Konstruksjonsdagen 2018 Ptil, 27 Aug Nordområdene. Prof. Sveinung Løset 1,2

Transcription

1 Konstruksjonsdagen 2018 Ptil, 27 Aug Nordområdene Prof. Sveinung Løset 1,2 1) Sustainable Arctic Marine and Coastal Technology (SAMCoT), Centre for Research-based Innovation (CRI), Norwegian University of Science and Technology, Trondheim, Norway 2) Arctic Intergrated Solutions AS (ArcISo), Trondheim, Norway 1

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3 Contents My background Arctic Drivers Field Development Challenges Design considerations for the Arctic Offshore Simulator for Arctic Marine Structures (SAMS) 3

4 Sea Ice and Iceberg Studies in the Barents Sea (ICEBASE 1987/1988, IDAP ) 4

5 Sustainable Arctic Marine and Coastal Technology (SAMCoT) Vision: Leading international centre for the development of robust technology needed by the industry operating in the Arctic region Strategy: Strong collaboration between Academia and Industry Team: 25 PhD candidates/post docs + approx. 25 professors ( ) 12 Industry Partners 9 Research Partners 2 Public Partners 5

6 Research Strategy

7 Mantra: Full-scale Data if possible SKT 2017 Oden Arctic Technology Research Cruises: 2012, 2013 and 2015 Arctic Ocean

8 Contents My background Arctic Drivers Field Development Challenges Design considerations for the Arctic Offshore Simulator for Arctic Marine Structures (SAMS) 8

9 Arctic Drivers Main drivers: Oil and gas Mining/Seabed mining Shipping Contributing industries: Fisheries, aquaculture Tourism Scientific research Coastal infrastructure/wind farms First unescorted LNG carrier; Hammerfest-> South Korea, 22 days, Aug (Kim, 2017) Arctic business scenarios: 1)Oil in demand Arctic take-off, 2)Green transformation Arctic tranquillity, 3)Re-freeze Arctic East- West division.

10 The Yamal LNG Project Northern Sea Route, NSR (The Ice Silk Road): China Ocean Shipping Company (COSCO), has increased activity on NSR over the past three years. In 2017, the company sent a dozen vessels through the Arctic, including five transit voyages. The container ship Venta Maersk (Arc4 ice-class container ship) is sailing the NSR from the Far East this week. (Source: highnorthnews.com, Aug. 2018) 10

11 Contents My background Arctic Drivers Field Development Challenges Design considerations for the Arctic Offshore Simulator for Arctic Marine Structures (SAMS) 11

12 Field Development Challenges Remoteness Logistics, delayed response Darkness Low visibility complicates operations Low temperatures Icing, winterization

13 Icing - K/V Nordkapp, Ice accretion: > Storm > T air =-15 C > 110 tons ice in 17 hrs

14 K/V Nordkapp,

15 Field Development Challenges (cont ) Presence of sea ice and icebergs Structural design, operations, emergency issues (Løset, 1993; 1994) Fragile environment Stronger impact and hard-to-eliminate consequences Human factors Lack of experience, decision taking under uncertainties

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17 Contents My background Arctic Drivers Field Development Challenges Design considerations for the Arctic Offshore Simulator for Arctic Marine Structures (SAMS) 17

18 Design Considerations... Some Site Specific Questions Water depth? Ice - no ice? In case of ice: How frequent? Type of ice feature? Level Rafted Ridged Icebergs Age of ice? First-year Multi-year

19 Design Considerations... Global Ice Actions N 1004 ISO FDIS (Arctic Offshore Structures, para 8.2.4): The determination of global ice actions shall be based on methods that incorporate relevant full-scale measurements, model experiments if they can be scaled reliably, or theoretical methods (analytical or numerical) that have been calibrated using experiments or full-scale measurements. Each of the following conditions shall be considered, and the governing ones shall be used to determine ice actions: a) quasi-static actions due to level ice (FY, rafted, or old ice), where inertial action effects within the structure can be neglected; b) dynamic actions due to level ice ( FY, rafted, or old ice), where inertial action effects within the structure are influential and a dynamic analysis is required; c) quasi-static actions due to ice rubble and ridges, where inertial action effects within the structure can be neglected; d) impacts from discrete features such as icebergs, ice islands and large old ice or FY ice features; e) quasi-static actions from features lodged against the structure, driven by the surrounding ice or directly by metocean actions; f) adfreeze action effects, including the frozen-in condition; and g) thermal action effects. 19

20 Design Considerations... Factors Associated with Ice Features and Ice Conditions Influencing Ice Actions (Løset et al., 2006)

21 Design Considerations... Ice Actions Global Time-averaged pressure over nominal contact area is needed Applications: Station-keeping assessment Design of moorings/dp systems Operations such as IM, towing, etc. Local High resolution image of pressure over contact area is needed Applications: Local damage assessment Design of structural elements e.g. plates and stiffeners

