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.

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.

scholarly journals The scattering of sound waves by a vortex: numerical simulations and analytical solutions

1994 ◽  
Vol 260 ◽  
pp. 271-298 ◽  
Author(s):  
Tim Colonius ◽  
Sanjiva K. Lele ◽  
Parviz Moin
Keyword(s):  
Boundary Conditions ◽  
Analytical Solutions ◽  
Acoustic Waves ◽  
Stokes Equations ◽  
Spatial Differentiation ◽  
Navier Stokes ◽  
Sound Waves ◽  
Navier Stokes Equations ◽  
Refraction Effect ◽  
Approximate Analytical Solutions

The scattering of plane sound waves by a vortex is investigated by solving the compressible Navier–-Stokes equations numerically, and analytically with asymptotic expansions. Numerical errors associated with discretization and boundary conditions are made small by using high-order-accurate spatial differentiation and time marching schemes along with accurate non-reflecting boundary conditions. The accuracy of computations of flow fields with acoustic waves of amplitude five orders of magnitude smaller than the hydrodynamic fluctuations is directly verified. The properties of the scattered field are examined in detail. The results reveal inadequacies in previous vortex scattering theories when the circulation of the vortex is non-zero and refraction by the slowly decaying vortex flow field is important. Approximate analytical solutions that account for the refraction effect are developed and found to be in good agreement with the computations and experiments.

scholarly journals Turbulence Modeling a Review for Different Used Methods

2021 ◽  
Vol 39 (1) ◽  
pp. 227-234
Author(s):  
Khelifa Hami
Keyword(s):  
Turbulence Modeling ◽  
Stokes Equations ◽  
Turbulence Models ◽  
Simulation Models ◽  
Navier Stokes ◽  
Future Research ◽  
Detached Eddy Simulation ◽  
Navier Stokes Equations ◽  
Eddy Simulation ◽  
Complicated Geometries

This contribution represents a critical view of the advantages and limits of the set of mathematical models of the physical phenomena of turbulence. Turbulence models can be grouped into two categories, depending on how turbulent quantities are calculated: direct numerical simulations (DNS) and RANS (Reynolds Averaged Navier-Stokes Equations) models. The disadvantage of these models is that they require enormous computing power, inaccessible, especially for large and complicated geometries. For this reason, hybrid models (combinations between DNS and RANS methods) have been developed, for example, the LES (“Large Eddy Simulation”) or DES (“Detached Eddy Simulation”) models. They represent a compromise - are less precise than DNS, but more precise than RANS models. The results presented in this contribution will allow and facilitate future research in the field the choice of the model approach necessary for the case studies whatever their difficulty factor.

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.

CFD Analysis for the Turbulent Flow Distribution in a Fuel Assembly with the Split-Type Mixing Vanes by Using the Advanced Scale-Resolving Turbulence Models

2015 ◽  
Vol 752-753 ◽  
pp. 902-907 ◽  
Author(s):  
Gong Hee Lee ◽  
Ae Ju Cheong
Keyword(s):  
Turbulent Flow ◽  
Fuel Assembly ◽  
Turbulence Models ◽  
Measured Data ◽  
Test Facility ◽  
Detached Eddy Simulation ◽  
Axial Velocity Component ◽  
Pressurized Water ◽  
Ansys Cfx ◽  
Significant Difference

In general, the turbulent flow inside PWR (Pressurized Water Reactor) fuel assembly depends on the mixing vane configuration and the pattern of the mixing vane arrangement on the strap of the spacer grid. In this study, in order to examine the turbulent flow structure inside fuel assembly with the split-type mixing vanes, simulations were conducted with the commercial CFD (Computational Fluid Dynamics) software, ANSYS CFX R.14. Two different types of turbulence models, i.e. SAS (Scale-Adaptive Simulation)-SST (Shear Stress Transport) and DES (Detached Eddy Simulation), were used. The predicted results were compared with the measured data from the MATiS-H (Measurement and Analysis of Turbulent Mixing in Subchannels-Horizontal) test facility. Although there were locally differences between the prediction and the measurement, ANSYS CFX R.14 predicted the time averaged velocity field in the reliable level. The predicted horizontal and vertical velocity components were more in agreement with the measured data than the axial velocity component. There was no significant difference in the prediction accuracy of both turbulence models.

