Temat: open-channel flow - Prolib Integro

Skocz do pozycji: 1.

Tytuł:: Numerical analysis of open channel steady gradually varied flow using the simplified Saint-Venant equations
Autorzy:: Artichowicz, W.
Tematy:: dynamic equation
open-channel flow
open-channel networks
steady flow; Pokaż więcej
Wydawca:: Politechnika Gdańska
Powiązania:: https://bibliotekanauki.pl/articles/1934022.pdf Link otwiera się w nowym oknie
Opis:: For one-dimensional open-channel flow modeling, the energy equation is usually used. There exist numerous approaches using the energy equation for open-channel flow computations, which resulted in the development of several very efficient methods for solving this problem applied to channel networks. However, the dynamic equation can be used for this purpose as well. This paper introduces a method for solving a system of non-linear equations by the discretization of the one-dimensional dynamic equation for open-channel networks. The results of the computations using the dynamic and energy equations were compared for an arbitrarily chosen problem. Also, the reasons for the differences between the solution of the dynamic and energy equation were investigated.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 2.

Tytuł:: Experimental Analysis of Relations Between Coherent Turbulent Structures and Formation of Bedforms
Autorzy:: Termini, D.
Sammartano, V.
Tematy:: open channel flow
sediment transport
bed forms
flow turbulence structure; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Budownictwa Wodnego PAN
Powiązania:: https://bibliotekanauki.pl/articles/241077.pdf Link otwiera się w nowym oknie
Opis:: The present paper describes an experimental investigation on the interactions between flow turbulence and sediment motion. During the experiments, detailed measurements of flow velocity components were carried out using an Acoustic Doppler Velocimeter (ADV). The occurrence of turbulent events (inward interaction, ejection, sweep and burst) was verified through conditioned quadrant analysis. The quantitative information on the spatial and temporal evolution of turbulent events was obtained through space-time correlations of the conditioned data. As the primary objective was to analyse how turbulent structures influence formation of bedforms, the spatial scale of turbulent event evolution has been compared with the wavelength of bed-forms (alternate bars) observed on the bed. The analysis has essentially highlighted that such spatial scale compares well with the wavelength of the bars.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 3.

Tytuł:: Lagrangian Model for a Single Saltating Grain in the Near-Wall Region of an Open-Channel Flow
Autorzy:: Czernuszenko, W.
Tematy:: Lagrangian model
open-channel flow
particle-particle interaction; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Budownictwa Wodnego PAN
Powiązania:: https://bibliotekanauki.pl/articles/241181.pdf Link otwiera się w nowym oknie
Opis:: A mathematical model for the continuous saltation of a particle near the granular bed in an open-channel flow is developed in detail. The model is based on the Lagrangian equations governing particle motion, and it takes into account the following forces: drag, lift, gravitation, virtual mass and the force responsible for particle-particle interactions. A model of particle-particle collisions is developed and used to determine the mean impulsive force acting upon a particle flowing and rebounding from the channel bed. The model can simulate the continuous saltation trajectories of a single particle in the near-bed region of turbulent flows, in which particle motion is controlled by collisions. The model has been calibrated and verified with available published data in a rather wide range of grain sizes from 0.53 mm to 15 mm. All parameters, such as lift, drag, restitution, friction coefficients and roughness height, have been set on the basis of a reanalysis of these published data.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 4.

