Transient Simulation Method Research Articles

Single-Event Multiple-Transient Characterization and Mitigation via Alternative Standard Cell Placement Methods

As fabrication technology scales towards smaller transistor sizes and lower critical charge, single-event radiation effects are more likely to cause errant behavior in multiple, physically adjacent devices in modern integrated circuits (ICs), and with higher operating frequencies, this risk increasingly impacts design logic over memory as well. In order to increase future system reliability, circuit designers need greater awareness of multiple-transient charge-sharing effects during the early stages of their design flow with standard cell placement and routing. To measure the propagation and observability of multiple transients from single radiation events, this work uses several intra-pipeline combinational logic circuits at the 32nm technology node, investigates several different standard cell placements of each design, and analyzes those placements with a novel, physically realistic transient injection and simulation method. It is shown that (1) this simulation methodology, informed by experimental data, provides an increased realism over other works in traditional fault injection fields, (2) different placements of the same circuit where standard cells are grouped by logical hierarchy can result in different reliability behavior and benefits especially useful within the area of approximate computing, and (3) improved reliability through charge-sharing transient mitigation can be gained with no area penalty and minimal speed and power penalties by adjusting the placement of standard cells.

Model order reduction for transient simulation of active distribution networks

With the increasing penetration of distributed generation, distribution networks are evolving from passive to active. New transient simulation methods are required to study the detailed dynamic characteristics of large-scale active distribution networks. A model order reduction method based on Krylov subspace theory is introduced in this study to reduce the overall model scale of active distribution networks for transient simulations. A modified state-space model of linear distribution networks is developed to replace the conventional models for improvement in model reduction efficiency, while guaranteeing the passivity and stability of the reduced models. The proposed model order reduction method is validated with the IEEE 123-node test network. The results prove that the proposed method is effective for different applications to improve the simulation efficiency of large-scale active distribution networks.

Fast alternating direction implicit method for efficient transient thermal simulation of integrated circuits

SummaryThis paper presents fast alternating direction implicit (FADI) method for efficient transient thermal simulation of integrated circuits. The FADI method is formulated from Peaceman–Rachford's ADI and Douglas–Gunn's ADI methods. The update procedure of the proposed method has basic implicit form that features derivative‐free right‐hand side and hence, better efficiency and conciseness. Subsequently, through the basic implicit form of FADI method, the relationship between classical Peaceman–Rachford's and Douglas–Gunn's ADI methods can be clarified and elucidated in detail. A unified boundary condition that can cater to common kinds of boundary conditions in thermal simulation is also introduced. To further accelerate FADI method, the graphics processing unit is also utilized through Compute Unified Device Architecture implementation. It is shown that high efficiency gain can be achieved using the proposed FADI method through large time step size and data parallelism, while maintaining stability and good accuracy. As numerical illustration, an integrated circuit structure with microchannel cooling is demonstrated. Numerical results further ascertain the cooling effect of the microchannels. Copyright © 2015 John Wiley & Sons, Ltd.

Gas-Dynamic Analysis of Processes in a Small-Sizes Two-Stroke Combustion Engine

The paper presents a procedure for gas-dynamic analysis of processes in the air-gas channel of a small-sized two-stroke combustion engine. All steps are described. At the first stage a three-dimensional model of the interior space of the air-gas channel of a piston small-power engine was built; this model was split into nine different volumes according to the methodology of volumes partition for different kinds of grids application, which is provided in source materials. At the second stage all required sizes and types of finite elements were set for the correct operation of functions of re- splitting and layer-by-layer re-formation of a grid in the cylinder volume and in the sub piston area. At the third stage all the necessary settings in the CFD-code ANSYS Fluent were made. Such as a transient simulation method, a turbulence model, parameters of mixture formation and fuel evaporation process, setup of intersection zones of the grid, setup of permeability of the boundaries between the calculated areas, setup of grid re-formation parameters, motion parameters of the piston and other moving elements of the simulated engine were introduced, setup of parameters and characteristics of the fuel injection process. User Defined Function (UDF) was used to set the rotation of the crankshaft. The calculations found fields of distribution of the basic parameters in the air-gas channel of the small-sized combustion engine, such as pressure, temperature, speed and composition of the working body. According to the simulation results power and fuel efficiency of the small-sized enginewere calculated. The technique of modeling of thermal processes in an air model small-power combustion engine is using CAD/CAE technologies was presented. The solution to this problem is one of the most important tasks in the field of combustion engines engineering. The purpose of the thermal processes modeling is visual representation of the operating principle of an air model two-stroke engine through its three-dimensional model. Simulation of thermal processes in the combustion engine is performed using ANSYS Fluent CFD-code (1). The efficiency of the combustion engine depends on a combination of complex processes, namely: fuel components supply, air- and-fuel mixture preparation, fuel combustion and combustion gases discharge, etc. The studies conducted using CFD- modeling at the early stages of the engine designing help us to optimize each of these processes. The complexity of the modeling process is associated with the analysis grid model building, which should move in line with the movement of the working bodyinside the piston engine cylinder (2). This technique can be used to obtain the fields of distribution of the main thermodynamic parameters in the piston-cylinder group of combustion engines with the help of ANSYS Fluent program, and allows to gets kills of working with moving analysis grids. 2. METHOD At the first stage a three-dimensional model of the small- sized combustion engine was built using Solid Works CAD- editor. Then with the help of volumes subtraction the internal volume of the air-gas channel of the engine was built. The air-gas channel of the engine was split into nine volumes, according to the authors' method of three-dimensional models preparation for grid elements application. As the result a three-dimensional model ready for creation of a grid model presented in Fig. (1) was built.

