Experimental Study Of Forces On Horizontal Cylinders Caused By Internal Waves

Long period, large amplitude and uncertainty are the characteristics of the internal waves which make the internal waves become an important limiting factor on the exploration and exploitation of marine resources. In recent years, scholars paid increasing attention to the study of the internal waves because of the frequently reported of the damage accidents of marine engineering structures caused by internal waves. The numerical simulation study about internal waves are more than the experimental study study about internal waves. The article will focus on the experimental study on the internal waves with the horizontal cylinders on different positions, study the forces on horizontal cylinders caused by the internal waves and factors.First, the article describes three theoretical models which are used in the research field of internal waves, combines the laboratory conditions and the design of experiment conditions to choose the appropriate mKdV theoretical model. Programming with MATLAB is combined with the Morison equation, then the forces of internal waves to the horizontal cylinders can be estimated. Selecting the appropriate range of the measurement system and the corresponding precision according to the estimates. Second, the experiment tests according to the experiment scheme. The experiment is divided into a periodic internal waves test and an internal solitary wave test. The factors of internal waves are measured by using dyeing photography, the internal wave forces on horizontal cylinders are measured and recorded through using the customized one-dimensional force transducer and two-dimensional force transducer that have small-range and high-precision. At the end, data analysis and processing is obtained during the experiment, then we can get some meaningful results. Details are as follows:1)The data should be filtered and denoised at first, and then the time-domain analysis of the processed data will be done with Matlab, the affect of the depth of cylinder and amplitude of internal waves to the vertical force will be analyzed. The results show that the vertical force of cylinder near to the pycnocline is bigger than the force of cylinder apart from the pvcnocline; the vertical force of cylinder will increase as the amplitude of internal waves increases.2) As to the horizontal cylinder arranged in the pycnocline, the affect of amplitude of internal waves to the horizontal forces will be analyzed, and it turns out that the horizontal force of cylinder will increase as the amplitude of internal waves increases.3) As for the test data obtained during the experiment of periodic internal waves, through performing FFT, dynamic response spectrogram of the force of cylinder under the internal wave action will be obtained. Analyzing the spectrogram finds that the main frequency of cylinder’s vertical force is consistent with the internal wave frequency, and there still is a component of twice the main frequency. In the pycnocline, the main frequency of the cylinder’s horizontal force is twice the main frequency of vertical force, at the same time, there also has a component close to the internal wave frequency. The shape of coupling the two directions force presents "8"...