Separation-induced boundary layer transition: Modeling with a non-linear eddy-viscosity model coupled with the laminar kinetic energy equation

2009 ◽  
Vol 30 (4) ◽  
pp. 617-636 ◽  
Author(s):  
Z. Vlahostergios ◽  
K. Yakinthos ◽  
A. Goulas
Keyword(s):  
Boundary Layer ◽  
Kinetic Energy ◽  
Eddy Viscosity ◽  
Energy Equation ◽  
Boundary Layer Transition ◽  
Viscosity Model ◽  
Layer Transition ◽  
Eddy Viscosity Model ◽  
Non Linear ◽  
Transition Modeling

Osborne Reynolds: Energy Methods in Transition and Loss Production: A Centennial Perspective

1995 ◽  
Vol 117 (1) ◽  
pp. 142-153 ◽  
Author(s):  
J. Moore ◽  
J. G. Moore
Keyword(s):  
Kinetic Energy ◽  
Turbulent Flows ◽  
Three Dimensional ◽  
Boundary Layer Transition ◽  
Turbulence Energy ◽  
Energy Methods ◽  
Layer Transition ◽  
Energy Balance Method ◽  
European Working ◽  
Transition Modeling

Osborne Reynolds’ developments of the concepts of Reynolds averaging, turbulence stresses, and equations for mean kinetic energy and turbulence energy are viewed in the light of 100 years of subsequent flow research. Attempts to use the Reynolds energy-balance method to calculate the lower critical Reynolds number for pipe and channel flows are reviewed. The modern use of turbulence-energy methods for boundary layer transition modeling is discussed, and a current European Working Group effort to evaluate and develop such methods is described. The possibility of applying these methods to calculate transition in pipe, channel, and sink flows is demonstrated using a one-equation, q-L, turbulence model. Recent work using the equation for the kinetic energy of mean motion to gain understanding of loss production mechanisms in three-dimensional turbulent flows is also discussed.

Simulation of Multi-Stage Compressor at Off-Design Conditions

2017 ◽  
Author(s):  
Feng Wang ◽  
Mauro Carnevale ◽  
Luca di Mare ◽  
Simon Gallimore
Keyword(s):  
Mass Flow ◽  
High Speed ◽  
Eddy Viscosity ◽  
Turbulence Models ◽  
Viscosity Model ◽  
Eddy Viscosity Model ◽  
Multi Stage ◽  
Pressure Profiles ◽  
Non Linear ◽  
The Right

Computational Fluid Dynamics (CFD) has been widely used for compressor design, yet the prediction of performance and stage matching for multi-stage, high-speed machines remain challenging. This paper presents the authors’ effort to improve the reliability of CFD in multistage compressor simulations. The endwall features (e.g. blade fillet and shape of the platform edge) are meshed with minimal approximations. Turbulence models with linear and non-linear eddy viscosity models are assessed. The non-linear eddy viscosity model predicts a higher production of turbulent kinetic energy in the passages, especially close to the endwall region. This results in a more accurate prediction of the choked mass flow and the shape of total pressure profiles close to the hub. The non-linear viscosity model generally shows an improvement on its linear counterparts based on the comparisons with the rig data. For geometrical details, truncated fillet leads to thicker boundary layer on the fillet and reduced mass flow and efficiency. Shroud cavities are found to be essential to predict the right blockage and the flow details close to the hub. At the part speed the computations without the shroud cavities fail to predict the major flow features in the passage and this leads to inaccurate predictions of massflow and shapes of the compressor characteristic. The paper demonstrates that an accurate representation of the endwall geometry and an effective turbulence model, together with a good quality and sufficiently refined grid result in a credible prediction of compressor matching and performance with steady state mixing planes.

Numerical Investigation of Low-Reynolds Number Airfoil Flows Using Transition-Sensitive and Fully Turbulent RANS Models

2014 ◽  
Author(s):  
Varun Chitta ◽  
Tausif Jamal ◽  
D. Keith Walters
Keyword(s):  
Boundary Layer ◽  
Turbulent Flows ◽  
Eddy Viscosity ◽  
Boundary Layer Transition ◽  
Transition Flow ◽  
Layer Transition ◽  
Laminar Separation ◽  
Viscosity Models ◽  
Separation Bubbles ◽  
Laminar Separation Bubbles

