Potential-Flow Predictions of a Semi-Displacement Vessel Including pplications to Calm-Water roaching CeSOS Conference 29-May-2013 abak Ommani www.cesos.ntnu.no 29-May-2013, CeSOS Conference CeSOS Centre abak for Ships Ommani and Ocean Structures 1
Semi-Displacement Vessels Fn 0.4 ~ 1.2 Fn U / Lg Fabbri et al. 2009, INSEN www.cesos.ntnu.no 29-May-2013, CeSOS Conference abak Ommani 2
Semi-Displacement Vessels Force Submerged Volume Hydrostatic Hydrodynamic Velocity squared Conventional Semi-Displacement Planning Hydrofoil Increase in the Role of Hydrodynamic Force Comparing to Hydrostatic Dynamic instability!! www.cesos.ntnu.no 29-May-2013, CeSOS Conference abak Ommani 3
General types of instability Increasing Froude number roaching Non-oscillatory Cohen and lount, 1986 www.cesos.ntnu.no 29-May-2013, CeSOS Conference abak Ommani 4
Calm-Water roaching Lugni et al. 2004, INSEN www.cesos.ntnu.no 29-May-2013, CeSOS Conference abak Ommani 5
Equations of Motion Sway acc. vel. Linear decomposition U Y Z X y z CG x 22 24 26 42 44 46 62 64 66 22 24 26 42 44 46 62 64 66 Roll Yaw 18 Coeffs. www.cesos.ntnu.no 29-May-2013, CeSOS Conference abak Ommani 6
Overview Introduction Numerical Implementation dvancing and Oscillating Flat Plate Linear Dynamic Stability nalysis Conclusions www.cesos.ntnu.no 29-May-2013, CeSOS Conference abak Ommani 7
Numerical Implementation 2 Potential flow 0 Neumann-Kelvin Linearization Ux Linearized ody oundary Condition Mean body position Linearized Free-Surface oundary Condition Mean free surface Initial Condition, Radiation Condition Linearized pressure on the body p U gz t x Forces and moments F j S pn ds j www.cesos.ntnu.no 29-May-2013, CeSOS Conference abak Ommani 8
Numerical Implementation Rankine Panel Method G p, q C( p) p q ds nq ( ) q G p, q ds nq ( ) Collocation Method Discretization S S www.cesos.ntnu.no 29-May-2013, CeSOS Conference abak Ommani 9
Simplification Transfer to center plane Semi-Displacement vessel to a Flat Plate y z CG x U Y Z X L H www.cesos.ntnu.no 29-May-2013, CeSOS Conference abak Ommani 10
Oscillatory motion of a Plate z x VS y FS ody Conservation of Vorticity Time-domain solver Y Z X Fourth order Runge-Kutta www.cesos.ntnu.no 29-May-2013, CeSOS Conference abak Ommani 11
Sway Motion Fn 0.96 =H/L=0.2 L/ g Fn 0.32 =H/L=0.2 L/ g www.cesos.ntnu.no 29-May-2013, CeSOS Conference abak Ommani 12
Vessel Model Vessel M www.cesos.ntnu.no 29-May-2013, CeSOS Conference abak Ommani Lugni et al. 2004, INSEN 13
Dynamic Stability nalysis ack to the simplified model Surface piercing flat plate dvancing and oscillating Hydrodynamic coefficients Sway-yaw (8 coeffs.) Sway-yaw-roll (18 coeffs) Frequency and Froude number dependent Computed ( Fn, ) ( Fn0, 0) plane Extrapolated www.cesos.ntnu.no 29-May-2013, CeSOS Conference abak Ommani 14
Dynamic Stability Sway-Yaw analysis, Computational Domain ( Fn0, 0) 22 26 62 66 22 26 62 66 Harmonic Motion a e st a i Stable every where Sway-Yaw Free-system response frequency www.cesos.ntnu.no 29-May-2013, CeSOS Conference abak Ommani 15
Dynamic Stability Sway-Roll-Yaw analysis, 22 Computational Domain ( Fn0, 0) 18 Coeffs. 22 24 26 42 44 46 62 64 66 24 26 42 44 46 62 64 66 C s C s C s 4 3 2 4 3 2 C1s C0 0 * s, s s, s * 1 1 2 2 Two Frequencies? Time-Domain analysis is needed www.cesos.ntnu.no 29-May-2013, CeSOS Conference abak Ommani 16
Dynamic Stability Sway-Roll-Yaw analysis, 22 Computational Domain ( Fn0, 0) 18 Coeffs. 22 24 26 42 44 46 62 64 66 24 26 42 44 46 62 64 66 C s C s C s 4 3 2 4 3 2 C1s C0 0 * s, s s, s * 1 1 2 2 Two Frequencies? Time-Domain analysis is needed Sway-Yaw Free-system response frequency www.cesos.ntnu.no 29-May-2013, CeSOS Conference abak Ommani 17
Dynamic Stability Sway-Roll-Yaw analysis, 22 Computational Domain Stable every where 18 Coeffs. 22 24 26 42 44 46 62 64 66 24 26 42 44 46 62 64 66 C s C s C s 4 3 2 4 3 2 C1s C0 0 * s, s s, s * 1 1 2 2 Two Frequencies? Time-Domain analysis is needed Sway-Yaw Free-system response frequency Roll Free-system response frequency www.cesos.ntnu.no 29-May-2013, CeSOS Conference abak Ommani 18
