Engineering topics

Shenoy, Rajarama K.

Publications and source records attributed to Shenoy, Rajarama K..

3 records

NASA NTRS1991

Development and validation of 'quiet tail rotor' technology

Systematic research leading to the development and validation of a 'quiet' full-scale tail rotor is described in this paper. Hover performance and acoustic test results acquired on the Sikorsky tail rotor whirl test facility, and some early results from the just-concluded flight tests are provided. The results show that substantial reduction in noise signature can be achieved simultaneously with improvements in performance when advances in aerodynamic and aeroacoustic technologies are judiciously applied.

Shenoy, Rajarama K.↗

NASA NTRS1989

Aeroacoustic flowfield and acoustics of a model helicopter tail rotor at high advance ratio

Some results, relevant to rotorcraft noise generation process at high advance ratio, are presented in this paper from schlieren flow visualization and acoustic tests of a model tail rotor. The measured in-plane noise trends are consistent with the growth of the tip supersonic region seen in the schlieren visuals. Schlieren flow visuals reveal a propagating pressure wave in the second quadrant. Simultaneously measured acoustic data and the results of two-dimensional transonic Blade-Vortex Interaction analysis code ATRAN-2 indicate that this pressure wave is attributable to BVI activity in the first quadrant. This paper establishes that the transonic Blade-Vortex Interactions contribute to noise at high advance ratio level flight conditions.

Shenoy, Rajarama K.↗

NASA NTRS1986

Acoustic characteristics of 1/20-scale model helicopter rotors

A wind tunnel test to study the effects of geometric scale on acoustics and to investigate the applicability of very small scale models for the study of acoustic characteristics of helicopter rotors was conducted in the United Technologies Research Center Acoustic Research Tunnel. The results show that the Reynolds number effects significantly alter the Blade-Vortex-Interaction (BVI) Noise characteristics by enhancing the lower frequency content and suppressing the higher frequency content. In the time domain this is observed as an inverted thickness noise impulse rather than the typical positive-negative impulse of BVI noise. At higher advance ratio conditions, in the absence of BVI, the 1/20 scale model acoustic trends with Mach number follow those of larger scale models. However, the 1/20 scale model acoustic trends appear to indicate stall at higher thrust and advance ratio conditions.

Shenoy, Rajarama K.↗