Abstract
A closed-cage fish farm was built at a rather sheltered location in northern Norway. The closed-cage solution is more ecology friendly than the frequently used net cage fish farms, since the fish breeding water is separated from the outside ocean space, thus preventing entry of the parasitic sea lice. Moreover, the fish food, waste, applied chemicals and medicines are under control and do not contaminate the outside sea water.
The fish farm structure was designed to be sound mechanically under local environmental loads occurring at the installation site. To verify initial estimates of the environmental loads due to current and waves, two sensors that measure vertical current speed profile and directional wave parameters were placed in the fish farm neighborhood.
The structural response was measured as well. Sensors that recorded forces in mooring lines, internal structural forces and motions (accelerations) of the fish farm moving components were placed at critical positions, based on foreknowledge obtained from numerical simulations.
The measurement campaign lasted for one year, thus covering all weather seasons. The acquired large data sets were analyzed statistically, but also an effort was made to find individual extreme environmental load occurrences. It is underlined that the measurements were made in full scale conditions (geometry and environment), and not on the geometrically scaled model as in a laboratory or experimental tank.
A detailed hydro-mechanical model of the fish farm was created. Numerical calculations of the structure’s response were performed with the OrcaFlex software. The detected individual extreme environmental load events were reproduced numerically, and the corresponding structural response was simulated in time domain. Acomparison of the field-measured data with the computational results is presented in the paper, followed by a discussion and conclusions.
