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

2. 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

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

4. 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

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

6. 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

7. 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

8. Bottom Slamming Design Pressure for Semi-Planing Monohulls

9. 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

10. 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

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

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

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

14. 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

15. 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

16. 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

17. 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

18. 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

19. Impact Force in Operational Condition

20. Impact Force in Survival Condition

21. Impact Force in Operational Condition

22. 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)

23. 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)

24. 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)

25. 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)

26. Wet-Deck Slamming Pressure for Multi-Hulls

27. 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

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

29. 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

30. 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

31. 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

32. Relative Motion in Model Test Condition
Relative Vertical Motion
Vertical Acceleration

33. Wet-Deck Slamming Pressure in Model Test Condition

34. Wet-Deck Slamming Pressure in Survival Condition

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

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

37. Wet-Deck Slamming Pressure in Survival Condition

38. Wet-Deck Slamming Pressure in Operational Condition

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

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

41. Wet-Deck Slamming in Operational Condition

42. 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

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

44. FANS Wet-deck Slamming of CAT-1

45. 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

46. 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