scholarly journals Hydrodynamic Study of the Flows Caused by Dam Break around Downstream Obstacles

2018 ◽  
Vol 12 (1) ◽  
pp. 225-238
Author(s):  
Atabak Feizi
Keyword(s):  
Safety Management ◽  
Flow Characteristics ◽  
Experimental Tests ◽  
3D Models ◽  
Dam Break ◽  
Flood Routing ◽  
Accurate Estimation ◽  
Effective Parameters ◽  
One Dimensional ◽  
The One

Introduction: Studying dam break and the resultant flood routing along with identifying critical areas at the dam downstream are of great importance in safety management of the dam break issues. To reduce the risk of the dam break, an accurate estimation of the effective parameters on the energy dissipation due to the collapse of dams and the flood routing around the downstream natural and artificial obstacles is necessary. Methods: In this research, effects of downstream obstacles (e.g. bridge piers) caused by dam break were investigated on different flood patterns in the flow characteristics. Accordingly, two different geometries of the long and wide reservoirs were considered in the experimental tests and 3D numerical simulations. Results and Conclusion: The results indicated the formation of different flow patterns at downstream of the long and wide reservoirs depends on the reservoir geometry. Due to the alignment of the channel and the reservoir in the long reservoir case, the dominant flow was one-dimensional up to the collision with the pier. Therefore, the one-dimensional solutions, including Ritter analytical solution could be applied in this range. After the flow passes through the pier, due to the formation of the wake vortices, the one-dimensional state was no longer valid. This caused turbulence at the surface of the water, which continued to the end of the channel. In the wide reservoir, from the beginning of the flow entry into the channel until its moment of collision with the pier, as well as passing through it, the flow lost its one-dimensional state. In such a case, the use of 3D models was necessary to achieve the appropriate accuracy.

scholarly journals Comparison of numerical schemes of river flood routing with an inertial approximation of the Saint Venant equations

RBRH ◽  
2018 ◽  
Vol 23 (0) ◽  
Author(s):  
Alice César Fassoni-Andrade ◽  
Fernando Mainardi Fan ◽  
Walter Collischonn ◽  
Artur César Fassoni ◽  
Rodrigo Cauduro Dias de Paiva
Keyword(s):  
Numerical Stability ◽  
Flood Routing ◽  
Computational Time ◽  
Numerical Schemes ◽  
Time Step ◽  
Simple Formulation ◽  
One Dimensional ◽  
Saint Venant Equations ◽  
Original Scheme ◽  
The One

ABSTRACT The one-dimensional flow routing inertial model, formulated as an explicit solution, has advantages over other explicit models used in hydrological models that simplify the Saint-Venant equations. The main advantage is a simple formulation with good results. However, the inertial model is restricted to a small time step to avoid numerical instability. This paper proposes six numerical schemes that modify the one-dimensional inertial model in order to increase the numerical stability of the solution. The proposed numerical schemes were compared to the original scheme in four situations of river’s slope (normal, low, high and very high) and in two situations where the river is subject to downstream effects (dam backwater and tides). The results are discussed in terms of stability, peak flow, processing time, volume conservation error and RMSE (Root Mean Square Error). In general, the schemes showed improvement relative to each type of application. In particular, the numerical scheme here called Prog Q(k+1)xQ(k+1) stood out presenting advantages with greater numerical stability in relation to the original scheme. However, this scheme was not successful in the tide simulation situation. In addition, it was observed that the inclusion of the hydraulic radius calculation without simplification in the numerical schemes improved the results without increasing the computational time.

Modeling of Wall Friction for Multispecies Solid-Gas Flows

1986 ◽  
Vol 108 (4) ◽  
pp. 486-488 ◽  
Author(s):  
E. D. Doss ◽  
M. G. Srinivasan
Keyword(s):  
Shear Stress ◽  
Flow Model ◽  
Flow Characteristics ◽  
Wall Friction ◽  
Gas Flows ◽  
Two Phase ◽  
One Dimensional ◽  
Friction Models ◽  
Wall Interaction ◽  
The One

The empirical expressions for the equivalent friction factor to simulate the effect of particle-wall interaction with a single solid species have been extended to model the wall shear stress for multispecies solid-gas flows. Expressions representing the equivalent shear stress for solid-gas flows obtained from these wall friction models are included in the one-dimensional two-phase flow model and it can be used to study the effect of particle-wall interaction on the flow characteristics.

