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Conceptual Design Prediction of the Buffet Envelope of Transport Aircraft
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
University of Bristol.
2009 (English)In: Journal of Aircraft, ISSN 0021-8669, E-ISSN 1533-3868, Vol. 46, no 5, 1593-1606 p.Article in journal (Refereed) Published
Abstract [en]

This paper describes a methodology that inexpensively predicts the buffet envelope of new transport airplane wing geometries at the conceptual design stage. The parameters that demonstrate a strong functional sensitivity to buffet onset were identified and their relative effect was quantified. To estimate the buffet envelope of any target aircraft geometry, the method uses fractional change transformations in consort with a generic reference buffet onset curve provided by the authors or the buffet onset of a known seed airplane. The explicit design variables required to perform buffet onset prediction are those describing the wing planform and the wingtip section. The mutually exclusive nature of the method's analytical construct provides considerable freedom in deciding the scope of free-design-variable complexity. The method has been shown to be adequately robust and flexible enough to deal with a wide variety of transport airplane designs. For the example transport airplanes considered, irrespective of aircraft morphology and en route flight phase, the relative error in prediction was found to be mostly within +/-5.0%, with occasional excursions not exceeding a +/-9.0% bandwidth. The standard error of estimate for the lift coefficient at 1.0 g buffet onset at a given Mach number was calculated to be 0.0262.

Place, publisher, year, edition, pages
2009. Vol. 46, no 5, 1593-1606 p.
Keyword [en]
Aircraft geometries, Design variables, En-route, Flight phase, Functional sensitivities, Lift coefficient, Relative errors, Standard errors, Transport airplane, Wing planforms, Mach number, Transport aircraft, Wings
National Category
Vehicle Engineering
Identifiers
URN: urn:nbn:se:kth:diva-9279DOI: 10.2514/1.41367ISI: 000270749600014Scopus ID: 2-s2.0-73649108600OAI: oai:DiVA.org:kth-9279DiVA: diva2:54414
Note
QC 20101104 Uppdaterad från submitted till published (20101104).Available from: 2008-10-16 Created: 2008-10-16 Last updated: 2017-12-07Bibliographically approved
In thesis
1. Method Development for Computer Aided Engineering for Aircraft Conceptual Design
Open this publication in new window or tab >>Method Development for Computer Aided Engineering for Aircraft Conceptual Design
2008 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

This thesis presents the work done to implement new computational tools and methods dedicated to aircraft conceptual design sizing and optimization. These tools have been exercised on different aircraft concepts in order to validate them and assess their relevance and applicability to practical cases. First, a geometry construction protocol has been developed. It is indeed essential to have a geometry description that supports the derivation of all discretizations and idealizations used by the different analysis modules (aerodynamics, weights and balance, stability and control, etc.) for which an aircraft concept is evaluated. The geometry should also be intuitive to the user, general enough to describe a wide array of morphologies and suitable for optimization. All these conditions are fulfilled by an appropriate parameterization of the geometry. In addition, a tool named CADac (Computer Aided Design aircraft) has been created in order to produce automatically a closed and consistent CAD solid model of the designs under study. The produced CAD model is easily meshable and therefore high-fidelity Computational Fluid Dynamics (CFD) computations can be performed effortlessly without need for tedious and time-consuming post-CAD geometry repair.Second, an unsteady vortex-lattice method based on TORNADO has been implemented in order to enlarge to scope of flight conditions that can be analyzed. It has been validated satisfactorily for the sudden acceleration of a flat plate as well as for the static and dynamic derivatives of the Saab 105/SK 60.Finally, a methodology has been developed to compute quickly in a semi-empirical way the buffet envelope of new aircraft geometries at the conceptual stage. The parameters that demonstrate functional sensitivity to buffet onset have been identified and their relative effect quantified. The method uses a combination of simple sweep theory and fractional change theory as well as the buffet onset of a seed aircraft or a provided generic buffet onset to estimate the buffet envelope of any target geometry. The method proves to be flexible and robust enough to predict within mainly 5% (and in any case 9%) the buffet onset for a wide variety of aircrafts, from regional turboprop to long-haul wide body or high-speed business jets.This work was done within the 6th European framework project SimSAC (Simulating Stability And Control) whose task is to create a multidisciplinary simulation environment named CEASIOM (Computerized Environment for Aircraft Synthesis and Integrated Optimization Methods), oriented toward stability and control and specially suited for aircraft conceptual design sizing and optimization.

Place, publisher, year, edition, pages
Stockholm: KTH, 2008. ix, 37 p.
Series
Trita-AVE, ISSN 1651-7660 ; 2008-57
Keyword
Aircraft conceptual design, Computer Aided Design (CAD), buffet onset, unsteady vortex-lattice method
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-9240 (URN)978-91-7415-137-4 (ISBN)
Presentation
2008-10-27, S 40, Teknikringen 8, Stockholm, 15:15 (English)
Opponent
Supervisors
Projects
SimSAC
Note
QC 20101104Available from: 2008-10-14 Created: 2008-10-10 Last updated: 2010-11-04Bibliographically approved

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