Structure Performance Analysis Of Composite Shell Under Internal Waves

Internal waves is a kind of gravity waves which is happened to ocean layered structure (such as the density is stable stratified).And its maximum amplitude occurs in the inside of the ocean. With the same dynamics as surface waves, internal waves play an important role in the ocean.This paper firstly reference other peoples'results on constructing a math model for internal waves based on theory of the boundary element method and numerical simulation about the force exerted by internal waves on an underwater composite shell in the stratified ocean. Based on this conclusion, I find that practical internal waves loading is uneven distributing on the surface of composite shell and its magnitude is also changing with the distance between structure and density-spring layer changing. In this paper, internal waves model select frequencyω= 0.08s?1, which is spring layer has a 50 meter distance to the surface of ocean, then divides structure surface into 480 pieces. After simplifying it just analysis eighth,which means giving different pressure on the areas of 60 pieces, so that we can get the data for analyzing structural stress of practical internal waves loading with ANSYS. It can also deal with the data in the position with 20 meter and 40 meter distance to density spring layer.Based on the above, this paper adopt moment theory analyzes composite shell on uniform external pressure. Spherical-drum shell is a representative structure as a kind of underwater body,which will change edge stress with different central angle of spherical shell. This paper illustrates six models which half-central angle is gradually changing from 90 degree to 50 degree and gets a conclusion that the result from spherical shell is same as from drum shell. Because of difference between theory model and practical model, I modify the theoretical equation and get a semi-empirical and semi-theoretical equation.And then, I adopt ANSYS to compute numerical simulation on 6 models above. After comparing the conclusion with semi-empirical and semi-theoretical equation results, I find that both of them are same. So the semi-empirical and semi-theoretical equation which is adequate for edge stress on spherical-drum shell (half-central angle from90°to 50°) under uniform load and reduce the error. I simulate the structural edge stress under the practical internal waves loading with ANSYS and also analyze and compare it with the result getting from semi-empirical and semi-theoretical equation. Finally I get the correction coefficient chart about angle and depth and using that I modify the theoretical equation again.Analysis results show that the effect of composite shell edge stress under internal waves has three reasons, first, internal waves loading is not even which means that every area bear different pressure after decomposition; Second, internal waves loading is different depending on different depths; Third, edge stress is different depending on different central angle. At last, I get a new equation after twice modification and hopefully it is applied by technicians in practice work.