Parameter Sensitivity in Numerical Modelling of Ice-Structure Interaction With Cohesive Element Method

2016 ◽  
Author(s):  
Dianshi Feng ◽  
Sze Dai Pang ◽  
Jin Zhang
Keyword(s):  
Element Model ◽  
Offshore Structures ◽  
Parameter Sensitivity ◽  
The Arctic ◽  
Cohesive Element ◽  
Structure Interaction ◽  
Marine Structure ◽  
Ice Loads ◽  
The Stability ◽  
Element Method

The increasing marine activities in the Arctic has resulted in a growing demand for reliable structural designs in this region. Ice loads are a major concern to the designer of a marine structure in the arctic, and are often the principal factor that governs the structural design [Palmer and Croasdale, 2013]. With the rapid advancement in computational power, numerical method is becoming a useful tool for design of offshore structures subjected to ice actions. Cohesive element method (CEM), a method which has been widely utilized to simulate fracture in various materials ranging from metals to ceramics and composites as well as bi-material systems, has been recently applied to predict ice-structure interactions. Although it shows promising future for further applications, there are also some challenging issues like high mesh dependency, large variation in cohesive properties etc., yet to be resolved. In this study, a 3D finite element model with the use of CEM was developed in LS-DYNA for simulating ice-structure interaction. The stability of the model was investigated and a parameter sensitivity analysis was carried out for a better understanding of how each material parameter affects the simulation results.

scholarly journals Simulation of Ice-Propeller Collision with Cohesive Element Method

2019 ◽  
Vol 7 (10) ◽  
pp. 349 ◽  
Author(s):  
Zhou ◽  
Wang ◽  
Diao ◽  
Ding ◽  
Yu ◽  
...  
Keyword(s):  
Rotational Speed ◽  
Constitutive Law ◽  
Impact Loads ◽  
Cohesive Element ◽  
Ice Loads ◽  
Ice Floes ◽  
The Time Domain ◽  
Contact Position ◽  
The Impact ◽  
Element Method

The existence of ice in ice-covered waters may cause damage to the propeller of polar ships, especially when massive ice floes are submerged around the hull. This paper aims to simulate an interaction process of a direct ice collision with a propeller based on the cohesive element method. A constitutive law is applied to model the ice material. The model of ice material is validated against model test results. The resulting impact loads acting on the contact surfaces and the corresponding ice block velocity are calculated in the time domain. The ice crushing, shearing and fracture failures are reproduced in the simulation. The convergence study with three meshing sizes of ice block is performed. To carry out a parametric study, five parameters are selected for analysis. These parameters are composed of rotational speed, direction of the propeller, initial speed of the ice block, contact position, and area between the ice and the propeller. The results show that the ice loads are affected by the five factors significantly. Ice loads tend to increase by decreasing the rotational speed, increasing the initial ice speed and the contact area, and changing the rotational direction from clockwise to counterclockwise. The effect of the contact position on the impact loads is relatively complex, depending on rotational speeds of the propeller.

Experimental Study of Sea Ice Forces on a Structure and its Stability

2011 ◽  
Vol 243-249 ◽  
pp. 4750-4753 ◽  
Author(s):  
Ji Wu Dong ◽  
Zhi Jun Li ◽  
Li Min Zhang ◽  
Guang Wei Li ◽  
Hong Wei Han
Keyword(s):  
Experimental Study ◽  
Sea Ice ◽  
Offshore Structures ◽  
Sea Bed ◽  
Ice Loads ◽  
Level Ice ◽  
Ice Floes ◽  
The Stability ◽  
Ice Forces ◽  
Concrete Model

A structure was designed to reduce the large forces exerted by level ice on offshore structures in shallow icy waters, by breaking the large ice floes into small pieces from flexing-induced failure. A series of model tests was conducted to simulate ice loads on the structure. A concrete model of it was adopted to verify the stability of the structure under the action of ice floes, which had five different thicknesses. The results show that ice forces on the structure are low and that the stability of the structure under different sea bed is good.