High Order and A-Stable Envelope Following Method for Transient Simulations of Oscillatory Circuits

A new enveloped following (EF) method based on high-order Obreshkov integration formula is presented. The new method is suitable for transient analysis of highly oscillatory circuits with widely separated time-scales. In addition, the proposed algorithm is capable of producing high-order numerically stable approximation of the transient response. The use of high-order formulas leads to a significant reduction in the computational time compared to low-order EF methods because it allows taking large steps in time while keeping the same accuracy.

Calculating the Maximum Penetration Capacity of Distributed Generation Considering Current Protection

The different penetration capacity of various distributed generation (DG) in distribution network has important effect on planning and dispatching scientifically. The dynamic model of a small synchronous generator is established in this paper, and we figure out the maximum acceptable power of distributed generation for each node in distribution network considering reliability of protection electromagnetic transient simulation method, and the limiting factors are also analyzed in it. Finally, some methods are proposed to improve maximum penetration capacity, so it can provide reference for farther research of maximum penetration capacity in next stage.

An actuator sector method for efficient transient wind turbine simulation

AbstractThis paper investigates a new method for transient simulation of flow through a wind turbine using an actuator technique. The aim, in the context of wind turbine wake simulation, is to develop an alternative to the widely used actuator disc model with an increased resolution and range of applications, for the same or less computational expense. In this new model, the actuator sector method, forces applied to the fluid are distributed azimuthally to maintain a continuous flow solution for increased time‐step intervals compared with the actuator line method. Actuator sector results are presented in comparison with actuator disc and actuator line models initially for a non‐dimensionalized turbine in laminar onset flow. Subsequent results are presented for a turbine operating in a turbulent atmospheric boundary layer. Results show significant increases in flow fidelity compared with actuator disc model results; this includes the resolution of diametric variation in rotor loading caused by horizontal or vertical wind shear and the helical vortex system shed from the turbine blade tips. Significant reductions in computational processing time were achieved with wake velocities and turbulence statistics comparable with actuator line model results. The actuator sector method offers an improved alternative to applications employing conventional actuator disc models, with little or no additional computational cost. This technique in conjunction with a Cartesian mesh‐based parallel flow solver leads to efficient simulation of turbines in atmospheric boundary layer flows. Copyright © 2014 John Wiley & Sons, Ltd.

Transient Simulation Studies of Squirrel-Cage Induction Motor Directly Supplied with Aircraft Variable Frequency Power

Aircraft variable frequency power and a new application of induction motor under the aero-power are introduced. The transient models and simulation of induction motor are reviewed. A new transient model and simulation method is presented that includes deep-bar effect and magnetic saturation. Dynamic magnetizing inductance, rotor resistance and leakage reactance are considered as varying parameters in state-space model. Base on known rotor structure and speed, these parameters can be calculated.

Characteristics of a micro-hydro turbine

Computational Fluid Dynamics, a crucial tool in exploring designs of hydraulic machinery, is used to evaluate the design of a non-uniform Archimedean spiral rotor. A transient simulation method is implemented using a frame of reference change between time-steps to capture the flow field correctly. The boundary conditions for this method are discussed and are validated with previously published experimental data using a flat plate propeller turbine. A spectral and temporal convergence study for the non-uniform Archimedean spiral rotor is performed to verify solution independence of mesh and time-step selection. Performance characteristics of the rotor are provided over a wide range of volumetric flow rates and rotation rates. The best hydraulic efficiency point is determined to be 72% for the presented rotor design and is compared with the performance of similar micro-hydro turbines.

Skin-Effect-Incorporated Transient Simulation Using the Laguerre-FDTD Scheme

In this paper, skin effect is incorporated into the unconditionally stable Laguerre finite-difference time-domain method for transient simulation of multiscale structures. The skin effect is modeled by imposing the surface impedance boundary condition (SIBC) to the surface of the conductor, which significantly reduces the computational effort. Two methods of applying SIBC are proposed and discussed in detail. A procedure for transferring the time-domain convolution into Laguerre domain in recursive form is also discussed. In addition, a method for embedding and de-embedding port resistors for fast simulation and accurate extraction of frequency-domain response is proposed. The results have been validated using measurements, along with the stability analysis of the two implementation methods. Simulation results from the multiscale structures are presented and are compared with measurements which show good accuracy and improved computational efficiency.

