Principles of Rankine source method for calculation of ...€¦ · • the fluid is incompressible...

Lecture 6:

Potential methods for calculation of forces acting on the oscillating ships

Principles of Rankine source method for calculation of seakeeping

N. Kornev,Lehrstuhl für Modellierung und Simulation

Fakultät für Maschinenbau und SchiffstechnikUniversität Rostock

Ausgewählte Kapitel Steuerbarkeit und Schwingungen Vorlesung 2

Ausgewählte Kapitel Steuerbarkeit und Schwingungen Vorlesung 6 2/17

Assumptions

• the fluid is incompressible and inviscid,• the effects of surface tension are negligible,• the fluid is irrotational and• frequency domain simulations

Each unsteady quantity q is represented in form:

The amplitudes are small enough to neglect the nonlinear terms containing amplitudes.

q̂

Method developed by Prof. Söding (TUHH)


Representaion of the potential

is not small !!!!!!!!

The potential describes flow around the ship withaccount for free surface effects. Determination of the potential isdiscussed in the wave resistance potential theory. This problemcan be solved utilizing either a full nonlinear or a linear formalism.Numerical linear method for two dimensional case is described inChapter 6.7 (Grundlagen der Schiffstheorie).


Steady part of the solution

is not small !!!!!!!!


Steady part of the solution

Bernoulli equation

Dynamic boundary equation

Steady case


Steady part of the solutionKinematic boundary condition


Steady part of the solutionSample: 2D method of Dawson

Es wird angenommen, dass• die durch das Schiff erzeugten Wellen kleine Amplituden haben• die Strömung stationär ist.

Mixed linearized boundaryCondition on free surface

No penetration BC

Rankine Source Method


Unsteady part of the solutionThe boundary conditions for are linearized. !!!!!!!

in original GLRANKINE


Unsteady part of the solution


Numerical solution


Ship motion simulation


Pressure calculation


Thank you very much for your attention!

Literature: 1. KornevN. Ship dynamics in waves. Chapter 10: Principles of Rankine

source method for calculation of seakeeping2. Bertram V. Practical ship hydromechanics, page 270 p. Butterworth-

Heinemann, 2000.

Principles of Rankine source method for calculation of ...€¦ · • the fluid is incompressible...

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