A Frequency-Domain Model of Bitumen-Coated Armor Wires in Subsea Power Cables, Umbilicals, and Power Umbilicals

2016 ◽  
Author(s):  
Magnus Komperød
Keyword(s):  
Viscoelastic Behavior ◽  
Bending Moment ◽  
Bending Stiffness ◽  
Domain Model ◽  
The Novel ◽  
Power Cables ◽  
Simple Analytical Model ◽  
Temperature Dependent ◽  
Anticorrosion Protection ◽  
Novel Model

Bitumen is commonly used as anticorrosion protection for armor wires in subsea power cables, umbilicals, and power umbilicals. Bitumen’s viscoelastic behavior influences the cable’s mechanical properties. The present paper derives a simple, analytical model of bitumen-coated armor wires. The model calculates the axial stresses of the armor wires and the armor wires’ contribution to the cable’s bending stiffness. The model shows that there is a phase shift between the sinusoidal curvature oscillations and the corresponding armor wire stresses and cable bending moment. Two examples show that the armor wire stresses and the cable’s bending stiffness are strongly temperature-dependent. The purpose of the novel model is to calculate bending stiffness, fatigue stresses, and capacity (allowed combinations of axial cable tension and cable bending curvature) more accurately and to study these variables’ sensitivity to temperature and frequency. The model may also be included in calculations of bitumen’s influence on VIV damping.

A Novel Fatigue Stress Model of Power Phases and Coated Tubes in Deep-Water Power Cables, Umbilicals, and Power Umbilicals

2016 ◽  
Author(s):  
Magnus Komperød
Keyword(s):  
Real Life ◽  
Power Cable ◽  
The Novel ◽  
Power Cables ◽  
Insulation System ◽  
Fatigue Stress ◽  
Water Power ◽  
Significant Challenge ◽  
Deep Waters ◽  
Novel Model

Short fatigue life is a significant challenge for power cables, umbilicals, and power umbilicals to be installed in ultra-deep and hyper-deep waters. This paper presents a novel model for calculating fatigue stresses in conductors of power phases and in tubes with coating. The novelty is that the axial displacement of the conductor within the electric insulation system, or the tube within the sheath, is taken into consideration. For a real-life power cable designed for 2 300 m water depth, the novel model gives a reduction in fatigue stress of 69% compared to the traditional resultant-based approach for oscillations smaller than the slip curvature. This corresponds to a reduction in fatigue damage of more than 99%.

Implementation and Verification of Cable Bending Stiffness in MoorDyn

2021 ◽  
Author(s):  
Matthew Hall ◽  
Senu Sirnivas ◽  
Yi-Hsiang Yu
Keyword(s):  
Wave Energy ◽  
Bending Moment ◽  
Bending Stiffness ◽  
Coupled Analysis ◽  
Axial Stiffness ◽  
Power Cable ◽  
Power Cables ◽  
Lumped Mass ◽  
Dynamic Power ◽  
Static Conditions

Abstract The relatively large motions experienced by floating wind turbines and wave energy converters pose a challenge for power cables, whose internal components provide significant bending resistance and are sensitive to deformation. The behavior and associated design considerations of power cables in these highly dynamic applications make coupled analysis relevant for design. Bending stiffness capabilities have recently been added to the lumped-mass mooring dynamics model MoorDyn to enable simulation of dynamic power cables. MoorDyn is a common modeling choice for floating wind energy simulation (often coupled with OpenFAST) and floating wave energy converter simulation (often coupled with WEC-Sim) but the model’s previous line elasticity formulation only considered axial stiffness. To properly capture the dynamics of power cables, a bending stiffness model has been added that approximates cable curvature based on the difference in tangent vectors of adjacent elements. The resulting bending moment is realized by applying forces on adjacent nodes, enabling cable modeling while leaving the underlying lumped-mass formulation unchanged. In this paper, the new bending stiffness implementation is verified in static conditions against analytical solutions and then in a dynamic power cable scenario in comparison with the commercial simulator OrcaFlex. The dynamic scenario uses prescribed motions and includes wave loadings on the cable. Results indicate correct implementation of bending stiffness and show close agreement with OrcaFlex.

