Study of maneuverability and behavior in the sea of the Light Cabotage and Logistics Support Vessel ( BALC-L )

Resumen Estudio de maniobrabilidad y comportamiento en la mar del Buque de Apoyo Logístico y Cabotaje Liviano (BALC-L) Date Received: April 15th, 2021 Fecha de recepción: 15 de abril del 2021 Date Accepted: July 18th, 2021 Fecha de aceptación: 18 de julio del 2021 Study of maneuverability and behavior in the sea of the Light Cabotage and Logistics Support Vessel (BALC-L) 1 Escuela Naval de Cadetes “Almirante Padilla”. Cartagena, Colombia. Email: david.467@hotmail.com 2 Escuela Naval de Cadetes “Almirante Padilla”. Cartagena, Colombia. Email: josedavidmunozortega@gmail.com 3 Escuela Naval de Cadetes “Almirante Padilla”. Cartagena, Colombia. Email: juan.manuelv@hotmail.com 4 Escuela Naval de Cadetes “Almirante Padilla”. Cartagena, Colombia. Email: chema.riola@rga-psi.es DOI: https://doi.org/10.25043/19098642.219 Ship Science & Technology Vol. 15 n.° 29 (37-44) July 2021 Cartagena (Colombia) 38 Th is research was developed with the purpose of carrying out a series of simulations of the maneuverability and behavior of the ship BALC-L within an R&D from the Francisco José de Caldas, project bank which is being carried out between ENAP and COTECMAR. It is of vital importance for the Colombian Navy to be able to simulate in advance how the ship will behave before its construction takes place, in order to be able to propose improvements and avoid later transformations in its design which will result in costs and elongating the development phase of this project. Consequently, and given the vessel's operational purpose, communities in need located in the Colombian Pacifi c region will benefi t from having a means of humanitarian aid when necessary. Th e BALC-L class vessel is a ship that is in the design phase at the COTECMAR shipyard, which can be said to be a derivative version of the conventional BALC, but designed to have a shallower draft and access to places of diffi cult access through the rivers and therefore inner and remote parts of the country. In addition, it is designed to provide fast, fl exible, modular and mobile logistical support and disaster relief, all this focused on the civilian population. Th anks to studies carried out (Carreño, 2011) with vessels that operate using pump-jet propulsion system in shallow waters, mathematical models have been developed that take into account the NS or "Non-Squat" eff ect, which translates into an increase of the turning capacity in shallow areas (Clarke, 1998) (Eloot, 2013) for vessels with BALC-L characteristics. Traditionally, this eff ect has been studied in conventional vessels, being called "Squat eff ect" (Sierra et al, 2000), which depending on the Froude number (Escalante, 2010) of the vessel can generate the opposite eff ect to the one mentioned above, evidencing that by increasing the draft when the vessel reaches shallow waters, there is a considerable decrease in the maneuverability capabilities of these vessels (Herreros, 2000). Th e seakeeping behavior of a ship (Riola et al, 2017) is described by the balance equation, expressing the sum of the restoring moments that the ship will have, where it must be equal to the external force exerted on it (Medina, 2016). Th e behavior of vessels at sea (Vidal, 2008) is represented by the Amplitude Response Operators (RAO) (CEHIPAR, 2020), which give the vessel's responses to motion in regular waves and represent the transfer function of input (waves) and output (motion) being of total importance in determining the necessary parameters for the design of a vessel. Where the spectral crossover (Sz (w)) is one of the most important aspects for these responses in irregular waves in space, and time where the sea spectrum (S(w)) is represented by the RAO or transfer function (France et al, 2001). Introduction Seakeeping

Th is research was developed with the purpose of carrying out a series of simulations of the maneuverability and behavior of the ship BALC-L within an R&D from the Francisco José de Caldas, project bank which is being carried out between ENAP and COTECMAR. It is of vital importance for the Colombian Navy to be able to simulate in advance how the ship will behave before its construction takes place, in order to be able to propose improvements and avoid later transformations in its design which will result in costs and elongating the development phase of this project. Consequently, and given the vessel's operational purpose, communities in need located in the Colombian Pacifi c region will benefi t from having a means of humanitarian aid when necessary.
Th e BALC-L class vessel is a ship that is in the design phase at the COTECMAR shipyard, which can be said to be a derivative version of the conventional BALC, but designed to have a shallower draft and access to places of diffi cult access through the rivers and therefore inner and remote parts of the country. In addition, it is designed to provide fast, fl exible, modular and mobile logistical support and disaster relief, all this focused on the civilian population.
