The extra-large parachutes were different from the common parachutes because of their size and opening process. Some undesirable inflation phenomena such as canopy winding and whipping usually appeared in their pre-inflation process. However, the mechanical mechanism of these phenomena was very difficult to be explained by experimental means. In this paper, the pre-inflation process in finite mass situation of an extra-large parachute was calculated by explicit finite elements. According to the results, the pre-inflation process can be subdivided into symmetric inflation stage, undesirable inflation stage, and stable inflation stage. The canopy winding and whipping mainly occurred in the second stage. With the continuous deceleration of parachute-payload system, the top of canopy without effective constraints would appear winding and whipping under the function of inertia force. The canopy winding and whipping increased the difficulty of canopy expanding and then caused asymmetric inflation. The above undesirable phenomena had a great influence on the deceleration effect and were easy to cause the recovery failure. The actual airdrop experiments also proved that the lack of effective constraints on the canopy top will cause undesirable inflation phenomena. The conclusions in this paper can also provide a reference for extra-large parachute design and research.
In order to study the influence of rainstorm on parachute dropping, the smoothed particle hydrodynamics/arbitrary Lagrangian–Eulerian coupling method is proposed. Finite elements are used to describe the continuous material such as fabric and air flow field, and the smoothed particle hydrodynamics particles are used to describe the discrete raindrops. The coupling between different fluid and structure is realized by penalty function. In order to distinguish the most influential factor of rainstorm environment on parachute, the effects of raindrop field and wind field in rainstorm are studied, respectively. It could be found that the raindrop fields with different droplet sizes have little effect on the parachute’s shape, opening shock, and performance according to the comparative analysis, while the vertical wind field has a great influence on parachute’s deceleration performance. The wind field, not the raindrop field, is the most important factor affecting the parachute’s deceleration performance. The method and conclusions in this article could provide some references for parachute design.
Since the society enters the information age, science and technology have changed with each passing day. Electronic information has deeply affected social development and people’s life. Based on the statistical correlation algorithm, this study analyzes the establishment model of statistical correlation algorithm. Then, the feature extraction technology of electronic information is obtained according to the statistical correlation algorithm, which promotes the development of electronic information., Afterwards, the feature extraction methods of electronic information among four cities of Beijing, Shanghai, Chongqing and Tianjin are compared and analyzed in detail. The experimental results show that the electronic information feature extraction method based on statistical correlation can be well applied in four municipalities directly under the central government, which provides some theoretical and experimental support for the electronic information feature extraction method in our country.
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