Numerical simulation of ice-induced vibrations of steady-state type

2019 ◽  
Vol 22 (12) ◽  
pp. 2635-2647
Author(s):  
Wenliang Qiu ◽  
Tianyu Wu
Keyword(s):  
Numerical Simulation ◽  
Steady State ◽  
Model Test ◽  
Simulation Method ◽  
Offshore Structures ◽  
Structural Safety ◽  
Simulation Methodology ◽  
State Type ◽  
Ice Floes ◽  
Ice Pressure

Ice force is one kind of nonnegligible external loads that nature exerts on structures. The action of drifting ice floes may induce strong vibrations of offshore structures, and further reduce the structural safety and serviceability. The aim of this article is to develop a method to simulate the most dangerous situation during the interaction between ice and structure, that is, the ice-induced vibrations of steady-state type. A simulation methodology to realize structural steady-state vibration is proposed; it can simulate a special phenomenon of negative damping. The calculation of effective ice pressure is accomplished by an empirical formula which considers the dependence of the crushing strength on the ice velocity. The most important contribution of the simulation method is to capture the steady-state vibration phenomenon. The presented simulation methodology is conducted on the same model test introduced in a referenced study to verify the efficacy. Calculational examples show good agreements with the results of the model test, and the frequency contents of the generations coincide well with the targets. They directly prove the validity of the proposed simulation method. In addition, the numerical simulation method can be used in connection with finite element programs to perform a steady-state vibration analysis of offshore structures.

scholarly journals A Dynamic Ice-structure Interaction Model for Prediction of Ice-induced Vibration

2019 ◽  
Author(s):  
Tianyu Wu ◽  
Wenliang Qiu
Keyword(s):  
Sea Ice ◽  
Model Test ◽  
Interaction Model ◽  
Simulation Method ◽  
Offshore Structures ◽  
Full Scale ◽  
Structural Safety ◽  
Offshore Structure ◽  
The Impact ◽  
Ice Induced Vibration

Sea ice crashing against offshore structures can cause strong ice-induced vibration and have a major impact on offshore structural safety and serviceability. This paper describes a numerical method for the prediction of ice-induced vibration when a vertical offshore structure is subjected to the impact of sea ice. In this approach, negative damping theory and fracture length theory are combined and, along with ice strength-stress rate curve and ice failure length, are coupled to model the internal fluctuating nature of ice load. Considering the elastic deformation of ice and the effect of non-simultaneous crushing failure of local contact between ice and structures, the present ice-induced vibration model is established, and the general features of the interaction process are captured. To verify its efficacy, the presented simulation methodology is subjected to a model test and two full-scale measurements based on referenced studies. Example calculations show good agreement with the results of the model test and full-scale measurements, which directly indicates the validity of the proposed simulation method. In addition, the numerical simulation method can be used in connection with FE programs to perform ice-induced vibration analysis of offshore structures.

Collision Character Research for Semi-Submersible Through Model Test, Simplified Analytical and Numerical Simulation Method

2010 ◽  
Author(s):  
Zhiqiang Hu ◽  
Zhenhui Liu ◽  
Jo̸rgen Amdahl
Keyword(s):  
Numerical Simulation ◽  
Model Test ◽  
Simulation Method ◽  
Tension Force ◽  
Test Results ◽  
Buffer Effect ◽  
Mooring Lines ◽  
Column Structure ◽  
Collision Force ◽  
Energy Absorbing

The characters of the collision scenario when a semi-submersible is struck by a containership are studied in this paper, through the model test, simplified analytical method and numerical simulation. The model test is conducted in the Deepwater Offshore Basin in Shanghai Jiao Tong University. Two special devices are designed to fulfill the model test. One is Ship Launching Device, simplified as SLD, who can launch the striking ship with controllable velocity and in any horizontal direction. The other is Energy Absorbing Device, simplified as EAD, who can simulate the buffer effect of the column structure and collect the collision force as well. A numerical simulation is completed to get the approximate stiffness of the column structure, which is used to adjust the property of EAD. The motions of semi-submersible are obtained, and the collision force and the tension forces of mooring lines are also got. Collision scenario characters for semi-motion and tension force are summarized by the analysis of the model test results. The second collision phenomenon is observed. The collision force dominates the collision moment and the tension force of the mooring lines lags behind. A NTNU in-house program developed by analytical simplified method is also verified by the model test result. The comparison proves the feasibility of the program.

scholarly journals Numerical Simulation of the Ice Breaking Process for Hovercraft

2021 ◽  
Vol 9 (9) ◽  
pp. 928
Author(s):  
Jiangjie Jin ◽  
Li Zhou ◽  
Shifeng Ding ◽  
Yingjie Gu
Keyword(s):  
Numerical Simulation ◽  
Model Test ◽  
Open Water ◽  
Structural Safety ◽  
Preliminary Design ◽  
Load Prediction ◽  
Ice Load ◽  
Hull Structure ◽  
Air Cushion ◽  
Ice Force

A hovercraft can adapt to an ice area, open water, land and other environments, owing to its unique hull structure. It also plays an important role in transporting supplies, rescuing people, breaking ice and conducting other tasks. Ice load prediction is very important for structural safety and navigation of a polar ship, especially in design of air cushion icebreakers or ice breaking platforms. In this paper, based on a simplified circumferential icebreaking pattern, the icebreaking force of the hovercraft operating on the ice sheet at low speed is simulated in a numerical way. Numerical analysis of the icebreaking process with different ice thicknesses and bending strengths are performed. The numerical results are compared with model test data in a time domain for three operating cases. By analyzing the average ice force, the errors between numerical simulation results and model test measurements are less than 30%. The present study is significant for the preliminary design of new icebreaking hovercraft and it assists the operation possibility for existing hovercraft.

