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.
Experimental evaluation of an active vibration control system for wind tunnel aerodynamic models
This study presents an active vibration control(AVC)system that can significantly suppress dangerous low-frequency resonant vibration of the wind tunnel aerodynamic model at high angles of attack.A novel learning controller is proposed to increase the damping of the stiff-mounted model structures to minimize certain resonant responses.The corresponding control algorithm has a very simple structure which consists of two time-domain learning components in additive form: a fixed gain learning mechanism and a variable gain learning mechanism,both of that are all based on present and previous response information so that no a priori system modeling is required.The interactions between the learning components have been explored and they have been shown to be complementary to each other.The developed AVC system is experimentally examined by a practical wind tunnel aerodynamic model test system for near-resonant excitation cases.The experimental results indicate the effectiveness and feasibility of the presented AVC system,and the proposed controller is highly promising for this application field.
Technical Evaluation Report on the Fluid Dynamics Panel Symposium on Aerodynamic Data Accuracy and Quality: Requirements and Capabilities in Wind Tunnel Testing
Abstract : This report presents a technical evaluation and assessment of the AGARD Fluid Dynamics Panel Symposium on 'Aerodynamic Data Accuracy and Quality: Requirements and Capabilities in Wind Tunnel Testing', held in September 1987 in Naples, Italy. The major issues addressed were: what data accuracy do users need; what accuracy is presently achieved; and what can be done to improve the situation? Users have asked that cruise drag be measured to a precision of one drag count for transports and two for military fighters; and it was shown that this is possible when reference methods can be used. However, one or two drag count uncertainty is not state-of-the-art for the direct scaling concept and improvement will require a thorough understanding of all those parameters which significantly contribute to wind tunnel uncertainty, including bias and precision. A reduction in total uncertainty appears possible but a reduction to a level of one or two drag count also appears formidable. Keywords: Aerodynamic characteristics; Accuracy; Wind tunnel tests; Precision; Measurement; NATO furnished.