Modeling Transition for the Cylinder Flow With Verification and Validation

2015 ◽  
Author(s):  
Guilherme F. Rosetti ◽  
Guilherme Vaz ◽  
André L. C. Fujarra
Keyword(s):  
Turbulence Models ◽  
Reynolds Numbers ◽  
Verification And Validation ◽  
Transition Model ◽  
Physical Conditions ◽  
Turbulent Transition ◽  
Solution Verification ◽  
Sst Turbulence Model ◽  
High Reynolds ◽  
Cylinder Flow

The widespread use of Computational Fluid Dynamics (CFD) tools for engineering applications is certainly positive. However, users must also be aware of the physics of the problems being modeled, as well as the shortcomings of turbulence models in use. New state-of-the-art turbulence models are currently being developed with the aim of enhancing the turbulent flow predictions but the laminar-turbulent transition is still out of the scope of most the models. Bearing upon those ideas, this paper investigates the performance of the Local Correlation Transition Model (LCTM) for the cylinder flow with Solution Verification and Validation at high Reynolds numbers. Furthermore, attention is paid to characteristics of the setup, numerics and physical conditions and we study how these features alter the results. We also bring recommendations on the use of the transition model regarding grid, setup and physical conditions. The results show much better comparison of numerical and experimental results regarding drag coefficients than seen with the SST turbulence model, even with the two-dimensional calculations done herein.

URANS Calculations for Smooth Circular Cylinder Flow in a Wide Range of Reynolds Numbers: Solution Verification and Validation

2012 ◽  
Vol 134 (12) ◽  
Author(s):  
Guilherme F. Rosetti ◽  
Guilherme Vaz ◽  
André L. C. Fujarra
Keyword(s):  
Large Range ◽  
Reynolds Numbers ◽  
Uncertainty Estimation ◽  
Wide Range ◽  
Modeling Errors ◽  
Solution Verification ◽  
Sst Turbulence Model ◽  
Validation Procedure ◽  
Cylinder Flow ◽  
Fixed Cylinder

The flow around circular smooth fixed cylinder in a large range of Reynolds numbers is considered in this paper. In order to investigate this canonical case, we perform CFD calculations and apply verification & validation (V&V) procedures to draw conclusions regarding numerical error and, afterwards, assess the modeling errors and capabilities of this (U)RANS method to solve the problem. Eight Reynolds numbers between Re = 10 and Re=5×105 will be presented with, at least, four geometrically similar grids and five discretization in time for each case (when unsteady), together with strict control of iterative and round-off errors, allowing a consistent verification analysis with uncertainty estimation. Two-dimensional RANS, steady or unsteady, laminar or turbulent calculations are performed. The original 1994 k-ω SST turbulence model by Menter is used to model turbulence. The validation procedure is performed by comparing the numerical results with an extensive set of experimental results compiled from the literature.

Workshop on Verification and Validation of CFD for Offshore Flows

2012 ◽  
Author(s):  
L. Eça ◽  
G. Vaz
Keyword(s):  
Reynolds Numbers ◽  
Verification And Validation ◽  
Test Cases ◽  
Code Verification ◽  
Complex Flow ◽  
Solution Verification ◽  
Manufactured Solution ◽  
Cylinder Flow ◽  
Flow Case ◽  
Paper Submission

This document introduces the Workshop on Verification and Validation (V&V) of CFD for Offshore Flows, to be held during OMAE2012. It presents a brief introduction to the purpose of Verification and Validation with the identification of the goals of code and solution verification and validation. Within this context, three test-cases are proposed: Case-I of code verification, Case-II of solution verification and Case-III of solution verification and validation. Case-I consists on a 3D manufactured solution of an unsteady turbulent flow. Case-II is an exercise on the canonical problem of the infinite smooth circular cylinder flow at different Reynolds numbers. Case-III is a more complex flow around a straked-riser. The participants are asked to perform at least one of these test-cases. The objectives for the three proposed test-cases are presented, together with a detailed description of the numerical settings to be used, and the results to be obtained and sent to the Workshop organization. At the end some considerations on general conditions, paper submission, deadlines, and encouragements are stated.

