科研之友
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摘要
Sonic boom pressure profiles calculated by modified linear theory are evaluated. These methods transform parametric descriptions of aircraft into F-functions, which are used to predict the pressure profiles after propagation through the atmosphere. Although Whitham's F-function equation is the most widely used method, it cannot be applied to aircraft that have discontinuities in their area profiles. Lighthill's F-function is explored as an alternative. Procedures are presented to adapt Lighthill's method so that it can be used for numerical calculations. Sonic boom pressure profiles from wind tunnel experiments, computational fluid dynamics, and flight tests are compared to profiles from Lighthill's method to explore its accuracy. In general, Lighthill's method is able to predict the sonic boom shape, magnitude, and duration within 10% and account for variations in lift, Mach number, and propagation angle. Sonic boom predictions are presented for the XB-70 to demonstrate limitations in modified linear theory. Its complex shape is not easily transformed into an axi-symmetric area profile, reducing the accuracy of the pressure profile. However, this study demonstrates that modified linear theory is a fast and sufficiently accurate method to predict sonic booms and is appropriate for the preliminary and conceptual design stages of quiet sonic boom aircraft.
- 出版日期2015-12
