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2014 | Buch

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Unsteady Computational Fluid Dynamics in Aeronautics

verfasst von: P.G. Tucker

Verlag: Springer Netherlands

Buchreihe : Fluid Mechanics and Its Applications

Enthalten in: Springer Professional "Wirtschaft+Technik" , Springer Professional "Technik" , Springer Professional "Wirtschaft"

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Über dieses Buch

The field of Large Eddy Simulation (LES) and hybrids is a vibrant research area. This book runs through all the potential unsteady modelling fidelity ranges, from low-order to LES. The latter is probably the highest fidelity for practical aerospace systems modelling. Cutting edge new frontiers are defined.

One example of a pressing environmental concern is noise. For the accurate prediction of this, unsteady modelling is needed. Hence computational aeroacoustics is explored. It is also emerging that there is a critical need for coupled simulations. Hence, this area is also considered and the tensions of utilizing such simulations with the already expensive LES.

This work has relevance to the general field of CFD and LES and to a wide variety of non-aerospace aerodynamic systems (e.g. cars, submarines, ships, electronics, buildings). Topics treated include unsteady flow techniques; LES and hybrids; general numerical methods; computational aeroacoustics; computational aeroelasticity; coupled simulations and turbulence and its modelling (LES, RANS, transition, VLES, URANS). The volume concludes by pointing forward to future horizons and in particular the industrial use of LES. The writing style is accessible and useful to both academics and industrial practitioners.

From the reviews:
"Tucker's volume provides a very welcome, concise discussion of current capabilities for simulating and modellng unsteady aerodynamic flows. It covers the various pos

sible numerical techniques in good, clear detail and presents a very wide range of practical applications; beautifully illustrated in many cases. This book thus provides a valuable text for practicing engineers, a rich source of background information for students and those new to this area of Research & Development, and an excellent state-of-the-art review for others. A great achievement."

Mark Savill FHEA, FRAeS, C.Eng, Professor of Computational Aerodynamics Design & Head of Power & Propulsion Sciences, Department of Power & Propulsion, School of Engineering, Cranfield University, Bedfordshire, U.K.

"This is a very useful book with a wide coverage of many aspects in unsteady aerodynamics method development and applications for internal and external flows."

L. He, Rolls-Royce/RAEng Chair of Computational Aerothermal Engineering, Oxford University, U.K.

"This comprehensive book ranges from classical concepts in both numerical methods and turbulence modelling approaches for the beginner to latest state-of-the-art for the advanced practitioner and constitutes an extremely valuable contribution to the specific Computational Fluid Dynamics literature in Aeronautics. Student and expert alike will benefit greatly by reading it from cover to cover."

Sébastien Deck, Onera, Meudon, France

Inhaltsverzeichnis

Frontmatter

Chapter 1. Introduction

Abstract

The future challenges faced in aeronautical engineering to meet legislative targets to protect the environmental are outlined. The numerous sources of unsteadiness found in both propulsive systems and also airframes are discussed and the demands that these pose for traditional modelling approaches are outlined. The need to perform large scale, unsteady simulations is outlined and the computational science problems that arise from making such simulations is given. Computational costs are explored and also the way these control the manner in which simulations are used.

P. G. Tucker

Chapter 2. Computational Methods for Unsteady Flows

Abstract

Computational methods for unsteady flows are discussed. These range from standard to modern advanced approaches. An extensive overview of temporal discretizations is given. Then adaptive time stepping approaches are outlined, including adjoint based methods. Spatial schemes are discussed, including modern higher order and resolution approaches. Numerical techniques for both density and pressure-based solvers are considered. The critical issue of numerical smoothing and its control are outlined. Also, the strong relationship between grid topology and solution accuracy is considered for a range of numerical schemes. Simultaneous equations solvers and also boundary conditions are discussed. For the latter there is a strong focus on non-reflective conditions. A survey of work suggests that even though a wide range of schemes is found, just small subsets of these find practical use.