Tytuł:: Numerical simulation of open channel flow between bridge piers
Autorzy:: Szydłowski, M.
Tematy:: numerical simulation
open channel flow
mathematical modeling
bridge piers; Pokaż więcej
Wydawca:: Politechnika Gdańska
Powiązania:: https://bibliotekanauki.pl/articles/1934025.pdf Link otwiera się w nowym oknie
Opis:: Free-surface flow in the vicinity of bridge piers on a fixed channel bed is a classical problem of open-channel hydraulics. This problem is usually analyzed using one-dimensional hydraulic models for steady-flow problems. The aim of this paper is to present a two-dimensional numerical simulation of water flow around obstacles, such as cylinders, which can act as a simplified model of real piers. The depth-averaged Navier-Stokes equations describing unsteady free-surface flow are solved using an explicit scheme of the finite-volume method. The numerical solution prepared for the simulations of unsteady free-surface flows was used here to analyze the case of steady flow. A numerical simulation of flow in the channel with the obstruction was performed for two different inflow discharges determining, respectively, the subcritical and supercritical flow in the cross-section of a channel constriction. In the second simulation, a hydraulic jump was observed downstream of the bridge section. The numerical results were compared with measurements. Water surface profiles were measured for both discharges in the hydraulic laboratory of the Faculty of Civil and Environmental Engineering at Gdansk University of Technology (GUT). Comparisons with laboratory data showed that the proposed approach constitutes a sufficiently accurate and reliable technique for predicting basic flow parameters. The method of two-dimensional modeling of flow in a river channel between bridge piers can be also integrated with the simulation of unsteady flood wave propagation, ensuring a uniform approach to the problem of flood modeling in river valleys. Moreover, a two-dimensional simulation yields detailed information about flow structure near the obstruction, which can be used to better elucidate debris transport and river bed deformation processes.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 5.

Tytuł:: Numerical Modelling of Fish Passage with Turning Pools
Autorzy:: Maniecki, Ł.
Tematy:: open channel flow
fishway
turbulence
numerical model
turning pool; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Budownictwa Wodnego PAN
Powiązania:: https://bibliotekanauki.pl/articles/241474.pdf Link otwiera się w nowym oknie
Opis:: An assessment of operating conditions in a baffled fish passage with pool dimensions of 2:2 3:0 m, and 180 horizontally turning pools, was carried out using numerical computations and a site survey of water flow velocity distribution. Velocity was measured with a PMS electromagnetic flowmeter and a hydrometric current meter in representative cross-sections of the fish passage in the pool centres and in the baffle barrier cross-section area. Numerical computations were also performed for two alternative baffle locations in the fishway. One reflected the actual conditions, and the other was an alternative arrangement designed to improve hydraulic conditions for fish migration. The numerical model used the Large Eddy Simulation (LES) method, which makes it possible to detect large vortexes. The study pays close attention to the velocity field analysis as well as the distribution and sizes of vortexes in the turning pool of the culvert. The results of numerical computations and the site survey show high consistency, and the proposed baffle placement modification significantly improves flow conditions, especially in the entry section of the passage.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 6.

Tytuł:: Lax-Wendroff and McCormack Schemes for Numerical Simulation of Unsteady Gradually and Rapidly Varied Open Channel Flow
Autorzy:: Machalińska-Murawska, J.
Szydłowski, M.
Tematy:: open channel flow
mathematical modeling
numerical simulation
FDM schemes; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Budownictwa Wodnego PAN
Powiązania:: https://bibliotekanauki.pl/articles/973864.pdf Link otwiera się w nowym oknie
Opis:: Two explicit schemes of the finite difference method are presented and analyzed in the paper. The applicability of the Lax-Wendroff and McCormack schemes for modeling unsteady rapidly and gradually varied open channel flow is investigated. For simulation of the transcritical flow the original and improved McCormack scheme is used. The schemes are used for numerical solution of one dimensional Saint-Venant equations describing free surface water flow. Two numerical simulations of flow with different hydraulic characteristics were performed – the first one for the extreme flow of the dam-break type and the second one for the simplified flood wave propagation problem. The computational results are compared to each other and to arbitrary solutions.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 7.

