Söding, HeinrichHeinrichSöding2018-03-022018-03-022014Proceedings of the Institution of Mechanical Engineers, Part M: Journal of Engineering for the Maritime Environment 1 (230): 22-32 (2014)http://tubdok.tub.tuhh.de/handle/11420/1566Perturbation methods up to first order with respect to motion or wave amplitude are common in seakeeping predictions. For higher than first order, lengthy theoretical analyses are required. They result in complicated formulae requiring high programming effort, and often the well-established numerical methods for first-order quantities fail when applied to second-order flow quantities. Both the derivation of the required expressions and their programming are simplified by using mathematical entities called perturbators. The concept of perturbators is described, and their application is demonstrated, for a two-dimensional test problem: A cylinder with horizontal axis partly immersed into an ideal fluid. The cylinder performs sinusoidal heave, sway, and roll motions. Stationary and double-frequency second-order forces are determined. For a heaving semicircle, vertical forces are determined numerically and compared to published results.en2041-3084201412232Sage Publ.http://rightsstatements.org/vocab/InC/1.0/potential flowfree surfaceoscillatory motionheaveswayflow forceIngenieurwissenschaftenJournal Articleurn:nbn:de:gbv:830-8821951010.15480/882.156311420/156610.1177/147509021452942510.15480/882.1563Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich. This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.Other