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.

Numerical Simulation of a Ceramic Furnace Burner - Capacity of Turbulent and Radiation Models

2009 ◽  
Vol 283-286 ◽  
pp. 243-249
Author(s):  
Anouar Souid ◽  
Wassim Kriaa ◽  
Hatem Mhiri ◽  
Georges Le Palec ◽  
Philippe Bournot
Keyword(s):  
Stokes Equations ◽  
Flow Characteristics ◽  
Turbulence Models ◽  
Modern Society ◽  
Navier Stokes ◽  
Combustion Model ◽  
Radiation Model ◽  
Navier Stokes Equations ◽  
Commercial Code ◽  
Furnace Burner

We intend in this work to model an industrial burner replica of the ceramic tunnel furnace of the Ceramics Modern Society (SOMOCER, TUNISIA). This study aims to evaluate the ability of turbulence and radiation models to predict the dynamics and heat transfer fields. The study is conducted by means of numerical simulations in presence of a reactive flow using the commercial code FLUENT. The 3D Navier-Stokes equations and four species transport equations are solved with the eddy-dissipation (ED) combustion model. We use three turbulence models (k- standard, k- RNG, and RSM) and two radiation models (DTRM and DO). The obtained results demonstrate that the k- standard turbulence model is unable to predict the flow characteristics whereas; the k- RNG and RSM models give a satisfying agreement with the experiments. Suitable results are provided by the DTRM radiation model; whereas, those given by the DO model can be improved.

scholarly journals The flow and flow-induced noise behaviour of a simplified high-speed train bogie in the cavity with and without a fairing

2017 ◽  
Vol 232 (3) ◽  
pp. 759-773 ◽  
Author(s):  
JY Zhu ◽  
ZW Hu ◽  
DJ Thompson
Keyword(s):  
High Speed ◽  
Stokes Equations ◽  
Current Model ◽  
Outer Region ◽  
Surface Shape ◽  
Aerodynamic Noise ◽  
High Speed Train ◽  
Detached Eddy Simulation ◽  
Acoustic Analogy ◽  
Flow Induced Noise

Aerodynamic noise is a significant source for high-speed trains but its prediction in an industrial context is difficult to achieve. In this article, the flow and aerodynamic noise behaviour of a simplified high-speed train bogie at scale 1:10 are studied through numerical simulations. The bogie is situated in a cavity beneath the train and the influence of a bogie fairing on the flow and flow-induced noise that developed around the bogie area is investigated. A two-stage hybrid method is used, which combines the computational fluid dynamics and an acoustic analogy. The near-field unsteady flow is obtained by solving the unsteady three-dimensional Navier–Stokes equations numerically using delayed detached-eddy simulation, and the data are utilised to predict the far-field noise based on the Ffowcs Williams–Hawkings acoustic analogy. Results show that when the bogie is located inside the bogie cavity, the shear layer developed from the leading edges of the cavity interacts strongly with the flow separated from the upstream components of the bogie and the cavity walls. Therefore, a highly turbulent flow is generated within the bogie cavity due to the strong flow impingements and flow recirculations occurring there. For the case without the fairing, the surface shape discontinuity in the bogie cavity along the carbody sidewalls generates strong flow unsteadiness around these regions. When the fairing is mounted in front of the bogie cavity, the flow interactions between the bogie cavity and the outer region are reduced and the development of turbulence outside the fairing is greatly weakened. Based on the predictions of the noise radiated to the trackside using a permeable data surface parallel to the carbody sidewall, it has been found that the bogie fairing is effective in reducing the noise generated in most of the frequency range, and a noise reduction of around 5 dB is achieved in the farfield for the current model case.

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.

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.

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