21st Congress of International Council of the Aeronautical Sciences, Melbourne, Australia, 13-18 September, 1998
Paper ICAS-98-2.8.1


Langlois M., MacDonald P.*, Masson C.**, Casalis G.***, Paraschivoiu I.*
Bombardier, Canada; *Ecole Poly technique de Montreal, Canada; **Ecole de Technologie Sup., Canada; ***ONERA, France

Keywords: stability analysis, os, pse approaches

The objective of the work described in this article is to conduct a detailed comparison of parallel and nonparallel stability results with experimental measurements. To this end, two stability analysers are used: the first one is based on the linear, three-dimensional, parallel stability equations (Orr-Sommerfeld problem) while the second one solves the incompressible Parabolised Stability Equations (PSE). The PSE formulation takes into account the variations of the mean flow and disturbance quantities in the principal direction of the flow (typically the chord wise direction) which are neglected in the parallel approach. In the PSE approach, the amplitude of a perturbation can be related to a "physically measurable" quantity, a possibility that does not exist with the parallel stability theory. It is therefore expected that the PSE results may provide a better reproduction of some experimentally observed features than has so far been obtained using the parallel theory. In this article, fluctuation spectra obtained by the OS and PSE approaches on the ONERA D and AFVD 82 swept wings are compared to hot-wire and hot-film experimental data. On the AFVD 82 wing, the theoretical spectra predicted by the PSE approach are indeed in much better agreement with the experimental data than those obtained with the parallel formulation. In the case of the ONERA D wing, the improvement in accuracy obtained by using the PSE approach instead of the parallel formulation is much less significant.

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