• Title, Summary, Keyword: transient simulations

Search Result 404, Processing Time 0.036 seconds

Effects of Initial Conditions on Transient Responses in Dynamic Simulation of FOWT (초기 조건이 부유식 풍력터빈 동역학 해석의 과도응답에 미치는 영향)

  • Song, Jin-Seop;Rim, Chae-Whan;Moon, Seok-Jun;Nam, Yong-Yun
    • Journal of Ocean Engineering and Technology
    • /
    • v.28 no.4
    • /
    • pp.288-293
    • /
    • 2014
  • The IEC standard for onshore or offshore wind turbines requires additional dummy simulations (at least 5 s) for the transient responses due to initial conditions. An increase in the dummy time causes a considerable increase in the computational cost considering multiple design spirals with several thousand design load analysis cases. A time of 30 s is typically used in practical simulations for a wind turbine design with a fixed platform. However, 30 s may be insufficient for floating offshore wind turbines (FOWT) because the platforms have lower natural frequencies, and the transient responses will last much longer. In this paper, an initial condition application algorithm is implemented for WindHydro, and the appropriate dummy simulation time is investigated based on a series of dynamic simulations of a FOWT. As a result, it is found that more than 300 s is required for the platform to have stationary motion after the initial transient responses for the FOWT under the conditions considered.

A Simple Dynamic Model and Transient Simulation of the Nuclear Power Reactor on Microcomputers

  • Han, Gee-Yang;Park, Cheol
    • Proceedings of the Korean Nuclear Society Conference
    • /
    • /
    • pp.605-610
    • /
    • 1997
  • A simple dynamic model is developed for the transient simulation of the nuclear power reactor. The dynamic model includes the normalized neutron kinetics model with reactivity feedback effects and the core thermal-hydraulics model. The main objective of this paper demonstrates the capability of the developed dynamic model to simulate various important variables of interest for a nuclear power reactor transient. Some representative results of transient simulations show the expected trends in all cases, even though no available data for comparison. In this work transient simulations are performed on a microcomputer using the DESIRE/N96T continuous system simulation language which is applicable to nuclear power reactor transient analysis.

  • PDF

Numerical Studies of Transient Opposed-Flow Flames using Adaptive Time Integration

  • Im, Hong-Geun
    • Journal of Mechanical Science and Technology
    • /
    • v.14 no.1
    • /
    • pp.103-112
    • /
    • 2000
  • Numerical simulations of unsteady opposed-flow flames are performed using an adaptive time integration method designed for differential-algebraic systems. The compressibility effect is considered in deriving the system of equations, such that the numerical difficulties associated with a high-index system are alleviated. The numerical method is implemented for systems with detailed chemical mechanisms and transport properties by utilizing the Chemkin software. Two test simulations are performeds hydrogen/air diffusion flames with an oscillatory strain rate and transient ignition of methane against heated air. Both results show that the rapid transient behavior is successfully captured by the numerical method.

  • PDF

Transient Queueing Approximation for Modeling Computer Networks (컴퓨터 통신망의 모델링을 위한 비정상 상태에서의 큐잉 근사화)

  • Lee, Bong-Hwan
    • Journal of the Korean Institute of Telematics and Electronics A
    • /
    • v.32A no.4
    • /
    • pp.15-23
    • /
    • 1995
  • In this paper, we evaluate the performance of a transient queueing approximation when it is applied to modeling computer communication networks. An operational computer network that uses the ISO IS-IS(Intermediate System-Intermediate System) routing protocol is modeled as a Jackson network. The primary goal of the approximation pursued in the study was to provide transient queue statistics comparable in accuracy to the results from conventional Monte Carlo simulations. A closure approximation of the M/M/1 queueing system was extended to the general Jackson network in order to obtain transient queue statistics. The performance of the approximation was compared to a discrete event simulation under nonstationary conditions. The transient results from the two simulations are compared on the basis of queue size and computer execution time. Under nonstationary conditions, the approximations for the mean and variance of the number of packets in the queue erer fairly close to the simulation values. The approximation offered substantial speed improvements over the discrete event simulation. The closure approximation provided a good alternative Monte Carlo simulation of the computer networks.

  • PDF

Damping Analysis using IEEEST PSS and PSS2A PSS

  • Lee Sang-Seung;Kang Sang-Hee;Jang Gwang-Soo;Li Shan-Ying;Park Jong-Keun;Moon Seung-Il;Yoon Yong-Tae
    • Journal of Electrical Engineering and Technology
    • /
    • v.1 no.3
    • /
    • pp.271-278
    • /
    • 2006
  • This paper scrutinized the damping effects of installing the prototype PSSs by a transient analysis for eight buses of faults in the South Korean power system. The PSSs used have the co-PSS blocks for IEEEST model with a single input and the co+power PSS blocks for PSS2A model with dual inputs. The simulation tool was a TSAT(Transient Security Assessment Tool) developed by Powertech Labs Inc. The voltages of the transmission line for simulations were 765kV and 345kV, and the faults for eight cases were sequenced by considering the open state and the close state of the lines. In the simulations, the three-phase line to ground (L-G) fault generated different points for each region. The simulations were compared to the cases of no PSS, partial IEEEST and PSS2A, absolute IEEEST, and absolute PSS2A to show that the power system oscillation can be effectively damped by PSS modules. Simulations were conducted to confirm the effectiveness for the KEPCO (Korea Electric Power Corporation) power system.

