This research focuses not only on the interaction between the floating platform for cage aquaculture and the waves but also on the incident wave¡¬s energy transformation. The floating platform was simulated with a 1:30 physical scale model in the hydrodynamic laboratory. A total four wave gages and one load cell were used in this study: two wave gages installed in the upstream of the platform, one gage in the net cage and one gage in the downstream side of the platform; while one load cell measuring the mooring line tension at the anchor. All of the measurements were recorded in the data acquisition system for further analyzing reflected waves, transmitted waves, the wave height in the net cage, and the correspondent mooring line tensions. Furthermore, the movement of the platform and volume deformation of the fish net are recorded by the video camera, and then analyzed by the image processing method. First, the true color images were transferred into grayscale images, and then passed through mean filter, noise filter and median filter step by step. Finally, a weighted-algorithm was used to calculate the coordinates of the desired point form the resulted image matrix. Thus, the motion of the floating platform and the volume deformation of the fish net can be obtained by analyzing the variation of these points captured through the image processing procedure.
For the ability of resistance to wave attack for a floating platform, it often estimated by inspecting the reflection and transmission coefficients of the platform. Besides the function of wave resistance ability, the stability of the floating platform, maximum tension in the mooring lines and the net volume deformation coefficient are also important factors for optimum design of a cage platform.
According to the results of this research, we conclude some important facts as below: (1) For short-period waves, the net mesh size and twine diameter have influenced the magnitude of reflected waves and the motion of platform; and it makes little difference in the transmission coefficients, wave height ratios inside of net cage, and the maximum tension force in the mooring cable. (2)With the respect of transmitted wave coefficients: the wave transmission phenomena are not obvious for short-period waves, but these phenomena will gradually increase when the incident wave periods are getting longer. (3)Under the pure wave test condition, the net volume deformation coefficients are about 1% only, which means that the deformation of the fish net does not change at all, and it may be due to the overweight of the bottom frame. (4) Tension-leg type mooring system seems able to provide better stability of the platform than catenary type mooring system.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0830106-062946 |
| Date | 30 August 2006 |
| Creators | Li, Sheng-tai |
| Contributors | none, none, none, none, none |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | Cholon |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0830106-062946 |
| Rights | unrestricted, Copyright information available at source archive |
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