Hydrodynamic Behaviors Of Small Scale Floating Tube

Small-scaled floating tube structure is the basic unit of marine engineering, and widely used in marine engineering facilities. But the hydrodynamic characteristics of the structure in the wave are controversial. Therefore, in this paper, the hydro-coefficients of the fixed rod have been studied and so as the motion and force of the double floating tube structure in the raft system.For a fixed bar, an upright lever was designed in the experiment to extract the horizontal wave force in time-series. Based on the reformed Morison equation, the hydrodynamic coefficients of CD and CM was calculated, and the varieties of coefficients with the wave phase was discovered. Wave height parameter KH, wave period parameter KT was investigated and defined. The impact of wave elements including KH, KT and Reynolds number Re was analyzed both on the hydrodynamic coefficient and their fitting coefficient. When the hydro-coefficients have no relationship with the time(wave phase), the results show: Both hydro-coefficients CD and CM decrease as the wave height KH increase with a powered fitted function; CD and CM also decrease as the wave period KT increase. However, the fitted relationship was not uniform; Given the same wave height, CM increases as Reynolds number(Re) increases, However, CD changes little. When the relationship between the hydro-coefficients and time was considered, the results show: CD changes like the letter “U”, and we suggest the value can be a constant in the same wave element; CM changes regularly the same as the periodic trigonometric function, and it can be make up with two harmonic trigonometric function in wave frequency and twice wave frequency. Based on the results achieved, the authors also gave an empirical formula for calculating hydro-coefficients CD and CM, which may give guidance in practical use.For the double floating tube structure, A CCD image acquisition system was designed to analyze the movement of the structure. Using 2008 data acquisition system, the dynamic response of the structure in different wave condition Including different wave height, period, wave direction angle) were obtained. The results show: Both the force response and the vertical motion decrease linearly, and the increase of front side is more significantly; The angle of raft decreases slightly as the period increasing, and the long period wave makes the front and back force more uniform; With the increasing of the raft‘s weight, the force and horizontal motion decrease on the whole, However, the rule was not uniform;When the angle between the wave direction and raft was 60 degrees, the maximum force appearance...