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Parameter: oswald

The Oswald efficiency, similar to the span efficiency, is a correction factor that represents the change in drag with lift of a three dimensional wing or airplane, as compared with an ideal wing having the same aspect ratio and an elliptical lift distribution.

This part of the Oswald factor calculation relates to the calculation of a theoretical lift factor for the wing of the aircraft. Further corrections are made for the Oswald factor on aircraft level.

Unit:[ ]
Wiki:http://en.wikipedia.org/wiki/Oswald_efficiency_number

Calculation Methods

oswald.calc()
This calculation is based on a multi-fidelity study that we did for the CEAS conference in 2011.
We ran a set of 500 LIFTING_LINE calculations and applied a symbolic regression application named Eurequa to the data that we obtained. The design space of this equation is:
  • taperRatio 0.1 - 0.6

  • phi25 -20deg - 30 deg

  • aspectRatio 6 - 16
    • twist -10 - 0
    • kinkRatio 0.2-0.4
Source :An Integrated Method for the Determination of the Oswald Factor in a Multi-Fidelity Design Environment, D. Boehnke, J. Jepsen, B. Nagel, V. Gollnick, C. Liersch, CEAS 2011 :Source: Distilling Free-Form Natural Laws from Experimental Data, M. Schmidt , H. Lipson, Science, Vol. 324, no. 5923, pp. 81 - 85., 2009 :Source: Ein Mehrfach-Traglinienverfahren und seine Verwendung fuer Entwurf und Nachrechnung nichtplanarer Fluegelanordnungen, K. H. Horstmann, DFVLR-FB 87-51, 1987
Dependencies :
Sensitivities :
../../../../_images/calc194.jpg
oswald.calcLiLi()

calculates the Oswald factor for the wing from LIFTING_LINE input read from CPACS. LIFTING_LINE is a multiple lifting-line code attached to CPACS. It computes the lift induced drag.

The aeroPerformanceMap created by LIFTING_LINE was imported by the cpacsImport method, if this method is triggered. A quadratic polynom will be fitted to the aeroPerformanceMap to find the Oswald factor.

Source :Ein Mehrfach-Traglinienverfahren und seine Verwendung fuer Entwurf und Nachrechnung nichtplanarer Fluegelanordnungen, K. H. Horstmann, DFVLR-FB 87-51, 1987
Dependencies :
oswald.calcRaymer()

Calculates the oswald factor for the wing. The method is taken from Raymer’s book. It is based on the aspectRatio of the wing and the sweep of the wing.

Two different formulas are applied one for a swept back wing and one for an unswept wing. The formula for the swept back wing is only taken into account for sweep angles larger than 30deg.

Source :Aircraft Design: A Conceptual Approach, D. P. Raymer, AIAA Education Series, 1992, Second Edition, p. 299
Dependencies :
Sensitivities :
Components\aircraft\wing\oswald\calcRaymer.jpg

CPACS Import

oswald.cpacsImport(path='.\cpacs.xml', TIXIHandle=None, TIGLHandle=None)

Overwrites the parameter’s cpacsImport method! Will get the value for the Oswald Factor from CPACS It will be assumed that the aeroperformanceMap holds LiLi values Does a monkey patch as it replaces oswald.calc with oswald.calcLiLi

Todo

cpacsImport oswald catch error if cfy is unequal zero