On the Effects of Turbulence Modeling on the Fluid-Structure Interaction of a Rigid Cylinder

2016 ◽  
Author(s):  
Guilherme Feitosa Rosetti ◽  
Guilherme Vaz ◽  
André Luís Condino Fujarra
Keyword(s):  
Turbulence Modeling ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Reynolds Numbers ◽  
Boundary Layer Separation ◽  
Turbulent Transition ◽  
Moving Cylinder ◽  
Wide Range ◽  
Cylinder Flow ◽  
Laminar Turbulent Transition

The cylinder flow is a canonical problem for Computational Fluid Dynamics (CFD), as it can display several of the most relevant issues for a wide class of flows, such as boundary layer separation, vortex shedding, flow instabilities, laminar-turbulent transition and others. Several applications also display these features justifying the amount of energy invested in studying this problem in a wide range of Reynolds numbers. The Unsteady Reynolds Averaged Navier Stokes (URANS) equations combined with simplifying assumptions for turbulence have been shown inappropriate for the captive cylinder flow in an important range of Reynolds numbers. For that reason, recent improvements in turbulence modeling has been one of the most important lines of research within that issue, aiming at better prediction of flow and loads, mainly targeting the three-dimensional effects and laminar-turbulent transition, which are so important for blunt bodies. In contrast, a much smaller amount of work is observed concerning the investigation of turbulent effects when the cylinder moves with driven or free motions. Evidently, larger understanding of the contribution of turbulence in those situations can lead to more precise mathematical and numerical modeling of the flow around a moving cylinder. In this paper, we present CFD calculations in a range of moderate Reynolds numbers with different turbulence models and considering a cylinder in captive condition, in driven and in free motions. The results corroborate an intuitive notion that the inertial effects indeed play very important role in determining loads and motions. The flow also seems to adapt to the motions in such a way that vortices are more correlated and less influenced by turbulence effects. Due to good comparison of the numerical and experimental results for the moving-cylinder cases, it is observed that the choice of turbulence model for driven and free motions calculations is markedly less decisive than for the captive cylinder case.

URANS Calculations for Smooth Circular Cylinder Flow in a Wide Range of Reynolds Numbers: Solution Verification and Validation

2012 ◽  
Author(s):  
Guilherme F. Rosetti ◽  
Guilherme Vaz ◽  
André L. C. Fujarra
Keyword(s):  
Large Range ◽  
Reynolds Numbers ◽  
Data Repository ◽  
Wide Range ◽  
Solution Verification ◽  
Sst Turbulence Model ◽  
Validation Procedure ◽  
Unsteady Rans ◽  
Cylinder Flow ◽  
Fixed Cylinder

The flow around circular smooth fixed cylinder in a large range of Reynolds numbers is considered in this paper. In order to investigate this canonical case, we perform CFD calculations and apply Verification & Validation (V&V) procedures to draw some conclusions regarding numerical error, and afterwards, assess the modelling errors and capabilities of URANS method to solve this problem. Eight Reynolds numbers between Re = 10 and Re = 5×105 will be presented with five geometrically similar grids and five time steps for each case, together with strict control of iterative and round-off errors, allowing a consistent verification analysis with uncertainty estimation. In these calculations, two-dimensional Unsteady RANS calculations were performed making use of the k–ω SST turbulence model. The Validation procedure is performed by comparing the numerical results with an extensive set of experimental results compiled from the literature and also made available in the VIV Data Repository website (http://oe.mit.edu/VIV/).

