On evaluation of buffeting of a swept wing with high aspect ratio at transonic speeds

Аuthors

Bragin N. N., Kovalev V. E., Skomorokhov S. I.^*, Slitinskaya A. Y.^**

Central Aerohydrodynamic Institute named after N.E. Zhukovsky (TsAGI), 1, Zhukovsky str., Zhukovsky, Moscow Region, 140180, Russia

*e-mail: skomorohov@tsagi.ru
**e-mail: flinas@yandex.ru

Abstract

The article presents to the development of a technique for buffet initialization boundary evaluation, occurring on a swept height aspect ratio wing at increasing angle of attack during cruising flight modes. The lift coefficient value of the buffet onset is one of the limitations that should be accounted for while designing the win aerodynamic layout of a subsonic aircraft. According to the norms, the margin between the cruise flight mode and the C_Lbuff value or the lift coefficient of the buffet onset should be at least 30%. Thus, knowing the C_Lbuff value through the entire operational speed range is a prerequisite for an aerodynamic wing configuration design beginning from the preliminary design stage. The problem of determining the C_Lbuff has become of special urgency at the transonic speeds due to the substantial aspect ratio increase of the (by 15–20%) of the long-range aircraft wings due to the composite materials application in load-carrying structure.

Despite the successes in CFD aerodynamics gained over the last years, non-stationary separation flow modes are studied, basically, using experimental tools, including wind tunnel tests of airplanes high scale models. Though the cost of such studies is high, they ensure required reliability of the obtained results. It is worth mentioning, that the time consuming computations on multiprocessor computers are costly as well. With this, the high accuracy and reliability of the obtained results are not guaranteed. Preparing mathematical model and building-up computational meshes with hundreds of millions of nodes are commensurable with costs of developing and manufacturing scaled models for tests in the wind tunnel. Thus, numerical methods do not always prove to be less labor consuming and costly than the experimental ones. Despite the fact that computer facilities and software develop rapidly, and the situation gradually changes, experimental methods remain as before the basic tool while performing the studies of complex flows.

The article presents the analysis of typical features of the wing flow-around at the angles of attack corresponding to the start of the buffet mode. The technology of application of the program for computing transonic flow-around based on the full potential method for the buffet initialization computing is demonstrated. Computational results comparison with the data of experimental studies obtained for the model of the wing with fuselage in the wind tunnel is presented.

Keywords:

high aspect ratio wing at transonic speeds, computational studies of a civil aircraft aerodynamic characteristics, lift coefficient of buffet initialization

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