Spar Platform Installation: Tank Flooding Simulation

2014 ◽  
Author(s):  
Abel Medellin ◽  
Michelle Arango-Turner ◽  
Curtis Fuhr
Keyword(s):  
Hydrostatic Pressure ◽  
Modeling And Simulation ◽  
Time Domain ◽  
Time Interval ◽  
Design Phase ◽  
Time Domain Simulation ◽  
Spar Platform ◽  
Software Suite ◽  
Dynamic Time ◽  
The Time Domain

Spars are towed to installation site horizontally and upended by progressive flooding of tanks. It is common practice to perform a dynamic time domain simulation for a self upending classic spar to determine hydrostatic pressures on compartments. There are many different flooding scenarios that create challenges in modeling and simulation during the design phase. In one particular scenario, the spar upending is initiated by opening valves that allow water to flood into the skirt tank. The skirt tank will progressively fill, based on the differential hydrostatic pressure at valves, and cause the spar to upend. Flooding into keel tanks will commence once respective openings become submerged. Several openings from the skirt tank into the keel tanks reduce the differential pressure experienced in the keel tanks during upending. Simulation of the transfer of water between tanks cannot be modeled with ease using the standard tank flooding options available within the software suite. This particular compartment flooding problem is solved by utilizing a scheme in which the time domain simulation was performed iteratively for a specified time interval. For every iteration the amount of water transferred between the skirt and keel tanks are calculated. The amount of water transferred is calculated using a custom modeling technique. The openings from the skirt tank into the keel tanks are not modeled as a typical hole or valve into a compartment, but the location of these holes are modeled. The amount of water flowing through these openings is determined by the water level in the skirt tank, friction through the opening, and pressure inside the keel tanks. This paper will describe in detail the scheme developed, the tank modeling requirements, and the results obtained.

scholarly journals Convolution-based time-domain simulation for fluidelastic instability in tube arrays

2021 ◽  
Author(s):  
Mingjie Zhang ◽  
Ole Øiseth
Keyword(s):  
Impulse Response ◽  
Response Function ◽  
Time Domain ◽  
Impulse Response Function ◽  
Time Domain Simulation ◽  
Unit Step ◽  
Tube Arrays ◽  
Unit Impulse ◽  
The Time Domain ◽  
Unit Impulse Response

AbstractA convolution-based numerical algorithm is presented for the time-domain analysis of fluidelastic instability in tube arrays, emphasizing in detail some key numerical issues involved in the time-domain simulation. The unit-step and unit-impulse response functions, as two elementary building blocks for the time-domain analysis, are interpreted systematically. An amplitude-dependent unit-step or unit-impulse response function is introduced to capture the main features of the nonlinear fluidelastic (FE) forces. Connections of these elementary functions with conventional frequency-domain unsteady FE force coefficients are discussed to facilitate the identification of model parameters. Due to the lack of a reliable method to directly identify the unit-step or unit-impulse response function, the response function is indirectly identified based on the unsteady FE force coefficients. However, the transient feature captured by the indirectly identified response function may not be consistent with the physical fluid-memory effects. A recursive function is derived for FE force simulation to reduce the computational cost of the convolution operation. Numerical examples of two tube arrays, containing both a single flexible tube and multiple flexible tubes, are provided to validate the fidelity of the time-domain simulation. It is proven that the present time-domain simulation can achieve the same level of accuracy as the frequency-domain simulation based on the unsteady FE force coefficients. The convolution-based time-domain simulation can be used to more accurately evaluate the integrity of tube arrays by considering various nonlinear effects and non-uniform flow conditions. However, the indirectly identified unit-step or unit-impulse response function may fail to capture the underlying discontinuity in the stability curve due to the prespecified expression for fluid-memory effects.

scholarly journals Enhancing Oscillation Damping in an Interconnected Power System with Integrated Wind Farms Using Unified Power Flow Controller

Energies ◽  
2019 ◽  
Vol 12 (2) ◽  
pp. 322 ◽  
Author(s):  
Ping He ◽  
Seyed Arefifar ◽  
Congshan Li ◽  
Fushuan Wen ◽  
Yuqi Ji ◽  
...  
Keyword(s):  
Power Systems ◽  
Power System ◽  
Time Domain ◽  
Power Flow ◽  
Unified Power Flow Controller ◽  
Time Domain Simulation ◽  
Interconnected Power System ◽  
Dynamic Time ◽  
Oscillation Damping ◽  
Power Flow Controller

The well-developed unified power flow controller (UPFC) has demonstrated its capability in providing voltage support and improving power system stability. The objective of this paper is to demonstrate the capability of the UPFC in mitigating oscillations in a wind farm integrated power system by employing eigenvalue analysis and dynamic time-domain simulation approaches. For this purpose, a power oscillation damping controller (PODC) of the UPFC is designed for damping oscillations caused by disturbances in a given interconnected power system, including the change in tie-line power, the changes of wind power outputs, and others. Simulations are carried out for two sample power systems, i.e., a four-machine system and an eight-machine system, for demonstration. Numerous eigenvalue analysis and dynamic time-domain simulation results confirm that the UPFC equipped with the designed PODC can effectively suppress oscillations of power systems under various disturbance scenarios.