A Cohesive Element Framework for Dynamic Ice-Structure Interaction Problems: Part III—Case Studies

2010 ◽  
Author(s):  
Ibrahim Konuk ◽  
Shenkai Yu
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Case Studies ◽  
General Framework ◽  
Element Model ◽  
Cohesive Element ◽  
Structure Interaction

The general framework for a cohesive finite element model for the analysis of ice-structure interaction problems incorporating plasticity and fracture was presented at OMAE 2009 as Parts I & II. This third paper presents the application of the framework to various ice-structure interaction problems. It investigates the important aspects of these scenarios and reveals their characteristics which may play a major role in the design of structures. The investigations include the geometry, size and velocity effects as well as the influence of the structure stiffness. The paper also studies the effects of ice characteristics, and interaction speeds.

Modelling Results With a New Simulator for Arctic Marine Structures - SAMS

2018 ◽  
Author(s):  
Andrei Tsarau ◽  
Marnix van den Berg ◽  
Wenjun Lu ◽  
Raed Lubbad ◽  
Sveinung Løset
Keyword(s):  
Case Studies ◽  
Offshore Structures ◽  
Scientific Models ◽  
The Arctic ◽  
High Fidelity ◽  
Marine Structures ◽  
Floating Structures ◽  
Ice Loads ◽  
Numerical Tool ◽  
Flow Effects

The Simulator for Arctic Marine Structures (SAMS) has emerged on the foundation of a number of scientific models developed at SAMCoT – Centre for Research-based Innovation - Sustainable Arctic Marine and Coastal Technology hosted by NTNU – as a versatile numerical tool for the analysis of sea ice actions and action effects on Arctic offshore structures. The current capabilities of SAMS allow engineers to analyse icefloe impacts and ice loads on arbitrary marine structures in various environmental conditions; simulations may involve both fixed and floating structures, non-rigid multi floe interactions, ice breaking and ice rubbling, wind, current and propeller-flow effects on both structures and ice. All these capabilities can be combined to model also complex marine operations in the Arctic and subarctic regions. As SAMS can be applied in both full- and model scales, a number of available experimental case studies from the field and ice tanks can be reanalysed with the new simulator to ensure the high fidelity of the simulations and to establish a validation basis. This paper presents several of such case studies and discusses further validation possibilities.

Simulating Ice-Sloping Structure Interactions With the Cohesive Element Method

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Wenjun Lu ◽  
Raed Lubbad ◽  
Sveinung Løset
Keyword(s):  
Cohesive Zone ◽  
Scale Up ◽  
Cohesive Element ◽  
Cohesive Elements ◽  
Initial Stiffness ◽  
Zone Method ◽  
Structure Interaction ◽  
Mesh Dependency ◽  
Level Ice ◽  
Element Method

The major processes that occur when level ice interacts with sloping structures (especially wide structures) are the fracturing of ice and upcoming ice fragments accumulating around the structure. The cohesive zone method, which can simulate both fracture initiation and propagation, is a potential numerical method to simulate this process. In this paper, as one of the numerical methods based on the cohesive zone theory, the cohesive-element–based approach was used to simulate both the fracturing and upcoming fragmentation of level ice. However, simulating ice and sloping structure interactions with the cohesive element method poses several challenges. One often-highlighted challenge is its convergence issue. Numerous attempts by different researchers have been invested in this issue either to prove or improve its convergence. However, these researchers work in different fields (e.g., fracture of concrete, ceramic, or glass fiber) with different scales (e.g., from a ceramic ring to a concrete block). As an attempt to study the cohesive element method's application in the current ice-structure interaction context (i.e., an engineering scale up to hundreds of meters), the mesh dependency of the cohesive element method was alleviated by both creating a mesh with a crossed triangle pattern and utilizing a penalty method to obtain the initial stiffness for the intrinsic cohesive elements. Furthermore, two potential methods (i.e., introduction of a random ice field and bulk energy dissipation considerations) to alleviate the mesh dependency problem were evaluated and discussed. Based on a series of simulations with the different aforementioned methods and mesh sizes, the global ice load history is obtained. The horizontal load information is validated against the test results and previous simulation results. According to the comparison, the mesh objectivity alleviation with different approaches was discussed. As a preliminary demonstration, the results of one simulation are summarized, and the load contributions from different ice-structure interaction phases are illustrated and discussed.

