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UNSTEADY AERODYNAMICS FOR ADVANCED CONFIGURATIONS. PART VII. VELOCITY POTENTIALS IN NON-UNIFORM TRANSONIC FLOW OVER A THIN WING
Final rept. 1 Jul 1965-30 Aug 1967
NORTH AMERICAN ROCKWELL CORP LOS ANGELES CA LOS ANGELES DIV
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Two methods were outlined in detail, and one of them was mechanized, for calculating acoustic ray paths emanating from any point in a non-uniform transonic flow field surrounding a wing. It gives the ray path, and the time, for the minimum time of travel from the acoustic source point to the field point. The resulting velocity potential is also computed. It was necessary to establish an accurate representation of the flow characteristics in the field surrounding the wing. Some ray lines travel over the planform and into the surrounding flow field. It was established that once off the planform they do not return. Available methods predict phase lags based on the assumption that acoustic rays travel in straight lines. The results of the study show this to be a very poor approximation at transonic speeds. Therefore, it is recommended that the method presented in the report be fully developed for the purpose of calculating generalized forces on wings in harmonic motion at transonic speeds. A computer program that would predict these phase lags with reasonable accuracy, and the corresponding flutter characteristics and unsteady aerodynamic loads on a wing responding to externally applied forces, such as gusts, would fill an important gap in the available technology.
APPROVED FOR PUBLIC RELEASE