Повышение эффективности испытаний моделей самолетов на флаттер с использованием измерительно-информационных систем в дозвуковой аэродинамической трубе

Abstract

The technology of testing dynamically and structurally similar aircraft models for flutter in subsonic wind tunnels using information and measurement systems (IMS) is based on collection and processing of experimental data obtained in subcritical modes. The data received feature a significant scatter, in view of which the critical flutter speed is determined with acceptable accuracy only after its statistical post-processing. In view of the need to study a number of model versions during the flutter tests, the technology involved significant time spent for wind tunnel air flow startups and for processing of experimental data. To decrease the above-mentioned time expenditures, a more efficient technology was developed, using which it becomes possible, owing to a more sophisticated IMS structure, to quickly determine the critical flutter speed with acceptable accuracy directly in the course of tests. The essence of the new technology is that it eliminates interference that occurs in the existing system by introducing data transmission equipment into the IMS structure via a wireless Wi-Fi network. In view of this feature, it becomes possible to do the following in the course of testing the model for flutter in subcritical modes: to record the model time response to the impulse force, perform its spectral analysis, and plot the amplitude spectrum. The plotted amplitude spectrum is then used to measure the fundamental harmonic component, calculate and plot the functional dependence of the quantity inverse to the amplitude of the model oscillations fundamental tone on the flow velocity using approximation and extrapolation methods. The critical flutter speed is determined with acceptable accuracy when the functional dependence graph crosses zero. It is shown that the use of the proposed technology in flutter tests makes it possible to shorten the time taken to start the wind tunnel by a factor of 5 and the time taken to process the experimental data by a factor of 6, with the resulting error not exceeding 5%. It is recommended to use the technology in the Central Aerohydrodynamic Institute's subsonic wind tunnels in performing aircraft models flutter tests.