Abstract
The influence of the flight attitude on aerodynamic coefficients and static stability of cylindrical bodies in hypersonic flows is of interest in understanding the re/entry of space debris, meteoroid fragments, launch-vehicle stages and other rotating objects. Experiments were therefore carried out in the hypersonic wind tunnel H2K at the German Aerospace Center (DLR) in Cologne. A free-flight technique was employed in H2K, which enables a continuous rotation of the cylinder without any sting interferences in a broad angular range from 0^{circ } to 90^{circ }. A high-speed stereo-tracking technique measured the model motion during free-flight and high-speed schlieren provided documentation of the flow topology. Aerodynamic coefficients were determined in careful post-processing, based on the measured 6-degrees-of-freedom (6DoF) motion data. Numerical simulations by NASA’s flow solvers Cart3D and US3D were performed for comparison purposes. As a result, the experimental and numerical data show a good agreement. The inclination of the cylinder strongly effects both the flowfield and aerodynamic loads. Experiments and simulations with concave cylinders showed marked difference in aerodynamic behavior due to the presence of a shock–shock interaction (SSI) near the middle of the model.Graphic abstract
Highlights
Aerodynamics of simple-shaped bodies in high-speed flows is generating renewed interest in the field of atmospheric entry of meteoroids, space debris and separating components of launch systems
NASA’s inviscid flow solver Cart3D and compressible Navier–Stokes solver US3D were employed for numerical simulations
In comparison to the present experimental results, the literature value for cylinders in axial flow by Hoerner (1965) slightly underestimates the aerodynamic drag coefficient, whereas a very good agreement is revealed for cylinders in crossflow
Summary
Aerodynamics of simple-shaped bodies in high-speed flows is generating renewed interest in the field of atmospheric entry of meteoroids, space debris and separating components of launch systems. In the past decade, the characterization of flowfields around single (Lee et al 2017; Seltner et al 2019; Rees et al 2020; Grossir et al 2020) and multiple bodies (Laurence et al 2012; Marwege et al 2018; Park and Park 2020; Register et al 2020) has gained importance with respect to fragmentation, demise and separation behaviors of these space objects undergoing atmospheric entry. Vennard (1940) and Rouse (1946) called attention that drag coefficient CD significantly depends on Mach number as well as it is affected by the forebody shape in axial flows at transonic and supersonic speeds They suggested to decrease drag by streamlining the body. Hoerner mentioned that the cylinder length has no noticeable effect on drag coefficient under supersonic axial-stream as tested in the aspect ratio (l/d) range from 2 to 5. Maslach and Schaaf (1962) investigated the drag of cylinders in the transition from continuum to free molecular flow under supersonic conditions, which suggests a continuous increase between the two flow regimes
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