Improved Accuracy
Enhancing the precision of net shape and behavior in the water
One of the things that worry fishermen is whether their nets are really maintaining the desired shape under the water. Nitto Seimo is helping to alleviate this worry with a system that simulates net conditions and makes it possible to visualize net behavior.
Challenges in Fishery
The difficulty in
ascertaining the shape
of fishing gears
under the water
In order to catch the target species efficiently, a fishing net’s shape and behavior should be considered before it is ever installed in the water. Fishing gears, however, are huge, ranging from several hundred to several thousand meters in length, and tens to hundreds of meters in depth. Further, their structure may deform depending on ocean conditions. Impacted by currents and waves, the actual shape of fishing gears under the water can be expected to experience constant and significant deformations, making it nearly impossible to know if they are behaving and retaining their shape as originally designed.
A scale model can
be used to make
predictions, but...
Until now, experiments with scale models in flume tanks have been used to solve this problem. However, obtaining reliable data required the use of large testing tanks, as well as the design and creation of elaborate scale models that faithfully adhere to the law of similitude (a law for reducing the effects of physics as a result of differences in scale). This was no easy task, requiring a great deal of labor, money, and time to produce.
Our Idea
Is it possible to
simulate the behavior
of a net in the water
on a PC?
Leveraging recent improvements in computer performance, Nitto Seimo took on the challenge of developing a computer-based system to simulate and ascertain the shape of a fishing gear as well as the loads acting on it during operation. Knowing exactly what shape a net is taking in the water and how much force is being applied to each part makes it possible to design nets that are more optimal for the required situation. Nitto Seimo worked together with Hokkaido University in an industry-academia partnership and, after much trial and error, invented the NaLA (Net-shape and Loading Analysis) system.
Solution
A system for
analyzing and visualizing
the behavior of fishing
gears in water
Fishing gear analysis conducted with NaLA system simulations eliminates the need for special models and testing equipment, and has been widely used by a variety of businesses to design, test, and improve set net, purse seine net, and other nets. Imagine a commercial fishing operation that wants to improve its net. Simulating the net system in advance to see if the intended improvements will perform as expected makes it possible to predict at the design stage whether the modifications will be cost-effective, making it easier for the business to proactively invest in its equipment.
First, a basic shape is created based on the net plans. Then, information such as net material, mesh size, and other details is input to the system. By providing numerical values (calculation conditions) based on the environment, such as tidal currents and waves, the shape and behavior of the net can be visualized on a PC.
Above, an example is presented comparing a purse seine net using nylon (left) and polyester netting (right). NaLA makes it possible to numerically quantify in advance how the sinking characteristics of a net will change based on material, and to consider what material would be best to use according to the target depth.