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Realistic simulations of delta wing aerodynamics using novel CFD methods
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
2005 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

The overall goal of the research presented in this thesis is to extend the physical understanding of the unsteady external aerodynamics associated with highly maneuverable delta-wing aircraft by using and developing novel, more efficient computational fluid dynamics (CFD) tools. More specific, the main purpose is to simulate and better understand the basic fluid phenomena, such as vortex breakdown, that limit the performance of delta-wing aircraft. The problem is approached by going from the most simple aircraft configuration - a pure delta wing - to more complex configurations. As the flow computations of delta wings at high angle of attack have a variety of unusual aspects that make accurate predictions challenging, best practices for the CFD codes used are developed and documented so as to raise their technology readiness level when applied to this class of flows.

Initially, emphasis is put on subsonic steady-state CFD simulations of stand-alone delta wings to keep the phenomenon of vortex breakdown as clean as possible. For half-span models it is established that the essential characteristics of vortex breakdown are captured by a structured CFD code. The influence of viscosity on vortex breakdown is studied and numerical results for the aerodynamic coefficients, the surface pressure distribution and breakdown locations are compared to experimental data where possible.

In a second step, structured grid generation issues, numerical aspects of the simulation of this nonlinear type of flow and the interaction of a forebody with a delta wing are explored.

Then, on an increasing level of complexity, time-accurate numerical studies are performed to resolve the unsteady flow field over half and full-span, stationary delta wings at high angle of attack. Both Euler and Detached Eddy Simulations (DES) are performed to predict the streamwise oscillations of the vortex breakdown location about some mean position, asymmetry in the breakdown location due to the interaction between the left and right vortices, as well as the rotation of the spiral structure downstream of breakdown in a time-accurate manner. The computed flow-field solutions are visualized and analyzed in a virtual-reality environment.

Ultimately, steady-state and time-dependent simulations of a full-scale fighter-type aircraft configuration in steady flight are performed using the advanced turbulence models and the detached-eddy simulation capability of an edge-based, unstructured flow solver. The computed results are compared to flight-test data.

The thesis also addresses algorithmic efficiency and presents a novel implicit-explicit algorithm, the Recursive Projection Method (RPM), for computations of both steady and unsteady flows. It is demonstrated that RPM can accelerate such computations by up to 2.5 times.

Place, publisher, year, edition, pages
Stockholm: KTH , 2005. , ix, 68 p.
Series
Trita-AVE, ISSN 1651-7660 ; 2005:01
Keyword [en]
Space and plasma physics, CFD, aerodynamics, flow physics, steady, unsteady, delta wing, vortical flow
Keyword [sv]
Rymd- och plasmafysik
National Category
Fusion, Plasma and Space Physics
Identifiers
URN: urn:nbn:se:kth:diva-125ISBN: 91-7283-938-4 (print)OAI: oai:DiVA.org:kth-125DiVA: diva2:7057
Public defence
2005-02-15, Kollegiesalen, Valhallavägen 79, Stockholm, 10:15
Opponent
Supervisors
Note
QC 20101019Available from: 2005-02-11 Created: 2005-02-11 Last updated: 2010-10-19Bibliographically approved
List of papers
1. Computational Study of Vortex Breakdown over Swept Delta Wings
Open this publication in new window or tab >>Computational Study of Vortex Breakdown over Swept Delta Wings
1999 (English)Conference paper, Published paper (Other academic)
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-4919 (URN)
Conference
17th AIAA Applied Aerodynamics Conference
Note
QC 20101018. AAIA Paper 99-3118Available from: 2005-02-11 Created: 2005-02-11 Last updated: 2010-10-18Bibliographically approved
2. Computing the High-Alpha Aerodynamics of Delta Wings: Evaluation and Analysis
Open this publication in new window or tab >>Computing the High-Alpha Aerodynamics of Delta Wings: Evaluation and Analysis
2001 (English)Conference paper, Published paper (Other academic)
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-4920 (URN)
Conference
39th AIAA Aerospace Sciences Meeting and Exhibit
Note
QC 20101018. AIAA Paper 01-0115Available from: 2005-02-11 Created: 2005-02-11 Last updated: 2010-10-18Bibliographically approved
3. Time-accurate Euler Simulations of a Full-Span Delta Wing at High Incidence
Open this publication in new window or tab >>Time-accurate Euler Simulations of a Full-Span Delta Wing at High Incidence
2003 (English)Conference paper, Published paper (Other academic)
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-4921 (URN)
Conference
21st AIAA Applied Aerodynamics Conference
Note
QC 20101018. AIAA Paper 03-4304Available from: 2005-02-11 Created: 2005-02-11 Last updated: 2010-10-18Bibliographically approved
4. Detached-Eddy Simulations of a Full-Span Delta Wing at High Incidence
Open this publication in new window or tab >>Detached-Eddy Simulations of a Full-Span Delta Wing at High Incidence
2003 (English)Conference paper, Published paper (Other academic)
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-4922 (URN)
Conference
AIAA 21st applied aerodynamics conference
Note
QC 20101018. AIAA Paper 03-4216Available from: 2005-02-11 Created: 2005-02-11 Last updated: 2010-10-18Bibliographically approved
5. Steady and Unsteady CFD Analysis of the F-16XL-1 at Flight-Reynolds Numbers and Comparison to Flight Test Data
Open this publication in new window or tab >>Steady and Unsteady CFD Analysis of the F-16XL-1 at Flight-Reynolds Numbers and Comparison to Flight Test Data
(English)Report (Other academic)
Series
NATO RTO Technical Report
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-4923 (URN)
Note
NQCAvailable from: 2005-02-11 Created: 2005-02-11 Last updated: 2012-03-26Bibliographically approved
6. Virtual-reality environment for visualization of unsteady three-dimensional CFD data
Open this publication in new window or tab >>Virtual-reality environment for visualization of unsteady three-dimensional CFD data
2004 (English)In: ECCOMAS 2004 - European Congress on Computational Methods in Applied Sciences and Engineering, 2004, 1-20 p.Conference paper, Published paper (Refereed)
Abstract [en]

