Register

NMRIW-Lite Web
(An analysis tool for ship responses in waves)

NMRIW-Lite Web is an analysis tool, which calculates ship motion, hull girder sectional forces, and pressure distribution in waves in frequency domain. You can choose a linear strip method or a linear 3D-panel method for calculation. As both methods have the same input and output format, they can be used as the same tool.

Outline

NMRIW-Lite Web is an analysis tool, which calculates ship motion, hull girder sectional forces, and pressure distribution in waves in frequency domain. You can choose a linear strip method or a linear 3D-panel method for calculation. As both methods have the same input and output format, they can be used on the same interface. Frequency response function, time series, and ship animation can be output if the data of ship information and the wave condition are input.


Calculation methods

  • ・Linear strip method
    …You can choose NSM[1]/ STFM[2], and the application of Mizoguchi/Watanabe correction method[3] to diffraction force.
  • ・Linear 3D-panel method
    3D Green’s function method: Kernel function is Green’s function with zero-speed. (based on encounter wave correction method[4])

Output item and output format

Output item

  • ・Motion and acceleration (6 DOFs)
  • ・Hull girder sectional forces at the selected cross-section (Axial force, Horizontal shear force, Vertical shear force, Vertical bending moment, Horizontal bending moment, and Torsional Moment)
  • ・Acceleration on the selected location (Longitudinal, Vertical, and Horizontal (coordinates fixed on a ship))
  • ・Water pressure on the selected location

Output format

  • ・Response function (Amplitude and Phase)
  • ・Time series
  • ・Long term prediction (Excel sheets with a macro)
  • ・Animation (VTK format)
  • ・Output data for DLSA-Basic system[5]

Interface

NMRIW-Lite Web can input data, execute an analysis, and confirm the results through the interface on the browser. Text files of input and output data can be uploaded and downloaded. You can edit and process data by text files as well as operate them on the browser.

Ship information screen

The input screen is as below, where principal particulars, ship type information, and weight distribution are input. Ship type information can be automatically made by importing Offset Table (CSV file).

入力項目:Ship Information, Input when IKEDA method is adopted for B44

Input screen of principle particulars, weight distribution, etc.

入力項目:SECTION No., AFT/FORE PROFILE

Input screen of ship sectional shapes and aft/fore profile

Function to check input data of a ship

There are functions to check ship information as below. A ship body plan, a buttock line, still water balance, and still water shear force/bending moment can be shown and checked. In addition to calculating of fineness coefficients and the roll natural period, weight distribution is automatically adjusted to balance in still water condition.

チェック項目:Body Plan, Buttock Line, Still Water Balance, Still Water Load

Results calculated by input data of a ship (Body Plan, Buttock Line, Still Water Balance, Still Water Load) (Body Plan, Buttock Line, Still Water Balance, Still Water Load)

Input parameters for the calculation setting

The number of hull surface elements, a method for calculating roll damping coefficient, wave conditions (wave height, wave direction, wave length, and ship speed), and output items and formats can be selected.

設定項目:Fluid Coefficient Table, Detail Settings, Series Calculation Parameter, Output Settings

Input screen for calculation parameters

Samples of the output results

Output results can be confirmed on the browser. The files of output results (CSV file) can be also downloaded.

1.斜め向波中の6自由土運動グラフ、2.全波向きの水平曲げモーメントグラフ、3.垂直曲げモーメントの船長方向分布グラフ、4.指定した4点の垂直加速度の時系列グラフ

Samples of the display of output results

Long-term prediction

Long-term prediction can be executed when all wave directions are calculated. Based on the frequency response function, a short/long-term prediction can be executed by the calculation in Excel sheets, and the most severe sea conditions can be identified.

表やグラフで出力された計算例

Samples of Excel sheets of long-term prediction
(upper: a long-term exceedance probability of vertical bending moment,lower: The most severe short-term sea condition in total responses and a long-term prediction value)

Animation of the ship response in waves

Animation of the ship response in the selected wave condition can be displayed on the browser. The incident wave, ship motion, distribution of hull girder sectional forces, and pressure distribution are visualized. By downloading the animation data files, the animation can be displayed by Desktop ParaView (free software) .

Animation of ship response in waves:Strip method

Animation of ship response in waves:


To use this application

Use of this app is limited to users in Japan.


Reference

  • [1]Tasai, F., Takagi, M.: Theory and Calculation Method for Ship Response in Regular Waves, The 1st Marine Dynamics Symposium, The Society of Naval Architects of Japan、pp.1-52, 1969. (in Japanese)
  • [2]Salvesen, N., Tuck, E., and Faltinsen, O.: SHIP MOTIONS AND SEA LOADS. 1970.
  • [3]Watanabe, I., Toki, N., Ito, A.: Chapter 2 Strip Method, The 11th Marine Dynamics Symposium, Applications of ship motion theory to design, 1994. (in Japanese)
  • [4]Papanikolaou, A. and Schellin, T.: A three-dimensional panel method for motions and loads of ships with forward speed, Ship Technology Research,Vol.39, pp.145, 1992.
  • [5]Matsui, S., Murakami, C., Hayashibara, H., and Fueki, R.: Development of Direct Load and Structure Analysis and Evaluation System on Whole Ship DLSA-Basic for Ship Structural Design, Papers of National Maritime Research Institute, Vol.19, pp.1-21, 2019. (in Japanese)