Simulation of Freeway Weaving Areas

2002 ◽  
Vol 1802 (1) ◽  
pp. 115-124 ◽  
Author(s):  
Alexander Skabardonis
Keyword(s):  
Operating Conditions ◽  
Model Parameters ◽  
Sensitivity Factor ◽  
Microscopic Simulation ◽  
Lane Changing ◽  
Wide Range ◽  
Design Characteristics ◽  
Predicted Values ◽  
Demand Patterns ◽  
Parameter Values

The operation of freeway weaving sections is characterized by intense lane-changing maneuvers and complex vehicle interactions that often create bottlenecks along freeway facilities. The CORSIM microscopic simulation model was applied to simulate the operation of eight realworld weaving sites in California under a wide range of operating conditions. The results indicate that CORSIM with default parameter values underpredicts the speeds in the weaving section by about 19% on average. Numerous simulation runs were made with different values of the model parameters. The following parameters were found to significantly affect the CORSIM results: ( a) car-following sensitivity factor, ( b) lane-changing aggressiveness factor, and ( c) percentage of freeway through vehicles that yield to merging traffic. The calibrated CORSIM model reasonably replicated observed traffic operations at all test sites. The predicted average speeds were within ±5 mph for most test sites. Good agreement between measured and predicted values was obtained for all the combinations of design characteristics and demand patterns.

Sensitivity analysis: from model parameters to system behaviour

2008 ◽  
Vol 45 ◽  
pp. 177-194 ◽  
Author(s):  
Brian Ingalls
Keyword(s):  
Sensitivity Analysis ◽  
Operating Conditions ◽  
Model Parameters ◽  
Analytical Treatment ◽  
System Behaviour ◽  
Local Case ◽  
Wide Range ◽  
Nominal Parameter ◽  
Address System ◽  
Parameter Values

Sensitivity analysis addresses the manner in which model behaviour depends on model parametrization. Global sensitivity analysis makes use of statistical tools to address system behaviour over a wide range of operating conditions, whereas local sensitivity analysis focuses attention on a specific set of nominal parameter values. This narrow focus allows a complete analytical treatment and straightforward interpretation in the local case. Sensitivity analysis is a valuable tool for model construction and interpretation, and can be applied in medicine and biotechnology to predict the effect of interventions.

scholarly journals Modelling Properties of an Alkaline Electrolyser

Energies ◽  
2020 ◽  
Vol 13 (12) ◽  
pp. 3073
Author(s):  
Krzysztof Górecki ◽  
Małgorzata Górecka ◽  
Paweł Górecki
Keyword(s):  
Potassium Hydroxide ◽  
Dynamic Properties ◽  
Operating Conditions ◽  
High Productivity ◽  
Electrolysis Process ◽  
Average Value ◽  
Current Voltage ◽  
Wide Range ◽  
Current Voltage Characteristics ◽  
Parameter Values

This paper proposes a model of an electrolyser in the form of a subcircuit dedicated for SPICE. It takes into account both the electric static and dynamic properties of the considered device and is devoted to the optimisation of the parameters of the signal feeding this electrolyser, making it possible to obtain a high productivity and efficiency of the electrolysis process. Parameter values the describing current-voltage characteristics of the electrolyser take into account the influence of the concentration of the potassium hydroxide (KOH) solution. A detailed description of the structure and all the components of this model is included in the paper. The correctness of the elaborated model is verified experimentally in a wide range of changes in the value of the feeding current and concentration of the KOH solution. Some computations illustrating the influence of the amplitude, average value, duty factor, and frequency of feeding current on the productivity and efficiency of the electrolysis process are performed. On the basis of the obtained results of the investigations, some recommendations for the operating conditions of electrolysers are formulated.

Application of an Improved Streamline Curvature Approach to a Modern, Two-Stage Transonic Fan: Comparison With Data and CFD

2002 ◽  
Author(s):  
Keith M. Boyer ◽  
Walter F. O’Brien
Keyword(s):  
Three Dimensional ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Model Parameters ◽  
Two Stage ◽  
Streamline Curvature ◽  
Wide Range ◽  
Improved Model ◽  
Transonic Fan ◽  
Streamline Curvature Method

A streamline curvature method with improvements to key loss models is applied to a two-stage, low aspect ratio, transonic fan with design tip relative Mach number of approximately 1.65. Central to the improvements is the incorporation of a physics-based shock model. The attempt here is to capture the effects of key flow phenomena relative to the off-design performance of the fan. A quantitative analysis regarding solution sensitivities to model parameters that influence the key phenomena over a wide range of operating conditions is presented. Predictions are compared to performance determined from overall and interstage measurements, as well as from a three-dimensional, steady, Reynolds-averaged Navier-Stokes method applied across the first rotor. Overall and spanwise comparisons demonstrate that the improved model gives reasonable performance trending and generally accurate results. The method can be used to provide boundary conditions to higher-order solvers, or implemented within novel approaches using the streamline curvature method to explore complex engine-inlet integration issues, such as time-variant distortion.

