Linear Stability Prediction of Vortex Structures on High Pressure Turbine Blades

Zauner, Markus; Sandham, Neil D.; Wheeler, Andrew P. S.; Sandberg, Richard D.

doi:10.3390/ijtpp2020008

Cited by 13 publications

(12 citation statements)

References 7 publications

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“…DNS data has firstly been analysed in terms of local and global linear stability in order to investigate the transonic buffet mechanism of a narrow wing section at α = 4 • and Mach and Reynolds numbers of M = 0.7 and Re = 500,000, respectively. Local linear stability theory associates KH roll-ups seen in the DNS with convective linear instabilities, as has been previously observed for a high-pressure turbine vane at similar freestream conditions [30]. The shear layer on the suction side shows significantly different characteristics during high-and low-lift phases.…”

Section: Resultssupporting

confidence: 68%

“…The frequency range agrees with Kelvin-Helmholtz instabilities reported by [16] for the present test case. Similar flow structures (St ≈ 25) in a simulation of a high-pressure turbine vane could also be associated with linear instabilities by [30]. The wavy pattern is likely to be due to upstream-moving pressure waves interacting with the boundary layer combined with short time averaging.…”

Section: Local and Global Linear Stabilitymentioning

confidence: 64%

“…Applying a temporal approach, the solution of an eigenvalue problem provides the temporal growth rate corresponding to an angular frequency for a given set of streamwise and spanwise wave numbers. More details on this methodology, including a full derivation of the equations, flow assumptions, and application to time-and space-averaged baseflows around airfoils are provided by [27] and [30]. For the global stability analysis, the linearised NSE are solved directly, applying a normal-mode ansatz with prescribed spanwise wavenumbers.…”

Section: Methodsmentioning

confidence: 99%

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Modal Analysis of a Laminar-Flow Airfoil under Buffet Conditions at Re = 500,000

Zauner

Sandham

2019

Flow Turbulence Combust

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An airfoil undergoing transonic buffet exhibits a complex combination of unsteady shockwave and boundary-layer phenomena, for which prediction models are deficient. Recent approaches applying computational fluid mechanics methods using turbulence models seem promising, but are still unable to answer some fundamental questions on the detailed buffet mechanism. The present contribution is based on direct numerical simulations of a laminar flow airfoil undergoing transonic buffet at Mach number M = 0.7 and a moderate Reynolds number Re = 500,000. At an angle of attack α = 4 • , a significant change of the boundary layer stability depending on the aerodynamic load of the airfoil is observed. Besides Kelvin Helmholtz instabilities, a global mode, showing the coupled acoustic and flow-separation dynamics, can be identified, in agreement with literature. These modes are also present in a dynamic mode decomposition (DMD) of the unsteady direct numerical solution. Furthermore, DMD picks up the buffet mode at a Strouhal number of St = 0.12 that agrees with experiments. The reconstruction of the flow fluctuations was found to be more complete and robust with the DMD analysis, compared to the global stability analysis of the mean flow. Raising the angle of attack from α = 3 • to α = 4 • leads to an increase in strength of DMD modes corresponding to type C shock motion. An important observation is that, in the present example, transonic buffet is not directly coupled with the shock motion.

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Section: Resultssupporting

confidence: 68%

Section: Local and Global Linear Stabilitymentioning

confidence: 64%

Section: Methodsmentioning

confidence: 99%

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Modal Analysis of a Laminar-Flow Airfoil under Buffet Conditions at Re = 500,000

Zauner

Sandham

2019

Flow Turbulence Combust

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“…The Smagorinsky model is the simplest and most robust option for the subgrid-scale modeling in LES computations [17]. Despite the well-known dissipative issues of this model, especially for shock flow situations, a wide number of researchers are still relying on this SGS model for their LES computations, even in complex bladed geometries for turbomachinery (rotor/stator stages), because of its simplicity and versatility [18][19][20]. Moreover, it is recognized to still provide a good prediction of the important flow patterns and also an accurate reproduction of secondary flow features in complex flows [21].…”

Section: Numerical Schemementioning

confidence: 99%

Wall-Resolved LES Modeling of a Wind Turbine Airfoil at Different Angles of Attack