Computer Simulation of Flow and Heat Transfer in Bare Tubes at Supercritical Parameters

2016 ◽  
Author(s):  
Alexander Zvorykin ◽  
Sergey Aleshko ◽  
Nataliia Fialko ◽  
Nikolay Maison ◽  
Nataliia Meranova ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Computer Simulation ◽  
Reynolds Number ◽  
Turbulence Models ◽  
Wall Functions ◽  
Physical Conditions ◽  
Flow And Heat Transfer ◽  
Sst Turbulence Model ◽  
High Reynolds ◽  
Vertical Tubes

This paper deals with CFD predictions for flow and heat transfer in supercritical water in a bare tube. Studies were performed using the software FLUENT for upward flows in vertical tubes with heated length of 4 m and an inner diameter of 10 mm at high values of mass flux (G > 1000 kg/m2s). Turbulence models verification data for the given physical conditions are presented. Besides the testing of different turbulence models that are presented in modern catalog of these models is carried out. Namely, the models related to the following three groups: High–Reynolds number k-ε models with wall functions, k-ω models and Low-Reynolds number k-ε models were considered. On the basis of performed studies the best compliance of known experimental data with computer simulation results fits the k-ω SST turbulence model is shown.

Detached-Eddy Simulations and Reynolds-Averaged Navier-Stokes Simulations of Delta Wing Vortical Flowfields

2002 ◽  
Vol 124 (4) ◽  
pp. 924-932 ◽  
Author(s):  
Scott Morton ◽  
James Forsythe ◽  
Anthony Mitchell ◽  
David Hajek
Keyword(s):  
Vortex Breakdown ◽  
Delta Wing ◽  
Turbulence Models ◽  
Reynolds Numbers ◽  
Navier Stokes ◽  
Detached Eddy Simulation ◽  
Fighter Aircraft ◽  
Eddy Simulation ◽  
Reynolds Averaged Navier Stokes ◽  
High Reynolds

An understanding of vortical structures and vortex breakdown is essential for the development of highly maneuverable vehicles and high angle of attack flight. This is primarily due to the physical limits these phenomena impose on aircraft and missiles at extreme flight conditions. Demands for more maneuverable air vehicles have pushed the limits of current CFD methods in the high Reynolds number regime. Simulation methods must be able to accurately describe the unsteady, vortical flowfields associated with fighter aircraft at Reynolds numbers more representative of full-scale vehicles. It is the goal of this paper to demonstrate the ability of detached-eddy Simulation (DES), a hybrid Reynolds-averaged Navier-Stokes (RANS)/large-eddy Simulation (LES) method, to accurately predict vortex breakdown at Reynolds numbers above 1×106. Detailed experiments performed at Onera are used to compare simulations utilizing both RANS and DES turbulence models.

scholarly journals Prediction of the Propeller Performance at Different Reynolds Number Regimes with RANS

2021 ◽  
Vol 9 (10) ◽  
pp. 1115
Author(s):  
João Baltazar ◽  
Douwe Rijpkema ◽  
José Falcão de Campos
Keyword(s):  
Reynolds Number ◽  
Turbulence Model ◽  
Scale Effects ◽  
Open Water ◽  
Reynolds Numbers ◽  
Navier Stokes ◽  
Transition Model ◽  
Sst Turbulence Model ◽  
Propeller Performance ◽  
Selection Of

In this study, a Reynolds averaged Navier-Stokes solver is used for prediction of the propeller performance in open-water conditions at different Reynolds numbers ranging from 104 to 107. The k−ω SST turbulence model and the γ−R˜eθt correlation-based transition model are utilised and results compared for a conventional marine propeller. First, the selection of the turbulence inlet quantities for different flow regimes is discussed. Then, an analysis of the iterative and discretisation errors is made. This work is followed by an investigation of the predicted propeller flow at variable Reynolds numbers. Finally, the propeller scale-effects and the influence of the turbulence and transition models on the performance prediction are discussed. The variation of the flow regime showed an increase in thrust and decrease in torque for increasing Reynolds number. From the comparison between the turbulence model and the transition model, different flow solutions are obtained for the Reynolds numbers between 105 and 106, affecting the scale-effects prediction.

How Turbulence Models Perform in Simulating Pipeflow Response to Targeted Wall-Shapes?

