Slamming Impact Loads on Large High-Speed Naval Craft ASNE 2008 Sungeun Kim, Derek Novak (ABS) Hamn-Ching Chen (TAMU)

Navy Vessels Displacement Hull Planing Hull High speed vs. length ratio Small high-speed naval craft: PT boats Hydrodynamic lift Displacement Hull Low speed vs. length ratio Large navy vessels: destroyers, cruisers, battleships Hydrostatic buoyancy Semi-Planing/Semi-Displacement Hull Intermediate speed vs. length ratio Large high-speed naval craft Partially dynamic & partially static support

Large High-Speed Naval Craft MONO-1 CAT-2 CAT-1 MONO-2 MONO-3

Design of High-Speed Naval Craft Consider all intended operating conditions of the craft specified by Naval Administration Significant wave height: H1/3 Operating speed: V Two design conditions in ABS HSNC Guides Operational Condition: maximum design speed Survival Condition: 10 knots Note: not to be less than L/12 HSNC 3-2-2/Table 1 Note: to be verified by Naval Administration

Design of High-Speed Naval Craft (cont’d) Design Wave Heights and Speeds Design Conditions Operational Survival

Objectives Current slamming design pressure in HSNC are originally developed for small planing hulls Speed vs. length ratio: Slamming pressure from Heller & Jasper (1960) Vertical acceleration from Savitsky & Brown (1976) Refine and expand current rules to cover the bottom slamming design pressure for large semi-planing monohulls Speed vs. length ratio Vertical acceleration using LAMP and model test Update wet-deck slamming design pressure for large high-speed multi-hulls Validate numerical simulation program LAMP

Large Amplitude Motion Program (LAMP) LAMP Development DARPA 1988 Project Advanced nonlinear ship motion simulation to complement linear methods Extreme wave loads Research sponsors U.S. Navy (ONR, NSWCCD) U.S. Coast Guard American Bureau of Shipping SAIC/MIT

Bottom Slamming Design Pressure for Semi-Planing Monohulls

Bottom Slamming Design Pressure Current: 3-2-2/3.1.1 (Heller & Jasper) Proposed: Pressure distribution factor FL Background: pressure reduction on bow and stern area considering 3D flow effect

Vertical Acceleration One of the most critical driving design factor for high-speed naval craft Current: 3-2-2/1.1 (Savitsky & Brown) where ncg 1/100 highest vertical acceleration h1/3 1/3 significant wave height Bw maximum waterline beam cg deadrise angle at LCG V design speed (3-2-2/Table 1)  displacement  running trim angle Note: overestimating for smaller vessels and underestimating for larger vessels

Vertical Acceleration (cont’d) Proposed ncg: Proposed Kv

Test Vessel: MONO-1 Design Conditions Large semi-planing monohull with ship length over 100 m ABS Class based on HSNC Guides Loading Conditions

LAMP Geometry Modeling for MONO-1 Nonlinear Geometry Model for Nonlinear Restoring and Froude-Krylov Forces Hydro Panel Model for Linear Radiation-Diffraction Forces

Vertical Acceleration in Operational Condition Bow Loading Condition: Full Load Departure Displacement: 3000 tons Speed: 38 knots Sea state: SS5 with Hs=4m Mid Stern

Vertical Acceleration in Survival Condition Bow Loading Condition:Full Load Departure Displacement: 3000 tons Speed: 10 knots Sea state: SS8 with Hs=9m Mid Stern

Statistical Analysis Peak Counting Pick a highest peak between zero-crossings Threshold: 10% of 1/100 highest peak average Transient: ignore the first 1/5 of time series 1/100th Highest Peak Average for Vertical Acceleration Weibull Fitting for Slamming Impact Force

1/100th Vertical Acceleration Operational Condition Full Load Departure: 3000 tons Speed: 38knots Sea state: SS5 with Hs=4m Operational Condition Full Load Arrival: 2900 tons Ship Speed: 40 knots Sea State: SS5 with Hs=4m

1/100th Vertical Acceleration Operational Condition Full Load Minimum: 2800 tons Ship Speed: 42 knots Sea State: SS5 with Hs=4m Survival Condition Full load departure: 3000 tons Speed: 10 knots Sea state: SS8 with Hs=9m

