Accuracy improvement of numerical simulation with the determination of drag coefficients of floating collars
2020
Park, Subong | Lee, Jihoon | Lee, Chun-Woo
To install aquaculture facilities in the open sea, which is significantly influenced by tidal currents and waves, technology must be developed to withstand severe natural conditions. Many studies have been performed on cage structures that can operate in such an environment. To analyze the performance of the cage structure, it is necessary to derive the drag coefficient of the floating collar according to the degree of submergence of the floating collar in the sea; however, studies on this have not been published. Therefore, in the present study, we determined the drag coefficients according to the extent of submersion of high-density polyethylene (HDPE) pipes, which are the most commonly used pipes for cage floating collars. Using three types of HDPE pipes with different diameters, we derived drag coefficients for 1/4, 2/4, 3/4, and complete submersion of the pipe’s cross section at different attack angles and current speeds. The drag coefficient of the HDPE pipe derived from a flume-tank experiment was employed for modeling the floating collar. Additionally, a numerical simulation was performed. The deformation of the sides of the cage according to the current speeds agreed well with the model test and numerical simulation results, and the overall calculation error for the tension of the mooring line was within ±5%. Furthermore, the accuracy of the simulation was improved by about 7% through the numerical calculation method of the floating collar applied in this study. According to the results of the model test and numerical simulation, cage structures with various properties can be modeled consistently using a mass–spring model, enabling relatively accurate numerical calculations and behavior simulation of the cage.
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