Sociology O Level Notes Pdf
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The negative effects of the phenomenon are obvious. Firstly, a larger wind speed decrement will be generated when the performance of an aircraft, ship, or vehicle is observed. In aviation, aircraft manufacturers constantly monitor the envelope of flight and combat aircraft. A smaller wind speed decrement may be the result of the phenomenon. Secondly, the pressure fluctuation phenomenon at different frequencies generates a great deal of noise in the surrounding environment, which is also a negative factor for human beings’ vision and hearing. Thirdly, the pressure fluctuation phenomenon in open-jet wind tunnels is directly related to the opening of the nozzle, which can cause the increase of the sound velocity and sound pressure. Short-wavelength sound waves may be superimposed on the wind tunnel sound waves, leading to the large amplitude fluctuations of a wind tunnel sound field; these fluctuations may cause cancellation of wave effects, resulting in a reduction of the amplitude of the original sound pressure field. Therefore, reducing the phenomenon is a core part of wind tunnel design and a kind of urgent self-protection or priority control nowadays.
In this paper, a preliminary model of open jet wind tunnel dynamics is established. Compared with the existing models of open jet wind tunnel, the ordered open jet model is equipped with obstacles, agenerator, and a return flow flow field device. The validity of the open jet model is verified by the model of Gorner3, which is based on the established model. Finally, the model establishment of an open jet wind tunnel with a return flow flow field device is also compared to the return flow open jet wind tunnel of Zhang et al. The core idea of the return flow open jet wind tunnel is to use the momentum flow of the return flow to increase the wind speed of the test section and enlarge the amplitude of the generated structure and thereby increase the lifetime of the structure. In the return flow structure, the velocity ratio of return flow to the main flow is 1.8. In this study, the open jet model is modified from the original model by adding the return flow and a generator. The return flow device in this paper is a generator with the axis length of 3.5 meters and the maximum diameter of 1.25 m. Other parameters are described in this paper. The open jet structure is made by aluminium, copper, and polycarbonate. The maximum temperature was used as 5000°C. The nozzle at an opening angle of 45° is equipped with six sets of row-inserted baffles. d2c66b5586