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Overview

Incorporation of Steady Flow Effects in Linear Three-dimensional Seakeeping Predictions for High Speed Hulls T.M. Ahmed 1 , D.A. Hudson 1 and P. Temarel 1 1 School of Engineering Sciences, Ship Science, University of Southampton, Southampton, UK. Overview. Introduction Mathematical model

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Overview

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  1. Incorporation of Steady Flow Effects in Linear Three-dimensional Seakeeping Predictions for High Speed Hulls T.M. Ahmed1, D.A. Hudson1 and P. Temarel1 1School of Engineering Sciences, Ship Science, University of Southampton, Southampton, UK.

  2. Overview • Introduction • Mathematical model • Hull forms • Hydrodynamic coefficients • Responses • Conclusions • Future Work

  3. Motivation • Detailed validation studies • Green’s function methods • Develop model to improve predictions • Steady-state flow in unsteady body boundary condition • Cannot include in free-surface condition

  4. Unsteady velocity potential in regular waves Mathematical Model (1) • Assume potential flow • Inviscid, homogenous, irrotational fluid motion • Steady flow velocity vector

  5. Need 2nd derivatives of steady flow Body Boundary Condition

  6. Mathematical Model (3) • Hydrodynamic forces

  7. Manipulate 1st derivatives Analytical Newman (1987) Mathematical Model (3) • Use Kelvin wave-making source for steady flow • Numerically efficient formulation of Baar and Price (1988) • Accuracy of 2nd derivatives important • Adopt analytical/numerical method

  8. Series 60 (1) • Series 60 (Cb=0.7) for initial verification • Pulsating source method applied 510 panels

  9. Series 60 (2) – Fn=0.2

  10. Series 60 (3) – Fn=0.2

  11. Series 60 (4) – Fn=0.2 Pitch RAO Heave RAO

  12. High Speed Monohull (1) • Based on NPL hull form - • Pulsating source method applied • Transom stern omitted 320 panels

  13. NPL Monohull (2) – Fn=0.53

  14. NPL Monohulll (3) – Fn=0.53

  15. NPL Monohull (4) – Fn=0.53 Pitch RAO Heave RAO

  16. Summary • Included steady flow in seakeeping analysis • Kelvin wave-making source for steady flow • Accurate and efficient method for 2nd derivatives • Pulsating source for unsteady analysis • Series 60 and NPL hullforms • Range of forward speeds

  17. Conclusions • Influence of steady flow small • Pitch actions most affected • Improvement in hydrodynamic coefficients • Little change in responses

  18. Future Work • Refine hull idealisations adopted • Investigate for translating pulsating source Green’s function for unsteady flow • Use improved model of transom stern flow for high speed craft • Apply to multi-vessels

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