Proximal bodies in hypersonic flow

STUART J. LAURENCE, R. DEITERDING, G. HORNUNG
2007 Journal of Fluid Mechanics  
The problem of proximal bodies in hypersonic flow is encountered in several important situations, both natural and man-made. The present work seeks to investigate one aspect of this problem by exploring the forces experienced by a secondary body when some part of it is within the shocked region created by a primary body travelling at hypersonic speeds. An analytical methodology based on the blast wave analogy is developed and used to predict the secondary force coefficients for simple
more » ... in both two and three dimensions. When the secondary body is entirely inside the primary shocked region, the nature of the lateral coefficient is found to depend strongly on the relative size of the two bodies. For two spheres, the methodology predicts that the secondary body will experience an exclusively attractive lateral force if the secondary diameter is larger then one-sixth the primary diameter. The analytical results are compared with numerical simulations carried out using the AMROC software and good agreement is obtained if an appropriate normalization for the lateral displacement is used. Results from a series of experiments in the T5 hypervelocity shock tunnel are also presented and compared with perfect-gas numerical simulations, again with good agreement. In order to model this situation experimentally, a new force-measurement technique for short-duration hypersonic facilities has been developed, and results from the validation experiments are included. Finally, the analytical methodology is used to model two physical situations. First, the entry of a binary asteroid system into the Earth's atmosphere is simulated. Sec-iv ond, a model for a fragmenting meteoroid in a planetary atmosphere is developed, and simulations are carried out to determine whether the secondary scatter patterns in the Sikhote-Alin crater field may be attributed to aerodynamic interactions between fragments rather than to secondary fragmentation. It is found that while aerodynamic interactions lead to increased secondary crater grouping, these groups do not exhibit the typically elliptical shape that we would expect secondary fragmentation to produce. v Acknowledgements This thesis would not have been possible without the input and assistance of a number of people. My advisor, Professor Hans Hornung, gave me the freedom to pursue my own ideas, but was ready with the right piece of advice when needed. I also thank the other members of my thesis committee, Professors Tim Colonius, Dale Pullin, Joseph Shepherd, and David Stevenson, for being willing to take the time to critique this work. Additional thanks to Professor Shepherd and also to Professor Ravichandran, for being willing to lend me their expensive (and in some cases, fragile) equipment. The numerical simulations in this thesis would have been quite impossible without the diligence and patience of Dr. Ralf Deiterding; Drs. Joseph Olejniczak and James Quirk also provided much-needed assistance in this area. Thanks also to Professor Dan Meiron for providing access to the various computational facilities on which the majority of the simulations were run. The models used in the experimental investigation were skilfully and efficiently constructed by Mr. Ali Kiani in the Aero machine shop. A number of students and ex-students also provided assistance and input: in particular, Drs. Florian Pintgen, Daniel Lieberman, and Patrick Lemieux and Mr. Christopher Mouton. Thanks are also due to Mr. Mike Rubel for sorting out the various computer problems I encountered during my time in GALCIT.
doi:10.1017/s0022112007007987 fatcat:3vj7ksq5y5a4lbqu3yzjgwulyu