays, a qualitatively higher level of solutions to such problems is attained by using numerical methods, and, most importantly, the finite element method. The application of software programmes and packages to filtration problem is reduced to solving the main differential equation of the filtration theory, if boundary and initial conditions are available.
 Results. A numerical solution to the filtration problem of the dam’s clay core that consists in its saturation with water in the process of the reservoir filling and operation was obtained. The 30-year period of operation was studied. Only the bottom part of the core was completely saturated with water during this period.
 Conclusions. The authors validated earlier conclusions, made using other methods, about the long-term establishment of the quasi-static filtration mode at similar structures. The discrepancy between the results is explained by earlier assumptions and a better filtration model, developed using Plaxis 2D software package. The model used there allows taking into account a change in the water permeability of soil depending on its water saturation rate.

SETTING THE REAL-TIME FLOOD FORECASTING MODELS IN UKRINA, TINJA AND BRKA UNGAUGED BASINS

<jats:p>Flood forecasting (FF) is one of the most challenging problems in Hydraulic Engineering. It is also most important due to tremendous contribution in reducing economic and life losses that usually occurs during flooding. Major part of the FF system is hydrologic and hydraulic model that simulate runoff and corresponding water levels in rivers, based on the input data that are results from the meteorologic forecasting model. Major uncertainty of the FF systems that operates in real time usually stems from combined hydrologic-hydraulic model, apart from the large uncertainty that comes from the meteorological model. This uncertainty significantly rises when the catchments of interests are ungauged. In this paper, methodology of setting hydrological and hydraulic model that operates in real time FF and early warning system is presented. Case study are ungauged basins of Ukrina, Tinja and Brka, tributaries of Sava River.</jats:p>

Comparison between the Lagrangian and Eulerian Approach for Simulating Regular and Solitary Waves Propagation, Breaking and Run-Up

The present paper places emphasis on the most widely used Computational Fluid Dynamics (CFD) approaches, namely the Eulerian and Lagrangian methods each of which is characterized by specific advantages and disadvantages. In particular, a weakly compressible smoothed particle (WCSPH) model, coupled with a sub-particle scale (SPS) approach for turbulent stresses and a new depth-integrated non-hydrostatic finite element model were employed for the simulation of regular breaking waves on a plane slope and solitary waves transformation, breaking and run-up. The validation of the numerical schemes was performed through the comparison between numerical and experimental data. The aim of this study is to compare the two modeling methods with an emphasis on their performance in the simulation of hydraulic engineering problems.

Comparative analysis of accuracy and efficiency of different contact algorithms

In order to solve contact problems, ANSYS provides a variety of contact algorithms. However, there is no basis for how to select the contact algorithm when solving the contact problem in hydraulic structure engineering. Therefore, this paper introduces the basic concepts of contact algorithms briefly, such as penalty method, lagrange method, augmented lagrange method and L&P method, which are commonly used in ANSYS. Then, different examples are used to compare the four contact algorithms in terms of accuracy, convergence and efficiency. Finally, considering the accuracy, convergence and efficiency, it is suggested to adopt L&P method in hydraulic structure contact analysis.