A numerical analysis is performed to study the pre-stall and post-stall aerodynamic characteristics over a group of six airfoils using commercially available transition-sensitive and fully turbulent eddy-viscosity models. The study is focused on a range of Reynolds numbers from 6 × 104 to 2 × 106, wherein the flow around the airfoil is characterized by complex phenomena such as boundary layer transition, flow separation and reattachment, and formation of laminar separation bubbles on either the suction, pressure or both surfaces of airfoil. The predictive capability of the transition-sensitive k-kL-ω model versus the fully turbulent SST k-ω model is investigated for all airfoils. The transition-sensitive k-kL-ω model used in this study is capable of predicting both attached and separated turbulent flows over the surface of an airfoil without the need for an external linear stability solver to predict transition. The comparison between experimental data and results obtained from the numerical simulations is presented, which shows that the boundary layer transition and laminar separation bubbles that appear on the suction and pressure surfaces of the airfoil can be captured accurately by the use of a transition-sensitive model. The fully turbulent SST k-ω model predicts a turbulent boundary layer on both surfaces of the airfoil for all angles of attack and fails to predict boundary layer transition or separation bubbles. Discrepancies are observed in the predictions of airfoil stall by both the models. Reasons for the discrepancies between computational and experimental results, and also possible improvements in eddy-viscosity models, are discussed.

Non Linear Eddy Viscosity Model Applied to U-Bend Industrial Geometry

2009 ◽  
Author(s):  
Riccardo Mereu ◽  
Emanuela Colombo ◽  
Fabio Inzoli
Keyword(s):  
Eddy Viscosity ◽  
Industrial Applications ◽  
Department Of Energy ◽  
Viscosity Model ◽  
Laboratory Research ◽  
Computational Time ◽  
Complex Flows ◽  
Eddy Viscosity Model ◽  
Non Linear ◽  
Strong Curvature

The use of numerical approach to support design and product development on industrial applications is nowadays quite widespread. Many industrial applications involve turbulent fluid flows, whose modeling still represents the bottleneck for a wider usage of numerical methods. Indeed, the application of the CFD approach to industrial problem has a number of high demanding requirements since it must deal with relatively short computational time, high geometrical complexity and high Reynolds numbers. These industrial constrains nowadays may be partially faced through RANS approach even if poor capability in predicting accurately the fluid dynamics of complex flows still represents their well known weakness. The aim of this work is to provide a model able to improve the prediction of the flow field in complex flows of industrial interest, with special attention to the presence of strong curvature. Therefore, in order to obtain an increase in the accuracy of the results compared with traditional k-ε models, the implementation of a two-equation Non Linear Eddy Viscosity Model (NLEVM) is proposed. The quadratic formulation of this model has already been validated by experimental and DNS data from literature. In the present work the cubic formulation of this model is applied to a strong-curve-geometry of industrial interest. The data are obtained through an experimental facility developed by the CFDLab of the Department of Energy at Politecnico di Milano. The measures are taken in cooperation with the Combustion and Optical Diagnostic Laboratory research group. The comparison between experimental and numerical data is carried out downstream a strong curvature by looking at mean axial velocity profiles and reattachment point prediction.

Numerical Simulation of the Boundary Layer Transition in Turbomachinery Flows

2001 ◽  
Author(s):  
Hans Thermann ◽  
Michael Müller ◽  
Reinhard Niehuis
Keyword(s):  
Boundary Layer ◽  
Separated Flow ◽  
Suction Side ◽  
Boundary Layer Transition ◽  
Test Cases ◽  
Compressor Cascade ◽  
Layer Transition ◽  
Transonic Compressor ◽  
Transition Models ◽  
Transition Modeling

The objective of the presented work is to investigate models which simulate boundary layer transition in turbomachinery flows. This study focuses on separated-flow transition. Computations with different algebraic transition models are performed three-dimensionally using an implicit Navier-Stokes flow solver. Two different test cases have been chosen for this investigation: First, a linear transonic compressor cascade, and second an annular subsonic compressor cascade. Both test cases show three-dimensional flow structures with large separations at the side-walls. Additionally, laminar separation bubbles can be observed on the suction and pressure side of the blades of the annular subsonic cascade whereas a shock-induced separation can be found on the suction side of the blades of the linear transonic cascade. Computational results are compared with experiments and the effect of transition modeling is analyzed. It is shown that the prediction of the boundary layer development can be substantially improved compared to fully turbulent computations when algebraic transition models are applied.

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