Impact Force in Operational Condition

Impact Force in Survival Condition

Impact Force in Operational Condition

Design Pressure: Operational at Full Load Depart. Bottom Slamming Pressure: Full Load Departure at Hs=4m and V=38 knots Sectional Impact Force: (Heller & Jasper)

Design Pressure: Operational at Full Load Arrival Bottom Slamming Pressure: Full Load Arrival at Hs=4m and V=40 knots Sectional Impact Force: (Heller & Jasper)

Design Pressure: Operational at Full Load Min. Bottom Slamming Pressure: Full Load Minimum at Hs=4m and V=42 knots Sectional Impact Force: (Heller & Jasper)

Design Pressure: Survival at Full Load Depart. Bottom Slamming Pressure: Full Load Departure at Hs=9m and V=10 knots Sectional Impact Force: (Heller & Jasper)

Wet-Deck Slamming Pressure for Multi-Hulls

Wet-Deck Slamming Design Pressure Current: HSNC 3-2-2/3.5 Proposed where FI pressure distribution factor VI relative impact velocity ha distance from waterline to deck H1/3 significant wave height

Wet-Deck Design Pressure (cont’d) Current Wet-Deck Design Pressure Proposed Wet-Deck Design Pressure

Test Vessel: CAT-1 High-speed wave-piercing catamaran Length: LWL=73m Speed: 40knots ABS Class Hull damage was reported, likely due to wet-deck slamming impact loads

LAMP Simulation for Wet-Deck Slamming LAMP simulation with wet-deck option 2D wedge impact theory (Ge, Faltinsen, Moan 2005) on longitudinal cuts Require smaller time step Require supplemental pitch damping model LMPRES to extract wet-deck slamming pressure PLMPRES to generate nodal pressure time series

Supplemental Pitch Damping in LAMP Based on the model test measurements of CAT-1, additional pitch damping is considered for pitch motion simulation Supplemental pitch damping model in LAMP

Relative Motion in Model Test Condition Relative Vertical Motion Vertical Acceleration

Wet-Deck Slamming Pressure in Model Test Condition

Wet-Deck Slamming Pressure in Survival Condition

Wet-Deck Slamming Pressure in Survival Condition x=0.9L from AP x=0.8L from AP

Wet-Deck Slamming Pressure in Survival Condition x=0.6L from AP x=0.2L from AP

Wet-Deck Slamming Pressure in Survival Condition

Wet-Deck Slamming Pressure in Operational Condition

Wet-Deck Slamming Pressure in Operational Condition x=0.9L from AP x=0.8L from AP

Wet-Deck Slamming Pressure in Operational Condition x=0.6L from AP x=0.2L from AP

Wet-Deck Slamming in Operational Condition

FANS (Finite Analytic Navier-Stokes) Code CFD solver developed by Texas A&M Unsteady incompressible/compressible two-phase flow solver Multi-block solver using overset grids Nonlinear free-surface capturing scheme using level-set method FANS developments in ABS-TAMU LNG sloshing impact pressure Wet-deck slamming impact pressure Bow/stern slamming and green sea loads

FANS Modeling of CAT-1: Overset Grid 25 blocks, 16 processors, 2.16 million grid points for half-domain

FANS Wet-deck Slamming of CAT-1

Summary Bottom slamming pressure for monohulls Vertical acceleration is one of the most driving design factor for high-speed naval craft. Vertical acceleration has been revised to cover large semi-planing naval craft based on numerical simulation and model test Slamming design pressure has been validated with existing design of high-speed naval craft Wet-deck slamming pressure for multi-hulls Numerical simulation for wet-deck slamming has been performed in time domain using LAMP Wet-deck design pressure is revised based on numerical simulation. Survival condition is found to be a governing condition for wet-deck slamming pressure

On-going/Future Projects in ABS-SAIC-TAMU Guide for direct analysis procedure Wave-induced design loads Whipping loads for monohulls Wet-deck slamming loads for multi-hulls Guide for slamming model test procedure Vertical acceleration Local vs. panel pressure Statistic analysis for design pressure Software validation of wet-deck slamming Numerical simulation using LAMP/FANS code Model test/Full scale measurements