Parametric sensitivity studies on the performance of a flat plate solar collector in transient behavior

In this paper, a numerical investigation of flat plate solar collectors is developed to determine the optimal performance and design parameters of these solar to thermal energy conversion systems. The collector is used to supply hot water. It consists of three main components, namely a transparent cover, an absorber and a transfer fluid. A transient simulation method has been developed to characterize the dynamic behavior. The model was established regarding the energy balance analysis. A set of equations representing the model was simultaneously solved. The results are used to investigate the effect of various parameters on the performance of the collector such as outlet water temperature and overall heat loss coefficient. The overall methodology has been developed on environmental data which are characteristic of the city of Gabes in Tunisia.

Development of a Transient Model of a Stirling-Based CHP System

Although the Stirling engine was invented in 1816, this heat engine still continues to be investigated due to the variety of energy sources that can be used to power it (e.g., solar energy, fossil fuels, biomass, and geothermal energy). To study the performance of these machines, it is necessary to develop and simulate models under different operating conditions. In this paper, we present a one-dimensional dynamic model based on components from Trnsys: principally, a lumped mass and a heat exchanger. The resulting model is calibrated using GenOpt. Furthermore, the obtained model can be used to simulate the machine both under steady-state operation and during a transient response. The results provided by the simulations are compared with data measured in a Stirling engine that has been subjected to different operating conditions. This comparison shows good agreement, indicating that the model is an appropriate method for transient thermal simulations. This new proposed model requires few configuration parameters and is therefore easily adaptable to a wide range of commercial models of Stirling engines. A detailed analysis of the system results reveals that the power is directly related to the difference of temperatures between the hot and cold sources during the transient and steady-state processes.

Efficient Simulation of Gear Contacts Including Transient Elastohydrodynamic Effects

This paper describes an efficient transient elastohydrodynamic simulation method for gear contacts. The model uses oil films and elastic deformations directly in the multibody simulation, and is based on the Reynolds equation including squeeze and wedge terms as well as an elastic half-space. Two transient solutions to this problem, an analytical and a numerical one, were developed. The analytical solution is accomplished using assumptions for the gap shape and the pressure in the middle of the gap. The numerical problem is solved using multilevel multi-integration algorithms. With this approach, tooth impacts during gear rattling as well as highly loaded power-transmitting gear contacts can be investigated and lubrication conditions like gap heights or type of friction may be determined. The method was implemented in the multibody simulation environment SIMPACK. Therefore it is easy to transfer the developed element to other models and use it for a multitude of different engineering problems. A detailed three-dimensional elastic multibody model of an experimental transmission is used to validate the developed method. Important values of the gear contact like normal and tangential forces, proportion of dry friction, and minimum gap heights are calculated and studied for different conditions. In addition, pressure distributions on tooth flanks as well as gap forms are determined based on the numerical solution method. Finally, the simulation approach is validated with measurements and shows good consistency. The simulation model is therefore capable of predicting transient gear contact under different operating conditions such as load vibrations or gear rattling. Simulations of complete transmissions are possible and therefore a direct determination of transmission vibration behavior and structure-borne noise as well as of forces and lubrication conditions can be done.

Transient Simulation Method for Autorotation in Forward Flight

This paper describes the Transient Simulation Method (TSM) which predicts the steady state and performance of autorotation in forward flight. Flapping and rotational equations of motion are integrated from an arbitrary initial rotor speed, and the steady state of autorotation is obtained as a periodic solution through a transient process. The induced velocity field update method and the average thrust, lift, and drag computations during the transition are described in detail. TSM is then applied to the model rotor to validate the feasibility. High speed autorotation is simulated using an aerodynamic data set that is analyzed by the two-dimensional compressible Navier-Stokes Solver. Rotor speed variation for increases in airspeed at low shaft angle is presented and discussed. When TSM is used with sophisticated aerodynamic data analyzed as functions of the blade angle of attack, the Reynolds number, and the Mach number, the autorotation range for the collective pitch, velocity, and shaft angle can be reasonably explored.

Fast Simulation of Microwave Circuits With Nonlinear Terminations Using High-Order Stable Methods

This paper describes a new method for transient simulation, using high-order stable methods, of microwave structures modeled using a large number of lumped components. The target of the proposed technique is circuit-based simulation of the large linear circuits that arise from full-wave modeling of distributed structures, such as transmission lines and microstrip elements, along with the terminating nonlinear devices. In this case, the cost of the solution of the linear system typically dominates the computational effort. The proposed method takes advantage of the special structure of the block matrices in these applications to reduce the computational cost significantly. The core of the proposed algorithm is based on the idea of “node tearing” to separate the large linear sub-circuits from the nonlinear devices. This idea faciliates handling the linear sub-circuits using a better matrix factorization technique, resulting in faster simulations compared to classical techniques.