Professor V. Ye. Timonov – the formation of the scientific worldview

The name of Vsevolod Timonov, an outstanding scientist-engineer, teacher, public figure, and popularizer of science, doctor of technical sciences, Honored worker of science and technology of the RSFSR, professor, is well known to a wide range of domestic and foreign scientists and technicians. Nowadays, the creative worky of the extraordinary personality of the scientist is particularly interesting to researchers for its inexhaustibility and versatility. In his activity, V. Ye. Timonov showed the features of a talented researcher, experimenter, organizer of science, an innovator in solving important theoretical and applied problems of hydraulic engineering. The article covers his early life and activities. This period of life of V. Ye. Timonov allows us to understand and reflect the conditions of the formation of the scientists’ worldview, the factors that influenced the formation of his creative personality, and to analyze the main directions of his activity. And let us note that his 60 years of scientific, pedagogical, and social activity is characterized by exceptional versatility and depth. The outstanding scientist boundlessly devoted to science until the last day, V. Ye. Timonov is the author of more than 700 scientific papers. Among his works are a number of textbooks, manuals, and monographs, which have received wide recognition of scientists of our country and foreign researchers. Several finely written books showcase his multifaceted talent as a memoirist. For more than 50 years V. Ye. Timonov was engaged in pedagogical work at high school. His lectures (at institutes, universities, and in the general public) have always been a huge success. He brought up a whole galaxy of scientists. Vsevolod Yevhenovych devoted a lot of effort and time to the promotion of science, active, purposeful struggle with anti-scientific concepts in hydrobiology, hydrography, hydraulic engineering. Timonov's scientific and organizational activity was also fruitful. A man of great and versatile culture, an eager admirer, and a deep connoisseur of poetry and literature, V. Ye. Timonov himself was a gifted promoter of scientific knowledge.

Experimental and Theoretical Study on Flood Bore Propagation and Forerunner Generation in Dam-Break Flow

Dam-break flows are not only an important practical problem in civil and hydraulic engineering, but also a fundamental problem of fluid mechanics. Due to property damage and the loss of numerous lives, it is critically important to have an exhaustive understanding of the landslide dam-break flow and sedimentation. The main objective of this study is a detailed analysis of the mechanisms of dam-breaking flows through physical and theoretical modeling. Our experimental work was focused on the initial stages of dam-break flow in the water channel, where a thin plate separating water at different levels is impulsively withdrawn in the vertical direction upwards, and as a result, a hydrodynamic bore is formed. The theoretical model of the dam-break flow is based on Benney’s shallow water equations. We separately studied the regimes of a breaking and non-breaking bore front. On the hydrodynamic bore, the laws of conservation of mass, momentum, and energy were required in contrast to the classical solutions of Ritter and Stoker, in which the conservation of energy law was not considered at all. The non-breaking flow includes several zones: a shock wave and a shear vorticity flow after it, a contact surface and a continuous discharge zone. The bore in our solution moves faster than the classical bore, which, in turn, propagates faster than the contact surface. The breaking bore is characterized by the generation of a “mushroom-jet” structure, including a pair of vortices, oppositely directed, and a forerunner formed by the plunging jet directed forward. We found that the forerunner of the breaking bore has a speed significantly higher than the speed of the bore. The experiments carried out in the wave flume of the Tainan Hydraulics Laboratory confirmed the theoretical predictions of the proposed dam breaking flow model for various initial conditions.

Selected applications of an open-source three-dimensional computational fluid dynamic code in hydraulic engineering

Exponential growth of computational power in the past decade on one hand and the success of numerical models in studying hydro-environmental flows on the other hand lead to an increasing usage of this technique in hydraulic engineering problems. In particular, three-dimensional numerical models are becoming the industry standard, especially in problems where capturing three-dimensional flow characteristics are important. Additionally, with availability of open-source computational fluid dynamic (CFD) codes, this type of modelling is more accessible. Among these codes, OpenFOAM (Open Source Field Operation and Manipulation) is a state-of-the-art CFD code with an extensive range of features for engineering and scientific applications. In this paper, selected studies are presented which the authors carried out using OpenFOAM. These studies include a wide range of applications from implementation of the new algorithms to modelling a practical application in hydraulic engineering.