A Component-Wise Approach to Analyse a Composite Launcher Structure Subjected to Loading Factor

2016 ◽  
Author(s):  
Tommaso Cavallo ◽  
Alfonso Pagani ◽  
Enrico Zappino ◽  
Erasmo Carrera
Keyword(s):  
Composite Structures ◽  
Computational Cost ◽  
Free Vibration Analysis ◽  
High Strength ◽  
3D Models ◽  
Advanced Materials ◽  
Space Structures ◽  
One Dimensional ◽  
Computational Costs ◽  
The One

The space structures are realized by combining skin and reinforced components, such as longitudinal reinforcements called stringers and transversal reinforcements called ribs. These reinforced structures allow two main design requirements to be satisfied, the former is the light weight and the latter is a high strength. Solid models (3D) are widely used in the Finite Element Method (FEM) to analyse space structures because they have a high accuracy, in contrast they also have a high number of degrees of freedoms (DOFs) and huge computational costs. For these reasons the one-dimensional models (1D) are gaining success as alternative to 3D models. Classical models, such as Euler-Bernoulli or Timoshenko beam theories, allow the computational cost to be reduced but they are limited by their assumptions. Different refined models have been proposed to overcome these limitations and to extend the use of 1D models to the analysis of complex geometries or advanced materials. In this work very complex space structures are analyzed using 1D model based on the Carrera Unified Formulation (CUF). The free-vibration analysis of isotropic and composite structures are shown. The effects of the loading factor on the natural frequencies of an outline of launcher similar to the Arian V have been investigated. The results highlight the capability of the present refined one-dimensional model to reduce the computational costs without reducing the accuracy of the analysis.

Modeling Shrouded Stator Cavity Flows in Axial-Flow Compressors

1999 ◽  
Vol 122 (1) ◽  
pp. 55-61 ◽  
Author(s):  
S. R. Wellborn ◽  
I. Tolchinsky ◽  
T. H. Okiishi
Keyword(s):  
Flow Analysis ◽  
Flow Characteristics ◽  
Axial Flow ◽  
Analysis Tool ◽  
Cavity Flows ◽  
Dimensional Model ◽  
Primary Flow ◽  
One Dimensional ◽  
Stage Matching ◽  
The One

Experiments and computational analyses were completed to understand the nature of shrouded stator cavity flows. From this understanding, a one-dimensional model of the flow through shrouded stator cavities was developed. This model estimates the leakage mass flow, temperature rise, and angular momentum increase through the cavity, given geometry parameters and the flow conditions at the interface between the cavity and primary flow path. This cavity model consists of two components, one that estimates the flow characteristics through the labyrinth seals and the other that predicts the transfer of momentum due to windage. A description of the one-dimensional model is given. The incorporation and use of the one-dimensional model in a multistage compressor primary flow analysis tool is described. The combination of this model and the primary flow solver was used to reliably simulate the significant impact on performance of the increase of hub seal leakage in a twelve-stage axial-flow compressor. Observed higher temperatures of the hub region fluid, different stage matching, and lower overall efficiencies and core flow than expected could be correctly linked to increased hub seal clearance with this new technique. The importance of including these leakage flows in compressor simulations is shown. [S0889-504X(00)00501-8]

Predictable Model for Characteristics of One-Dimensional Solid-Gas-Liquid Three-Phase Mixtures Flow Along a Vertical Pipeline With an Abrupt Enlargement in Diameter

1999 ◽  
Vol 121 (2) ◽  
pp. 330-342 ◽  
Author(s):  
Natsuo Hatta ◽  
Masaaki Omodaka ◽  
Fumitaka Nakajima ◽  
Takahiro Takatsu ◽  
Hitoshi Fujimoto ◽  
...  
Keyword(s):  
Gas Flow ◽  
Sudden Change ◽  
Flow Characteristics ◽  
Point Of View ◽  
Solid Particles ◽  
Governing Equations ◽  
One Dimensional ◽  
Three Phase ◽  
Experimental Values ◽  
The One

This paper treats the numerical analysis of the rising process of a solid-gas-liquid three-phase mixture along a vertical pipeline with an abrupt enlargement in diameter. The system of governing equations used is based upon the one-dimensional multifluid model and the transitions of gas flow pattern are taken into account in the system of governing equations. For the case of a sudden enlargement in diameter in a coaxial pipeline, the procedure of the numerical calculation to obtain the flow characteristics in the pipeline section after a sudden change in diameter has been established here. Furthermore, in order to confirm the validity of the present theoretical model by the comparison between the calculated and experimental values, the experiments have been made using four kinds of lifting pipes, including the straight one. Thereby, it has been found that the numerical model proposed here gives good fit to the prediction of the flow rates of lifted water and solid particles against that of air supplied for the case of a sudden change in diameter. In addition, the flowing process for each phase has been investigated from a photographic point of view. As a result, we found that the moving process of the solid particles depends strongly upon the volumetric flux of gas-phase as well as the submergence ratio.

scholarly journals 1D and 2D Numerical Modeling for Solving Dam-Break Flow Problems Using Finite Volume Method

2012 ◽  
Vol 2012 ◽  
pp. 1-14 ◽  
Author(s):  
Szu-Hsien Peng
Keyword(s):  
Shallow Water ◽  
Finite Volume Method ◽  
Finite Volume ◽  
Shallow Water Equation ◽  
Dam Break ◽  
Flume Experiments ◽  
One Dimensional ◽  
Dam Break Flow ◽  
The One ◽  
Volume Method

The purpose of this study is to model the flow movement in an idealized dam-break configuration. One-dimensional and two-dimensional motion of a shallow flow over a rigid inclined bed is considered. The resulting shallow water equations are solved by finite volumes using the Roe and HLL schemes. At first, the one-dimensional model is considered in the development process. With conservative finite volume method, splitting is applied to manage the combination of hyperbolic term and source term of the shallow water equation and then to promote 1D to 2D. The simulations are validated by the comparison with flume experiments. Unsteady dam-break flow movement is found to be reasonably well captured by the model. The proposed concept could be further developed to the numerical calculation of non-Newtonian fluid or multilayers fluid flow.

