Testing of a new algebraic laminar-turbulent transition model on a range of airfoils at moderate Reynolds numbers

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.

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THE INFLUENCE OF FREE AND DISTURBED LAMINAR-TURBULENT TRANSITION FOR THE WORTMANN FX 66-S-196 V1 AND EPPLER E 385 AIRFOILS AT LOW REYNOLDS NUMBERS

Mechanika ◽

10.5755/j01.mech.19.2.4158 ◽

2013 ◽

Vol 19 (2) ◽

Author(s):

L. Naujokaitis ◽

E. Lasauskas

Keyword(s):

Reynolds Numbers ◽

Low Reynolds Numbers ◽

Turbulent Transition ◽

Low Reynolds ◽

Laminar Turbulent Transition

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Recurrent neural network for end-to-end modeling of laminar-turbulent transition

Data-Centric Engineering ◽

10.1017/dce.2021.11 ◽

2021 ◽

Vol 2 ◽

Author(s):

Muhammad I. Zafar ◽

Meelan M. Choudhari ◽

Pedro Paredes ◽

Heng Xiao

Keyword(s):

Neural Network ◽

Recurrent Neural Network ◽

Transition Model ◽

Large Set ◽

Two Dimensional ◽

Turbulent Transition ◽

Wide Range ◽

Network Methods ◽

End To End ◽

Laminar Turbulent Transition

Abstract Accurate prediction of laminar-turbulent transition is a critical element of computational fluid dynamics simulations for aerodynamic design across multiple flow regimes. Traditional methods of transition prediction cannot be easily extended to flow configurations where the transition process depends on a large set of parameters. In comparison, neural network methods allow higher dimensional input features to be considered without compromising the efficiency and accuracy of the traditional data-driven models. Neural network methods proposed earlier follow a cumbersome methodology of predicting instability growth rates over a broad range of frequencies, which are then processed to obtain the N-factor envelope, and then, the transition location based on the correlating N-factor. This paper presents an end-to-end transition model based on a recurrent neural network, which sequentially processes the mean boundary-layer profiles along the surface of the aerodynamic body to directly predict the N-factor envelope and the transition locations over a two-dimensional airfoil. The proposed transition model has been developed and assessed using a large database of 53 airfoils over a wide range of chord Reynolds numbers and angles of attack. The large universe of airfoils encountered in various applications causes additional difficulties. As such, we provide further insights on selecting training datasets from large amounts of available data. Although the proposed model has been analyzed for two-dimensional boundary layers in this paper, it can be easily generalized to other flows due to embedded feature extraction capability of convolutional neural network in the model.

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TURBINE VANE CASCADE HEAT TRANSFER PREDICTIONS USING A MODIFIED VERSION OF THE γ × Reοt % LAMINAR-TURBULENT TRANSITION MODEL

Proceedings of International Symposium on Heat Transfer in Gas Turbine Systems ◽

10.1615/ichmt.2009.heattransfgasturbsyst.370 ◽

2009 ◽

Cited By ~ 3

Author(s):

Alexander Smirnovsky ◽

Evgueni M. Smirnov

Keyword(s):

Heat Transfer ◽

Transition Model ◽

Turbulent Transition ◽

Turbine Vane ◽

Laminar Turbulent Transition

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The flow structure of submerged round jets at low Re numbers

EPJ Web of Conferences ◽

10.1051/epjconf/201919600046 ◽

2019 ◽

Vol 196 ◽

pp. 00046

Author(s):

Vadim Lemanov ◽

Konstantin Sharov ◽

Vitaly Matyunin

Keyword(s):

Experimental Investigation ◽

Transition Zone ◽

Initial Conditions ◽

Longitudinal Velocity ◽

Cylindrical Tube ◽

Reynolds Numbers ◽

Submerged Jet ◽

Round Jets ◽

Turbulent Transition ◽

Laminar Turbulent Transition

An experimental investigation of a laminar-turbulent transition in a round jet flowing from a cylindrical tube with a diameter of 3.2 mm have been carried out. The range of Reynolds numbers in the experiments Re = Ud / v were of 700-12000. The measurements have been carried out via the PIV system. The profiles of average velocities and their pulsations in the laminar-turbulent transition zone have been obtained, as well as axial distributions of the longitudinal velocity and longitudinal velocity pulsations. Based on a comparison with the data of other authors, the effect of the initial conditions on the laminar-turbulent transition in a submerged jet has been shown.

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Modeling Transition for the Cylinder Flow With Verification and Validation

Volume 2: CFD and VIV ◽

10.1115/omae2015-42310 ◽

2015 ◽

Cited By ~ 1

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.

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