A multi-objective sparse evolutionary framework for large-scale weapon target assignment based on a reward strategy

2021 ◽  
Vol 40 (5) ◽  
pp. 10043-10061
Author(s):  
Xiaoping Shi ◽  
Shiqi Zou ◽  
Shenmin Song ◽  
Rui Guo
Keyword(s):  
Large Scale ◽  
The Novel ◽  
Genetic Operators ◽  
Multi Objective ◽  
Target Assignment ◽  
Solution Selection ◽  
Battlefield Environment ◽  
Sparse Problems ◽  
Novel Model ◽  
Error Parameter

 The asset-based weapon target assignment (ABWTA) problem is one of the important branches of the weapon target assignment (WTA) problem. Due to the current large-scale battlefield environment, the ABWTA problem is a multi-objective optimization problem (MOP) with strong constraints, large-scale and sparse properties. The novel model of the ABWTA problem with the operation error parameter is established. An evolutionary algorithm for large-scale sparse problems (SparseEA) is introduced as the main framework for solving large-scale sparse ABWTA problem. The proposed framework (SparseEA-ABWTA) mainly addresses the issue that problem-specific initialization method and genetic operators with a reward strategy can generate solutions efficiently considering the sparsity of variables and an improved non-dominated solution selection method is presented to handle the constraints. Under the premise of constructing large-scale cases by the specific case generator, two numerical experiments on four outstanding multi-objective evolutionary algorithms (MOEAs) show Runtime of SparseEA-ABWTA is faster nearly 50% than others under the same convergence and the gap between MOEAs improved by the mechanism of SparseEA-ABWTA and SparseEA-ABWTA is reduced to nearly 20% in the convergence and distribution.

A novel fractional discrete grey model with an adaptive structure and its application in electricity consumption prediction

Kybernetes ◽  
2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Yitong Liu ◽  
Yang Yang ◽  
Dingyu Xue ◽  
Feng Pan
Keyword(s):  
Fractional Order ◽  
Electricity Consumption ◽  
Grey Model ◽  
The Novel ◽  
Raw Data ◽  
Content Type ◽  
Power Load ◽  
Grey Models ◽  
Novel Model ◽  
Consumption Prediction

PurposeElectricity consumption prediction has been an important topic for its significant impact on electric policies. Due to various uncertain factors, the growth trends of electricity consumption in different cases are variable. However, the traditional grey model is based on a fixed structure which sometimes cannot match the trend of raw data. Consequently, the predictive accuracy is variable as cases change. To improve the model's adaptability and forecasting ability, a novel fractional discrete grey model with variable structure is proposed in this paper.Design/methodology/approachThe novel model can be regarded as a homogenous or non-homogenous exponent predicting model by changing the structure. And it selects the appropriate structure depending on the characteristics of raw data. The introduction of fractional accumulation enhances the predicting ability of the novel model. And the relative fractional order r is calculated by the numerical iterative algorithm which is simple but effective.FindingsTwo cases of power load and electricity consumption in Jiangsu and Fujian are applied to assess the predicting accuracy of the novel grey model. Four widely-used grey models, three classical statistical models and the multi-layer artificial neural network model are taken into comparison. The results demonstrate that the novel grey model performs well in all cases, and is superior to the comparative eight models.Originality/valueA fractional-order discrete grey model with an adaptable structure is proposed to solve the conflict between traditional grey models' fixed structures and variable development trends of raw data. In applications, the novel model has satisfied adaptability and predicting accuracy.

Assessing Bypassed Hydrocarbons

2021 ◽  
Author(s):  
Stanley Oifoghe ◽  
Nora Alarcon ◽  
Lucrecia Grigoletto
Keyword(s):  
Continental Shelf ◽  
Reservoir Characterization ◽  
Gamma Ray ◽  
West African ◽  
The Novel ◽  
The West ◽  
Present Case Study ◽  
Novel Model

Abstract Hydrocarbons are bypassed in known fields. This is due to reservoir heterogeneities, complex lithology, and limitations of existing technology. This paper seeks to identify the scenarios of bypassed hydrocarbons, and to highlight how advances in reservoir characterization techniques have improved assessment of bypassed hydrocarbons. The present case study is an evaluation well drilled on the continental shelf, off the West African Coastline. The targeted thin-bedded reservoir sands are of Cenomanian age. Some technologies for assessing bypassed hydrocarbon include Gamma Ray Spectralog and Thin Bed Analysis. NMR is important for accurate reservoir characterization of thinly bedded reservoirs. The measured NMR porosity was 15pu, which is 42% of the actual porosity. Using the measured values gave a permeability of 5.3mD as against the actual permeability of 234mD. The novel model presented in this paper increased the porosity by 58% and the permeability by 4315%.

scholarly journals Comparison of bending stiffness of six different colours of copolymer polypropylene

