Papers by Keyword: Aerodynamic Model

Abstract: Systematic monitoring of rotational vibration (both torsion and swivelling) of guyed mast shafts has been performed in ITAM since 2005. The occurrence of this phenomenon is conditioned by the fact that the guy ropes are attached to the construction of the shaft, i.e. out of its axis. The simple static calculation model serves for making the proof of the occurrence of the torsional moment, affecting the shaft, which is guyed by three ropes. The exact theoretical solution of the real phenomenon assumes the introduction of dynamics of guy ropes, which vibrate in 3D shapes during the shaft’s movement along the orbit and it ́s torsion (swivelling).

Abstract: Based on the analysis of the flight stability, the research progress of the unsteady aerodynamic model was comprehensively introduced. Bryan, first of all, the aerodynamic load of traditional dynamic derivative model is put forward, still used today in some engineering issues. However, Bryan state parameters of the model is not complete, not exactly reflect the unsteady aerodynamic force time history effect and nonlinear effect. Etkin models, by retaining the item of high order Taylor expansion, including the influence of nonlinear effect. Improved Etkin model can explain the actual flight of some of the common transient response, including due to stall the mutation and aerodynamic force/torque caused by unsteady flow dynamic bifurcation and chaos of the aerodynamic force/torque value and uncertain phenomenon. Finally, the unsteady flow field of a reduced order model development trends and application prospect were analyzed, and pointing out that the CFD simulation is still accurately predict the plane stability and handling the most important method.

Abstract: The torsion of the mast shaft has been monitored on several masts in the Institute of Theoretical and Applied Mechanics (ITAM) since 2005. The occurrence of this phenomenon is conditioned by the fact that the guy ropes are attached out of the axis of the mast shaft. An experimental mast-shaft model of 15 m height guyed in 3 directions was used for the more detailed study of its rotational motion. The excitation was realized by transversal auxiliary rope drawn by harmonic human force in resonance. The displacement of the shaft top results in translation caused by the guy force and the rotation, caused by the eccentricities of the guy-ropes, attached out of the shaft axis. The resulting movement of the shaft support is an elliptical orbit. The shaft of our experimental mast was equipped in two levels with accelerometers for registration of horizontal x, y motions. The two x, y signals in two levels were monitored and analysed.

Abstract: To describe the dynamic characteristics of flight vehicle accurately, a Relevance Vector Machine (RVM) aerodynamic modeling method is proposed. RVM is a learning method which is based on Bayesian learning theory. Compared with Support Vector Machine (SVM), it has the benefits such as probabilistic predictions, sparser model, facilities to select arbitrary basis function and so on. Experimental results show that the proposed method can obtain the aerodynamic model with higher accuracy by less relevance vector. It is also effective and feasible for aerodynamic modeling.

Abstract: The structure of vertical axis wind turbine with wind speed-adapting is based on Darrieus straight-bladed turbine. It features that its blades are composed of movable and fixed blades. Through the opening and closing of the movable blades to adapt to the wind speed automatically, the turbine not only can start up in low wind speed, but also realize the conversion from drag-mode to lift-mode. Due to the special structure, the aerodynamic model of this turbine in drag-mode is different from that of Savonius and Darrieus turbine. So in this article, the aerodynamic model of this turbine in drag-mode is established. Then the coefficient of start-up torque is calculated and compared with that of Darrieus straight-bladed turbine which has the same size. The results show that the start-up performance of this turbine is obviously better than that of Darrieus straight-bladed turbine.

Abstract: The expansion chamber mufflers compounding with the perforated panels are commonly used in the suppression of intermittent exhaust noise (IEN) generated by the exhaust air from the cylinder and ducts of pneumatic devices. The flow resistance and noise reduction performances of IEN are both important. A simplified aerodynamic model is presented to study the flow characteristics in the pneumatic cylinder and chambers of the muffler with perforated panels. The relationship between pressure and mass flow rate is established in the transient exhaust process. Validation experiments measuring the cylinder pressure and exhaust noise of the pneumatic friction clutch and brake (PFC/B) exhaust system installed a three-level perforated panel muffler which can be separated show that the calculated results are very close to that of the actual exhaust process.

Abstract: This study presents an approach to leak detection of pipeline review in terms of theoretical analysis such as acoustics and hydromechanics that should be accompanied by explanation of leakage. The acoustic emission signals during leak from circular hole of different geometries were studied both analytically and experimentally. The relationships between acoustic parameters and fluid mechanical parameters also were derived analytically. A quadrupole aerodynamic model was applied for the analysis of leak from the circular hole. Computer simulation results demonstrate the effectiveness of the proposed approach. In addition, it was confirmed that the wavelet transform (WT) was an effective tool to determine source location. That is, arrival times of each frequency component needed in the velocity calculation could be determined from the peak of the magnitude of wavelet transform data on the time-frequency plane.