22 Design Considerations... Dynamic Ice Actions Illustration of structural response and global ice load in the 3 regimes of IIV (Hendrikse, 2017) 22

23 Design Considerations... Local Ice Actions (Kim, 2014) 23

24 Design Considerations... Local Ice Actions (massive ice features) N 1004 ISO FDIS (Arctic Offshore Structures, para ): Data derived from indentation tests and load panels on Molikpaq, both Beaufort Sea. The local pressure, P L, is based on mean + 3 SD of the data. [P L ] =MPa, [A] =m 2 Assuming normally distributed data, the probability of exceedance for 3 SD is 0.13%. For comparison, for the White Rose FPSO development ice pressures and contact areas for bow and side impacts corresponding to an annual probability of occurrence of 10-4 were taken as 0.7 p _ bow 6.24A 0.7 and p _ side 4.59A, this is significantly lower than those listed in ISO

25 Design Considerations... Iceberg Origin 25

26 Design Considerations... Icebergs Requested Data for Design Purposes 1. Spatial and temporal distributions 2. Size and geometry 3. Drift speeds and patterns 4. Mechanical properties Typical 100-year design parametres (Løset, 1988; 1993) 26

27 Ice Features Driven by Waves Glacial ice accelerated by waves may e.g. hit the vessel above the strengthened part of the hull.

28 Design Considerations... Heat Fluxes from Waves and Current Due to oscillating velocities from the wave near the solid surface an oscillating turbulent layer is formed. This will cause periodic heat transfer to the surface, that can be averaged. The wave friction can be related with the heat transfer via Reynolds analogy. 28

29 Design Considerations... Wave-induced Iceberg Deterioration Heat transfer - governing equations: T 1 T T c ( kr ) ( k ) Ml t r r r z z T (0) T T init m q 0 r at r 0 (adiabatic due to symmetry) q qinput r q qinput z at at b z 0, r a z b,0 r a f 29

30 Design Considerations... Wave-induced Deterioration of Icebergs Simulation parameters: The total potential Buoyancy, air and current effects are enabled Calving is enabled H wave 1m Twave 3sec depth 200m T0 8 C Tair 10 C Twater 1 C qair hair (T Tair ) qwater hwater (T Twater ) qwave h(t Twater ) qinsulation 0 critical 1MPa 30

31 Design Considerations... Global Ice Actions N 1004 ISO FDIS (Arctic Offshore Structures, para 8.2.4): The determination of global ice actions shall be based on methods that incorporate relevant full-scale measurements, model experiments if they can be scaled reliably, or theoretical methods (analytical or numerical) that have been calibrated using experiments or full-scale measurements. Each of the following conditions shall be considered, and the governing ones shall be used to determine ice actions: a) quasi-static actions due to level ice (FY, rafted, or old ice), where inertial action effects within the structure can be neglected; b) dynamic actions due to level i ce ( FY, rafted, or old ice), where inertial action effects within the structure are influential and a dynamic analysis is required; c) quasi-static actions due to ice rubble and ridges, where inertial action effects within the structure can be neglected; d) impacts from discrete features such as icebergs, ice islands and large old ice or FY ice features; e) quasi-static actions from features lodged against the structure, driven by the surrounding ice or directly by metocean actions; f) adfreeze action effects, including the frozen-in condition; and g) thermal action effects. 31

32 Design Considerations.../Global Ice Actions Global Pressure for Sea Ice n m h w p C f G R AR h1 h P G (MPa) - global average ice pressure f C R AR - ice strength coefficent; 2.8, 2.4, 1.8 intact ice sheets (Arctic, Subarctic, temperate) w h 3h e 1 5, disregarded for w 5 w h Note: C R values are for undeformed ice sheets 32

33 Design Considerations... Dynamic Ice Actions N 1004 ISO FDIS (Arctic Offshore Structures, para 8.2.5): The time-varying nature of ice actions and the corresponding ice-induced vibration shall be considered in the design. The potential for dynamic amplification of the action effects due to lock-in of ice failure and natural frequencies shall be assessed. Particular attention shall be given to dynamic actions on narrow structures, flexible structures and structures with vertical faces exposed to ice action. Figure Hendrikse 33

34 Design Considerations... How to handle the various Ice Conditions? Floe ice frequently observed Level ice Floe ice Increasing interests in understanding ice loads from broken ice fields, or each individual ice floe Ice Management Arctic 82 N, 0.7 km 1.3 km Arctic Ocean, Summer KV Svalbard (Hamilton et al., 2011) (OATRC2015) (Rothrock and Thorndike, 1984) 34

