A Computational Model for Hydraulic Labyrinth Seals

2010 ◽  
Author(s):  
Re´mi Bouderlique ◽  
Franc¸ois Guibault ◽  
Andre´ Garon ◽  
Thi Vu
Keyword(s):  
Turbulence Models ◽  
Francis Turbine ◽  
Leakage Loss ◽  
Labyrinth Seals ◽  
Empirical Prediction ◽  
Ansys Cfx ◽  
Commercial Code ◽  
Viscous Losses ◽  
Flow Through ◽  
Low Reynolds

Every Francis turbine has a thin gap between rotating and non-rotating parts, which prevents contact between the two units. Although necessary, hydraulic seals create energetic losses: some fluid does not flow through the runner (leakage loss) and exerts a torque on the rotor (friction loss). Only analytical and empirical prediction methods of a seal efficiency had been developed before 1980. Numerical methods are now used to predict seals performance. However, most of the studies known to the authors deal with gas labyrinth seals and use the k–ε turbulence model. In hydraulic seals, since the viscous losses in the boundary layer influence the leakage loss, low Reynolds turbulence models appear more appropriate. Our study aims to implement an accurate model to predict losses in labyrinth seals using a low Reynolds model, and validate it using experimental results. The issues of the mesh and boundary conditions are addressed. The commercial code ANSYS CFX 12 is used.

scholarly journals Study on Hydraulic Performances of a 3-Bladed Inducer Based on Different Numerical and Experimental Methods

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
Yanxia Fu ◽  
Yujiang Fang ◽  
Jiangping Yuan ◽  
Shouqi Yuan ◽  
Giovanni Pace ◽  
...  
Keyword(s):  
Boundary Conditions ◽  
Flow Model ◽  
Static Pressure ◽  
Pressure Rise ◽  
Turbulence Models ◽  
Experimental Methods ◽  
Hydraulic Performance ◽  
Outlet Pressure ◽  
Ansys Cfx ◽  
Flow Through

The hydraulic performances of a 3-bladed inducer, designed at Alta, Pisa, Italy, are investigated both experimentally and numerically. The 3D numerical model developed in ANSYS CFX to simulate the flow through the inducer and different lengths of its inlet/outlet ducts is illustrated. The influence of the inlet/outlet boundary conditions, of the turbulence models, and of the location of inlet/outlet different pressure taps on the evaluation of the hydraulic performance of the inducer is analyzed. As expected, the predicted hydraulic performance of the inducer is significantly affected by the lengths of the inlet/outlet duct portions included in the computations, as well as by the turbulent flow model and the locations of the inlet/outlet pressure taps. It is slightly affected by the computational boundary conditions and better agreement with the test data obtained when adopting the k-ω turbulence model. From the point of the pressure tap locations, the pressure rise coefficient is much higher when the inlet/outlet static pressure taps were chosen in the same locations used in the experiments.

Numerical Analysis of Turbulent Flow Over a Wavy Wall in a Channel

2016 ◽  
Author(s):  
Vinicius Martins Segunda ◽  
Scott Ormiston ◽  
Mark Tachie
Keyword(s):  
Turbulent Flow ◽  
Turbulence Models ◽  
Moment Closure ◽  
Recirculation Region ◽  
Wavy Wall ◽  
Viscosity Models ◽  
Ansys Cfx ◽  
Commercial Code ◽  
Flow Phenomena ◽  
Second Moment Closure

A commercial CFD code (ANSYS CFX, release 16.2) is used to predict the turbulent flow phenomena over a wavy wall. The present work will provide numerical simulations of flow in a channel with a wavy lower wall using a variety of turbulence models available in the CFD commercial code. Eddy viscosity models and Second Moment Closure models were used with wall function available. Those turbulence models had different predictions for the flow field, in which were evaluated: velocity profiles, pressure distribution, wall shear stress, recirculation region and turbulence quantities. A comparison between their predictions will be presented. The validation of results is performed by comparison to experimental data from previous studies and also LES simulations.

Numerical Study on the Flow Characteristics of the Francis Turbine With Various Blade Profiles

2013 ◽  
Author(s):  
J.-H. Jeon ◽  
S.-S. Byeon ◽  
Y.-J. Kim
Keyword(s):  
Stokes Equations ◽  
Numerical Study ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Francis Turbine ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Ansys Cfx ◽  
Commercial Code ◽  
Sst Turbulence Model

The Francis turbine is a kind of reaction turbines, which means that the potential energy of water converted to rotational kinetic energy. In this study, the flow characteristics have been investigated numerically in a Francis turbine on the 15 MW hydropower generation with various blade profiles (NACA 65 and NACA 16 series) and discharge angles (14°, 15°, 17°, and 18°), using the commercial code, ANSYS CFX. The k-ω SST turbulence model is employed in the Reynolds averaged Navier-Stokes equations. The computing domain includes the spiral casing, guide vanes, and draft tube, which are discretized with a full three-dimensional mesh system of unstructured tetrahedral shapes. The results showed that the change of blade profiles and discharge angles significantly influenced the performance of the Francis turbine.

scholarly journals Simplified CFD model of coolant channels typical of a plate-type fuel element: an exhaustive verification of the simulations