Time-Domain Coupled Dynamic Analysis of Mooring Systems in Extreme Sea Condition

2018 ◽  
Author(s):  
Xuliang Han ◽  
ShiSheng Wang ◽  
Bin Xie ◽  
Wenhui Xie ◽  
Weiwei Zhou
Keyword(s):  
Dynamic Analysis ◽  
Body Surface ◽  
Time Domain ◽  
Mooring Line ◽  
Mooring System ◽  
Dynamic Coupling ◽  
Spar Platform ◽  
Coupled Dynamic Analysis ◽  
Motion Responses ◽  
The Time Domain

In order to predict the coupled motion and external wave load for the design of deepwater floating structure system, based on the three-dimensional time-domain potential flow theory, this paper present the indirect time-domain dynamic coupling method and the body nonlinear dynamic coupling method. The perturbation expansion theory is adopted to evaluate hydrodynamic on the fixed mean wetted body surface for the former method. The transient free surface Green function has been extended and applied to calculate the nonlinear hydrodynamic on the instantaneous wetted exact body surface for the latter method. The finite element model is employed to solve dynamic response of mooring line. Then asynchronous coupled method is adopted to achieve the coupled dynamic analysis of platform and mooring lines. The time-domain motion responses and spectrum analysis of Spar platform are verified and compared with the traditional indirect time-domain coupling dynamic method when the mooring system is completed. Also the time-domain motion responses and statistical characteristic of Spar platform are investigated with one mooring line broken in extreme sea condition. Some conclusions are obtained, that is, dynamic coupling effects are significant and transient position hydrodynamic calculation of platform has a great influence on the low frequency motion. The results also show that the influence on the global performance of mooring system is different when the broken line is in different place. A remarkable influence occurs when the broken mooring line is in the head-wave direction.

scholarly journals An Experimental Data-Driven Model of a Micro-Cogeneration Installation for Time-Domain Simulation and System Analysis

Energies ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2759 ◽  
Author(s):  
Wojciech Uchman ◽  
Janusz Kotowicz ◽  
Leszek Remiorz
Keyword(s):  
Time Domain ◽  
Electricity Generation ◽  
System Analysis ◽  
Data Driven ◽  
Maximum Efficiency ◽  
Time Domain Simulation ◽  
Term Operation ◽  
Operating Modes ◽  
Laboratory Setup ◽  
The Time Domain

In this article, an investigation of a free-piston Stirling engine-based micro-cogeneration (μCHP) unit is presented. This work is a step towards making the system calculations more reliable, based on a data-driven model, which enables the time-domain simulation of the μCHP behavior. A laboratory setup was developed that allowed for the measurement of a micro-cogeneration unit during long-term operation with a variable thermal load. The maximum efficiency of electricity generation was equal to 13.2% and the highest overall efficiency was equal to 95.7%. A model of the analyzed μCHP system was developed and validated. The simulation model was based on the device’s characteristics that were obtained from the measurements; it enables time-domain calculations, taking into account the different operating modes of the device. The validation of the system showed satisfactory compliance of the model with the measurements: for the period modeled of 24 h, the error in the heat generation fluctuated in the range 0.31–4.50%, the error in the electricity generation was in the range 2.48–4.70%, the error in the natural gas consumption was in the range 0.26–4.59%, and the engine’s runtime error was in the range 0.14–8.58%. The modelling process is easily applicable to other energy systems for detailed analysis.

The Effects of Inner-Liquid Motion on LNG Vessel Responses

2010 ◽  
Vol 132 (2) ◽  
Author(s):  
S. J. Lee ◽  
M. H. Kim
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Surface Profile ◽  
Ship Motion ◽  
Liquid Sloshing ◽  
Diffraction Radiation ◽  
Time Domain Simulation ◽  
Coupling Effects ◽  
The Time Domain ◽  
Vessel Motion

The coupling and interactions between ship motion and inner-tank sloshing are investigated by a potential-viscous hybrid method in the time domain. For the time-domain simulation of vessel motion, the hydrodynamic coefficients and wave forces are obtained by a potential-theory-based 3D diffraction/radiation panel program in the frequency domain. Then, the corresponding simulations of motions in the time domain are carried out using the convolution-integral method. The liquid sloshing in a tank is simulated in the time domain by a Navier–Stokes solver. A finite difference method with SURF scheme assuming the single-valued free-surface profile is applied for the direct simulation of liquid sloshing. The computed sloshing forces and moments are then applied as external excitations to the ship motion. The calculated ship motion is in turn inputted as the excitation for liquid sloshing, which is repeated for the ensuing time steps. For comparison, we independently developed a 3D panel program for linear inner-fluid motions, and it is coupled with the vessel-motion program in the frequency domain. The developed computer programs are applied to a barge-type floating production storage and offloading (FPSO) hull equipped with two partially filled tanks. The time-domain simulation results show reasonably good agreement when compared with Maritime Research Institute Netherlands (MARIN’s) experimental results. The frequency-domain results qualitatively reproduce the trend of coupling effects, but the peaks are in general overpredicted. It is seen that the coupling effects on roll motions appreciably change with filling level. The most pronounced coupling effects on roll motions are the shift or split of peak frequencies. The pitch motions are much less influenced by the inner-fluid motion compared with roll motions.