scholarly journals A review of discrete element simulation of ice–structure interaction

2018 ◽  
Vol 376 (2129) ◽  
pp. 20170335 ◽  
Author(s):  
Jukka Tuhkuri ◽  
Arttu Polojärvi
Keyword(s):  
Sea Ice ◽  
Failure Process ◽  
Discrete Element ◽  
Offshore Structures ◽  
Lessons Learned ◽  
Structure Interaction ◽  
Large Numbers ◽  
Ice Loads ◽  
Discontinuous Medium ◽  
Ice Failure

Sea ice loads on marine structures are caused by the failure process of ice against the structure. The failure process is affected by both the structure and the ice, thus is called ice–structure interaction. Many ice failure processes, including ice failure against inclined or vertical offshore structures, are composed of large numbers of discrete failure events which lead to the formation of piles of ice blocks. Such failure processes have been successfully studied by using the discrete element method (DEM). In addition, ice appears in nature often as discrete floes; either as single floes, ice floe fields or as parts of ridges. DEM has also been successfully applied to study the formation and deformation of these ice features, and the interactions of ships and structures with them. This paper gives a review of the use of DEM in studying ice–structure interaction, with emphasis on the lessons learned about the behaviour of sea ice as a discontinuous medium. This article is part of the theme issue ‘Modelling of sea-ice phenomena’.

Computational Methods for Solving Dynamic Ice Structure Interaction Problems

2011 ◽  
Author(s):  
Ibrahim Konuk
Keyword(s):  
Dynamical System ◽  
Boundary Value Problem ◽  
Initial Boundary ◽  
Initial Boundary Value Problem ◽  
Element Model ◽  
Cohesive Element ◽  
Structure Interaction ◽  
Initial Boundary Value ◽  
Well Posed ◽  
Cohesive Element Model

A framework based on a complex dynamical system viewpoint for formulating and solving dynamic ice-structure interaction problems is introduced. Important constituents required for formulating a well posed initial-boundary value problem are discussed. Significance of these constituents is illustrated using a Cohesive Element model of several example problems.

Ice Model Tests for Semi-Submersible Platforms in Pack Ice Conditions

2019 ◽  
Author(s):  
Liu Luping ◽  
Li Xin ◽  
Wu Xiao ◽  
Wu Bo
Keyword(s):  
Offshore Structures ◽  
The Arctic ◽  
Floating Platform ◽  
Oil Exploitation ◽  
Pack Ice ◽  
Ice Drift ◽  
Load Cells ◽  
Ice Conditions ◽  
Ice Loads ◽  
Similar Density

Abstract As development of the Arctic grows in intensity, semi-submersible platforms are one of promising type of offshore structures used for arctic oil exploitation. Generally a good ice management is equipped by a moored floating platform to reduce ice loads to manageable levels, thus the most common scenario for a polar operating semi-submersible platform is pack ice conditions. The resistance test of a 4-columns structure is performed in a normal towing tank in China using synthetic non-refrigerated material with similar density to model sea ice. Three component load cells on top of each column and a batch of single component load cells embedded in the surface of the columns near the waterline are used to measure indirect and direct ice loads on the structures. The effects of a series of parameters such as column shapes, orientations, column spacing ratios, ice floe shapes, ice drift speeds and ice concentrations are analyzed.

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