Application of A Monte Carlo Approach to Surface Complexation Modelling

2004 ◽  
Vol 824 ◽  
Author(s):  
M.M. Askarieh ◽  
T.G. Heath ◽  
W.M. Tearle
Keyword(s):  
Monte Carlo ◽  
Model Parameters ◽  
Surface Complexes ◽  
Monte Carlo Approach ◽  
Ion Sorption ◽  
Wide Range ◽  
Complex Models ◽  
Chemical Conditions ◽  
Parameter Values

AbstractA Monte Carlo-based approach has been adopted for development of a chemical thermodynamic model to describe the goethite surface in contact with sodium nitrate solutions. The technique involves the calculation of the goethite surface properties for the chemical conditions corresponding to each experimental data point. The representation of the surface was based on a set of model parameters, each of which was either fixed or was randomly sampled from a specified range of values. Thousands of such model representations were generated for different selected sets of parameter values with the use of the standard geochemical speciation computer program, HARPHRQ. The method allowed many combinations of parameter values to be sampled that might not be achieved with a simple least-squares fitting approach. It also allowed the dependence of the quality of fit on each parameter to be analysed. The Monte Carlo approach is most appropriate in the development of complex models involving the fitting of several datasets with several fitting parameters.Introduction of selenate surface complexes allowed the model to be extended to represent selenate ion sorption, selenium being an important radioelement in evaluation of the long-term safety of ILW disposal. The sorption model gave good agreement with a wide range of experimental sorption datasets for selenate.

Validation of a Novel Model for Shell and Tube Heat Exchangers Undergoing Crude Oil Fouling

2010 ◽  
Author(s):  
Francesco Coletti ◽  
Sandro Macchietto
Keyword(s):  
Heat Exchanger ◽  
Crude Oil ◽  
Operating Conditions ◽  
Process Conditions ◽  
Model Parameters ◽  
Fluid Temperature ◽  
Oil Companies ◽  
Wide Range ◽  
Shell And Tube ◽  
Oil Fouling

Fouling in refinery heat transfer units is a major problem that affects plant’s economics, operability, safety and environmental impact. Traditional heat exchanger design methodologies based on fixed values for the fouling resistance (e.g. TEMA fouling factors) have drawn several critiques in the past 40 years and were found responsible for exacerbating fouling rather than mitigating it. The fouling factors approach is, in fact, highly empirical and neglects fouling dynamics and its dependency on process conditions. The ability of capturing such dependency is therefore pivotal to overcome traditional design limitations. A novel dynamic, distributed model for a multi–pass shell–and–tube heat exchanger undergoing crude oil fouling was recently proposed by Coletti and Macchietto. The model takes into account the exchanger geometry and configuration, the variation of fluid temperature, velocity, physical properties and fouling rate along the length of each unit and captures the interactions between the fouling layer growth and the fluid–dynamics by solving a moving boundary problem. In this paper, the model is validated over a wide range of operating conditions (i.e. temperatures and flowrates) with data from four different industrial units (2 single and 2 double shells). Geometries and process conditions used are those of two refineries belonging to major oil companies (ExxonMobil and Shell). Some model parameters are estimated for each exchanger using measurements during the first 60 days after a mechanical cleaning. The model is then used in a fully predictive mode for subsequent times. Results indicate that for all units the outlet temperatures (in °C) are predicted over extended periods (i.e. 4–16 months) with an excellent accuracy of ±1% for the tube-side and ±2% for the shell-side. It is concluded that the model can be used with confidence on a wide range of operating conditions to calculate reliable temperatures and fouling resistances.

Nonlinear Dynamic Model of a Two-Stage Pressure Relief Valve for Designers

2001 ◽  
Vol 124 (1) ◽  
pp. 62-66 ◽  
Author(s):  
Pei-Sun Zung ◽  
Ming-Hwei Perng
Keyword(s):  
Dynamic Model ◽  
Nonlinear Dynamic ◽  
Dynamic Models ◽  
Operating Conditions ◽  
Model Parameters ◽  
Nonlinear Dynamic Model ◽  
Relief Valve ◽  
Two Stage ◽  
Pressure Relief ◽  
Wide Range

This paper presents a handy nonlinear dynamic model for the design of a two stage pilot pressure relief servo-valve. Previous surveys indicate that the performance of existing control valves has been limited by the lack of an accurate dynamic model. However, most of the existing dynamic models of pressure relief valves are developed for the selection of a suitable valve for a hydraulic system, and assume model parameters which are not directly controllable during the manufacturing process. As a result, such models are less useful for a manufacturer eager to improve the performance of a pressure valve. In contrast, model parameters in the present approach have been limited to dimensions measurable from the blue prints of the valve such that a specific design can be evaluated by simulation before actually manufacturing the valve. Moreover, the resultant model shows excellent agreement with experiments in a wide range of operating conditions.