Dynamic Stability Sway-Roll-Yaw analysis, sensitivity Many uncertain parameters Hydrodynamic coefficients Due to simplification Vessel geometrical properties Due to insufficient data GM KM KG GM KM KG www.cesos.ntnu.no 29-May-2013, CeSOS Conference abak Ommani 19
Dynamic Stability Sway-Roll-Yaw analysis, sensitivity (1 v) www.cesos.ntnu.no 29-May-2013, CeSOS Conference abak Ommani 20
Dynamic Stability Sway-Roll-Yaw analysis, sensitivity Unstable roots www.cesos.ntnu.no 29-May-2013, CeSOS Conference abak Ommani 21
Dynamic Stability Sway-Roll-Yaw analysis, Computational Domain KG 0.675 0.5 D Computational Domain www.cesos.ntnu.no 29-May-2013, CeSOS Conference abak Ommani 22
Dynamic Stability Sway-Roll-Yaw analysis, KG D 0.5 Computational Domain Sway-Yaw Free-system response frequency www.cesos.ntnu.no 29-May-2013, CeSOS Conference abak Ommani 23
Dynamic Stability Sway-Roll-Yaw analysis, KG D 0.5 Roll Free-system response frequency Computational Domain Sway-Yaw Free-system response frequency www.cesos.ntnu.no 29-May-2013, CeSOS Conference abak Ommani 24
Dynamic Stability Sway-Roll-Yaw analysis, KG D 0.5 Roll Free-system response frequency Unstable System a1 0 Re( s1 ) s, s * 1 1 1 Im( s1 ) Computational Domain Sway-Yaw Free-system response frequency Recorded Instability www.cesos.ntnu.no 29-May-2013, CeSOS Conference abak Ommani 25
Dynamic Stability Sway-Roll-Yaw analysis, KG D 0.5 Roll Free-system response frequency Unstable System a1 0 Re( s1 ) s, s * 1 1 1 Im( s1 ) Computational Domain Sway-Yaw Free-system response frequency www.cesos.ntnu.no 29-May-2013, CeSOS Conference abak Ommani 26
Conclusions simplified hydrodynamic model is used for semidisplacement vessel. Roll motion influences the dynamic stability in sway and yaw. Cross coupling hydrodynamic coefficients matter. It seemed that high stiffness in Roll can cause instability in sway-yaw!! It was not possible to capture instability induced by Loss of restoring moment in Roll Simplified hydrodynamic model may be the reason www.cesos.ntnu.no 29-May-2013, CeSOS Conference abak Ommani 27
Thank you! www.cesos.ntnu.no 29-May-2013, CeSOS Conference abak Ommani 28
References Chapman, R. (1975), Numerical solution for hydrodynamic forces on a surface-piercong plate oscillating in yaw and sway, in `Proc. 1st International Conference on Numerical Ship hydrodynamics', ethesda, MD,US, pp. 330-350. Fabbri, L., Di Memmo,., Palini, M. and Lugni, C. (2009), Prova di manovrabilita su uno scafo semidislocante, Technical Report 2009-084rt, INSEN, Rome, Italy. Faltinsen, O.M. (2005). Hydrodynamics of High-Speed Marine Vehicles. New York: Cambridge University Press. Lugni, C., Colagrossi,., Landrini, M. and Faltinsen, O. (2004), Experimental and numerical study of semi-displacement monohull and catamaran in calm water and incident waves, in `Proc. of 25th Symposium on Naval Hydrodynamics', Canada. Ommani, abak, and O. M. Faltinsen. 2011. Study on Linear 3D Rankine Panel Method for Prediction of Semi-Displacement Vessels Hydrodynamic Characteristics at High Speed. In Proceedings of the 11th International Conference on Fast Sea Transportation (FST 2011). Honolulu, HI, US. Ommani, abak, O. M. Faltinsen, and C. Lugni. 2012. Hydrodynamic Forces on a Semi-Displacement Vessel on Straight Course with Drift ngle. In Proceedings of the 10th International Conference on Hydrodynamics (ICHD). St. Petersburg, Russia. Ommani, abak, O. M. Faltinsen, 2013. Linear dynamic stability analysis of a surface piercing plate advancing at high forward speed. ccepted for publication in, Proceedings of the SME 2013 32nd International Conference on Ocean, Offshore and rctic Engineering(OME2013). Nantes, France. van den rug, J.., eukelman, w. and Prins, G. J. (1971), Hydrodynamic forces on a surface piercing at plate, Technical Report 325, Delft University of Technology, Ship uilding Labratory. www.cesos.ntnu.no 29-May-2013, CeSOS Conference abak Ommani 29