By: Jeroen Berger, July 14, 2017
Nodosa Shipyard is a Spanish yard specialized in designing, building and repairing fishing vessels for short sea and coastal shipping. Since 1982, the shipyard has built different types of fishing vessels. For a newbuilding fishing vessel (in this case a longliner), our partner VICUSdt has been selected as the supplier for different types of CFD optimization studies. The studies have concerned on the hull form, the ship rudder design and ship propeller design, whereby VICUSdt also the CFD optimized ship propeller has delivered.
About the longliner
The fishing vessel from Nodosa Shipyard, called Longliner CN282, is 59.5 meters in length, 12.5 meters in width and 4.75 meters in depth (see Figure 1). Its gross tonnage is 1560 GT. Unlike other fishing vessels, longliners use a long line, called the main line, with baited hooks attached at intervals by means of branch lines called snoods (or gangions). Longliners commonly target swordfish, tuna, halibut and sablefish.
Figure 1: fishing vessel Longliner CN282
What was VICUSdt’s approach?
For the different type of optimization studies, VICUSdt has used advanced Computational Fluid Dynamics (CFD) software. With the help of this technique, the hydrodynamic performance of the fishing vessel could be analyzed accurately. For example, VICUSdt has studied preliminary the hull shape from two loading conditions and three different speeds. This analysis included a powering prediction in order to check if the selected engine would be sufficient for the target speed and this hull form. Due the results of this preliminary study, a CFD optimization of the hull shape was carried out, in order to decrease the wave resistance and brake power for the same speed.
What was the result?
Through a modification in the bulbous bow an important resistance reduction was obtained. Based on the optimization studies, a change for the main engine or maximum speed was not necessary. To improve the wake field, another modification was carried out in the aft bulb. This new hull has a more uniform wake comparing with the original one leading to a better propeller-hull interaction.
Another small modifications, like appendages alignments, were also suggested to the yard taking into account the stream lines. Based on the CFD optimization studies, VICUSdt has designed and delivered a 5 blades and 2.7 m CFD optimized propeller and a twisted rudder with bulb is designed and manufactured locally (see Figure 2).
Figure 2: CFD optimized propeller with twisted rudder with bulb
Finally, the CFD optimization studies have led to an improved hydrodynamic shape for the newbuilding fishing vessel. Nodosa Shipyard was impressed by VICUSdt’s practical approach and was happy with the achieved result.