| Presently, the cylindrical sludge digester is wildly used at home, and its sesmic analysis is a typical problem concerning fluid-structure interaction. But the systemic study about the digester is scarce, and the mass-added method which isn't calculating wave effects of free surface, can't realize the actural fluid-structure interaction. So make use of advanced fluid-structure coupling theory and with the separate modeling in ADINA program, this paper wants to deeply research dynamical characteristics of the digester. The main research achievements are as follows:1. Present research on liquid-solid coupled system is described in brief, and the theroy and computing method of a cylindrical sludge digester are choosed.2. Computing the coupled modes of the cylindrical sludge digester and tank with the velocity potential-displacement format. To study their nature frequencies with fluid and mode shapes, it is analyzed in four aspects: structure shape, deepness of liquid, stlffness of shell wall and wave effects of free surface. The result is that, the anterior three factors are more influential, while wave effects of free surface make no difference.3. In the seismic analysis, we separately analyze the dynamic response of a sludge digester under the EL Centro wave and Tianjin wave.Basing on ALE method and separate modeling, It can realize the instantaneous changing of free surface and liquid-solid interface gridding, without more supposition of the fluid. The sesmic result of the cylindrical sludge digester is that: (1) Maximal hydrodynamic pressures under these two sesmic waves are less than 40 percents of relevant hydrostatic pressures. (2) Dynamic response of the digester is very sensitive to wave shape and frequency characteristic of the input sesmic wave.
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