A Computational Fluid Dynamics Study of Transitional Flows in Low-Pressure Turbines Under a Wide Range of Operating Conditions

Suzen, Yildirim; Huang, P. G.; Ashpis, David E.; Volino, Ralph J.; Corke, Thomas; Thomas, Flint O.; Lake, James; King, Paul I.

doi:10.1115/1.2218888

Cited by 20 publications

(10 citation statements)

References 25 publications

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“…However, several studies like the ones of Menter et al [11], Langtry et al [12], Kožulović et al [13], and Suzen et al [14] have shown that they can be inefficient, or barely adequate when dealing with flows affected by separationinduced transition mechanisms. A number of approaches have been proposed to address this problem.…”

Section: Introductionmentioning

confidence: 99%

An assessment of the laminar kinetic energy concept for the prediction of high-lift, low-Reynolds number cascade flows

Pacciani

Marconcini

Arnone

et al. 2011

Proceedings of the Institution of Mechanical Engineers, Part A:

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Abstract:The laminar kinetic energy (LKE) concept has been applied to the prediction of lowReynolds number flows, characterized by separation-induced transition, in high-lift airfoil cascades for aeronautical low-pressure turbine applications. The LKE transport equation has been coupled with the low-Reynolds number formulation of the Wilcox's k À ! turbulence model. The proposed methodology has been assessed against two high-lift cascade configurations, characterized by different loading distributions and suction-side diffusion rates, and tested over a wide range of Reynolds numbers. The aft-loaded T106C cascade is studied in both high-and low-speed conditions for several expansion ratios and inlet freestream turbulence values. The front-loaded T108 cascade is analysed in high-speed, low-freestream turbulence conditions. Numerical predictions with steady inflow conditions are compared to measurements carried out by the von Kármán Institute and the University of Cambridge. Results obtained with the proposed model show its ability to predict the evolution of the separated flow region, including bubble-bursting phenomenon and the formation of open separations, in high-lift, low-Reynolds number cascade flows.

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Section: Introductionmentioning

confidence: 99%

An assessment of the laminar kinetic energy concept for the prediction of high-lift, low-Reynolds number cascade flows

Pacciani

Marconcini

Arnone

et al. 2011

Proceedings of the Institution of Mechanical Engineers, Part A:

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“…It was combined with a turbulence indicator function which switches off the production and destruction terms of the turbulence model if separation is detected and switches these again on if the Mayle-criterion for start of transition in separated state (17) is satisfied. Suzen, Huang et al [74,129,130] used an intermittency equation which is a combination of the equations of Steelant and Dick [83] and Cho and Chung [127]. In their model, the intermittency is a multiplier factor of the eddy viscosity by the SST k-ω turbulence model and is used in the Navier-Stokes equations, but the turbulence equations are not modified.…”

Section: Other Transport Modelsmentioning

confidence: 99%

Transition Models for Turbomachinery Boundary Layer Flows: A Review

Dick

Kubacki

2017

IJTPP

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Current models for transition in turbomachinery boundary layer flows are reviewed. The basic physical mechanisms of transition processes and the way these processes are expressed by model ingredients are discussed. The fundamentals of models are described as far as possible, with a common structure of the equations and with emphasis on the similarities between the models. Tests of models reported in the literature are summarized and our own test is added. A conclusion on the performance of models is formulated.Keywords: turbomachinery flows; transition models; boundary layers; bypass transition; separationinduced transition; wake-induced transition; Reynolds-averaged Navier-Stokes; intermittency; laminar kinetic energy Transition MechanismsWith the objective of modelling with Reynolds-averaged Navier-Stokes (RANS) or URANS (unsteady or time-accurate RANS) description of a flow, generally, four types of transition from laminar state to turbulent state in turbomachinery boundary layer flows are distinguished [1,2]. These are: natural transition in attached boundary layer state, bypass transition in attached boundary layer state under a statistically steady mean flow, separation-induced transition in the free shear layer formed by separation of a boundary layer under a statistically steady mean flow, and wake-induced transition due to periodically unsteady impact of wakes on boundary layers in attached or separated state. Despite the vast amount of studies on these transition types during the last 4 or 5 decades, understanding of the mechanisms is still not complete, although large progress has been made in the last decade thanks to direct numerical simulation (DNS) and large-eddy simulation (LES). Hereafter, we summarise the mean mechanisms, taking into account the inherent limitations of modelling with Reynolds-averaged Navier-Stokes description of a flow. This means that secondary effects, which mostly are the least understood and sometimes still are a matter of controversy, are not discussed, because, anyhow these features cannot be represented by RANS or URANS. Natural TransitionUnder a statistically steady mean flow of low turbulence level, transition in an attached boundary layer is initiated by 2D viscosity-dependent Tollmien-Schlichting instability waves, followed by a 3D instability, leading to formation of spanwise periodic hairpin vortices, which, farther downstream, cause breakdown of the laminar layer with generation of turbulent spots. These spots finally merge resulting in the formation of a turbulent boundary layer [1,2]. This type of transition is called natural transition. It is a rather slow process and, under a very low mean-flow turbulence level, as in external Int.