Research on the Crashworthiness of FLNG Side Structures in the Side-by-Side Offloading Operation With LNGC

2015 ◽  
Author(s):  
Dongwei Zhang ◽  
Zhiqiang Hu ◽  
Gang Chen
Keyword(s):  
Numerical Simulation ◽  
Finite Element ◽  
Model Test ◽  
High Probability ◽  
Structural Response ◽  
Simulation Method ◽  
Finite Element Models ◽  
Basic Design ◽  
Probability Of Collision ◽  
Special Limit

On purpose of evaluating the crashworthiness of FLNG side structures in case of the collision accident during the side-by-side offloading operation, a unique research is conducted in this paper with numerical simulation method. According to the model test completed in Deepwater Offshore Basin in Shanghai Jiao Tong University, there does exist a high probability of collision between FLNG and LNGC in the side-by-side offloading operation. To perform numerical simulations, finite element models were built. For the FLNG model, the side structures contain the detailed LNG cargo containment system. According to the parameters obtained from the model test, two typical collision scenarios are defined. Then the collision scenarios are simulated by the LS_DYNA code. A special limit collision state is proposed based on the structural response of LNG CCS. With respect to the numerical results, great attention is paid to the structural response of CCS to evaluate the safety of FLNG side structures. Furthermore, some insights useful for the basic design of FLNG are put forward.

scholarly journals An Approach to Determine Optimal Bow Configuration of Polar Ships under Combined Ice and Calm-Water Conditions

2021 ◽  
Vol 9 (6) ◽  
pp. 680
Author(s):  
Hui Li ◽  
Yan Feng ◽  
Muk Chen Ong ◽  
Xin Zhao ◽  
Li Zhou
Keyword(s):  
Numerical Simulation ◽  
Water Resistance ◽  
Numerical Technique ◽  
Experimental Studies ◽  
Resistance Index ◽  
Simulation Method ◽  
Present Approach ◽  
Calm Water ◽  
Level Ice ◽  
Ice Resistance

Selecting an optimal bow configuration is critical to the preliminary design of polar ships. This paper proposes an approach to determine the optimal bow of polar ships based on present numerical simulation and available published experimental studies. Unlike conventional methods, the present approach integrates both ice resistance and calm-water resistance with the navigating time. A numerical simulation method of an icebreaking vessel going straight ahead in level ice is developed using SPH (smoothed particle hydrodynamics) numerical technique of LS-DYNA. The present numerical results for the ice resistance in level ice are in satisfactory agreement with the available published experimental data. The bow configurations with superior icebreaking capability are obtained by analyzing the sensitivities due to the buttock angle γ, the frame angle β and the waterline angle α. The calm-water resistance is calculated using FVM (finite volume method). Finally, an overall resistance index devised from the ship resistance in ice/water weighted by their corresponding weighted navigation time is proposed. The present approach can be used for evaluating the integrated resistance performance of the polar ships operating in both a water route and ice route.

A numerical simulation method for molten material behavior in nuclear reactors

2017 ◽  
Vol 322 ◽  
pp. 301-312 ◽  
Author(s):  
Susumu Yamashita ◽  
Takuya Ina ◽  
Yasuhiro Idomura ◽  
Hiroyuki Yoshida
Keyword(s):  
Numerical Simulation ◽  
Nuclear Reactors ◽  
Simulation Method ◽  
Material Behavior ◽  
Molten Material ◽  
Numerical Simulation Method

scholarly journals Strata behavior and control strategy of backfilling collaborate with caving fully-mechanized mining

2020 ◽  
Vol 12 (1) ◽  
pp. 703-717
Author(s):  
Yin Wei ◽  
Wang Jiaqi ◽  
Bai Xiaomin ◽  
Sun Wenjie ◽  
Zhou Zheyuan
Keyword(s):  
Numerical Simulation ◽  
Control Strategy ◽  
Three Dimensional ◽  
Simulation Method ◽  
Mine Pressure ◽  
Hydraulic Support ◽  
Transition Area ◽  
Pressure Concentration ◽  
Strata Behavior ◽  
And Control

AbstractThis article analyzes the technical difficulties in full-section backfill mining and briefly introduces the technical principle and advantages of backfilling combined with caving fully mechanized mining (BCCFM). To reveal the strata behavior law of the BCCFM workface, this work establishes a three-dimensional numerical model and designs a simulation method by dynamically updating the modulus parameter of the filling body. By the analysis of numerical simulation, the following conclusions about strata behavior of the BCCFM workface were drawn. (1) The strata behavior of the BCCFM workface shows significant nonsymmetrical characteristics, and the pressure in the caving section is higher than that in the backfilling section. φ has the greatest influence on the backfilling section and the least influence on the caving section. C has a significant influence on the range of abutment pressure in the backfilling section. (2) There exits the transition area with strong mine pressure of the BCCFM workface. φ and C have significant effect on the degree of pressure concentration but little effect on the influence range of strong mine pressure in the transition area. (3) Under different conditions, the influence range of strong mine pressure is all less than 6 m. This article puts forward a control strategy of mine pressure in the transition area, which is appropriately improving the strength of the transition hydraulic support within the influence range (6 m) in the transition area according to the pressure concentration coefficient. The field measurement value of Ji15-31010 workface was consistent with numerical simulation, which verifies the reliability of control strategy of the BCCFM workface.

Sign in / Sign up

Export Citation Format

Share Document