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This Defense Intelligence Reference Document from the Defense Intelligence Agency, dated 20 November 2010, was one of a series of advanced technology reports produced in FY 2010 under the Advanced Aerospace Weapon System Applications (AAWSA) Program. It reviews the theory of subsonic, supersonic and hypersonic flow. It then compares electromagnetic, optical, and acoustic and seismic methods for detecting and tracking hypersonic objects, and it makes four recommendations for progress over the next 30 years.
“Anderson”2 pages
UNCLASSIFIED// FOR OFFICIAL "31!! SUL¥ viscous f"orces V D Re= • =-- inertial forces v (3) In this expression, Vis the velocity of the projectile, D is its effective diameter, and v is the kinematic viscosity of the fluid. As flow passes over the projectile in Figure 1, viscous forces are especially strong near the surface where the velocity changes from zero at the surface of the projectile to the free stream velocity. .---- Streamlines Boundary Layer ' ' ' '''' Direction of Flow Figure 1. Boundary Layer Development in Subsonic Flow About a Projectile. The region where this transition in velocity occurs is called a "boundary layer," which grows in thickness as flow moves along the surface from the nose to the rear of the projectile. The boundary layer forms around the surface of the projectile and "separates" from the surface at the back end of the projectile. Pockets of fluid spill off of the back end of the projectile and form rotating pockets of fluid called Strauhal eddies or vortices. These eddies "shed" from the surface at a rate that is strongly dependent upon the Reynolds number in the flow. Figure 2 demonstrates that these eddies form a "wake" downstream of the projectile that can extend far into the fluid. 4 UNCLASSIFIED//r;Oll oi;i;1111,t.k Wliili a,11e~·
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Report, from the dia collection. The PDF is mirrored here; the original link is above. 46 pages are in the text index: search them above, or from the library's search.