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In a previous paper "Effects of Flow Field Aerodynamics on Imaging Sensor Resolution" - SPIE 1977, it was shown that various flowfield phenomena can degrade sensor performance by causing air density variations. These phenomena were identified (Figure 1) and the degradation quantified (Figure 2). Simple aerodynamic shapes and empirical data were used to establish the relative importance of each type of flow. It was concluded that the mainstream flow field and the separated boundary layer are the major influences on sensor performance. Separated flow regions can be eliminated through proper vehicle design (elimination of abrupt mold line changes). This leaves mainstream flow as the critical phenomena--especially for large aperture sensors (Figure 2). Computer analysis techniques are now available that can accurately model mainstream flow. The program called AFTEND computes the vehicle flow field in three dimensions from freestream to the vehicle surface including the turbulent boundary layer. The location and strength of local shocks also are identified. Details of this analytic technique will be available later this year in a paper authored by Ray Cosner of McDonnell Aircraft Company (MCAIR). (Reference 1). The following paragraphs apply this program and present results for a typical reconnaissance aircraft.© (1981) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only. |