1999 ◽  
Vol 23 (1) ◽  
pp. 63-71 ◽  
Author(s):  
R. S. Ross ◽  
R. J. Greig ◽  
P. Convery
Keyword(s):  
Electron Microscope ◽  
Wall Thickness ◽  
Modulus Of Elasticity ◽  
Microscope Study ◽  
Electron Microscope Study ◽  
Bending Moment ◽  
Bending Stiffness ◽  
Ankle Foot Orthosis ◽  
Uniform Wall ◽  
Foot Orthosis

This paper compares the bending stiffness of 5 different colours of copolymer polypropylene (CCP) with that of natural copolymer polypropylene (NCP). Flesh coloured and natural sheets are supplied thicker than other pigmented sheet. The bending stiffness of a specimen may be defined as EI, i.e. the product of E, Young's modulus of elasticity and I, the 2nd moment of area. Strips of “as supplied” (AS) and “post-draped” (PD) specimen were clamped and subjected to bending to assess the effect of pigmentation on bending characteristics. The gradient of the graph of bending deflection δ versus bending moment enables EI to be estimated. The process of thermoforming polypropylene reduces EI, the bending stiffness. However, the manual draping and vacuum procedure introduces so many variables that it is difficult to quantify the effect of pigmentation. The E of a bent specimen may be estimated from the gradient of the graph of δI versus bending moment. In the case of AS sheet, the effect of pigmentation on E is inconclusive. PD specimens indicate a significant reduction in E due to thermoforming. This was verified by an electron-microscope study of AS and PD specimens. Draping an ankle-foot orthosis (AFO) results in a non-uniform wall thickness. The results of this study with respect to the effects of pigmentation on the bending stiffness of AFOs are inconclusive. More detailed studies require to be completed in order to confirm which factors are responsible for this non-uniformity in wall thickness and consequent variation in bending stiffness.

scholarly journals CONTROL NOVEL MODEL OF KNEE CPM DEVICE

2009 ◽  
Vol 12 (4) ◽  
pp. 18-29
Author(s):  
Thanh Diep Cong Tu
Keyword(s):  
Weight Ratio ◽  
Artificial Muscle ◽  
Network Control ◽  
Continuous Passive Motion ◽  
The Novel ◽  
Highly Nonlinear ◽  
Cord Injury ◽  
And Control ◽  
Novel Model ◽  
Interesting Alternative

In recent years, CPM - Continuous Passive Motion has been proved to be one of the most effective therapeutic methods for patients who have problems with motion such as spinal cord injury, ankle and knee injury, parkinson and so on. Many commercial CPM devices are found in market but all of them use motors as the main actuators. The lack of human compliance of electric actuators, which are commonly used in these machines, makes them potentially harmful to patients. An interesting alternative, to electric actuators for medical purposes, particularly promising for rehabilitation, is a pneumatic artificial muscle (PAM) actuator because of its high power/weight ratio and compliance properties. However, the highly nonlinear and hysteresis of PAM make it the challenging for design and control. In this study, a PID compensation using neural network control is studied to improve the control performance of the novel model of Knee CPM device.

An Analytical Model to Predict the Bending Behavior of Unbonded Flexible Pipes

2013 ◽  
Vol 57 (03) ◽  
pp. 171-177
Author(s):  
Leilei Dong ◽  
Yi Huang ◽  
Qi Zhang ◽  
Gang Liu
Keyword(s):  
Bending Moment ◽  
Bending Stiffness ◽  
Nonlinear Formulation ◽  
Flexible Pipe ◽  
Flexible Pipes ◽  
Bending Behavior ◽  
Interlayer Slip ◽  
Unbonded Flexible Pipes ◽  
Relationship Of ◽  
Theoretical Results

Analytical formulations are presented to determine the bending moment-curvature relationship of a helical layer in unbonded flexible pipes. Explicit expressions describing the variation of both bending stiffness and moment as a function of the applied curvature are given. The approach takes into account the nonlinearity of the response caused by the interlayer slip. The contribution of local bending and torsion of individual helical elements to the bending behavior of helical layers is included. Theoretical results for a typical unbonded flexible pipe using the nonlinear formulation for helical layers are compared with experimental data from the available literature. Encouraging correlations are found and the importance of the initial interlayer pressures is seen. The influence of local bending and torsion of individual helical elements on the bending behavior of the entire pipe is also evaluated. The results show that the inclusion of this local behavior significantly influences the full-slip bending stiffness.

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