A Virtual-Reality (VR) environment has been set up to visualize, explore and interact with steady and time-dependent three-dimensional CFD solutions in a fully immersive way. The paper presents the VR system and provides some examples of currently investigated applications in the area of computational aerodynamics, such as the unsteady flow over a full-span delta wing at high angle of attack, the steady hypersonic flow around an atmospheric reentry vehicle and the steady airflow around a human female standing in a strong headwind. These pre-computed three-dimensional flows have been visualized interactively in a six-sided CAVE, demonstrating that the sheer sensual impact of the immersive display has a powerful effect on the physical intuition. Several user can move around freely in the VR environment, without being distracted from the flow to be investigated by the analytical tools and menus. The users have a common experience and can discuss the visualized flow field while interacting with it. Our experience with using VR for visualizing, exploring and analyzing complex unsteady three-dimensional CFD data are summarized and benefits and limitations are highlighted.

Keyword
Virtual reality, CAVE, unsteady aerodynamics, CFD, visualization, delta wing, vortex breakdown
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-4924 (URN)2-s2.0-84893519295 (Scopus ID)
Conference
European Congress on Computational Methods in Applied Sciences and Engineering, ECCOMAS 2004; Jyvaskyla; Finland; 24 July 2004 through 28 July 2004
Note

QC 20101018

Available from: 2005-02-11 Created: 2005-02-11 Last updated: 2014-04-23Bibliographically approved
7. Recursive Projection Method for efficient unsteady CFD simulations
Open this publication in new window or tab >>Recursive Projection Method for efficient unsteady CFD simulations
2004 (English)In: / [ed] P. Neittaanmäki, T. Rossi, K. Majava, and O. Pironneau, 2004, 1-20 p.Conference paper, Published paper (Refereed)
Abstract [en]

The Recursive Projection Method (RPM) has been implemented into the unstructured grid CFD code EDGE to accelerate the inner-loop convergence of dual time stepping. The method tries to identify the slowly converging subspace and applies Newton iterations in this subspace together with a fixed point scheme in the complement. The method has been employed to compute the steady and unsteady viscous flow around a circular cylinder for a Reynolds number of 100. When converging to machine accuracy, RPM accelerated the convergence of the steady-state solution by a factor of 2.5. The time-accurate simulations were accelerated by a factor of about two.

Keyword
recursive Projection Method, unsteady aerodynamics, CFD, convergence, dual time stepping, vortex street
National Category
Computer Engineering
Identifiers
urn:nbn:se:kth:diva-4925 (URN)2-s2.0-84893505605 (Scopus ID)
Conference
European Congress on Computational Methods in Applied Sciences and Engineering, ECCOMAS 2004; Jyvaskyla; Finland; 24-28 July 2004
Note

QC 20141210

Available from: 2005-02-11 Created: 2005-02-11 Last updated: 2014-12-10Bibliographically approved
8. Evaluation of the Recursive Projection Method for Efficient Unsteady Turbulent CFD Simulations
Open this publication in new window or tab >>Evaluation of the Recursive Projection Method for Efficient Unsteady Turbulent CFD Simulations
2004 (English)In: 24th INTERNATIONAL CONGRESS OF THE AERONAUTICAL SCIENCES, 2004, 1-13 p.Conference paper, Published paper (Refereed)
Abstract [en]

The Recursive Projection Method (RPM) hasbeen implemented into an unstructured CFD code to improve the efficiency of dual time steppingfor unsteady turbulent CFD simulations.RPM is a combined implicit-explicit method that enhances convergence. It can easily be implementedinto existing codes and the solver’s existing acceleration techniques can be used withoutchange. The method has been evaluated by computing the periodic self-induced shock oscillations over an 18% thick biconvex airfoil at0◦ angle of attack, a Mach number of 0.76 anda Reynolds number of 11 million. On average,RPM accelerated the convergence of the innerloop of dual time stepping to a predefined convergencecriterion by a factor of about 2.5.

Keyword
Recursive Projection Method, CFD, dual time stepping, convergence, unsteady flow, buffet
National Category
Computer Engineering Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-4907 (URN)
Conference
24th INTERNATIONAL CONGRESS OF THE AERONAUTICAL SCIENCES
Note
QC 20101015Available from: 2005-02-02 Created: 2005-02-02 Last updated: 2010-10-19Bibliographically approved

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CiteExportLink to record
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