Th anks to studies carried out (Carreño, 2011) with vessels that operate using pump-jet propulsion system in shallow waters, mathematical models have been developed that take into account the NS or "Non-Squat" eff ect, which translates into an increase of the turning capacity in shallow areas (Clarke, 1998) (Eloot, 2013) for vessels with BALC-L characteristics. Traditionally, this eff ect has been studied in conventional vessels, being called "Squat eff ect" (Sierra et al, 2000), which depending on the Froude number (Escalante, 2010) of the vessel can generate the opposite eff ect to the one mentioned above, evidencing that by increasing the draft when the vessel reaches shallow waters, there is a considerable decrease in the maneuverability capabilities of these vessels (Herreros, 2000).
Th e seakeeping behavior of a ship  is described by the balance equation, expressing the sum of the restoring moments that the ship will have, where it must be equal to the external force exerted on it (Medina, 2016).
Th e behavior of vessels at sea (Vidal, 2008) is represented by the Amplitude Response Operators (RAO) (CEHIPAR, 2020), which give the vessel's responses to motion in regular waves and represent the transfer function of input (waves) and output (motion) being of total importance in determining the necessary parameters for the design of a vessel. The aim of this project is to study the behavior at sea of the BALC-L through a series of simulations with Maxsurf Motions Advanced of a 3D prototype provided by the shipyard. The shape plan and the hydrodynamic coefficients (Holtrop et al, 1978) of the ship were obtained in order to transfer them to the Maxsurf Motions Advanced program, in which the simulations were carried out by varying the speed with increments from knot to knot and course changes every 15°.
To later analyze the validation of the results obtained and full fill a greater characterization of the ship with the Transas full vision simulator of the Center for Research, Development and Innovations for Marine Activities (CIDIAM) of ENAP, a similar simulation was made in the Maxsurf program, varying the speed from 0 to 8 knots and the course every 15°, with the same conditions, however this simulator does not use only the shape plans but, takes advantage to complete the characteristics of the ship with the values extrapolated from those it has in its database of other ships. The idea is to determine the characteristics of interest of the ship and to propose its possible improvement for this purpose it was studied in 2 maritime conditions according to Douglas scale (Cazatormentas, 2019), as shown in Fig, 1.
The limit criteria defined by STANAG 4154 (NATO, 2000) for a patrol and transit vessel in its wheelhouse of 4° RMS for rolling and 1.5° RMS for pitching are used to study the ship's movements and accelerations.
The values obtained contribute to know if the vessel will be a risk for the safety of the ship, the habitability and comfort of the personnel, and the relevant operation of the equipment, systems and weapons, and thus contribute these results to this design that COTECMAR is carrying out in order to optimize the vessel to the maximum.
Mathematical models (Carreño, 2011)  come, among other factors, from the need to economize the evaluation of vessels. They usually work in an inertial reference system whose center with coordinates is located at the point where the maneuver starts (Cipriano, 2009). And they generally require obtaining hydrodynamic derivatives by means of tests whose validation is subsequently performed with full-scale tests (Aláez, 1996). For three degrees of freedom, the following equations are considered (Cipriano, 2009): These three differential equations express the respective forces and moments as seen from the inertial reference frame on the right side of each equation, while the left side presents the accelerations as seen from the body-centered, non-inertial reference frame (Inoue et al, 1981). To achieve this, the two reference systems are related by means of a transformation matrix (Carreño, 2011).
The forces and moments must be decomposed into the different factors that affect the maneuvers to be studied, in which the vessel must be subjected to the regulations reflected in resolution MSC.137 (76) (IMO, 2002). It is important to mention that one of the critical aspects to take into account in the preliminary design stage of a vessel that navigates in rivers with strong currents, is the level of control that can be expected of it, in the horizontal plane, when navigating, which is known as its behavior or maneuverability. This can also be defined as the percentage of efficiency in achieving a certain position of the bow of a boat with respect to a defined space (Sagarra, 1998).
For the Society of Naval Architects and Marine Engineers (SNAME) not only maneuverability should be studied, but also controllability, taking into account that in order to define maneuverability the human factor should be taken into account.

