Benchmark study on uncertainty assessment in numerical predictions of global wave loads in damaged ships J. Parunov, C. Guedes Soares, S. Hirdaris, Y. Lee, S. Liu, A. Papanikolau, J. Prpić-Oršić , M. Rodrigues, P. Ruponen ISSC-ITTC Workshop on load uncertainties - Wuxi, China 16/09/2017

Background & Aims Initiated within MARSTRUCT Virtual Institute in December 2016 Challenges: How to incorporate damage effects in seakeeping analysis ? Quantification and modelling of wave load uncertainties (ISSC-ITTC Special Task Committee) . Goals: To conduct the first uncertainty study on numerical prediction of loads on damaged ships; Aquiring valuable information regarding damage modelling in seakeeping analysis of damaged ship; Providing a rational basis for definition of the uncertainty model to be used in structural reliability studies of damaged ships.

Benchmark ship Lee, Y., Chan, H.-S., Pu, Y., Incecik, A. and Dow, R. S., 2012., Global wave loads on a damaged ship, Ships and Offshore Structures, 7(3). pp. 237-268. SSC-459, Reliability-Based Performance Assessment of Damaged Ships, Ship Structure Committee, 2011. E. Begovic,A.H. Day, A. Incecik: An experimental study of hull girder loads on an intact and damaged naval ship, Ocean Engineering 133 (2017) 47–65

Benchmark ship

Benchmark ship

Benchmark participants NTUA - Newdrift (3D panel code ) (S. Liu, A. Papanikolau) University of Rijeka -WASIM(3D panel code) (J.Prpić-Oršić, N. Vitali ) NAPA - Strip method (P. Ruponen, S. Kalske and T. Manderbacka) University of Zagreb - BV HydroSTAR (J. Parunov, M.Ćorak) Lloyd’s register– WAVELOAD-FD software (3D panel frequency domain ship motion analysis) ( Y. Lee) University of Lisbon - Weakly nonlinear (nonlinear Froude-Krylov ) time-domain method with GAMPIT (Generalized Adaptive Mesh Pressure Integration Technique) (M. Rodrigues, C. Guedes Soares)

Model visualisation (panelization of wetted surface)

Test matrix and model verification Hydrostatic particulars : V (m3) LCB (m) UNIRI 8690 72.4 IST ---- ----- NAPA 8774 70.1 LR 8749 69.8 NTUA 8379 70.2 UNIZG 8351 70.6

Quantification of uncertainties Also known as ”Frequency-Independent Modal Error” (FIME)

Results for intact ship X-axis : ω sqrt (L/g) Y-axis: non-dimensional transfer function

FIME for intact ship

Results for damaged ship - symetrical damage DS3

FIME for damaged ship - symetrical damage DS3

Results for damaged ship - unsymetrical damage DS2

FIME for damaged ship - unsymetrical damage DS2

Comparison of FIME

Comparison of FIME

Conclusions Provisional results of uncertainty assessment using Frequency Independent Model Error (FIME) indicate: Motion components are in good agreement with experiments for intact and damaged ship, for both head waves (HW) & quartering waves (QW). FIME is always within +/-10% error band. VWBM in HW for intact ship shows good agreement with experiments. FIME of VWBM in HW for damaged ship is note worse compared to the intact ship (surprising!) Even more surprising, FIME of VWBM for QW is improved compared to the intact ship. Strip theory overestimates VWBM amidships for HS for intact and damaged ship. For QS, however, such conclusion is not valid as FIME is not always larger then 1. TM shows large discrepancy compared to the experiments. (It could be meaningful to investigate the effects due to linearised viscous roll damping values.)  Experimental uncertainties: carried out the model tests in 2004 and 2005, and that time error bars have not been used (used averaged values).  These conclusions may be useful for classification societies, SOLAS and navies as they show that the added mass method for modelling effects of damage leads to the results of the same level of accuracy for damaged as for the intact ship.

Aknowledgement Croatian Science Foundation - projects 8722 & 8658 SHOPERA - Energy Efficient Safe SHip OPERAtion, which was partially funded by the EU under contract 605221 and the University of Rijeka (contract no. 13.09.1.1.05) European Commission research project HOLISHIP under the European Union Horizon 2020 research and innovation program with grant agreement no. 689074 University of Zagreb – International Mobility Grant and Research Support Grant