Efficient infinite-swept wing solver for steady and unsteady compressible flows

Franciolini, Matteo; Ronch, Andrea Da; Drofelnik, Jernej; Raveh, Daniella E.; Crivellini, Andrea

doi:10.1016/j.ast.2017.10.034

Cited by 9 publications

(7 citation statements)

References 19 publications

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“…This specialised algorithm was implemented by the authors in DLR-Tau (Drofelnik and Da Ronch, 2017) and is now being used for production. More details about the algorithm, boundary conditions, and application on a variety of test cases are found in (Franciolini et al, 2017). The infinite-swept wing solver is a key capability for the work herein presented, and this paper may well be the first work demonstrating the use of the solver for buffeting flows around wing planforms commonly used in preliminary/conceptual design phases.…”

Section: Methodsmentioning

confidence: 99%

“…The exploration of the ′ − Λ plane was carried out using the infinite sweptwing flow solver on a purely 2D grid stencil, and results are summarised in Figure 4. The influence of the wing sweep angle within the context of a purely 2D grid stencil is dealt with imposing appropriate boundary conditions at the far-field (Franciolini et al, 2017). In practice, the search was conducted, for each sweep angle, increasing the angle of attack between 1 and 7 deg, at increments of 1 deg initially.…”

Section: Efficient Identification Of Buffet Envelopementioning

confidence: 99%

“…The first objective is related to the validation of the present flow solver and numerical settings by comparison with experimental data of the RA16SC1 aerofoil. The second objective demonstrates the deployment of an efficient infinite-swept wing flow solver (2D grid stencil), recently developed by the authors (Franciolini et al, 2017), for the identification of the buffet envelope. The third objective addresses the challenge of improving the accuracy of the buffet envelope with higher fidelity (3D URANS) at a minimal additional cost.…”

Section: Introductionmentioning

confidence: 99%

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Fast identification of transonic buffet envelope using computational fluid dynamics

Drofelnik

Ronch

Franciolini

et al. 2019

AEAT

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Purpose This paper aims to present a numerical method based on computational fluid dynamics that allows investigating the buffet envelope of reference equivalent wings at the equivalent cost of several two-dimensional, unsteady, turbulent flow analyses. The method bridges the gap between semi-empirical relations, generally dominant in the early phases of aircraft design, and three-dimensional turbulent flow analyses, characterised by high costs in analysis setups and prohibitive computing times. Design/methodology/approach Accuracy in the predictions and efficiency in the solution are two key aspects. Accuracy is maintained by solving a specialised form of the Reynolds-averaged Navier–Stokes equations valid for infinite-swept wing flows. Efficiency of the solution is reached by a novel implementation of the flow solver, as well as by combining solutions of different fidelity spatially. Findings Discovering the buffet envelope of a set of reference equivalent wings is accompanied with an estimate of the uncertainties in the numerical predictions. Just over 2,000 processor hours are needed if it is admissible to deal with an uncertainty of ±1.0° in the angle of attack at which buffet onset/offset occurs. Halving the uncertainty requires significantly more computing resources, close to a factor 200 compared with the larger uncertainty case. Practical implications To permit the use of the proposed method as a practical design tool in the conceptual/preliminary aircraft design phases, the method offers the designer with the ability to gauge the sensitivity of buffet on primary design variables, such as wing sweep angle and chord to thickness ratio. Originality/value The infinite-swept wing, unsteady Reynolds-averaged Navier–Stokes equations have been successfully applied, for the first time, to identify buffeting conditions. This demonstrates the adequateness of the proposed method in the conceptual/preliminary aircraft design phases.

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Section: Methodsmentioning

confidence: 99%

Section: Efficient Identification Of Buffet Envelopementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Fast identification of transonic buffet envelope using computational fluid dynamics

Drofelnik

Ronch

Franciolini

et al. 2019

AEAT

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“…Due to its computational efficiency compared to existing state-of-the-art options, the implementation is denoted as 2.5D+. The steady and unsteady 2.5D+ flow solver was demonstrated [23] around single and multi-element wing sections in low-and high-speed of flight, using laminar and various turbulence models. The flow solver was applied to study transonic buffet for a family of wing configurations [24] and in aerodynamic shape optimisation using solvers of different fidelity [25].…”

Section: B Infinite-swept Wing Navier-stokes Solvermentioning

confidence: 99%

Fast Aerodynamic Calculations Based on a Generalized Unsteady Coupling Algorithm

et al. 2021

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An aerodynamic model for applications to external flows is formulated that provides a great trade-off between computational cost and prediction accuracy. The novelty of the work is the ability to deal with any unsteady flow problem, irrespective of the frequency of motion and motion kinematics. The aerodynamic model, baptised FALCon, combines an in-house unsteady vortex lattice method with an infinite-swept wing Navier-Stokes solver. The two specialised methods are orchestrated by an unsteady coupling algorithm that represents our main research contribution. The paper gives the formulation and algorithmic implementation. FALCon is demonstrated on three test cases of increasing complexity in flow physics, up to flow conditions well outside its validity range. On average, FALCon achieves a computational speed up of a factor of about 50, compared to a full Navier-Stokes run, while capturing relevant flow physics: three-dimensional, viscous, compressible and unsteady phenomena.

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“…This test case concerns transonic flow predictions for the NACA 0012 aerofoil undergoing a forced sinusoidal motion in pitch around one-quarter of the chord. The flow The unstructured grid, which was also used in a previous work [7], consists of about 15.3 thousand mesh elements, see Fig. 10a.…”

Section: Naca 0012 Aerofoil Forced Sinusoidal Motionmentioning

confidence: 99%

Sensitivity and calibration of turbulence model in the presence of epistemic uncertainties

et al. 2019

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The solution of Reynolds-averaged Navier-Stokes equations employs an appropriate set of equations for the turbulence modelling. The closure coefficients of the turbulence model were calibrated using empiricism and arguments of dimensional analysis. These coefficients are considered universal, but there is no guarantee this property applies to test cases other than those used in the calibration process. This work aims at revisiting the calibration of the closure coefficients of the original Spalart-Allmaras turbulence model using machine learning, adaptive design of experiments and accessing a highperformance computing facility. The automated calibration procedure is carried out once for a transonic, wall-bounded flow around the RAE 2822 aerofoil. It was found that: (a) an optimal set of closure coefficients exists that minimises numerical deviations from experimental data; (b) the improved prediction accuracy of the calibrated turbulence model is consistent across different flow solvers; and (c) the calibrated turbulence model outperforms slightly the standard model in analysing complex flow features around additional test cases (ONERA M6 wing, axisymmetric transonic bump, forced sinusoidal motion of NACA 0012 aerofoil). A by-product of this study is a fully calibrated turbulence model that leverages on current state-of-the-art computational techniques, overcoming inherent limitations of the manual fine-tuning process.

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Efficient infinite-swept wing solver for steady and unsteady compressible flows

Cited by 9 publications

References 19 publications

Fast identification of transonic buffet envelope using computational fluid dynamics

Fast identification of transonic buffet envelope using computational fluid dynamics

Fast Aerodynamic Calculations Based on a Generalized Unsteady Coupling Algorithm

Sensitivity and calibration of turbulence model in the presence of epistemic uncertainties

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