Maneuverability
(4)  Fig. 4 shows the virtual model of the BALC-L vessel navigating in the mouth of the San Juan river. Th is location was chosen because of its diffi cult maneuvering characteristics due to the strong currents and tides in the area.
According to the proposed methodology, a model of the BALC-L was designed with the help of the Virtual Shipyard software to perform a validation of the results in ambient conditions in Simulator Transas. Thus, after performing the pertinent maneuverability validations in said program in deep waters, and the necessary adaptations to the propulsion with pump-jets, the model was taken to the virtual scenario of the river at the mouth of the San Juan River, in which two types of maneuvers were performed: evolutionary circles and zig-zag maneuvers.
The Fig. 5 shows the trajectory of the BALC-L, at the moment of executing an evolutionary circle maneuver at 35° to starboard and a Zig-Zag maneuver at 20°, this was developed by the MANSIM maneuverability software, which was executed in this case in deep water conditions and with a propeller and rudder maneuvering system. Due to this situation, maneuverability has gained importance in recent years, to such an extent that diff erent international organizations interested in maximizing effi ciency maritime transport, trying to avoid material losses and mainly to protect the lives of crew members and passengers, have made great eff orts to standardize regulations to assess the maneuverability of most vessels in most cases. In our study and in order to carry out the maneuverability tests to the BALC-L in shallow waters, the mouth of the San Juan river has been simulated, for which it was necessary to compile the bathymetry of the river provided by the Center for Oceanographic and Hydrographic Research (CIOH), the ship design data and the hydrodynamic theories related to the evaluation of the maneuverability of a warship. In order to carry out this maneuverability study, the

Naranjo, Muñoz, Valderrama, Riola
Th e following graph shows the trajectory of the BALC-L, at the time of executing an evolutionary circle maneuver at 35 degrees to starboard,     this was developed by the Virtual Shipyard maneuverability software, which executed it in deep and shallow water conditions, with a pumpjet maneuvering system.
Th e following graph shows the trajectory of the BALC-L, at the time of executing an evolutionary circle maneuver at 35 degrees to starboard, this was developed by ENAP's Full Vision simulator, which was executed at the mouth of the San Juan river and with a pump-jet maneuvering system.   Table 5. Overshoot angles in zig-zag maneuvers. its maneuvers with the degree of accuracy required by a ship of the Colombian Navy.
• By having a draft of 1.45m and its hull forms almost flat, the vessel will not have a good performance at sea according to STANAG limits, as extracted from the results of the Maxsurf program as in the CIDIAM program, for neither of the 2 cases, however the vessel is in optimal conditions to be able to navigate in shallow waters.
• The vessel should navigate in open waters with swell less than SS3 for transit between river areas.
• With a sea state SS3 her minimum RMS pitch value were 1.49° respectively allowing her to sail at a heading 060° with a speed between 6 knots. This is the limit sea state in which the vessel will be able to sail but trying to avoid taking the waves other than by the bow or stern.
[ In Fig. 8, data comparisons were made between the results of the Maxsurf Motions Advanced simulator and the CIDIAM full-vision simulator. At the 060° heading the highest RMS values were given in the 2 simulators therefore, to compare the data it was evaluated for this heading when the wave has crashes on the port or starboard side of the vessel, meaning this will be at its maximum wave resonance and hence simulate as accurately as possible real sea conditions, where significant waves reach heights of 1.2 m with periods of 10 s. This is the equivalent of this of this wave height found in the data that was supplied by the CIOH, taken at a speed between 4 to 8 knots that are the values at which warships tend to sail.
• Despite its shallow draft, the BALC-L Vessel developed by COTECMAR, both in propeller and rudder propulsion and in pump jet propulsion, meets the maneuverability criteria contemplated by IMO and STANAG • It is confirmed and validated that the turning diameter of the maneuver is reduced when the rudder angle is increased, and when the depth is lowered, improving considerably in shallow waters, such as those found in the San Juan River at the Colombian Pacific.
• When comparing the results obtained with the software used by CICEN, the MANSIM and virtual shipyard simulators (Zubaly, 1996) , a difference can be appreciated, however, the data of these mentioned sims are taken as an approximation and those of CICEN as the real validation. The results for both programs allow us to conclude that the BALC-L complies with the international standards mentioned above.
• Despite the good results obtained, the operational performance of the BALC-L cannot yet be assured, since the approach has been entirely theoretical and no use was made of scale models to perform tests with free or captive models in order to calculate