scholarly journals Numerical study on deployment of subsea template using coupled and uncoupled model

2021 ◽  
Vol 1201 (1) ◽  
pp. 012020
Author(s):  
N O Hauge ◽  
L Li
Keyword(s):  
Time Domain ◽  
Numerical Study ◽  
Coupled Model ◽  
Simulation Software ◽  
Time Domain Simulation ◽  
Coupled Models ◽  
Sea State ◽  
The Time Domain ◽  
Vessel Motion ◽  
Simulation Time

Abstract This study compares deployment of a subsea template simulated as a coupled model and as an uncoupled model in the time domain simulation software Orcaflex. Defining vessel motion as prescribed simplifies the model and will therefore also decrease the simulation time. Models with predefined vessel motions are called uncoupled models. Vessel motion in a coupled model is a continuously calculated reaction to the forces acting on the vessel. Some software might struggle to run coupled models. The deployment simulations are narrowed down to focus on the incident where the template crosses the splash zone when lifted with an offshore construction vessel. Noticeable differences between the allowable sea state results are observed from the two different simulation methods. Running the time domain simulation as an uncoupled model gives lower allowable sea states than the results from the coupled time domain simulation model.

An Improved Time Domain Simulation for Dynamic Milling at Small Radial Immersions and Large Depths of Cut

2001 ◽  
Author(s):  
Marc L. Campomanes ◽  
Yusuf Altintas
Keyword(s):  
Surface Finish ◽  
Time Domain ◽  
Dynamic Models ◽  
Three Dimensional ◽  
Domain Model ◽  
Time Domain Simulation ◽  
Chatter Stability ◽  
Linear Effects ◽  
Deep Cuts ◽  
The Time Domain

Abstract This paper presents an improved time domain model for milling, which can simulate vibratory cutting conditions at very small radial widths of cut and large depths of cut. The improved kinematics model allows simulation of very small radial immersions. The varying dynamics modeled along the cutting depth allows milling with very flexible cutters and/or flexible workpieces at very deep cuts to be simulated. The model can predict forces, surface finish, and chatter stability, accurately accounting for non-linear effects that are difficult to model analytically. The discretized cutter and workpiece kinematics and dynamic models are used to represent the exact trochoidal motion of the cutter, and to investigate the effects of forced vibrations and changing radial immersion due to deflection and vibrations on chatter stability. Three dimensional surface finish profiles are predicted and are compared to measured results. Stability lobes generated from the time domain simulation are also shown for various cases.

Time‐domain simulation of SH-wave‐induced electromagnetic field in heterogeneous porous media: A fast finite‐element algorithm

Geophysics ◽  
2001 ◽  
Vol 66 (2) ◽  
pp. 448-461 ◽  
Author(s):  
Qiyu Han ◽  
Zhijing (Zee) Wang
Keyword(s):  
Finite Element ◽  
Porous Media ◽  
Time Domain ◽  
Heterogeneous Porous Media ◽  
Matrix Equations ◽  
Time Domain Simulation ◽  
Sh Wave ◽  
Fe Method ◽  
Streaming Current ◽  
The Time Domain

When a horizontally polarized rotational mechanical wave (SH-wave) travels through a porous rock, acceleration of the rock frame induces a streaming current in the SH particle motion plane. This streaming current is parallel to the particle displacement and has an associated electromagnetic (EM) field. This phenomenon is often described as the electroseismic (EOS) conversion. Numerically, the EOS phenomenon can be simulated in either the frequency or the time domain. Frequency‐domain numerical simulation has huge memory and computational requirements. Traditional time‐domain simulation, on the other hand, must restrict the time steps to be very small to satisfy stability conditions, resulting in large workload. In this paper, we present a fast finite‐element (FE) method simulating the EOS conversion in the time domain. In our method, we decompose the large 2-D FE matrix equations into a set of 1-D matrix equations and solve the problem using the approximate 1-D multistep process. We present numerical examples of 1-D and 2-D models to illustrate the coevolution of the seismic and electromagnetic fields. Our simulation results show that the diffusive electrical field is induced from the spatial variations of mechanical and electrical properties of the porous media due to the imbalance of the induced electric current. Besides the direct SH-wave itself, the transmitted waves, multiple waves, reflected waves, and diffracted waves also induce diffusive electrical fields. The EOS conversion is potentially useful for reservoir characterization, but the EOS data may be difficult to interpret due to the complexity of the superposed wave fields. The diffusive nature of the induced EM fields suggests that antennas should be positioned close to the target of interest in in‐situ measurements. As a result, borehole EOS surveys are likely to be more practical than surface surveys.

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