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contributor authorAlexandre N. Simos
contributor authorCelso P. Pesce
contributor authorMichael M. Bernitsas
contributor authorStuart B. Cohen
date accessioned2017-05-09T00:08:20Z
date available2017-05-09T00:08:20Z
date copyrightNovember, 2002
date issued2002
identifier issn0892-7219
identifier otherJMOEEX-28195#174_1.pdf
identifier urihttp://yetl.yabesh.ir/yetl/handle/yetl/127274
description abstractSeveral models of the hydrodynamic forces acting on a ship hull in maneuvering have been developed in the last 50 years. These models make possible analysis of ship maneuverability in high and low speeds. Following Bernitsas et al. [1], such hydrodynamic models may be classified into two major schools: the hydrodynamic derivatives (HD) models (first school) and “cross-flow” models (second school). The former is based on Taylor series expansion of the forces while the corresponding coefficients are determined experimentally and remain velocity independent for relatively low velocities. The second school heuristically combines short-wing theory (Jones) and cross-flow experimental data. The aim of this work is to establish and review a certain discrepancy observed in post pitchfork bifurcation paths depending on which school of modeling is adopted. This discrepancy exists in the practical problem of a Single-Point Mooring (SPM) system in a steady ocean current. This discrepancy appears immediately after the point of pitchfork bifurcation of the equilibrium yaw angle versus the longitudinal position of the line attachment point on the hull. According to HD models (e.g., Abkowitz [2]) such a bifurcation curve is a square-root post pitchfork path (e.g., Papoulias and Bernitsas [3]) while cross-flow models (e.g. Leite et al. [4]) predict a different shape of this path at the onset of the post bifurcation curve. Although the practical effect of such a discrepancy may be negligible for SPM systems, this is valuable in assessing an important difference in the distinct approaches followed by the hydrodynamic schools of modeling. Specifically, viscous forces are modeled by odd nonlinear terms in velocity, which are bilinear in the cross-flow models and cubic in the HD models. In this work, experimental results on the aforementioned post pitchfork bifurcation paths are presented and the origin and relevance of the observed discrepancy are discussed. Finally, results presented by Hooft [5] show that yaw angle dependence on bilinear velocity terms regarding cross-flow coefficients would be necessary for a more precise representation of bifurcation patterns near the pitchfork bifurcation. Such patterns may be strongly influenced by hull form.
publisherThe American Society of Mechanical Engineers (ASME)
titleHydrodynamic Model Induced Differences in SPM Post Pitchfork Bifurcation Paths
typeJournal Paper
journal volume124
journal issue4
journal titleJournal of Offshore Mechanics and Arctic Engineering
identifier doi10.1115/1.1510872
journal fristpage174
journal lastpage178
identifier eissn1528-896X
keywordsCarbon fibers
keywordsEquilibrium (Physics)
keywordsScanning probe microscopy
keywordsBifurcation
keywordsShips
keywordsHull
keywordsShapes
keywordsForce
keywordsFlow (Dynamics)
keywordsDrag (Fluid dynamics)
keywordsContainers AND Tankers
treeJournal of Offshore Mechanics and Arctic Engineering:;2002:;volume( 124 ):;issue: 004
contenttypeFulltext


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