netsse.model.ship ================= .. py:module:: netsse.model.ship .. autoapi-nested-parse:: Closed-form expressions of the linear wave-to-motion transfer functions for a box-shaped uniformly-loaded **monohull ship**. .. dropdown:: Copyright (C) 2023-2026 Technical University of Denmark, R.E.G. Mounet :color: primary :icon: law *This code is part of the NetSSE software.* NetSSE is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. NetSSE is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program. If not, see https://www.gnu.org/licenses/. To credit the author, users are encouraged to use below reference: .. code-block:: text Mounet, R. E. G., & Nielsen, U. D. NetSSE: An open-source Python package for network-based sea state estimation from ships, buoys, and other observation platforms (version 2.2). Technical University of Denmark, GitLab. February 2026. https://doi.org/10.11583/DTU.26379811. *Last updated on 20-02-2026 by R.E.G. Mounet* Functions --------- .. autoapisummary:: netsse.model.ship.heaveCF netsse.model.ship.pitchCF netsse.model.ship.rollCF Module Contents --------------- .. py:function:: heaveCF(om0, beta_deg, U, L, B0, T, C_B=1) Computes the heave transfer function amplitude, using the closed-form expressions presented in Jensen et al. (2004). :param om0: Vector of absolute wave frequencies [rad/s]. :type om0: array_like of shape (Nom0,) :param beta_deg: Vector of heading angles [deg]. :type beta_deg: array_like of shape (Nbeta,) :param U: Vessel forward speed [m/s]. :type U: float :param L: Length of the ship [m]. :type L: float :param B0: Breadth of the ship [m]. :type B0: float :param T: Draft of the ship [m]. :type T: float :param C_B: Block coefficient of the ship [-]. :type C_B: float, default 1 :returns: **heave** -- Coefficients of the heave transfer function amplitude [m/m]. :rtype: numpy.ndarray of shape (Nom0,Nbeta) .. seealso:: :py:obj:`pitchCF`, :py:obj:`rollCF` .. rubric:: References Jensen, J. J., Mansour, A. E., & Olsen, A. S. (2004). Estimation of ship motions using closed-form expressions. Ocean Engineering, 31(1), 61–85. https://doi.org/10.1016/S0029-8018(03)00108-2 .. rubric:: Example >>> heave = heaveCF(om0,beta_deg,U,L,B0,T,C_B=1) .. py:function:: pitchCF(om0, beta_deg, U, L, B0, T, C_B=1) Computes the pitch transfer function amplitude, using the closed-form expressions presented in Jensen et al. (2004). :param om0: Vector of absolute wave frequency [rad/s]. :type om0: array_like of shape (Nom0,) :param beta_deg: Vector of heading angle [deg]. :type beta_deg: array_like of shape (Nbeta,) :param U: Vessel forward speed [m/s]. :type U: float :param L: Length of the ship [m]. :type L: float :param B0: Breadth of the ship [m]. :type B0: float :param T: Draft of the ship [m]. :type T: float :param C_B: Block coefficient of the ship [-]. :type C_B: float, default 1 :returns: **pitch** -- Coefficients of the pitch transfer function amplitude [rad/m]. :rtype: numpy.ndarray of shape (Nom0,Nbeta) .. seealso:: :py:obj:`heaveCF`, :py:obj:`rollCF` .. rubric:: References Jensen, J. J., Mansour, A. E., & Olsen, A. S. (2004). Estimation of ship motions using closed-form expressions. Ocean Engineering, 31(1), 61–85. https://doi.org/10.1016/S0029-8018(03)00108-2 .. rubric:: Example >>> pitch = pitchCF(om0,beta_deg,U,L,B0,T,C_B=1) .. py:function:: rollCF(om0, beta_deg, U, L, B0, T, C_B, C_WP, GM_T, kappa, mu, T_N=0) Computes the roll transfer function amplitude, using the closed-form expressions presented in Jensen et al. (2004). :param om0: Vector of absolute wave frequencies [rad/s]. :type om0: array_like of shape (Nom0,) :param beta_deg: Vector of heading angles [deg]. :type beta_deg: array_like of shape (Nbeta,) :param U: Vessel forward speed [m/s]. :type U: float :param L: Length of the ship [m]. :type L: float :param B0: Breadth of the ship [m]. :type B0: float :param T: Draft of the ship [m]. :type T: float :param C_B: Block coefficient of the ship [-]. :type C_B: float :param C_WP: Waterplane area coefficient of the ship [-]. :type C_WP: float :param GM_T: Transverse metacentric height [m]. :type GM_T: float :param kappa: Custom parameter (chosen between 0 and ``C_WP``) representing the ratio between the length of the aft beam and the whole ship length in the simplified ship model for roll. :type kappa: float :param mu: Ratio between added viscous damping and critical damping. :type mu: float, default 0 :param T_N: Roll natural period [s]. .. note:: If not specified as input, ``T_N`` is calculated using empirical formulas from ADA147598. :type T_N: float, optional :returns: **roll** -- Coefficients of the roll transfer function amplitude [rad/m]. :rtype: numpy.ndarray of shape (Nom0,Nbeta) .. seealso:: :py:obj:`heaveCF`, :py:obj:`pitchCF` .. rubric:: References 1. Jensen, J. J., Mansour, A. E., & Olsen, A. S. (2004). Estimation of ship motions using closed-form expressions. Ocean Engineering, 31(1), 61–85. https://doi.org/10.1016/S0029-8018(03)00108-2 2. ADA147598, 1973. Code of Safety for Fishermen and Fishing Vessels. Part B. Safety and Health Requirements for the Construction and Equipment of Fishing Vessels. Inter-Governmental Maritime Consultative Organization, London, England. .. rubric:: Example >>> roll = rollCF(om0,beta_deg,U,L,B0,T,C_B,C_WP,GM_T,kappa,mu,T_N=0)