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“…The SST-LR with imposed transition proved superior to the traditional SST with imposed transition in predicting LSB characteristics. As reported by Steelant and Dick [25], Savill [26] found that most low-Reynolds-number turbulence models tend to predict transition too early or too fast.The final method of transition prediction encountered in the literature couples the intermittency ( ), an empirical factor indicating the temporal fraction of turbulent flow during transition, with an algebraic transition onset location and/or transition length correlation [25,[27][28][29][30]. For example, Steelant and Dick [27] followed on the early work by Dhawan and Narasimha [31], and accounted for the growth and transport of turbulent spots via a transport equation for .…”

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confidence: 99%

Validating the URANS shear stress transport γ −Re_θ model for low‐Reynolds‐number external aerodynamics

Counsil

Boulama

2011

Numerical Methods in Fluids

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SUMMARY A numerical investigation on low‐Reynolds‐number external aerodynamics was conducted using the transitional unsteady Reynolds‐averaged Navier–Stokes shear stress transport γ −Reθ model and the ANSYS‐CFX computational fluid dynamics suite. The NACA 0012 airfoil was exposed to chord‐based Reynolds numbers of 5.0 ×104, 1.0 ×105 and 2.5 ×105 at 0°, 4°and 8°angles of attack. Time‐averaged and instantaneous flow features were extracted and compared with fully turbulent shear stress transport results, XFLR5 panel e N method results, and published higher order numerical and experimental studies. The current model was shown to reproduce the complex flow phenomena, including the laminar separation bubble dynamics and aerodynamic performance, with a very good degree of accuracy. The sensitivity of the model to domain size, grid resolution and quality, timestepping scheme, and free‐stream turbulence intensity was also presented. In view of the results obtained, the proposed model is deemed appropriate for modelling low‐Reynolds‐number external aerodynamics and provides a framework for future studies for the better understanding of this complex flow regime. Copyright © 2011 John Wiley & Sons, Ltd.

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A Computational Fluid Dynamics Study of Transitional Flows in Low-Pressure Turbines Under a Wide Range of Operating Conditions

Cited by 20 publications

References 25 publications

An assessment of the laminar kinetic energy concept for the prediction of high-lift, low-Reynolds number cascade flows

An assessment of the laminar kinetic energy concept for the prediction of high-lift, low-Reynolds number cascade flows

Transition Models for Turbomachinery Boundary Layer Flows: A Review

Validating the URANS shear stress transport γ −Re_θ model for low‐Reynolds‐number external aerodynamics

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A Computational Fluid Dynamics Study of Transitional Flows in Low-Pressure Turbines Under a Wide Range of Operating Conditions

Cited by 20 publications

References 25 publications

An assessment of the laminar kinetic energy concept for the prediction of high-lift, low-Reynolds number cascade flows

An assessment of the laminar kinetic energy concept for the prediction of high-lift, low-Reynolds number cascade flows

Transition Models for Turbomachinery Boundary Layer Flows: A Review

Validating the URANS shear stress transport γ −Reθ model for low‐Reynolds‐number external aerodynamics

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Validating the URANS shear stress transport γ −Re_θ model for low‐Reynolds‐number external aerodynamics