P. G. Tucker

Chapter 3. Turbulence and Its Modelling

Abstract

Averaging procedures used to form the Unsteady Reynolds Averaged Navier-Stokes (URANS) and Large Eddy Simulation (LES) equations are outlined. Also, turbulence modelling hierarchies for unsteady flows are presented. These range from URANS to DNS (Direct Numerical Simulation). The grid requirements for different approaches are also discussed. The LES models that are used for results in later chapters are given, along with details of others. Different types of LES filters are outlined. Their potential strong impact on results is discussed. A hierarchy of key elements for industrial LES is proposed. Notably, for flows without transition, the actual explicit LES model comes low down. More the key element is the numerical schemes discussed in Chap. 3. Key hybrid RANS-LES approaches are given. The advantages and disadvantages of these are outlined. The discussion shows that considerable expertise is needed to safely use hybrid RANS-LES techniques. Hence, the need for best practice guidelines is proposed. Methods for generating turbulence inflow are outlined. It is shown that many of these have limited applicability to complex engineering systems and so suitable strategies proposed.

P. G. Tucker

Chapter 4. Computational Aerodynamics Methods

Abstract

An overview of the various unsteady modelling hierarchies in aerospace is given ranging from linear harmonic to direct numerical simulation. Unsteady reduced order modelling encompassing deterministic stresses and body forces are discussed. Hierarchies are presented for different modelling lineages and fidelity levels. Mixed fidelity methods are proposed, where low and high fidelity treatments are combined. For example, URANS being combined with body forces to provide appropriate system boundary conditions. This concept is extended further in later chapters. For URANS, the occurrence of a spectral gap in many turbomachinery zones is found to be uncertain. The wide range of other aspects needed to model aeronautical flows and their limitations is discussed.

P. G. Tucker

Chapter 5. Applications of Eddy Resolving Methods

Abstract

The application of eddy resolving methods to a wide range of propulsive and airframe systems is reviewed. For propulsive systems the following areas are addressed: turbines, compressors, fans, internal air systems, turbine blade cooling and combustors. For airframes the following zones are looked at: airfoil and trailing edges flows, multi-component airfoils, swept and delta wings, full aircraft configurations, base flows, landing gear, cavity and other miscellaneous flows. The frequency of use for the different turbulence modelling techniques described in Chap. 3 is outlined. As might be expected, hybrid RANS-LES methods find much greater use for airframes. The grid densities used are contrasted with expected theoretically based estimates discussed in Chaps. 1 and 3. For propulsion system studies, simulations are found to be generally under resolved. Notably, for all of the above, levels of validation are defined. It is found that there is a lack of detailed validation data to explore in depth the performance of LES and thus refine it. This is especially so for turbomachinery. The need for LES best practices is again discussed.

P. G. Tucker

Chapter 6. Computational Aeroacoustics

Abstract

A wide range of far field sound prediction techniques is outlined. Also, their hybridization is considered. Computational process challenges relating to connecting the flow field simulation elements outlined in previous chapters to the acoustic propagation methods is discussed. The form of acoustic source correlation coefficients is given. A range of eddy resolving simulations used for acoustics is reviewed. The frequency of use of different eddy resolving, numerical schemes and far field sound prediction approaches in acoustics is assessed along with validation data levels. Areas where validation is lacking are outlined. The use of LES to define low order acoustics models is considered. The need for more holistic simulations is identified.

P. G. Tucker

Chapter 7. Coupled Computational Aerodynamics

Abstract

Coupled computational aerodynamics is discussed. In relation to this, mesh movement, conservation, geometry alignment, stability, data interpolation, and other matters related to using moving meshes is overviewed. Code coupling software is discussed. The coupled simulations addressed encompass aeroelasticity; conjugate heat transfer and coupled aerodynamic simulations. Numerical approaches in relation to these are outlined. Examples of coupled eddy resolving simulations are reviewed along with validation levels for them and schemes used. As would be expected, there are much less examples of eddy resolving simulations for more complex, multifaceted coupled problems. However, for practical systems, such simulations are identified as being vital to gaining physically plausible solutions.

P. G. Tucker

Chapter 8. Future Outlook

Abstract

The future outlook for unsteady aeronautical flows is explored and overall conclusions given. The nature of potential best practices is discussed. Flow taxonomies are proposed as a basis for an expert system to allow the industrial use of eddy resolving simulations. A process chain for such simulations is proposed. Also, the use of eddy resolving simulations in coupled problems is briefly explored.

P. G. Tucker

Backmatter

Titel: Unsteady Computational Fluid Dynamics in Aeronautics
verfasst von: P.G. Tucker
Verlag: Springer Netherlands
Electronic ISBN: 978-94-007-7049-2
Print ISBN: 978-94-007-7048-5
DOI: https://doi.org/10.1007/978-94-007-7049-2

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