Solís-Gallego

Díaz

Oro

et al. 2020

JMSE

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Noise has arisen as one of the main restrictions for the deployment of wind turbines in urban environments or in sensitive ecosystems like oceans for offshore and coastal applications. An LES model, adequately planned and resolved, is useful to describe the noise generation mechanisms in wind turbine airfoils. In this work, a wall-resolved LES model of the turbulent flow around a typical wind turbine airfoil is presented and described in detail. The numerical results obtained have been validated with hot wire measurements in a wind tunnel. The description of the boundary layer over the airfoil provides an insight into the main noise generation mechanism, which is known to be the scattering of the vortical disturbances in the boundary layer into acoustic waves at the airfoil trailing edge. In the present case, 2D wave instabilities are observed in both suction and pressure sides, but these perturbations are diffused into a turbulent boundary layer prior to the airfoil trailing edge, so tonal noise components are not expected in the far-field noise propagation. The results obtained can be used as input data for the prediction of noise propagation to the far-field using a hybrid aeroacoustic model.

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“…Zauner et al [6] extracted velocity profiles from time-and span-averaged direct numerical simulation data, describing the flow over a high-pressure turbine vane linear cascade near engine-scale conditions with reduced inlet disturbance levels. Based on these velocity profiles, local as well as non-local linear stability analysis of the boundary-layer over the suction side of the vane were carried out in order to characterize a linearly unstable region close to the trailing edge.…”

mentioning

confidence: 99%

Excellence in Turbomachinery Research: The Best of the 12th European Turbomachinery Conference

Manna

2018

IJTPP

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Turbomachines are undoubtedly the key components of all power systems, and despite the impressive advances of the past century, there seems to still be room for improvement. While the reduction in the specific fuel consumption directly related to the components efficiency enhancement is the most natural and pursued objective, other aspects progressively acquire importance. Noise, life, reliability, and safety, to quote a few examples, require technological leaps that can only stem from solid, well-conceived, fundamental, and applied research. Those concerns are equally shared by the power generation world, the aerospace community, and the automotive one, all mainly focused on efficiency innovations.This Special Issue appearing in the International Journal of Turbomachinery, Propulsion, and Power [1] (www.mdpi.com/journal/ijtpp), collects original research articles addressing advances in computational and measurement techniques as applied to the above mentioned fields for the benefit of the academic and industrial research communities. These manuscripts originate from the 12th European Turbomachinery Conference (ETC12) held in Stockholm (Sweden) in March 2017 under the local coordination of the Swedish Royal Institute of Technology. The conference main objectives are the presentation of the latest developments in the turbomachinery field; the promotion of the transfer of this technology across Europe; and the creation of a forum suitable to disseminate and advertise the results of the research projects funded by the European Commission, as well the resultant benefits from the support by the Commission.The ETC series, started in 1995, is managed and organized by Euroturbo (www.euroturbo.eu), the European Turbomachinery Society, a not-for-profit international scientific organization legally established in February 2012, specifically organized to enhance the dissemination, exchange, and publication of top quality research in the field of turbomachinery. Yet, the policy of the society has always been to seek papers documenting good quality research rather than simply increasing their numbers, so that striving for quality rather than quantity has always been the society's motto.The research works appearing in this Special Issue were selected from a pool of two hundred full manuscripts submitted for review to the ETC12. They represent the outcome of a rigorous review process completed with the help of three independent referees supervised by a senior scientist, who rated them of journal quality.Six of the papers appearing in this issue are of computational nature, two deal with experimental work, one is of theoretical imprinting, and one is of the mixed experimental-computational type.

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Linear Stability Prediction of Vortex Structures on High Pressure Turbine Blades

Cited by 13 publications

References 7 publications

Modal Analysis of a Laminar-Flow Airfoil under Buffet Conditions at Re = 500,000

Modal Analysis of a Laminar-Flow Airfoil under Buffet Conditions at Re = 500,000

Wall-Resolved LES Modeling of a Wind Turbine Airfoil at Different Angles of Attack

Excellence in Turbomachinery Research: The Best of the 12th European Turbomachinery Conference

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