Modeling of Wake-Induced Transition in Linear Low-Pressure Turbine Cascades

Lardeau, Sylvain; Leschziner, M. A.

doi:10.2514/1.16470

Cited by 19 publications

(5 citation statements)

References 28 publications

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“…The abilities of non-linear eddy-viscosity models for bypass transition in steady flow and for wake-induced transition were investigated by Lardeau et al [103,104]. The predictions of the basic models were found to be qualitatively in good agreement with the experiments, but important quantitative discrepancies were observed.…”

Section: Low-reynolds-number Turbulence Modelssupporting

confidence: 50%

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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Section: Low-reynolds-number Turbulence Modelssupporting

confidence: 50%

Transition Models for Turbomachinery Boundary Layer Flows: A Review

Dick

Kubacki

2017

IJTPP

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“…However, their model retains a data correlation for transition and γ is a prescribed function. Lardeau and Leschziner (2006) applied this model to turbine blades with incident wakes. The base RANS model predicted early transition.…”

Section: Laminar Fluctuationsmentioning

confidence: 99%

Perspectives on the Phenomenology and Modeling of Boundary Layer Transition

Durbin

2017

Flow Turbulence Combust

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This article is a perspective review of boundary layer transition. Both orderly and bypass transition are discussed, but with a decided emphasis on bypass routes. The focus is on transition in a natural, perturbed environment. Then orderly transition occurs through Λ vortices, that develop locally on instability waves. The precursors to bypass transition are boundary layer 'streaks'. Transition proceeds through inner and outer mode secondary instability, leading to patches of turbulence: in zero pressure gradient, bypass transition develops through local, undulatory, outer mode breakdown; in sufficiently adverse pressure gradient, bypass transition proceeds through inner mode instability, which may be of varicose or of helical form.Phenomenology of the creation, growth and breakdown of streaks is surveyed. Theories of shear sheltering, transient and optimal growth, and Orr-Sommerfeld continuous mode resonance are summarized.Recent developments in predictive modeling are summarized. These include laminar fluctuation, and intermittency models.Some open questions are discussed, as are needs for further research.

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“…Walters and Leylek [15,16] and Lardeau et al [17] exploited the LKE concept, originally introduced by Mayle and Schultz [18], to make a two-equation model sensitive to the onset of natural and bypass transition. Examples of successful applications of the LKE approach to LP turbines have been provided by Lardeau and Leschziner [19] and Pacciani et al [20,21]. This article assesses the application of a new LKE model to the calculation of high-lift cascades tested in LP turbine conditions.…”

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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Modeling of Wake-Induced Transition in Linear Low-Pressure Turbine Cascades

Cited by 19 publications

References 28 publications

Transition Models for Turbomachinery Boundary Layer Flows: A Review

Transition Models for Turbomachinery Boundary Layer Flows: A Review

Perspectives on the Phenomenology and Modeling of Boundary Layer Transition

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

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