| 1. |
- Rizzi, Arthur, et al.
(författare)
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Aeronautical CFD and Turbulence : Progress and Challenges
- 2022
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Ingår i: 33rd Congress of the International Council of the Aeronautical Sciences, ICAS 2022. - : International Council of the Aeronautical Sciences. ; , s. 1921-1943
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Konferensbidrag (refereegranskat)abstract
- Separated flows often set aerodynamic limits for an aircraft flight envelope, and many of these flows remain difficult to predict with Computational Fluid Dynamics (CFD). This paper reviews and explores how CFD simulations have been used for predicting separated flows, and the associated aerodynamic performance, throughout the flight envelope, giving special focus to military aircraft. The review entails: a summary of the physics of flow separation that is especially difficult to model accurately; an historical sketch of seven decades of CFD developments to meet many of the challenges of separated flow predictions; three case studies for an assessment of the current CFD capabilities; and future prospects for further improvements in the CFD simulations using direct numerical simulations (DNS). DNS can be utilized as a virtual wind tunnel to understand complex separated flow and the results used in modelling improvements for RANS and LES CFD methods. Several examples of the capabilities of DNS methods to predict separated aeronautical flows are given. However, significant advances are still needed for separated flow simulations to become practical with reliability comparable to those of attached flow simulations. A possible path forward for future work to achieve this goal is included.
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| 2. |
- Tomac, Maximilian, et al.
(författare)
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Factors in fluencing accurate shock vortex interaction prediction on F-16XL aircraft
- 2014
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Ingår i: 52nd AIAA Aerospace Sciences Meeting - AIAA Science and Technology Forum and Exposition, SciTech 2014. - Reston, Virginia : American Institute of Aeronautics and Astronautics Inc.. - 9781624102561
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Konferensbidrag (refereegranskat)abstract
- Computational Fluid Dynamics methods continues to play an increasingly important role in design and validation. Some examples are conditions that can not be tested prior to flight test. In order to rely on these methods it is essential that these methods are validated and evaluated to state-of-the-art wind tunnel test and/or in-flight data. In a previous project \Cranked-Arrow Wing Aerodynamics Project International" (CAWAPI)it was clear that all CFD methods failed to some degree in the transonic regime where shock vortex interaction phenomena was present. Detailed analysis of surface pressure distribution showed that CFD where not able replicate the correct flow field and produce acceptable results.This paper aim to map out the flight conditions for which CFD is likely to fail, and try to answer or shed light in the question why? This with the main focus on the factors that influence shock vortex interaction in the flow field.
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| 3. |
- Hirschel, Ernst Heinrich, et al.
(författare)
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Separated and Vortical Flow in Aircraft Wing Aerodynamics : Basic Principles and Unit Problems
- 2020
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Bok (övrigt vetenskapligt/konstnärligt)abstract
- Fluid mechanical aspects of separated and vortical flow in aircraft wing aerodynamics are treated. The focus is on two wing classes: (1) large aspect-ratio wings and (2) small aspect-ratio delta-type wings. Aerodynamic design issues in general are not dealt with. Discrete numerical simulation methods play a progressively larger role in aircraft design and development. Accordingly, in the introduction to the book the different mathematical models are considered, which underlie the aerodynamic computation methods (panel methods, RANS and scale-resolving methods). Special methods are the Euler methods, which as rather inexpensive methods embrace compressibility effects and also permit to describe lifting-wing flow. The concept of the kinematically active and inactive vorticity content of shear layers gives insight into many flow phenomena, but also, with the second break of symmetry---the first one is due to the Kutta condition---an explanation of lifting-wing flow fields. The prerequisite is an extended definition of separation: “flow-off separation” at sharp trailing edges of class (1) wings and at sharp leading edges of class (2) wings. The vorticity-content concept, with a compatibility condition for flow-off separation at sharp edges, permits to understand the properties of the evolving trailing vortex layer and the resulting pair of trailing vortices of class (1) wings. The concept also shows that Euler methods at sharp delta or strake leading edges of class (2) wings can give reliable results. Three main topics are treated: 1) Basic Principles are considered first: Boundary-layer flow, vortex theory, the vorticity content of shear layers, Euler solutions for lifting wings, the Kutta condition in reality and the topology of skin-friction and velocity fields. 2) Unit Problems treat isolated flow phenomena of the two wing classes. Capabilities of panel and Euler methods are investigated. One Unit Problem is the flow past the wing of the NASA Common Research Model. Other Unit Problems concern the lee-side vortex system appearing at the Vortex-Flow Experiment 1 and 2 sharp- and blunt-edged delta configurations, at a delta wing with partly round leading edges, and also at the Blunt Delta Wing at hypersonic speed. 3) Selected Flow Problems of the two wing classes. In short sections practical design problems are discussed. The treatment of flow past fuselages, although desirable, was not possible in the frame of this book.
