Measuring Vortex-Induced Vibration with Hot Wire in Wind Tunnel
Long cantilever stings that support aerodynamic models in wind tunnels are a potential source of vibration problems which would damage test data quality, many documents use the methods of setting acceleration sensors on model to measure vibration of model-sting system, but setting sensors on little scale model is hard to realize, and sensors could interfere with flow field around the model. For purpose of reducing flow field interference, a method of hot wire probe measuring wake to acquire vibration parameters of model is tried, this way is easy to realize for little scale model. At the same time, methods of accelerator signal frequency domain filtering and frequency domain integration are used to acquire vibration model parameters of model-sting for comparison with data of hot wire, this method could improve the SNR of effective signal. Using method of accelerator signal power spectrum analysis, three order vibration frequencies of 31.1Hz¡¢120.9 Hz and 221.4Hz of the system are acquired. Using method of frequency domain filtering and frequency domain integration, the vibration mode and node of the system are acquired. Using method of hot wire measuring wake, vortex shedding frequencies of 31.1Hz and 124.1 Hz, and the model buffet boundary are acquired. Experiment results show that, the method of hot wire measuring model wake vortex shedding frequency for analysis of aircraft model vibration, is convenient for little scale model test, is a practical method for vortex-induced vibration measurement.
Measurement and analysis of a gust generator flow field in wind tunnel
A pilot gust generator is as experiment object,by measuring the flow field of the gust generator in different situations with two dimension hot wire anemometer,the measurement scheme and online measuring angle correction,and the calculation of the gust amplitude and flow fluctuation are proposed.Experiment results show that online angle correction used can improve the accuracy and efficiency of two dimension hot wire in Ydirection,phase analysis used can satisfy the calculate the amplitude and fluctuation of periodic gust.Gust amplitude is in direct ratio with the vane oscillation frequency of 4~15Hz,oscillation angle of 8°~30°,and vane chord length of 50~100mm.Unstability(velocity fluctuation at same phase)of the gust flow has a certain linear relationship with the vane oscillation angle and wind speed,which increases while the vane oscillation angle and wind speed increase in the test range,at the same time,proper vane oscillation frequency can decrease unstability.The conclusion is helpful for the gust generator development and flow field measurement in wind tunnel.
National Transonic Facility model and model support vibration problems
Vibrations of models and model support system were encountered during testing in the National Transonic Facility. Model support system yaw plane vibrations have resulted in model strain gage balance design load limits being reached. These high levels of vibrations resulted in limited aerodynamic testing for several wind tunnel models. The yaw vibration problem was the subject of an intensive experimental and analytical investigation which identified the primary source of the yaw excitation and resulted in attenuation of the yaw oscillations to acceptable levels. This paper presents the principal results of analyses and experimental investigation of the yaw plane vibration problems. Also, an overview of plans for development and installation of a permanent model system dynamic and aeroelastic response measurement and monitoring system for the National Transonic Facility is presented.