Variation of Coefficient of Friction and Friction Head Losses Along a Pipe with Multiple Outlets

The flow in a pipe having multiple outlets is considered as an advanced problem in hydraulic engineering; many discrepancies were found in the literature, in addition to the lack of experimental and field studies. The main goal of this study is to simulate the flow in a pipe with multiple outlets in order to examine the existing methodologies for estimation of the friction head losses, and to propose a methodology that is based on experimental data. The main physical model in this study consisted of a water supply tank, a pipe with multiple outlets having a piezometer at each outlet. Different pipe diameters were used in this study, the pipe diameters were 25.4 mm (1 in), 38.1 mm (1.5 in), 50.8 (2 in) and 76.2 mm (3 in). The inlet heads used were 1.7 m and 2.2 m. The data collected from different flow conditions were used to assess the variation in the coefficient of friction and friction head losses along the pipe length. It can be concluded that the spacing between any two successive outlets (S) and area ratio (AR = Area of outlet/Area of the main pipe) are the main factors affecting the friction head losses along the pipe. The ratio of total friction head losses along a pipe with outlets having the same properties (length (L), discharge (Q), diameter (d) and material) to a pipe without outlets and having the same properties is called the G factor. The G factor calculated using selected formulae was overestimated in comparison to the calculated G factor obtained from experimental data. For large values of S/d (spacing between outlets/diameter of main pipe), the difference between coefficient of friction in first segment (f1) and last segment (fn) of the multiple outlet pipe was noted to be minimal.

Complex coastal protective measures to protect the sandy beach

The environmental impact of the engineering project was taken into account when carrying out comprehensive studies of shore protection engineering measures for the Lazurnoye region of the Kherson region of Ukraine on the north-western coast of the Black Sea. The optimal configuration of hydrotechnical structures are choosen to protect the beach in the region of the incoming wave impact. The entire coastline of the Lazurnoye region is about 3000 meters. In the course of modelling and numerical experiments, the transfer of bottom sediments to the coast, the evolution of the coastline and beaches, and other coastal processes were studied. The project of comprehensive coastal protection of the Lazurnoye region, presented on the basis of mathematical and hydraulic modelling, has allowed the development of engineering solutions that meet coastal protection and environmental requirements. The most expedient variant of coastal protective measures was the creation of a system of the beachprotected structures capes from sections of the permeable slope-steps designs with wave damping chambers. The presented research results and the solution of many problems of the dynamics of the coastal zone of the sea can be considered as an attempt to manage coastal processes on rather large and complex sections of the coast with a joint solution to the problems of hydraulic engineering, management of water quality in the coastal zone of the sea, and the choice of optimal options with the least impact on the environment.

A CAD/CAE integration technology and its application in hydraulic engineering

The CAD and CAE technologies are usually applied independently in water conservancy projects, and the connection between the design and analysis procedures is not close enough, which greatly reduces the efficiency of the application of these two technologies. Taking a typical pumping station as an example, a CAD/CAE integration technology is studied on and applied for the precise modelling and the simulation calculation of a complex finite element analysis problem in hydraulic engineering, and the parametric technology is utilized for the structural optimal design in this paper. It turns out that the technology can help significantly improve the efficiency of the iterative design-analysis-optimization process and provide a feasible and efficient analysis method for the design of water conservancy projects.

3D Hydrodynamic Modelling Enhances the Design of Tendaho Dam Spillway, Ethiopia

Hydraulic structures are often complex and in many cases their designs require attention so that the flow behavior around hydraulic structures and their influence on the environment can be predicted accurately. Currently, more efficient computational fluid dynamics (CFD) codes can solve the Navier–Stokes equations in three-dimensions and free surface computation in a significantly improved manner. CFD has evolved into a powerful tool in simulating fluid flows. In addition, CFD with its advantages of lower cost and greater flexibility can reasonably predict the mean characteristics of flows such as velocity distributions, pressure distributions, and water surface profiles of complex problems in hydraulic engineering. In Ethiopia, Tendaho Dam Spillway was constructed recently, and one flood passed over the spillway. Although the flood was below the designed capacity, there was an overflow due to superelevation at the bend. Therefore, design of complex hydraulic structures using the state-of- art of 3D hydrodynamic modelling enhances the safety of the structures. 3D hydrodynamic modelling was used to verify the safety of the spillway using designed data and the result showed that the constructed hydraulic section is not safe unless it is modified.