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| 4. |
- Da Ronch, A., et al.
(författare)
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A framework for constrained control allocation using CFD-based tabular data
- 2011
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Ingår i: AIAA Aerosp. Sci. Meet. Incl. New Horiz. Forum Aerosp. Expos.. - Reston, Virigina : American Institute of Aeronautics and Astronautics. - 9781600869501
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Konferensbidrag (refereegranskat)abstract
- This paper describes a framework for control allocation problem using Computational Fluid Dynamics (CFD) aerodata, which is represented by a multidimensional array of dimensionless coefficients of aerodynamic forces and moments, stored as a function of the state vector and control-surface deflections. The challenges addressed are, first, the control surface treatment for the automated generation of aerodata using CFD and, second, sampling and data fusion to allow the timely calculation of large data tables. In this framework, the generation of aerodynamic tables is described based on an efficient sampling/data fusion approach. Also, the treatment of aerodynamics of control surfaces is being addressed for three flow solvers: TORNADO, a vortex-lattice method, and two CFD codes, EDGE from the Swedis Defence Agency and PMB from the University of Liverpool. In TORNADO, the vortex points located at the trailing edge of the flaps are rotated around the hinge line to simulate the deflected surfaces. The transpiration boundary conditions approach is used for modeling moving flaps in EDGE, whereas, the surface deflection is achieved using mode shapes in PMB. The test cases used to illustrate the approaches is the Ranger 2000 fighter trainer and a reduced geometry description of Boeing 747-100. Data tables are then generated for the state vector and multiple control surface deflections. The look-up table aerodata are then used to resolve the control allocation problem under the constraint that each surface has an upper and lower limit of deflection angle.
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| 5. |
- Eliasson, Peter, et al.
(författare)
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IMPROVING STALL CHARACTERISTICS OF UCAV WING WITH VORTEX GENERATORS
- 2022
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Ingår i: 33rd Congress of the International Council of the Aeronautical Sciences, ICAS 2022. - : International Council of the Aeronautical Sciences. ; , s. 2990-2998
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Konferensbidrag (refereegranskat)abstract
- Recent Unmanned Combat Air Vehicle (UCAV) configurations have not-so-slender wings with moderate leading-edge sweepangles of 45◦ to 60◦. Planforms vary from pure delta to diamond and even lambda more or less blended wing bodies with a relatively small thickness ratio at the inner wing/fuselage region. The performance and low-observable signature considerations require a compromise between a small radar cross-section and lifting surface shapes for long range and sufficient agility. The airflow is governed largely by the progression of vortices shed from the wing leading edge which interact and produce non-linear aerodynamics. Like early swept wing fighters like the Saab 32 the UCAV may exhibit undesirable flying characteristics over part of the envelope with tip stall and pitch-up. Such problems were mitigated by vortex control "devices" like leading edge fences and notches which violate the low observable requirement. The AVT-181 SACCON is a well studied case. We attempt to improve its stalling characteristics by mimicking the leading edge fence action by a configuration of very small vortex generators and study their effect by CFD.
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| 6. |
- Goetzendorf-Grabowski, Tomas, et al.
(författare)
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Coupling Adaptive-Fidelity CFD with S&C Analysis to Predict Flying Qualities
- 2009
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Ingår i: 27th AIAA Applied Aerodynamics Conference.
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Konferensbidrag (refereegranskat)abstract
- CEASIOM, the Computerized Environment for Aircraft Synthesis and Integrated Optimization Methods, is a framework tool that integrates discipline-specific tools for conceptual design. At this early stage of the design it is very useful to be able to predict the °ying and handling qualities of this design. In order to do this, the aerodynamic database needs to be computed for the configuration being studied which then has to be coupled to the stability and control tools to carry out the analysis. This paper describes how the adaptive-fidelity CFD module of CEASIOM computes the aerodynamic dataset of an air craft configuration, and how that dataset is analyzed by the SDSA module to determine the °ying qualities of the aircraft. These predicted °ying qualities are then compared with the °ight-test data of the Ranger 2000 trainer aircraft in order to verify the goodness of the overall approach.
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| 7. |
- Irving, J. P., et al.
(författare)
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Development of an aerodynamic simulation model of a generic configuration for S&C analyses
- 2014
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Ingår i: 32nd AIAA Applied Aerodynamics Conference. - Reston, Virginia : American Institute of Aeronautics and Astronautics (AIAA).
