netsse.analys.enc_spec ====================== .. py:module:: netsse.analys.enc_spec .. autoapi-nested-parse:: Functions to compute spectra in a **body-fixed** reference system. .. 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.analys.enc_spec.resp_spec_1d netsse.analys.enc_spec.resp_spec_2d Module Contents --------------- .. py:function:: resp_spec_1d(f0, ws, TRF1, TRF2, fe, U, beta) Computes a response cross-spectrum in both the absolute and encountered frequency domains, in a case of long-crested seas. :param f0: Vector of absolute frequencies [Hz]. :type f0: array_like of shape (Nf0,1) :param ws: 1-D wave spectrum, as a function of (absolute) wave frequency ``f0`` [Hz]. :type ws: array_like of shape (Nf0,1) in 1-D :param TRF1: Transfer functions of two response components, as a function of frequency ``f0`` [Hz]. :type TRF1: array_like of shape (Nf0,1) :param TRF2: Transfer functions of two response components, as a function of frequency ``f0`` [Hz]. :type TRF2: array_like of shape (Nf0,1) :param fe: Vector of encounter frequencies [Hz]. :type fe: array_like of shape (Nfe,1) :param U: Ship speed [m/s]. :type U: float :param beta: Ship heading, relative to the wave direction [deg]. :type beta: float :returns: * **RspecAbs** (*array_like of shape (Nf0,1)*) -- Response spectrum, as a function of absolute wave frequency ``f0`` [Hz]. * **RspecEnc** (*array_like of shape (Nfe,1)*) -- Response spectrum, as a function of encountered frequency ``fe`` [Hz]. .. seealso:: :py:obj:`resp_spec_2d` Computes a response cross-spectrum in the encounter-frequency domain, in case of short-crested sea. .. rubric:: Example >>> RspecAbs, RspecEnc = resp_spec_1d(f0,ws,TRF1,TRF2,fe,U,beta) .. py:function:: resp_spec_2d(freq0, mu, ws0, beta_TRF, TRF1, TRF2, freqE, U, psi, conv='from', unit_freq='rad/s') Computes a response cross-spectrum in the encounter-frequency domain, in a case of short-crested seas. .. note:: This is a Python implementation of the algorithm given in Nielsen et al. (2021). :param freq0: Vector of absolute frequencies, in which the wave spectrum and the transfer functions are expressed. :type freq0: array_like of shape (Nf0,) :param mu: Vector of wave directions [deg], relative to North (in a NED-reference frame). :type mu: array_like of shape (Nmu,) :param ws0: 2-D wave spectrum, as a function of (absolute) wave frequency ``freq0`` and wave direction ``mu`` [rad]. :type ws0: array_like of shape (Nf0,Nmu) in 2-D :param beta_TRF: Vector of relative wave headings [deg], in which the transfer functions are expressed. :type beta_TRF: array_like of shape (Nbeta,) :param TRF1: Transfer function of the first and second response component, respectively, as a function of frequency ``freq0`` and relative wave heading. :type TRF1: array_like of shape (Nf0,Nbeta) :param TRF2: Transfer function of the first and second response component, respectively, as a function of frequency ``freq0`` and relative wave heading. :type TRF2: array_like of shape (Nf0,Nbeta) :param freqE: Vector of encounter frequencies for the output response spectrum. :type freqE: array_like of shape (Nfe,) :param U: Ship speed [m/s] :type U: float :param psi: Ship heading [deg], relative to North (in a NED-reference frame). :type psi: float :param conv: The convention that is used to express the direction ``mu`` of wave spectrum: - 'from' : The naval architecture convention, indicating where the waves are COMING FROM. - 'to' : The oceanographic convention, indicating where the waves are GOING TO. The default is "from" direction. :type conv: {'from','to'}, optional :param unit_freq: Unit of the frequencies: - 'rad/s' : The variables ``freq0`` and ``freqE`` denote the angular frequencies in radians per second. - 'Hz' : The 2-D wave spectrum ``ws0`` is expressed as a function of frequency in Hertz. The default is 'rad/s'. :type unit_freq: {'rad/s','Hz'}, optional :returns: **RspecEnc** -- Response spectrum, as a function of encounter frequency ``freqE``. :rtype: array_like of shape (Nfe,) .. seealso:: :py:obj:`resp_spec_1d` Computes a response cross-spectrum in both the absolute and encountered frequency domains, in a case of long-crested seas. .. rubric:: References Nielsen, U. D., Mounet, R. E. G., & Brodtkorb, A. H. (2021). Tuning of transfer functions for analysis of wave-ship interactions. Marine Structures, 79, 103029. https://doi.org/10.1016/j.marstruc.2021.103029 .. rubric:: Example >>> RspecEnc = ... resp_spec_2d(freq0,mu,ws0,beta_TRF,TRF1,TRF2,freqE,U,psi,'from','rad/s')