Machine Learning Models for Spring Discharge Forecasting

Nowadays, drought phenomena increasingly affect large areas of the globe; therefore, the need for a careful and rational management of water resources is becoming more pressing. Considering that most of the world’s unfrozen freshwater reserves are stored in aquifers, the capability of prediction of spring discharges is a crucial issue. An approach based on water balance is often extremely complicated or ineffective. A promising alternative is represented by data-driven approaches. Recently, many hydraulic engineering problems have been addressed by means of advanced models derived from artificial intelligence studies. Three different machine learning algorithms were used for spring discharge forecasting in this comparative study: M5P regression tree, random forest, and support vector regression. The spring of Rasiglia Alzabove, Umbria, Central Italy, was selected as a case study. The machine learning models have proven to be able to provide very encouraging results. M5P provides good short-term predictions of monthly average flow rates (e.g., in predicting average discharge of the spring after 1 month, R2=0.991, RAE=14.97%, if a 4-month input is considered), while RF is able to provide accurate medium-term forecasts (e.g., in forecasting average discharge of the spring after 3 months, R2=0.964, RAE=43.12%, if a 4-month input is considered). As the time of forecasting advances, the models generally provide less accurate predictions. Moreover, the effectiveness of the models significantly depends on the duration of the period considered for input data. This duration should be close to the aquifer response time, approximately estimated by cross-correlation analysis.

A simple measuring set-up for the experimental determination of the dynamics of a large particle in the 3D velocity field around a free surface vortex

Vortices are a very common phenomenon to consider in many hydraulic engineering problems, e.g. when designing pump sumps or intake works for turbines. Until now, the focus is on avoiding the development of vortices because of induction of cavitation and air entrainment by a fully developed air core. However, vortices may also be used in a more positive manner e.g. by taking advantage of the capacity to transport (floating) particles to avoid the built up of scum layers in wastewater pump sumps. To the authors’ knowledge only little literature is available in this specific field of research. In order to obtain state-of-the art data on the dynamics of large particles in a free-surface vortex flow field and to examine the vortex transport capacity, a simple but novel 3D-PTV (Particle Tracking Velocimetry) method using 6 iPhones was designed, built, tested and employed to measure the 3D-motion of a large particle in the vortex flow. The experimental set-up, particle detection method and the post-processing of the raw data are described in detail along with some first experimental results. The presented 3D-PTV method showed to be able to obtain data that can be used for detailed analysis of the dynamics of large particles in the vortex flow. The overall standard uncertainty of the particle centre position is in the order of magnitude of 0.1 mm in each direction in a volume of a diameter of 0.6 m and a height of about 1 m, while recording at 240 fps.

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.

Establishment and application of three-dimensional realistic river terrain in the numerical modeling of flow over spillways

AbstractWe present an integrated three-dimensional (3D) spillway model where the realistic and complicated river terrain is implemented by the platform CATIA (Computer Aided Three Dimensional Interactive Application). This integrated 3D spillway model allows for complicated topographic and geomorphic conditions and describes the spatial distribution of the spillway dam (upstream reservoir, downstream river channel and the spillway dam itself) precisely, thus making it a real alternative to the physical model. Furthermore, this model provides the premise and possibility of a full-scale simulation of the spillway flow, that is, it can not only be used to study the hydraulics on the spillway face, but also can be used to study the hydraulics along the downstream river channel and estimate the scour problem associated with both the spillway flow and downstream river channel. In this model, turbulence was simulated using RNG k−ɛ equations. The flow velocity and surface pressure from the numerical model were verified by the data from experiments. Moreover, the river flow was studied and flow velocities downstream were obtained. The scour formed downstream of a ski-jump was also studied in this study on the location and shape of a scour hole. In all, this study provides new approaches for solving relevant hydraulic engineering problems.