A method to simplify perturbation analyses of periodical flows. (February 2016)

• Record Type: Journal Article
• Authors: Söding, Heinrich
• Is Part Of: Proceedings of the Institution of Mechanical Engineers. Volume 230:Number 1(2016:Feb.)
• Page Start: 22
• Page End: 32
• Publication Date: 2016-02
• Subjects: Potential flow -- free surface -- oscillatory motion -- heave -- sway -- flow force; Marine engineering -- Periodicals; 623.805
• DOI: 10.1177/1475090214529425
• Languages: English
• ISSNs: 1475-0902

Abstract

Perturbation 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.