Analysis Of Wave Height To Ship Motion With Displacement Of 7,597 Tons By Finite Element Method

Seakeeping is the ship's ability to stay afloat on the waves. The ship's maneuverability is greatly influenced by external factors related to the state of the sea and the waters in which the ship sails. Calculating seakeeping with various variations of depth, current, and wave height is needed for ship safety when sailing in the calculation of seakeeping using linear strip theory to calculate the response of heaving and pitching movements while roll damping theory for rolling movements. In this study, the ship's motion is calculated using the Finite element method software Hydrodynamic Diffraction and Hydrodynamic Time Response. For variations in wave height and water depth, referring to the conditions of Indonesian waters, from the reference, variations in wave height of 3 m, and 5 m (based on sea state WMO). In contrast, the current variation uses a current with a speed of 10 knots and a current depth of 10 T, 15 T, and 20 T. Based on the data obtained in data processing, it can be seen that the high value of the wave frequency obtained at 90 and 270 degrees wave direction is relatively high. The value of the roll spectrum in the direction of 0 and 270 degrees is large and can cause rolling on the ship. In the direction of 0 and 270 degrees, the wave resistance can be reduced by the


Introduction
By their very nature, the oceans and the atmosphere form a combined thermodynamic system, which constantly exchanges heat, mass, and momentum.It means that any force imposed from one fluid to another causes a change in boundary conditions between them, sometimes called "inter facial-conditions.
Due to the strong coupling between the two fluids, the movement in the atmosphere will create movement at the sea surface.These waves created by the movement of the atmosphere are "Wind Waves."The wind that blows on the sea surface is the primary generator of ocean waves.
The ship is a form of sea transportation that transports goods, passengers, and mining materials.in all areas with certain water areas.Because most of the 2/3 of the earth's surface are water, ships have been by humans since ancient times as an essential means of transportation for trade relations, the spread of religion, the search for gold or spices, diplomatic relations, and others.
In operating the ship, there are several obstacles, one of which is the environmental load in the form of wave height.Wave height affects the ship's operation, which can hinder the ship on its way to its destination.The response of rolling, pitching, and heaving motion will ultimately affect the comfort and safety of the crew and the goods being transported.The ship's shape is very influential on the characteristics of the operability movement.Vessel operability is the amount of time at sea during which the structure can still operate by the specified performance and the correlation of wave height at which the criteria will be exceeded.Characteristics of ship models that can emphasize the ship's response to operational conditions at sea are the main criteria that must be met by ships, which are closely related to ship movement characteristics.
In the study of ship motion, the motion of what is reviewed is a movement that is only capable of responding by the ship, namely rolling, heaving, and pitching.In obtaining treatment from ship waves have two types of motion.General equation of ship in heaving condition below: Where Inertial Force  is (-) , Damping Force  is b, Restoring Force  is cz and Exciting Force F is 0 cos ωet.General equation of ship in pitching condition is: Where inertial moment is

Materials and Methods
The ship data used in the research, in the research the ship used is a general cargo ship.The following is the main size data of the ship:

Fig. 2. Ship Modeler
The ship model in this study uses the finite element method, and for analysis of ship, motion using Maxsurf motion advanced while analyzing the influence of currents on ship movement using hydrodynamic time response.Then after getting the results of the RMS value from the software, a manual calculation of the ship's motion was carried out using excel for seakeeping validation.

Types of Ships and Damping Factors
At the data input stage is complete, the modeler of the ship that has been made is opened in the maxsurf motion advance application.The speed variation used in the ROA calculation experiment this time is 10 knots, and In the spectra table menu, there are variations in wave height, namely: 1m, 2m, and 3m. and the adjustment of the type of ship and the damping factor is as follows:   Based on the data obtained in data processing, it can be seen that the high value of the wave frequency obtained at 90 and 270 degrees wave direction is relatively high.The value of the roll spectrum in the direction of 0 and 270 degrees is large and can cause rolling on the ship.In the direction of 0 and 270 degrees, the wave resistance can be reduced by the ship.

Conclusions
Based on the results of data processing using Maxsurf, it can be concluded that the direction of the waves on the ship greatly affects the degree of balance of the ship.It can be seen that there is not much rolling in the direction of waves 0 and 270 degrees, while in the direction of waves 90 and 180 degrees, it is most likely that the ship will be rolling.Critical damping can reduce the force of freedom.
Copyright © 2022 by Maritime Technology and Society | E-ISSN: 2828-6669; P-ISSN: 2828-7010 This work is licensed under a Creative Commons Attribution 4.0 International License.
Copyright © 2022 by Maritime Technology and Society | E-ISSN: 2828-6669; P-ISSN: 2828-7010 This work is licensed under a Creative Commons Attribution 4.0 International License.