Transient simulation of hydropower station with consideration of three-dimensional unsteady flow in turbine

To study the interaction between the transient flow in pipe and the unsteady turbulent flow in turbine, a coupled model of the transient flow in the pipe and three-dimensional unsteady flow in the turbine is developed based on the method of characteristics and the fluid governing equation in the accelerated rotational relative coordinate. The load-rejection process under the closing of guide vanes of the hydraulic power plant is simulated by the coupled method, the traditional transient simulation method and traditional three-dimensional unsteady flow calculation method respectively and the results are compared. The pressure, unit flux and rotation speed calculated by three methods show a similar change trend. However, because the elastic water hammer in the pipe and the pressure fluctuation in the turbine have been considered in the coupled method, the increase of pressure at spiral inlet is higher and the pressure fluctuation in turbine is stronger.

Rapid Transient Pressure Field Computations in the Nearfield of Circular Transducers Using Frequency-Domain Time-Space Decomposition

The fast nearfield method, when combined with time-space decomposition, is a rapid and accurate approach for calculating transient nearfield pressures generated by ultrasound transducers. However, the standard time-space decomposition approach is only applicable to certain analytical representations of the temporal transducer surface velocity that, when applied to the fast nearfield method, are expressed as a finite sum of products of separate temporal and spatial terms. To extend time-space decomposition such that accelerated transient field simulations are enabled in the nearfield for an arbitrary transducer surface velocity, a new transient simulation method, frequency-domain time-space decomposition (FDTSD), is derived. With this method, the temporal transducer surface velocity is transformed into the frequency domain, and then each complex-valued term is processed separately. Further improvements are achieved by spectral clipping, which reduces the number of terms and the computation time. Trade-offs between speed and accuracy are established for FDTSD calculations, and pressure fields obtained with the FDTSD method for a circular transducer are compared with those obtained with Field II and the impulse response method. The FDTSD approach, when combined with the fast nearfield method and spectral clipping, consistently achieves smaller errors in less time and requires less memory than Field II or the impulse response method.

자동회전의 성능해석(1) : 해석 기법과 공력 테이블의 영향

Performance analysis was performed for an autorotating rotor. For a given airspeed, shaft angle, and collective pitch, the steady state of autorotation was judged by using the transient simulation method(TSM), then the thrust, lift, and drag coefficient for that state were computed. Average thrust was calculated from the instantaneous thrusts, in which the TSM was used in blade thrust integration. The analysis method was applied to the model rotor that had been tested by wind tunnel. Some comparison between analysis and test was provided. Two types of two-dimensional airfoil aerodynamic data were utilized in analysis, and they were made by Navier-Stokes Solver in terms of Reynolds and Reynolds-Mach number. The quantitative difference of results using two data set was examined and compared.

자동회전의 성능해석(2) : 고속 자동회전의 성능

Performance variation of autorotating rotor was investigated. The shaft angle of the rotor is reduced while the flight velocity is increased. The BO-105 helicopter rotor blade was replaced by untwisted NACA 0012 airfoil and the rotor was simulated by using Transient Simulation Method(TSM) to judge the autorotation region for the variables. To simulate the compressibility effect at high speed flight, two-dimensional aerodynamic data was analyzed by compressible Navier-Stokes solver and Pitt/Peters inflow theory was adopted to simulate the induced velocity field. Thrust and lift coefficients, lift to drag ratio variations were investigated, also the lift and power were compared to those of BO-105 helicopter. Sharing lift and power between the autorotating rotor and wing was considered when the compound aircraft concept is introduced.

A Precision and High-Speed Behavioral Simulation Method for Transient Response and Frequency Characteristics of Switching Converters

We propose a fast and precise transient response and frequency characteristics simulation method for switching converters. This method uses a behavioral simulation tool without using a SPICE-like analog simulator. The nonlinear operation of the circuit is considered, and the nonlinear function is realized by defining the nonlinear formula based on the circuit operation and by applying feedback. To assess the accuracy and simulation time of the proposed simulation method, we designed current-mode buck and boost converters and fabricated them using a 0.18-µm high-voltage CMOS process. The comparison in the transient response and frequency characteristics among SPICE, the proposed program on a behavioral simulation tool which we named NSTVR (New Simulation Tool for Voltage Regulators) and experiments of fabricated IC chips showed good agreement, while NSTVR was more than 22 times faster in transient response and 85 times faster in frequency characteristics than SPICE in CPU time in a boost converter simulation.