| With the rapid development of ship industry and quickly changing of naval equipment construction, the need of water supply in ship increases, so more and more ships set up suction boxes which locate in the stem, amidships and stern, in that suction boxes transfix bottom plating and hull bottom connect with sea water. Moreover they are cave-in cavity without free surface at the top. Represented by the suction box the problem of fluid induced oscillation of cave-in cavity is paid close attention again by many researchers.Under certain conditions the alternating force caused by fluid induced oscillation will lead to phenomenon of "fluid force resonance" and "fluid induced vibration", finally fatigue life of cave-in cavity would be damaged, which will have adverse influence on normal operations. If reasonable forecast of fluid induced oscillation characteristic can be given in complex fluid, their fatigue life will be increased greatly, at the same time the foundation of cave-in cavity'design will be put forward.Aiming at many problems of fluid induced oscillation of cave-in cavity, combining basic research projects of national defense science, technology and industry, besides searching many latest research results on fluid induced oscillation of cavity, a series of experimental and contrastive research methods are carried out in this paper. The purpose is to open out mechanism of fluid induced oscillation on cave-in cavity, and the influencing rule of all kinds of parameter on fluid induced oscillation is given. The main content of this thesis includes the following aspects:1,On the basis of validly grasping numerical calculation method of cavity separation numerical design method on experimental project is opened out. Aiming at experimental influencing factors and taking on new phenomena a series of numerical experiment are carried out. The problems of cave-in cavity's FSO and ship model's Green Water are studied using CFD method, then experimental project is optimized, forever experimental phenomena is predicted.2,Aiming at the problem of cave-in cavity's FSO LES calculating model is adopt to complete numerical research in uniform. Based on the calculating results combining basic theory of vortex dynamics, shear layer oscillation and internal dynamic mechanism of cavity flow are analyzed.3,Aiming at different cavity types, experimental method of constructive analysis is adopted to complete a series of experimental research on flow induced oscillation problem of three dimensional cave-in cavity, which subjected to uniform field and wave flow field. Moreover the pressure signals of cavity's sidewall are measured, and the influence of attack angle, wave cycle and wave height on the characteristics of fluid induced oscillation of cavity are considered. The influencing rule is presented and estimating formula of Cp and St are opened out.4,Considering the conditions at different incoming and wave flow, the rules of flow forces versus Re number and KC number separately are analyzed. At the same time the influence of wave height, wave frequency, incoming velocity and incoming angle on frequency of the shear layer are analyzed. Then the rule of shear layer versus velocity is given.5,Aiming at the problem of flow of cavity inner having the mass exchange with outside, the different cavity type's experimental research with mass exchange are carried out, which separately subjected to uniform field and wave field. Then the influence rules of mass exchange on the distribution of flow forces of cavity inner and characteristic of shear layer oscillation are given. |
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