scholarly journals Time Domain Simulation of Damage Flooding Considering Air Compression Characteristics

Water ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 796 ◽  
Author(s):  
XinLong Zhang ◽  
Zhuang Lin ◽  
Ping Li ◽  
Yue Dong ◽  
Fei Liu
Keyword(s):  
Time Domain ◽  
Time Domain Simulation ◽  
Cruise Ship ◽  
Accurate Analysis ◽  
Factors Affecting ◽  
Computational Fluid Dynamics Cfd ◽  
The Stability ◽  
Air Compression ◽  
Damaged Stability ◽  
Compression Characteristics

An accurate analysis of the entire flooding process is critical to assess the damaged stability when a ship encounters distressed accidents such as collision, stranding, or grounding. Among many factors affecting the flooding process and damaged stability, the complex effect of air compression is significant and worthy of further research. In this paper, through establishing scenarios of the damage flooding for a cruise ship, the commercial software CD Adapco STARCCM+ is applied to perform time domain simulation of flooding processes under different ventilation levels. The basic mathematical models about air compression and specific simulation settings of computational fluid dynamics (CFD) are presented in detail. The simulation results show that water ingression results in an increase of air pressure and density inside the flooded compartment. The corresponding air compression can significantly delay the flooding process if the ventilation level is limited to a certain ratio. Finally, the stability of the damaged ship is affected.

scholarly journals OPTIMAL DESIGN OF MICROGRID IN AN AUTONOMOUS MODE USING ANTCOLONY OPTIMIZATION

2013 ◽  
pp. 14-18
Author(s):  
N. CHITRA ◽  
TAMIZHARASI. G ◽  
A. SENTHIL KUMAR
Keyword(s):  
Time Domain ◽  
Power Sharing ◽  
Time Domain Simulation ◽  
Stability And Control ◽  
Control Effectiveness ◽  
Damping Characteristics ◽  
Autonomous Mode ◽  
The Stability ◽  
And Control ◽  
Nonlinear Time Domain

The dynamic nature of the distribution network challenges the stability and control effectiveness of the microgrid in autonomous mode. In this paper, nonlinear model of microgrid operating in autonomous mode has been presented. The controller parameters and power sharing coefficients are optimized in case of autonomous mode. The control problem has been formulated as an optimization problem where Ant colony optimization is employed to search for optimal settings of the optimized parameters. In addition, nonlinear time-domain-based objective function has been proposed to minimize the error in the measured power and to enhance the damping characteristics, respectively. Finally, the nonlinear time-domain simulation has been carried out to assess the effectiveness of the proposed controllers under different disturbances and loading conditions. The results show satisfactory performance with efficient damping characteristics of the microgrid considered in this study.

scholarly journals Analysis of Effective Operation Performance of Wireless Control Downhole Choke

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Yukun Fu ◽  
Huiyun Ma ◽  
Chenggang Yu ◽  
Liangliang Dong ◽  
Yunshan Yang ◽  
...  
Keyword(s):  
Flow Field ◽  
Flow Resistance ◽  
Key Factors ◽  
Operation Performance ◽  
Factors Affecting ◽  
Ground Pressure ◽  
Wireless Control ◽  
Effective Operation ◽  
Computational Fluid Dynamics Cfd ◽  
The Stability

Wireless control downhole throttle is designed to control the opening of downhole throttle remotely by ground pressure wave signal to regulate downhole production in a wireless and intelligent manner. The throttle’s production regulation capability and the noise immunity of the signal receiver are the key factors affecting the reliability of the throttle operation. Based on computational fluid dynamics (CFD) theory, the flow field of downhole throttle is simulated numerically to study the flow resistance characteristics of wireless control downhole throttle and the stability of flow field at signal receiver. Finally, the field test proves that the tool achieves the design capacity of production regulation and can accurately receive signals to regulate downhole production in a wireless and intelligent manner. The research content of this paper provides theoretical and experimental basis for the further improvement and optimization of the wireless control downhole throttle’s structure and has certain guiding significance for the field use of the throttle, achieving the purpose of downhole wireless intelligent production adjustment.

scholarly journals Theoretical and Experimental Study of Heading Stability and Heading Control of a Turret-Moored FPSO

2017 ◽  
Author(s):  
Karl E. Kaasen ◽  
Halgeir Ludvigsen ◽  
Ivar Nygaard ◽  
Kristian Aas
Keyword(s):  
Time Domain ◽  
Theoretical Study ◽  
Stability Study ◽  
Time Domain Simulation ◽  
Wave Excitation ◽  
Hypothetical Case ◽  
Simple Criterion ◽  
Heading Control ◽  
Basic Parameters ◽  
The Stability

The behaviour and characteristics of a turret-moored FPSO subjected to loading from waves, wind and current are investigated. Of particular importance is to find out if fishtailing instabilities may occur, and if such instability can be disclosed by simple criteria involving basic parameters of the system’s mathematical model. Eight cases from model tests are chosen for theoretical study and time domain simulation. Four of the cases involve heading control with thrusters. For the stability study, a simplified linear model in sway and yaw is formulated. It is shown that the inherent characteristics of the model depend on the strengths and relative directions of the metocean processes. The eigenvalues of the sway-yaw model are computed for the eight selected cases to check the stability. A simple approximate criterion for heading stability is derived from the sway-yaw model. It is assumed, but not proven, that the criterion is a sufficiency criterion for stability. Both the experiments and the simulations show that the eight cases are stable. This is also confirmed by the eigenvalues of the sway-yaw model, while the simple criterion wrongly deems several cases unstable. The simple stability criterion is therefore probably conservative, at least when there is significant damping in the system. In one additional hypothetical case with only wave excitation and weak or lacking stability, the simplified criterion agrees well with the model test and simulation. Heading control is necessary when a heading different from the natural weathervaning heading is wanted. The controller used in the experiments and simulations is of simple SISO PID type. With control, the heading variations are reduced significantly.

