Re-Computation of Numerical Results Contained in NACA Report No. 496.

摘要

An extensive examination of NACA Report No. 496 (NACA 496), "General Theory of Aerodynamic Instability and the Mechanism of Flutter," by Theodore Theodorsen, is described. The examination included checking equations and solution methods and re?computing interim quantities and all numerical examples in NACA 496. The checks revealed that NACA 496 contains computational shortcuts (time? and effort?saving devices for engineers of the time) and clever artifices (employed in its solution methods), but, unfortunately, also contains numerous tripping points (aspects of NACA 496 that have the potential to cause confusion) and some errors. The re?computations were performed employing the methods and procedures described in NACA 496, but using modern computational tools. With some exceptions, the magnitudes and trends of the original results were in fair?to?very?good agreement with the re?computed results. The exceptions included what are speculated to be computational errors in the original in some instances and transcription errors in the original in others. Independent flutter calculations were performed and, in all cases, including those where the original and re?computed results differed significantly, were in excellent agreement with the re?computed results. Appendix A contains NACA 496; Appendix B contains a Matlab(Reistered) program that performs the re?computation of results; Appendix C presents three alternate solution methods, with examples, for the two?degree?of-freedom solution method of NACA 496; Appendix D contains the three?degree?of?freedom solution method (outlined in NACA 496 but never implemented), with examples.