Calculation of High-Lift Cascades in Low Pressure Turbine Conditions Using a Three-Equation Model

Pacciani, Roberto; Marconcini, Michele; Fadai-Ghotbi, A.; Lardeau, Sylvain; Leschziner, M. A.

doi:10.1115/1.4001237

Cited by 51 publications

(34 citation statements)

References 31 publications

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“…The code features several turbulence closures ranging from simple algebraic models to one-, two- and three-equation, transition-sensitive, turbulence models. 18…”

Section: Methodsmentioning

confidence: 99%

Evaluation of unsteady computational fluid dynamics models applied to the analysis of a transonic high-pressure turbine stage

Giovannini

Marconcini

Arnone

et al. 2014

Proceedings of the Institution of Mechanical Engineers, Part A:

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This paper presents an efficient ‘Phase-Lagged’ method developed for turbomachinery applications. The method is based on the generalized-shape-correction model. Moving average techniques as well as double-passage domain formulation were adopted in order to reduce memory requirements and improve the model robustness. The model was used to evaluate the aerodynamic performance of the high-pressure transonic turbine stage CT3, experimentally studied at the von Kármán Institute for Fluid Dynamics in the framework of the EU funded TATEF2 project. The results are discussed and compared with both the available experimental data and the results obtained by means of both steady and unsteady scaled full-annulus approaches. Computational requirements of the generalized-shape-correction model are evaluated and discussed showing that nowadays unsteady results can be obtained at an affordable computational cost.

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“…The code features several turbulence closures ranging from simple algebraic models to one-, two- and three-equation, transition-sensitive, turbulence models. 18…”

Section: Methodsmentioning

confidence: 99%

Evaluation of unsteady computational fluid dynamics models applied to the analysis of a transonic high-pressure turbine stage

Giovannini

Marconcini

Arnone

et al. 2014

Proceedings of the Institution of Mechanical Engineers, Part A:

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“…This parameter is used in the laminar fluctuation kinetic energy models of Pacciani et al [90,91]. However, they do not formulate a strict justification for this use.…”

Section: Onset Of Transition In Separated Boundary Layer Statementioning

confidence: 99%

“…The model uses transport equations for turbulent and laminar kinetic energy and dissipation rate, supplemented with an equation for an indicator function. The model is an adapted version of the earlier three-equation model by Pacciani et al [90], specifically for transition in separated state. The symbol I stands for the turbulence indicator function associated with wake turbulence.…”

Section: The K-k L -ω-I Model Of Pacciani Et Almentioning

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 review papers by Sieverding [7] and Langston [8] provide an extensive summary of the results of several decades of investigations on linear cascades. Low-pressure-turbine (LPT) profiles losses have been successfully analyzed with the aid of LES and DNS [9] as well as URANS [10,11]. Koschichow et al [12] used DNS to study the secondary flow dynamics, the associated losses in the attempt to shed more light on this complex flow region.…”

Section: Introductionmentioning

confidence: 99%

LES and RANS Analysis of the End-Wall Flow in a Linear LPT Cascade With Variable Inlet Conditions: Part II — Loss Generation

Marconcini

Pacciani

Arnone

et al. 2018

Volume 2B: Turbomachinery

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In low-pressure-turbines (LPT) at design point around 60–70% of losses are generated in the blade boundary layers far from end-walls, while the remaining 30%–40% is controlled by the interaction of the blade profile with the end-wall boundary layer. Increasing attention is devoted to these flow regions in industrial design processes. Experimental techniques have shed light on the mechanism that controls the growth of the secondary vortices, and scale-resolving CFD have provided a detailed insight into the vorticity generation. Along these lines, this paper discusses the end-wall flow characteristics of the T106 profile with parallel end-walls at realistic LPT conditions, as described in the experimental setup of Duden and Fottner (1997) “Influence of Taper, Reynolds Number and Mach Number on the Secondary Flow Field of a Highly Loaded Turbine Cascade”, P. I. Mech. Eng. A-J. Pow., 211 (4), pp.309–320. The simulations target first the same inlet conditions as documented in the experiments, and determines the impact of the incoming boundary layer thickness by running additional cases with modified incoming boundary layers. Calculations are carried out by both RANS, due to its continuing role as the design verification workhorse, and highly-resolved LES. Part II of the paper focuses on the loss generation associated with the secondary end-wall vortices. Entropy generation and the consequent stagnation pressure losses are analyzed following the aerodynamic investigation carried out in the companion paper. The ability of classical turbulence models generally used in RANS to discern the loss contributions of the different vortical structures is discussed in detail and the attainable degree of accuracy is scrutinized with the help of LES and the available test data. The purpose is to identify the flow features that require further modelling efforts in order to improve RANS/URANS approaches and make them able to support the design of the next generation of LPTs.

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Calculation of High-Lift Cascades in Low Pressure Turbine Conditions Using a Three-Equation Model

Cited by 51 publications

References 31 publications

Evaluation of unsteady computational fluid dynamics models applied to the analysis of a transonic high-pressure turbine stage

Evaluation of unsteady computational fluid dynamics models applied to the analysis of a transonic high-pressure turbine stage

Transition Models for Turbomachinery Boundary Layer Flows: A Review

LES and RANS Analysis of the End-Wall Flow in a Linear LPT Cascade With Variable Inlet Conditions: Part II — Loss Generation

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