Tytuł:: Hydraulic Loss Coefficients in 1D Flows
Autorzy:: Sawicki, J. M.
Tematy:: hydraulic loss
closed-conduits flows
water hammer
open channel flow; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Budownictwa Wodnego PAN
Powiązania:: https://bibliotekanauki.pl/articles/241418.pdf Link otwiera się w nowym oknie
Opis:: Determination of hydraulic losses is a very important problem, both from the cognitive and practical points of view. For the uniform and steady fluid streams these losses are described by the well known algebraic expressions, containing some experimental coefficients. In technical practice it is commonly assumed, that these coefficients can be applied also for more complex kinds of flow (non-uniform and even unsteady). However, the problem analysis shows that the proper level of conformity between the results of calculations and measurements can be obtained only after a considerable enlargement of the loss coefficient. Investigation of available characteristics of non-uniform and unsteady 1D velocity fields, presented in this article, leads to the conclusion that this enlargement is physically justified and in some cases it is possible to determine correction factors, which enable recalculation of "basic" coefficients into their new values, suitable for more complex models of 1D flows.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 8.

Tytuł:: Experimental Analysis of Horizontal Turbulence of Flow over Flat and Deformed Beds
Autorzy:: Termini, D.
Tematy:: open-channel flow
flow turbulence structure
burst cycle
bed forms
laboratory experiments; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Budownictwa Wodnego PAN
Powiązania:: https://bibliotekanauki.pl/articles/241285.pdf Link otwiera się w nowym oknie
Opis:: Laboratory experiments in a straight flume were carried out to examine the evolution of large-scale horizontal turbulent structures under flat-bed and deformed-bed conditions. In this paper, the horizontal turbulence of flow under these conditions is analyzed and compared. The conditioned quadrant method is applied to verify the occurrence of turbulent events. The distributions of horizontal Reynolds shear stress and turbulent kinetic energy are also presented and discussed. Results show the occurrence of an “initial” sequence of horizontal vortices whose average spatial length scales with the channel width. Under deformed-bed conditions, this spatial length does not change.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 9.

Tytuł:: A turbulence model for 3-d flows with anisotropic structure of turbulence
Autorzy:: Czernuszenko, W.
Rylov, A.
Tematy:: 3D flow
mathematical model
numerical simulation
open channel flow
turbulence model; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Budownictwa Wodnego PAN
Powiązania:: https://bibliotekanauki.pl/articles/241364.pdf Link otwiera się w nowym oknie
Opis:: A new turbulence model for flows in open channels with compound cross-sections is presented. The structure of turbulence in these channels can be anisotropic. This structure is described by the turbulent stress tensor that is presented here as the sum of two tensors, namely, normal and shear stress tensors. The normal and shear turbulent stresses are expressed by the turbulence intensities and the mixing length tensor (MLT), respectively. The turbulence intensities can be learned from measurements or another suitable approaches. One such approach that allows calculating the main component of the normal stresses is presented in the paper. The components of MLT are defined based on a new concept of generic mixing length (GML). The generic mixing length is assumed to depend on both distances; from the nearest wall and from the water surface. To demonstrate how the new model works the basic hydrodynamic equations (parabolic approximation of Reynolds equations) together with the turbulence model are solved. The well-known Patankar and Spalding (1972) algorithm was used when solving these equations. A series of numerical simulations were performed for different components of MLT and different channel geometries.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 10.

Tytuł:: The application of cumulants to flow routing
Autorzy:: Romanowicz, Renata J.
Doroszkiewicz, Joanna
Tematy:: open channel flow
linearized St. Venant equation
analytical solutions
moments
cumulants; Pokaż więcej
Wydawca:: Instytut Meteorologii i Gospodarki Wodnej - Państwowy Instytut Badawczy
Powiązania:: https://bibliotekanauki.pl/articles/108562.pdf Link otwiera się w nowym oknie
Opis:: This paper aims to fill a gap between present and past research approaches to modelling flow in open channels. In particular, a history of the analytical solutions of a linearized St. Venant equation is presented. A solution of the linearized St. Venant equation, describing the response of a river channel to a single impulse forcing, the so called Instantaneous Unit Hydrograph (IUH), can be described using cumulants, defined as the moments of a logarithm of a variable. A comparison of analytical and numerical solutions of flood wave propagation under various flow conditions is given. The river reach of Biała Tarnowska is used as an illustration of both approaches. A practical application of simplified solutions to the emulator of a flood wave propagation is suggested showing a link between theory and practice.
Dostawca treści:: Biblioteka Nauki

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