Hypersonic Static and Dynamic Stability of Axisymmetric Shapes - A Comparison of Prediction Methods and Experiment,
SOUTHAMPTON UNIV (UNITED KINGDOM) DEPT OF AERONAUTICS AND ASTRONAUTICS
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The stability of oscillatory motions of vehicles flying at hypersonic Mach numbers is of considerable relevance to their initial design. Methods are needed for quick and accurate predictions of stability and control which are applicable over a wide range of body shapes, angles of attack and flow conditions, without the need to resort to computationally time consuming numerical flow field calculation methods. The purpose of this paper is to present experimental data, obtained over a range of angles of attack, concerning the static and dynamic pitching stability of a wide range of both pointed and blunted axisymmetric shapes including cones and blunted cylinder flares. These data have been obtained from free oscillation experiments at M 6.85 in a short duration free piston driven hypersonic wind tunnel. Inviscid embedded Newtonian theory, which accounts for the reduced dynamic pressure and lower flow velocity in the embedded flow downstream of the strong bow shock, provides surprisingly good agreement with the experimental data over a wide range of conditions. A particular aspect is the ability of the inviscid embedded Newtonian theory to predict the effects of nose bluntness, flare geometry, angle of attack and centre of gravity position on single-degree-of-freedom oscillatory motions. Comparisons with experimental results show the broad flow features and their effect on static and dynamic stability are well described in regimes not containing flow structural change. However, in some cases discrepancies exist between the predictions and experimental observations and these have been attributed to a variety of viscous flow phenomena involving boundary layer transition and flow separation, including complex lee surface vortical flows.
- Fluid Mechanics
- Research and Experimental Aircraft