The FA5 test case is an industrially relevant full aircraft configuration with a small aspect ratio delta wing. Two operating conditions have been selected featuring vortex dominated and highly unsteady flow around this aircraft. In the E1 condition with all control surfaces in neutral position the flow field consists of a complex vortex system with several vortices and vortex break down phenomena. All previous simulations were not able to predict the right level of the mean axial velocity or the unsteadiness of the flow (RMS values, spectral content) with sufficient accuracy. Also vortex breakdown is predicted too early. The correct prediction of vortex breakdown is essential for the manoeuvre performance and flight control stability. The configuration already has been part of the DESider project, thus now the emphasis of this application is to show the improvements gained with the new DES/LES models within the ATAAC project by comparing the results with the final simulation of the DESider project. Also parameter studies like time step variations for example may be performed showing their effects upon the result with regard to the former computations.

Q criterion iso-surface colored by vorticity

The N5 configuration at a considerably higher angle of attack is characterised by completely a separated flow over the whole the wing and a high unsteadiness. Therefore it is an ideal application for hybrid DES or LES calculations. The configuration is partially trimmed with canard and leading edge slats being deflected. Therefore it is an application featuring more realistic flight conditions. The unsteadiness of the flow is significantly higher and the velocity fluctuations show maxima greater than 20% of the free stream value for all three velocity components. Is is expected that advanced methods can simulate the flow more precisely than present results and allow for better prediction of force and moment behaviour.

Topic revision: r1 - 2011-04-19 - 12:55:50 - FlavienBillard
04 Jun 2020
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