35 Design Considerations... ICE ACTIONS Ice Features Ice Properties Limiting Mechanism Interaction Geometry Failure Modes Level Crystallography Limit stress Single Creep Rafted Temperature Limit momentum Multi-leg Crushing Ridge Salinity Limit force Out- of-plane shape Bending Rubble Porosity Water depth Buckling Iceberg Surface tension Waterline shape Split/Spallin g (Løset et al., 2006) ISO 19906/FDIS/Arctic Offshore Structures

36 36 Multi-Body Dynamics 6DOF + fracture (crushing/ bending/ splitting) 6DOF Body forces (gravitational forces) Hydrostatic forces (buoyancy forces) Hydrodynamic (Aerodynamic) forces Contact forces -an NTNU spin-off Company 36

37 Design Considerations... ICE ACTIONS Ice Features Ice Properties Limiting Mechanism Interaction Geometry Failure Modes Level Crystallography Limit stress Single Creep Rafted Temperature Limit momentum Multi-leg Crushing Ridge Salinity Limit force Out- of-plane shape Bending Rubble Porosity Water depth Buckling Iceberg Surface tension Waterline shape Splitting (Løset et al., 2006)

38 Design Considerations... Failure Modes 300 m For ice floe with: Limited size Moderate confinement The conventional local bending failure is accompanied with frequent splitting failures. Splitting failure is considered as a load releasing mechanism; The splitting failure involves initiation and propagation of a long crack; Fracture mechanics is a natural choice for this failure mode. 38

39 Design Considerations... Bow camera pointing forward (KV Svalbard; Fram Strait, March 2012) 39

40 Design Considerations... Ice is a rather complicated material; We do not have a consensus on its fracture properties, e.g. fracture toughness, and the 3-parameter cohesive law ( GC, t, cr ) Among many discussions, size effects and load rates are often raised. 40

41 Design Considerations... The Svea Site (Vallunden Lagoon) 41

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43 Design Considerations... Experimental Setup Tests typically run 2 hours after cutting Animation 43

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45 2016 Displacement sensor 45

46 Design Considerations... Sampling for X-ray Test 2017 Test Rate: 0.6 mm/s or 100 kpa ms -1 46

47 Design Considerations... Small Scale Test Ideally brittle material G F s 2 Surface energy Plastic material G F s P Plastic dissipation Brittle material G F s True Area Projected Area (Anderson, 2005) 47

48 Design Considerations... X-ray Test Crack (Sønke et al., 2017) 48

49 Design Considerations... Thin Section, Test #9 (S8) Trans-granular, S8 (z =-29 cm, d av 3-4 mm)

50 Contents My background Arctic Drivers Field Development Challenges Design considerations for the Arctic Offshore Simulator for Arctic Marine Structures (SAMS) 50

51 SAMS Simulator for Arctic Marine Structures (SAMS) Theoretical Basis The building blocks of SAMS are illustrated in this figure, namely: 1) the NDEM or multibody dynamics module, 2) the fracture module, and 3) the hydrodynamic module. Norwegian University of Science and Technology -an NTNU spin-off Company 51

52 SAMS Theoretical Basis NDEM or multi-body dynamics module Rigid contact: F init df dδ The normal force where crushing is initiated The increase of normal force with penetration F init and df are determined based on the current overlap dδ volume and the change of overlap volume with penetration Norwegian University of Science and Technology -an NTNU spin-off Company 52

53 SAMS Theoretical Basis Fracture Module Norwegian University of Science and Technology -an NTNU spin-off Company

54 SAMS Theoretical Basis Fracture Module Norwegian University of Science and Technology -an NTNU spin-off Company

55 SAMS Current capabilities Station keeping (DP) Station keeping on mooring Fixed structures Towing carriage Ice tank Coastal structures Self-propelled vessels Ice drift due to wind and current Ice-channel resistance Floe ice, level ice, rubble Moored conical structure in level ice Norwegian University of Science and Technology -an NTNU spin-off Company 55

56 SAMS Theoretical Basis hydrodynamic module Aside from the basic buoyancy of all bodies, the hydrodynamic forces, including the force due to the propeller flow, upon each individual ice floe and the structure are assigned explicitly, and ice drift simulations are possible given wind and/or current conditions. The total hydrodynamic force on a rigid body is considered here as a combination of the so-called form drag and skin-friction drag. Norwegian University of Science and Technology -an NTNU spin-off Company 56

57 SAMS SAMS Capabilities Multibody dynamics Propeller wash Wave + ice Fracture Wave breaking ice

58 ArcISo AS Simulator for Arctic Marine Structures (SAMS) Vision Pioneering sustainable development of Arctic marine activities. Business Idea Safer and more profitable Arctic marine activities through assessment of structure designs and operational procedures, and delivery of decision support tools using superior sea-ice simulation technology. Mission Securing the integrity of your Arctic operations.