Numerical Study of Contaminant Transport Coupled with Large Strain Consolidation

  • Lee, Jang-Guen
    • Journal of The Korean Society of Agricultural Engineers
    • /
    • v.50 no.2
    • /
    • pp.45-52
    • /
    • 2008
  • Contaminant transport has been widely studied in rigid porous media, but there are some cases where a large volumetric stain occurs such as dewatering of dredged contaminated sediment, landfill liner, and in-situ capping. This paper presents a numerical investigation of contaminant transport coupled with large strain consolidation. Consolidation test was performed with contaminated sediments collected in Gary, Indiana, U.S. to obtain constitutive relationships, which are required for numerical simulations. Numerical results using CST2 show an excellent agreement with measured settlement and excess pore pressure. CST2 is then used to simulate contaminant transport during and after in-situ capping. Numerical simulations provide that transient advective flows caused by consolidation significantly increase the contaminant transport rate. In addition, the numerical simulations revealed that active capping with Reactive Core Mat (RCM) significantly decelerates consolidation-induced contaminant transport.

Vibration Suppression Control for an Articulated Robot;Effects of Model-Based Control Integrated into the Position Control Loop

  • Itoh, Masahiko
    • 제어로봇시스템학회:학술대회논문집
    • /
    • /
    • pp.2016-2021
    • /
    • 2003
  • This paper deals with a control technique of eliminating the transient vibration with respect to a waist axis of an articulated robot. This control technique is based on a model-based control in order to establish the damping effect on the driven mechanical part. The control model is composed of reduced-order electrical and mechanical parts related to the velocity control loop. The parameters of the control model can be obtained from design data or experimental data. This model estimates a load speed converted to the motor shaft. The difference between the estimated load speed and the motor speed is calculated dynamically, and it is added to the velocity command to suppress the transient vibration. This control method is applied to an articulated robot regarded as a time-invariant system. The effectiveness of the model-based control integrated into the position control loop is verified by simulations. Simulations show satisfactory control results to reduce the transient vibration at the end-effector.

  • PDF

Numerical analysis of steady and transient processes in a directional solidification system

  • Lin, Ting-Kang;Lin, Chung-Hao;Chen, Ching-Yao
    • Coupled systems mechanics
    • /
    • v.5 no.4
    • /
    • pp.341-353
    • /
    • 2016
  • Manufactures of multi-crystalline silicon ingots by means of the directional solidification system (DSS) is important to the solar photovoltaic (PV) cell industry. The quality of the ingots, including the grain size and morphology, is highly related to the shape of the crystal-melt interface during the crystal growth process. We performed numerical simulations to analyze the thermo-fluid field and the shape of the crystal-melt interface both for steady conditions and transient processes. The steady simulations are first validated and then applied to improve the hot zone design in the furnace. The numerical results reveal that, an additional guiding plate weakens the strength of vortex and improves the desired profile of the crystal-melt interface. Based on the steady solutions at an early stage, detailed transient processes of crystal growth can be simulated. Accuracy of the results is supported by comparing the evolutions of crystal heights with the experimental measurements. The excellent agreements demonstrate the applicability of the present numerical methods in simulating a practical and complex system of directional solidification system.

A Study on the Control of ICB Circuits (ICB 회로의 제어에 관한 연구)

  • Hong, Soon-Chan;Kim, Kyu-Sung
    • Proceedings of the KIEE Conference
    • /
    • /
    • pp.314-318
    • /
    • 1990
  • This paper deals with the transient analyses of both the one-phase ICB circuit and the three-phase ICB circuit. During the transient switching intervals, overvoltages or voltage unbalances may be produced on the capacitors. The three-step and four-step transient switching sequences were discussed and compared on the basis of phase shifting. Also, simple control method using bang-bang control was proposed and the digital simulations were carried out. As the results, it is verified that the proposed control technique is efficient.

  • PDF

Construction of a robust dead beat control system considered a transient response

  • Yoshida, Satoru;Kamiya, Yuji
    • 제어로봇시스템학회:학술대회논문집
    • /
    • /
    • pp.106-109
    • /
    • 1995
  • First, in this paper we propose a new dead best control system design technique by which we can specify a transient response before the settling time. Though the resultant system has the same system configuration as Reference[1], that is realized by adapting the performance index which includes the term of the square of difference between specified and pracitical responses. Next, we state a technique which gives the dead beat control system robustness and construct a robust dead beat control system. Simulations of the proposed dead beat control and robust dead beat control systems show expected results.

  • PDF