Prediction of Base-Flows,
OFFICE NATIONAL D'ETUDES ET DE RECHERCHES AEROSPATIALES CHATILLON-SOUS-BAGNEUX (FRANCE)
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The base region of a missile or a launcher is the seat of complex phenomena which can have important repercussions on vehicle performance. Prediction of these phenomena is of great practical interest for missile design. This paper presents the basic principles underlying most of the methods currently used to compute base-flows. These methods belong essentially to the following three categories In the inviscidViscous Interactive approach, the outer inviscid flow and the viscous regions are computed together and made compatible along a common boundary. In the Multi-Component approach, the flowfield is decomposed into a limited number of regions which are treated by approximate methods and then patched together. This approach has led to the development of a large variety of practical methods which are still routinely used in industry. The most recent approach consists in solving the time averaged Navier-Stokes equations. Base-flows in the jet-off and jet-on situations are now computed by solving the full Navier-Stokes equations or the thin layer approximation of these equations. Although still costly in computer time and not always in good agreement with experiment because of the difficulty of modeling turbulence in such complex flows, the Navier-Stokes approach is particularly promising. It appears as the most straightforward way to extend prediction capability to three-dimensional flows. Presentation of these approaches is illustrated by applications as well as comparisons with experiment.
- Fluid Mechanics
- Guided Missiles