Time Domain Simulation of Milling Chatter Stability

2016 ◽  
Vol 836-837 ◽  
pp. 94-98 ◽  
Author(s):  
Ying Chao Ma ◽  
Min Wan ◽  
Wei Hong Zhang
Keyword(s):  
Time Domain ◽  
Chip Thickness ◽  
Time Algorithm ◽  
Milling Process ◽  
Time Domain Simulation ◽  
Chatter Stability ◽  
Stability Lobe ◽  
Machining System ◽  
The Stability ◽  
Milling Chatter

In this paper, time domain simulation has been carried out to study the chatter stability of milling process. Dynamic chip thickness is calculated by analyzing the kinematics of the cutter, and thus dynamic governing equation revealing the dynamic behaviors between the cutter and workpiece is established. Solving framework is constructed by using the Simulink module and S-Function of Matlab software, and dynamic deflection is achieved with the four-order Runge-Kutta algorithm. With the simulated cutting forces, a criterion for the construction of the stability lobe is suggested. At the same time, algorithm for the prediction of the surface topography involving the dynamic response of the machining system is developed.

scholarly journals Dynamical Modeling of Spindle with Active Magnetic Bearing for Milling Process

2011 ◽  
Vol 423 ◽  
pp. 200-209 ◽  
Author(s):  
Etienne Gourc ◽  
Sébastien Seguy ◽  
Gilles Dessein
Keyword(s):  
Time Domain ◽  
Forced Vibrations ◽  
Magnetic Bearing ◽  
Milling Process ◽  
Active Magnetic Bearing ◽  
Time Domain Simulation ◽  
Dynamical Modeling ◽  
Machining Center ◽  
Simulation Results ◽  
The Stability

A dynamical modeling of spindle with Active Magnetic Bearing (AMB) is presented. All the required parameters are included in the model for stability analysis. The original map of stability is generated by Time Domain Simulation. The major importance of forced vibrations is highlighted for a spindle with AMB. Milling test are used to quickly evaluate the stability. Finally, the simulation results are then validated by cutting tests on a 5 axis machining center with AMB.

Equivalent Analysis of Elastic Constants and Stability Calculation of Corrugated-Arch Metal Roof

2012 ◽  
Vol 542-543 ◽  
pp. 106-110
Author(s):  
Li Tong Sun ◽  
Le Su Lin
Keyword(s):  
Elastic Constants ◽  
Calculation Model ◽  
The Finite Element Method ◽  
Orthotropic Plates ◽  
Accurate Analysis ◽  
Stability Calculation ◽  
Factors Affecting ◽  
Overall Stability ◽  
The Stability ◽  
Simplified Calculation

Corrugated-arch Metal Roof has anisotropic properties because of transverse small corrugations covering the surface of the structure. Thus the panels should be considered as orthotropic plates for more accurate analysis. Based on the principle of stressed skin diaphragm, elastic constants of Corrugated-arch Metal Roof with corrugations are analyzed using equivalent methods; the formulas for equivalent elastic constants are produced and the simplified calculation model is established. The stability of the structure is analyzed and evaluated by use of the finite element method. The results are compared with experimental results, and the method of equivalent analysis is validated. The results indicate that the theoretical bearing capacity is determined by overall stability under full-span and half-span loading without considering the initial defects. Through the equivalent analysis, the length and depth of corrugations are main factors affecting the equivalent elastic constants. Design recommendations are finally presented.

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.

Study of HVDC System and Subsynchronous Oscillation

2015 ◽  
Vol 1092-1093 ◽  
pp. 356-361
Author(s):  
Peng Fei Zhang ◽  
Lian Guang Liu
Keyword(s):  
Power Plant ◽  
Time Domain ◽  
Simulation Method ◽  
Time Domain Simulation ◽  
Stable Convergence ◽  
Turbine Generator ◽  
Plant Model ◽  
Subsynchronous Oscillation ◽  
Hvdc System ◽  
Simulation Results

With the application and development of Power Electronics, HVDC is applied more widely China. However, HVDC system has the possibilities to cause subsynchronous torsional vibration interaction with turbine generator shaft mechanical system. This paper simply introduces the mechanism, analytical methods and suppression measures of subsynchronous oscillation. Then it establishes a power plant model in islanding model using PSCAD, and analyzes the effects of the number and output of generators to SSO, and verifies the effect of SEDC and SSDC using time-domain simulation method. Simulation results show that the more number and output of generators is detrimental to the stable convergence of subsynchronous oscillation, and SEDC、SSDC can restrain unstable SSO, avoid divergence of SSO, ensure the generators and system operate safely and stably

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