2019 ◽  
Vol 7 (2B) ◽  
Author(s):  
Javier González Mantecón ◽  
Miguel Mattar Neto
Keyword(s):  
Fuel Element ◽  
Turbulence Models ◽  
Nuclear Research ◽  
Index Method ◽  
Ansys Cfx ◽  
Commercial Code ◽  
Grid Convergence ◽  
Grid Convergence Index ◽  
Type Fuel ◽  
Plate Type

The use of parallel plate-type fuel assemblies is common in nuclear research reactors. One of the main problems of this fuel element configuration is the hydroelastic instability of the plates caused by the high flow velocities. The current work is focused on the hydrodynamic characterization of coolant channels typical of a flat-plate fuel element, using a numerical model developed with the commercial code ANSYS CFX. Numerical results are compared to accurate analytical solutions, considering two turbulence models and three different fluid meshes. For this study, the results demonstrated that the most suitable turbulence model is the k-e model. The discretization error is estimated using the Grid Convergence Index method. Despite its simplicity, this model generates precise flow predictions.

Modeling of Aerodynamic Noise Using Hybrid SAS and DES Methods

2010 ◽  
Author(s):  
Sebastian Rulik ◽  
Slawomir Dykas ◽  
Wlodzimierz Wroblewski
Keyword(s):  
Boundary Conditions ◽  
Acoustic Waves ◽  
Stokes Equations ◽  
Turbulence Models ◽  
Aerodynamic Noise ◽  
Fast Fourier Transformation ◽  
Fast Method ◽  
Detached Eddy Simulation ◽  
Ansys Cfx ◽  
Commercial Code

The purpose of the presented studies is to compare simple and fast CFD methods based on the unsteady Reynolds-Averaged Navier-Stokes equations (uRANS) with the so called hybrid uRANS/LES methods like Detached Eddy Simulation (DES) and Scale Adaptive Simulation (SAS) implemented in the commercial code ANSYS CFX. The goal of this comparison is to find an efficient and relatively fast method for both the flow dynamic and aerodynamic noise prediction in the near and far field, which would be suitable for engineering applications. The CFD calculations were carried out using the commercial code ANSYS CFX 11. The non-reflective boundary conditions and grid stretching were used to avoid the reflections of the acoustic waves from the outer boundaries. The different boundary conditions and turbulence models were used in the calculations. For the acoustic calculations the Fast Fourier Transformation (FFT) was applied to obtain the sound spectrum. The CFD results were compared with the experimental data obtained in references.

Numerical Calculations of the Turbulent Flow Through a Controlled Diffusion Compressor Cascade

1995 ◽  
Vol 117 (2) ◽  
pp. 223-230 ◽  
Author(s):  
Shin-Hyoung Kang ◽  
Joon Sik Lee ◽  
Myung-Ryul Choi ◽  
Kyung-Yup Kim
Keyword(s):  
Reynolds Number ◽  
Control Volume ◽  
Low Reynolds Number ◽  
Turbulence Models ◽  
Compressor Cascade ◽  
Mean Velocity ◽  
Flow Angle ◽  
Controlled Diffusion ◽  
Flow Through ◽  
Low Reynolds

The viscous flow through a controlled diffusion (CD) compressor cascade was calculated and compared with the measured data for two different test conditions. A control volume method was used, which has been developed for a generalized nonorthogonal coordinate system. The discretized equations for the physical covariant velocity components were obtained by an algebraic manipulation of the discretized equations for the Cartesian velocity components. Low Reynolds number k–ε turbulence models were used to obtain the eddy viscosity. The numerical scheme using the low Reynolds number k–ε turbulence model reasonably predicted the general performance, i.e, mean outlet flow angle and loss coefficients. The development of the shear layer along the pressure and suction sides was well estimated, and the physical features found in the experiment were reasonably well confirmed in the simulation. However, the calculated profiles of mean velocity and turbulent kinetic energy in the near wake show considerable disagreement with the measured values.

scholarly journals Simulations of Steady Cavitating Flow in a Small Francis Turbine

2016 ◽  
Vol 2016 ◽  
pp. 1-15 ◽  
Author(s):  
Ahmed Laouari ◽  
Adel Ghenaiet
Keyword(s):  
Draft Tube ◽  
Safety Margin ◽  
Hydraulic Turbine ◽  
Cavitation Number ◽  
Hydrodynamic Performance ◽  
Francis Turbine ◽  
Two Phase ◽  
Ansys Cfx ◽  
Flow Through

The turbulent flow through a small horizontal Francis turbine is solved by means of Ansys-CFX at different operating points, with the determination of the hydrodynamic performance and the best efficiency point. The flow structures at different regimes reveal a large flow eddy in the runner and a swirl in the draft tube. The use of the mixture model for the cavity/liquid two-phase flow allowed studying the influence of cavitation on the hydrodynamic performance and revealed cavitation pockets near the trailing edge of the runner and a cavitation vortex rope in the draft tube. By maintaining a constant dimensionless head and a distributor vane opening while gradually increasing the cavitation number, the output power and efficiency reached a critical point and then had begun to stabilize. The cavitation number corresponding to the safety margin of cavitation is also predicted for this hydraulic turbine.

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