Comparative Measurements in Four European Wind Tunnels of the Unsteady Pressures on an Oscillating Model (The NORA Experiments),
Abstract
To obtain experience of the influence of tunnel wall interference on flutter and other unsteady tests in transonic wind tunnels, a programme of oscillatory pressure measurements was repeated in four tunnels: 3ft RAE Bedford, 1M DFVLR Gottingen, S2 ONERA Modane, and HST NLR Amsterdam. These tunnels differ in the size of working section, their cross-section areas ranging from approximately 0.6 to 3.2 sq m; they also differ in the form of wall ventilation. In each tunnel, small amplitude harmonic oscillations were applied to the same rigid half-model of a low aspect ratio lifting surface, and chordwise distributions of the fundamental components of the oscillatory pressures were measured. Measurements were also made of the steady pressure distributions for the mean position about which the oscillations occurred. Some measurements were also made of the oscillatory pressures at a wall of each tunnel. Stream Mach number was varied between 0.60 and 1.10, and the mean steady incidence of the model from 0 to 5.5 deg. Tests were made for three frequencies of oscillation, the lowest, 5Hz, being regarded as a quasi-steady variation, the others, 40Hz and 60Hz, giving values of frequency parameter, based on mean chord, between 0.3 and 0.8 depending on Mach number. The results of the comparisons, whilst unable on their own to lead to rules regarding acceptable model-to-tunnel size ratios, tend to confirm current procedure. They do, however, draw attention to a possible defect in the practice of mounting a half-model at a tunnel wall that is itself ventilated.
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 01, 1980
- Accession Number
- ADA082958
Entities
People
- K. Kienappel
- N. Lambourne
- R. Destuynder
- R. Roos
Organizations
- AGARD