Simplified and Monod kinetics in one-dimensional biofilm reactor modelling: a comparison

2001 ◽  
Vol 43 (1) ◽  
pp. 295-302 ◽  
Author(s):  
L. Bonomo ◽  
G. Pastorelli ◽  
E. Quinto
Keyword(s):  
Liquid Film ◽  
Removal Rate ◽  
Experimental Tests ◽  
Biofilm Reactor ◽  
Kinetic Approach ◽  
Monod Kinetics ◽  
One Dimensional ◽  
Monod Kinetic ◽  
The One ◽  
Reactor Models

A theoretical study supported by some experimental tests has been carried out with the aim of comparing one-dimensional (1-D) biofilm reactor models that use simplified (zero- and first-order) and Monod kinetics. Two different situations have been compared: one rate-limiting substrate with or without liquid film diffusion. The results obtained show that the use of a simplified kinetic approach compared to the Monod kinetic approach determines (1) an unjustified overestimate of the removal rate, especially for thin biofilms, and (2) an excessive overestimate of the liquid film layer thickness necessary to justify high kinetic orders. Even if recent research projects show that biofilm structure is more complicated than the one assumed in the modelling approach used in this study, nevertheless 1-D models still now continue to be the only ones that can reasonably support process engineers in biofilm reactor design, due to their intrinsic simplicity and the need for small sets of input data and parameters that can be obtained theoretically or often empirically.

A Study on Flow in Duct Constructed of Nonwoven Fabric

2003 ◽  
Author(s):  
Masahiko Sakamoto ◽  
Toshiyuki Sawabe ◽  
Kiichiro Izumi
Keyword(s):  
Pipe Flow ◽  
Flow Direction ◽  
Flow Characteristics ◽  
Nonwoven Fabric ◽  
Circular Pipe ◽  
Small Range ◽  
Air Filter ◽  
One Dimensional ◽  
Circular Pipe Flow ◽  
The One

The purpose of this paper is to investigate both the flow characteristics in the sock type of the air filter constructed of nonwoven fabric and the effect on drag reduction in a circular pipe flow by means of the wall coated with nonwoven fabric. The nonwoven fabric used in these experiments is an electret one made of polypropylene, and the fiber distribution is a random laying. The fiber is about 4 μ m in diameter and 0.6 mm in thickness of web. The nonwoven fabric without adhesion of dust was used in these experiments. The pressure distribution along the flow direction was measured for various parameters such as Reynolds number, shape of the air filter, and type of nonwoven fabric. The value of the permeability for the present nonwoven fabric is on the order of 10−11(m2) within the limits of this experiment. The pressure in the sock type of the air filter increases with increasing Re. The experimental results can be explained by Darcy’s law as d/L is larger than 0.1. In the small range of Re the calculated values obtained by the one-dimensional flow model qualitatively agree with those obtained by this experiment. It was proven that the wall coated with the nonwoven fabric is effective to reduce the drag in the circular pipe flow.

scholarly journals Modeling Shrouded Stator Cavity Flows in Axial-Flow Compressors

1999 ◽  
Author(s):  
Steven R. Wellborn ◽  
Ilya Tolchinsky ◽  
Theodore H. Okiishi
Keyword(s):  
Flow Analysis ◽  
Flow Characteristics ◽  
Axial Flow ◽  
Analysis Tool ◽  
Cavity Flows ◽  
Dimensional Model ◽  
Primary Flow ◽  
One Dimensional ◽  
Stage Matching ◽  
The One

Experiments and computational analyses were completed to understand the nature of shrouded stator cavity flows. From this understanding, a one-dimensional model of the flow through shrouded stator cavities was developed. This model estimates the leakage massflow, temperature rise and angular momentum increase through the cavity, given geometry parameters and the flow conditions at the interface between the cavity and primary flow path. This cavity model consists of two components, one which estimates the flow characteristics through the labyrinth seals and the other which predicts the transfer of momentum due to windage. A description of the one-dimensional model is given. The incorporation and use of the one-dimensional model in a multistage compressor primary flow analysis tool is described. The combination of this model and the primary flow solver was used to reliably simulate the significant impact on performance of the increase of hub seal leakage in a twelve stage axial-flow compressor. Observed higher temperatures of the hub region fluid, different stage matching and lower overall efficiencies and core flow than expected could be correctly linked to increased hub seal clearance with this new technique. The importance of including these leakage flows in compressor simulations is shown.

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