A study of the characteristics of transonic buffet pressures on a large hammerhead configuration /

The transonic fluctuating pressures over a large hammerhead configuration are investigated. The study examines existing experimental data on other configurations, presents fluid-mechanical arguments, derives a number of concepts and scaling parameters, and finally makes estimates of the fluctuating pressure characteristics for a large hammerhead configuration. The significant findings are as follows: (1) All the fluctuating pressure fields examined seem to indicate a strong influence of a square-wave type of random fluctuation in the low-frequency region; (2) A square-wave type of pressure fluctuation can arise from the random oscillation of the separation point because of stream-wise disturbances or cross-stream disturbances, or from the intermittency of a free boundary; (3) In a narrow range of high subsonic Mach numbers, a periodic modulation of the random pressure fluctuation can arise from shock-wave oscillation. (4) The turbulence field seems to have a 'memory' - a short one at least. (5) The large eddies in the turbulence field apparently dominate the statistical properties; (6) The magnitude of the fluctuating pressures seems to be linearly dependent upon the mixing region or shear layer thickness and can be enhanced by a positive pressure gradient. (7) The unsteadiness of the separation surface behind the backward-facing step of a hammerhead configuration can be visualized as a series of 'teeter-totters' lined up side-by-side around the perimeter and randomly going up-and-down. Thus, a revolving motion of the hammerhead about the flow axis might be induced. (Author)."June 1967."Includes bibliographic references (pages 69-71).The transonic fluctuating pressures over a large hammerhead configuration are investigated. The study examines existing experimental data on other configurations, presents fluid-mechanical arguments, derives a number of concepts and scaling parameters, and finally makes estimates of the fluctuating pressure characteristics for a large hammerhead configuration. The significant findings are as follows: (1) All the fluctuating pressure fields examined seem to indicate a strong influence of a square-wave type of random fluctuation in the low-frequency region; (2) A square-wave type of pressure fluctuation can arise from the random oscillation of the separation point because of stream-wise disturbances or cross-stream disturbances, or from the intermittency of a free boundary; (3) In a narrow range of high subsonic Mach numbers, a periodic modulation of the random pressure fluctuation can arise from shock-wave oscillation. (4) The turbulence field seems to have a 'memory' - a short one at least. (5) The large eddies in the turbulence field apparently dominate the statistical properties; (6) The magnitude of the fluctuating pressures seems to be linearly dependent upon the mixing region or shear layer thickness and can be enhanced by a positive pressure gradient. (7) The unsteadiness of the separation surface behind the backward-facing step of a hammerhead configuration can be visualized as a series of 'teeter-totters' lined up side-by-side around the perimeter and randomly going up-and-down. Thus, a revolving motion of the hammerhead about the flow axis might be induced. (Author).Report prepared by Aerospace Corporation, Applied Mechanics Division, El Segundo, California, for Space Systems and Ballistic Systems Divisions, United States Air Force, under contract No.Mode of access: Internet