Linear and Non-Validation of a Linear Multigrid Accelerated Unstructured Navier-Stokes Solver for the Computation of Turbine Blades on Hybrid Grids

Corral, Roque; Escribano, Antonio G.; Gisbert, Fernando; Serrano, Adolfo; Vasco, Cárlos

doi:10.2514/6.2003-3326

Cited by 38 publications

(13 citation statements)

References 15 publications

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“…It is similar in many respects to LN1. The main difference is the use of a linearized Navier-Stokes (LNS) solver called Mu 2 s 2 T − L [57] to calculate the acoustic response instead of LINSUB. The objective of the BBNANEMS code is to work for turbomachine components like turbines, where for example, the infinitely thin flat plate approximation is no longer satisfying.…”

Section: Solution Bb1mentioning

confidence: 99%

“…Certain model features, which are seemingly negligible for the investigated case, may be essential for such cases. [9] free OPTIBRUI OB2 [7] stripwise field [27] cascade of flat swirling flow OB3 [25] plates with χ S,A [12] axial uniform infinite duct with hard walls BBNANEMS BB1 [56] Liepmann cascade of real parallel blades [57] LN1 [55] cascade of flat stripwise free plates with χ S,A [53] swirling flow field…”

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confidence: 99%

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ACAT1 Benchmark of RANS-Informed Analytical Methods for Fan Broadband Noise Prediction: Part II—Influence of the Acoustic Models

et al. 2020

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A benchmark dedicated to RANS-informed analytical methods for the prediction of turbofan rotor–stator interaction broadband noise was organised within the framework of the European project TurboNoiseBB. The second part of this benchmark focuses on the impact of the acoustic models. Twelve different approaches implemented in seven different acoustic solvers are compared. Some of the methods resort to the acoustic analogy, while some use a direct approach bypassing the calculation of a source term. Due to differing application objectives, the studied methods vary in terms of complexity to represent the turbulence, to calculate the acoustic response of the stator and to model the boundary and flow conditions for the generation and propagation of the acoustic waves. This diversity of approaches constitutes the unique quality of this work. The overall agreement of the predicted sound power spectra is satisfactory. While the comparison between the models show significant deviations at low frequency, the power levels vary within an interval of ±3 dB at mid and high frequencies. The trends predicted by increasing the rotor speed are similar for almost all models. However, most predicted levels are some decibels lower than the experimental results. This comparison is not completely fair—particularly at low frequency—because of the presence of noise sources in the experimental results, which were not considered in the simulations.

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Section: Solution Bb1mentioning

confidence: 99%

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confidence: 99%

ACAT1 Benchmark of RANS-Informed Analytical Methods for Fan Broadband Noise Prediction: Part II—Influence of the Acoustic Models

et al. 2020

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“…The CV model has been already partially assessed on the tip-shroud of an LP turbine (Corral et al, 2019) using a well-validated frequency-domain linearized Navier-Stokes solver (Corral et al, 2003;Vega and Corral, 2016). In this work, a two-dimensional hybrid grid has been constructed in the meridional plane of the seal and extruded in the circumferential direction to form triangular prisms and hexahedra.…”

Section: Numerical Setupmentioning

confidence: 99%

Numerical validation of an analytical seal flutter model

Greco

Corral

2021

J. Glob. Power Propuls. Soc.

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An analytical model to describe the flutter onset of straight-through labyrinth seals has been numerically validated using a frequency domain linearized Navier-Stokes solver. A comprehensive set of simulations has been conducted to assess the stability criterion of the analytical model originally derived by Corral and Vega (2018), “Conceptual Flutter Analysis of Labyrinth Seals Using Analytical Models - Part I: Theoretical Support,” ASME J. Turbomach., 140 (12), pp. 121006. The accuracy of the model has been assessed by using a simplified geometry consisting of a two-fin straight-through labyrinth seal with identical gaps. The effective gaps and the kinetic energy carried over are retained and their effects on stability are evaluated. It turns out that is important to inform the model with the correct values of both parameters to allow a proper comparison with the numerical simulations. Moreover, the non-isentropic perturbations included in the formulations are observed in the simulations at relatively low frequencies whose characteristic time is of the same order as the discharge time of the seal. This effect is responsible for the bending of the stability limit in the <inline-formula><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:mn>0</mml:mn><mml:mi>t</mml:mi><mml:mi>h</mml:mi></mml:math></inline-formula> ND stability map obtained both in the model and the simulations. It turns out that the analytical model can predict accurately the stability of the seal in a wide range of pressure ratios, vibration mode-shapes, and frequencies provided that this is informed with the fluid dynamic gaps and the energy carried over to the downstream fin from a steady RANS simulation. The numerical calculations show for the first time that the model can be used to predict accurately not only the trends of the work-per-cycle of the seal but also quantitative results.

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“…The inlet and exit angle are respectively, α 1 = 44 • and α 2 = 60 • , the exit isentropic Mach number is M exit = 0.75, the Reynolds number based on the exit velocity Re 10 6 to avoid separations in the airfoil suction side and the airfoil spacing, s/c = 0.96. The space is discretized using an hybrid grid made up of triangles and quadrilaterals, containing about 30,000 nodes per passage and solved using the Mu 2 s 2 T suite of codes [7,10]. A close-up of the grid may be seen in Fig.…”

Section: Discretised Equationsmentioning

confidence: 99%

“…The Navier-Stokes equations may then be linearized about the mean flow to obtain: which is a system of linear equations with complex coefficients and where the first term is an additional time-derivative added to solve the equations marching in the pseudo-time τ. The linear system of equations is marched in the pseudo time with a RungeKutta and a multigrid technique to accelerate the convergence to the steady state [7]. Turbulent effects are accounted for using the Wilcox 98 turbulence model.…”

Section: Discretised Equationsmentioning

confidence: 99%

Physics of Vibrating Airfoils at Low Reduced Frequency

Vega

Corral

2013

Volume 7B: Structures and Dynamics

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The unsteady aerodynamics of low pressure turbine vibrating airfoils in flap mode is studied in detail using a frequency domain linearized Navier-Stokes solver. Both the travelling-wave and influence coefficient formulations of the problem are used to highlight key aspects of the physics and understand different trends such as the effect of reduced frequency and Mach number. The study is focused in the low-reduced frequency regime which is of paramount relevance for the design of aeronautical low-pressure turbines and compressors. It is concluded that the effect of the Mach number on the unsteady pressure phase can be neglected in first approximation and that the unsteadiness of the vibrating and adjacent airfoils is driven by vortex shedding mechanisms. Finally a simple model to estimate the work-percycle as a function of the reduced frequency and Mach Number is provided. The edge-wise and torsion modes are presented in less detail but it is shown that acoustic waves are essential to explain its behaviour. The non-dimensional work-per-cycle of the edge-wise mode shows a large dependence with the Mach number while in the torsion mode a large number of airfoils is needed to reconstruct the work-per-cycle departing from the influence coefficients.

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Linear and Non-Validation of a Linear Multigrid Accelerated Unstructured Navier-Stokes Solver for the Computation of Turbine Blades on Hybrid Grids

Cited by 38 publications

References 15 publications

ACAT1 Benchmark of RANS-Informed Analytical Methods for Fan Broadband Noise Prediction: Part II—Influence of the Acoustic Models

ACAT1 Benchmark of RANS-Informed Analytical Methods for Fan Broadband Noise Prediction: Part II—Influence of the Acoustic Models

Numerical validation of an analytical seal flutter model

Physics of Vibrating Airfoils at Low Reduced Frequency

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