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Konferensbidrag (refereegranskat)abstract
- The development of an aerodynamic simulation model for the inclusion in an open-loop Stability & Control model is presented. The model, based on a generic UCAV configuration, is derived from data gathered during a number of experimental campaigns conducted using various test models and facilities, and covers the full subsonic flight regime. The model includes uncertainties in key model parameters to yield an expected range of model outputs for any given condition.
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| 8. |
- Jungo, Aidan, et al.
(författare)
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Benchmarking New CEASIOM with CPACS adoption for aerodynamic analysis and flight simulation
- 2018
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Ingår i: AIRCRAFT ENGINEERING AND AEROSPACE TECHNOLOGY. - : EMERALD GROUP PUBLISHING LTD. - 1748-8842. ; 90:4, s. 613-626
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Tidskriftsartikel (refereegranskat)abstract
- Purpose The purpose of this paper is to present the status of the on-going development of the new computerized environment for aircraft synthesis and integrated optimization methods (CEASIOM) and to compare results of different aerodynamic tools. The concurrent design of aircraft is an extremely interdisciplinary activity incorporating simultaneous consideration of complex, tightly coupled systems, functions and requirements. The design task is to achieve an optimal integration of all components into an efficient, robust and reliable aircraft with high performance that can be manufactured with low technical and financial risks, and has an affordable life-cycle cost. Design/methodology/approach CEASIOM (www.ceasiom.com) is a framework that integrates discipline-specific tools like computer-aided design, mesh generation, computational fluid dynamics (CFD), stability and control analysis and structural analysis, all for the purpose of aircraft conceptual design. Findings A new CEASIOM version is under development within EU Project AGILE (www.agile-project.eu), by adopting the CPACS XML data-format for representation of all design data pertaining to the aircraft under development. Research limitations/implications Results obtained from different methods have been compared and analyzed. Some differences have been observed; however, they are mainly due to the different physical modelizations that are used by each of these methods. Originality/value This paper summarizes the current status of the development of the new CEASIOM software, in particular for the following modules: CPACS file visualizer and editor CPACSupdater (Matlab) Automatic unstructured (Euler) & hybrid (RANS) mesh generation by sumo Multi-fidelity CFD solvers: Digital Datcom (Empirical), Tornado (VLM), Edge-Euler & SU2-Euler, Edge-RANS & SU2-RANS Data fusion tool: aerodynamic coefficients fusion from variable fidelity CFD tools above to compile complete aero-table for flight analysis and simulation.
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| 9. |
- Luckring, J. M., et al.
(författare)
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Toward improved CFD predictions of slender airframe aerodynamics using the F-16XL aircraft (CAWAPI-2)
- 2017
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Ingår i: Journal of Aircraft. - : American Institute of Aeronautics and Astronautics Inc.. - 0021-8669 .- 1533-3868. - 9781624102561 ; 54:2, s. 378-387
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Tidskriftsartikel (refereegranskat)abstract
- A coordinated project has been underway to improve CFD predictions of slender airframe aerodynamics. The work is focused on two flow conditions and leverages a unique flight data set obtained with an F-16XL aircraft. These conditions, a low-speed high angle-of-attack case and a transonic low angle-of-attack case, were selected from a prior prediction campaign wherein the CFD failed to provide acceptable results. In this paper the background, objectives and approach to the current project are presented. The work embodies predictions from multiple numerical formulations that are contributed from multiple organizations, and the context of this campaign to other multi-code, multi-organizational efforts is included. The relevance of this body of work toward future supersonic commercial transport concepts is also briefly addressed.
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| 10. |
- Luckring, J M, et al.
(författare)
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Toward improved CFD predictions of slender airframe aerodynamics using the F-16XL aircraft (CAWAPI-2)
- 2014
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Ingår i: 52nd AIAA Aerospace Sciences Meeting - AIAA Science and Technology Forum and Exposition, SciTech 2014. - Reston, Virginia : American Institute of Aeronautics and Astronautics Inc..
-
Konferensbidrag (refereegranskat)abstract
- A coordinated project has been underway to improve CFD predictions of slender airframe aerodynamics. The work is focused on two flow conditions and leverages a unique flight data set obtained with an F-16XL aircraft. These conditions, a low-speed high angle-of-attack case and a transonic low angle-of-attack case, were selected from a prior prediction campaign wherein the CFD failed to provide acceptable results. In this paper the background, objectives and approach to the current project are presented. The work embodies predictions from multiple numerical formulations that are contributed from multiple organizations, and the context of this campaign to other multi-code, multi-organizational efforts is included. The relevance of this body of work toward future supersonic commercial transport concepts is also briefly addressed.
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