2021 ◽  
Author(s):  
Mehran Masoumifar ◽  
Suyash Verma ◽  
Arman Hemmati
Keyword(s):  
Three Dimensional ◽  
Turbulence Models ◽  
Reynolds Numbers ◽  
Navier Stokes ◽  
Flow Response ◽  
High Reynolds Numbers ◽  
Flow Features ◽  
Rans Models ◽  
Response And Recovery ◽  
High Reynolds

Abstract This study evaluates how Reynolds-Averaged-Navier-Stokes (RANS) models perform in simulating the characteristics of mean three-dimensional perturbed flows in pipes with targeted wall-shapes. Capturing such flow features using turbulence models is still challenging at high Reynolds numbers. The principal objective of this investigation is to evaluate which of the well-established RANS models can best predict the flow response and recovery characteristics in perturbed pipes at moderate and high Reynolds numbers (10000-158000). First, the flow profiles at various axial locations are compared between simulations and experiments. This is followed by assessing the well-known mean pipeflow scaling relations. The good agreement between our computationally predicted data using Standard k-epsilon model and those of experiments indicated that this model can accurately capture the pipeflow characteristics in response to introduced perturbation with smooth sinusoidal axial variations.

scholarly journals Experimental and Numerical Icing Penalties of an S826 Airfoil at Low Reynolds Numbers

Aerospace ◽  
2020 ◽  
Vol 7 (4) ◽  
pp. 46 ◽  
Author(s):  
Richard Hann ◽  
R. Jason Hearst ◽  
Lars Roar Sætran ◽  
Tania Bracchi
Keyword(s):  
Wind Tunnel ◽  
Turbulence Models ◽  
Reynolds Numbers ◽  
Low Reynolds Numbers ◽  
3D Printed ◽  
Numerical Tools ◽  
Low Reynolds ◽  
Performance Penalty ◽  
High Reynolds ◽  
Ice Shapes

Most icing research focuses on the high Reynolds number regime and manned aviation. Information on icing at low Reynolds numbers, as it is encountered by wind turbines and unmanned aerial vehicles, is less available, and few experimental datasets exist that can be used for validation of numerical tools. This study investigated the aerodynamic performance degradation on an S826 airfoil with 3D-printed ice shapes at Reynolds numbers Re = 2 × 105, 4 × 105, and 6 × 105. Three ice geometries were obtained from icing wind tunnel experiments, and an additional three geometries were generated with LEWICE. Experimental measurements of lift, drag, and pressure on the clean and iced airfoils have been conducted in the low-speed wind tunnel at the Norwegian University of Science and Technology. The results showed that the icing performance penalty correlated to the complexity of the ice geometry. The experimental data were compared to computational fluid dynamics (CFD) simulations with the RANS solver FENSAP. Simulations were performed with two turbulence models (Spalart Allmaras and Menter’s k-ω SST). The simulation data showed good fidelity for the clean and streamlined icing cases but had limitations for complex ice shapes and stall.

Efficient Computation of Three-Dimensional Flow in Helically Corrugated Hoses Including Swirl

2009 ◽  
Author(s):  
Bas J. van der Linden ◽  
Emmanuel Ory ◽  
Jacques Dam ◽  
Arris S. Tijsseling ◽  
Maxim Pisarenco
Keyword(s):  
Friction Factor ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Reynolds Numbers ◽  
Efficient Computation ◽  
Time Saving ◽  
Fully Developed Flow ◽  
High Reynolds ◽  
Positive Effect ◽  
Moody Diagram

In this article we propose an efficient method to compute the friction factor of helically corrugated hoses carrying flow at high Reynolds numbers. A comparison between computations of several turbulence models is made with experimental results for corrugation sizes that fall outside the range of validity of the Moody diagram. To do this efficiently we implement quasi-periodicity. Using the appropriate boundary conditions and matching body force, we only need to simulate a single period of the corrugation to find the friction factor for fully developed flow. A second technique is introduced by the construction of an appropriately twisted wedge, which allows us to furthermore reduce the problem by a further dimension while accounting for the Beltrami symmetry that is present in the full three-dimensional problem. We make a detailed analysis of the accuracy and time-saving that this novelty introduces. We show that the swirl inside the flow, which is introduced by the helical boundary, has a positive effect on the friction factor. Furthermore, we give a prediction for which corrugation angles the assumption of axisymmetry is no longer valid. It then has to make place for Beltrami-symmetry if accurate results are required.

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