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Regan, D. R.

Publications and source records attributed to Regan, D. R..

Two-dimensional wake characteristics of inlet vanes for open-circuit wind tunnels

This paper summarizes the near-field flow characteristics measured downstream of a half-scale two-dimensional wind-tunnel model of the inlet vanes designed for the National Full-Scale Facilities Complex at NASA Ames Research Center. Variations on this baseline were tested to determine how the downstream flow field is affected. Evaluations of the various configurations were made by the use of hot-wire surveys across the flow-field. These traverses yielded the properties of total pressure, boundary layers, and turbulence in the wake of the vanes. It was found that large variations in the flow field characteristics downstream of the vanes are achieved by the use of various arrangements of splitter vanes, vortex generators, screens, tail extensions, and honeycomb. Separation on the boat-tails of the vanes can be controlled and turbulence reduced by suitable combinations of screens or honeycomb or both. The penalties associated with each modification in terms of increased pressure loss are also presented.

Dudley, M. R.↗

Multitube turbojet noise-suppression studies using cross-correlation techniques

The noise-generating region of a suppressed turbojet exhaust is studied by cross-correlating static pressure fluctuations within the exhaust with far-field sound for Mach numbers up to 0.99, using a 31-tube nozzle having an area ratio of 3.1. Measurements made with an unsuppressed turbojet exhaust having an equivalent area ratio and operating under effectively equal thrust loads serve as the experimental control. Static pressure-level measurements, made with a calibrated high-temperature acoustically damped probe tube, show that noise suppression by multitube nozzles results from reduced turbulence levels. The maximum fluctuating static-pressure level in the unsuppressed turbojet exhaust is typically 5-6 dB higher than static-pressure levels in the suppressed exhaust under conditions of effectively equal static thrust. This suggests that the turbulence intensity in the multitube suppressor flow is reduced in excess of 20% compared with the unsuppressed jet exhaust.

Regan, D. R.↗

Cross-correlation of noise produced inside a hot turbojet exhaust with and without suppression using a new, hot probe

The noise producing region of a hot turbojet exhaust is studied by cross-correlating hydrodynamic pressure fluctuations within the exhaust with far field sound for Mach numbers up to 0.99. Measurements are made on unsuppressed engine and on a suppressed engine fitted with a 31-tube multijet nozzle. Hydrodynamic pressure fluctuations inside the hot exhaust are measured using a special 1/4 inch diameter probe tube (acoustically damped and air cooled), fitted with a ported nose cone. Maximum, normalized cross-correlations of 0.2 are found for Ma = 0.99 at an angle of 30 deg.

Meecham, W. C.↗