scholarly journals Generalized Behavioral Modelling Methodology of Switch-Diode Cell for Power Loss Prediction in Electromagnetic Transient Simulation

Energies ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1500
Author(s):  
Yanming Xu ◽  
Carl Ngai Man Ho ◽  
Avishek Ghosh ◽  
Dharshana Muthumuni
Keyword(s):  
Power Loss ◽  
Process Analysis ◽  
Operating Conditions ◽  
Transient Simulation ◽  
Oxide Semiconductor ◽  
Model Parameters ◽  
Electromagnetic Transient ◽  
Proposed Model ◽  
Wide Range ◽  
Electromagnetic Transient Simulation

Modern wide-bandgap (WBG) devices, such as silicon carbide (SiC) or gallium nitride (GaN) based devices, have emerged and been increasingly used in power electronics (PE) applications due to their superior switching feature. The power losses of these devices become the key of system efficiency improvement, especially for high-frequency applications. In this paper, a generalized behavioral model of a switch-diode cell (SDC) is proposed for power loss estimation in the electromagnetic transient simulation. The proposed model is developed based on the circuit level switching process analysis, which considers the effects of parasitics, the operating temperature, and the interaction of diode and switch. In addition, the transient waveforms of the SDC are simulated by the proposed model using dependent voltage and current sources with passive components. Besides, the approaches of obtaining model parameters from the datasheets are given and the modelling method is applicable to various semiconductors such Si insulated-gate bipolar transistor (IGBT), Si/SiC metal–oxide–semiconductor field-effect transistor (MOSFET), and GaN devices. Further, a multi-dimensional power loss table in a wide range of operating conditions can be obtained with fast speed and reasonable accuracy. The proposed approach is implemented in PSCAD/ Electromagnetic Transients including DC, EMTDC, (v4.6, Winnipeg, MB, Canada) and further verified by the hardware setups including different daughter boards for different devices.

Mechanics-Based Acceleration Modeling of Multilane Traffic Flow

2017 ◽  
Vol 2622 (1) ◽  
pp. 117-124
Author(s):  
Liang Wang ◽  
Fangliang Chen ◽  
Huiming Yin
Keyword(s):  
Traffic Flow ◽  
Present Model ◽  
Interaction Force ◽  
Model Parameters ◽  
Particle Interactions ◽  
Microscopic Simulation ◽  
Lane Changing ◽  
Present Complex ◽  
Safety Consideration ◽  
Force Element

Inspired by the similarity between vehicle interactions and particle interactions, a mechanical system with force elements is introduced to simulate a vehicle’s acceleration behavior in a multilane traffic flow. On the basis of Newton’s second law of motion, a subject vehicle’s longitudinal behavior is simulated with the interaction force induced by the neighboring vehicles and the driver’s driving preference. Five important factors—( a) subject vehicle’s speed, ( b) acceleration sensitivity, ( c) safety consideration, ( d) relative speed sensitivity, and ( e) gap-reducing desire—are considered; each is modeled by a force element. A recently developed data collection system is used to capture the testing driver’s acceleration behavior; the model parameters are calibrated with the traveler’s driving behavior. To demonstrate the present model, a microscopic simulation program was developed with MATLAB. The simulated trajectories not only describe a driver’s acceleration behavior in common scenarios but also accurately present complex, high-order behavior during multifaceted scenarios, such as lane changing or lead gap changing. The present model can be applied to single-lane and multilane car-following scenarios with the same algorithm.

scholarly journals Catchment classification: hydrological analysis of catchment behavior through process-based modeling along a climate gradient

2011 ◽  
Vol 15 (11) ◽  
pp. 3411-3430 ◽  
Author(s):  
G. Carrillo ◽  
P. A. Troch ◽  
M. Sivapalan ◽  
T. Wagener ◽  
C. Harman ◽  
...  
Keyword(s):  
Time Scales ◽  
Climate Model ◽  
Model Parameters ◽  
Hydrologic Response ◽  
Dimensionless Numbers ◽  
Landscape Features ◽  
Climate Gradient ◽  
Catchment Characteristics ◽  
Wide Range ◽  
Parameter Values

Abstract. Catchment classification is an efficient method to synthesize our understanding of how climate variability and catchment characteristics interact to define hydrological response. One way to accomplish catchment classification is to empirically relate climate and catchment characteristics to hydrologic behavior and to quantify the skill of predicting hydrologic response based on the combination of climate and catchment characteristics. Here we present results using an alternative approach that uses our current level of hydrological understanding, expressed in the form of a process-based model, to interrogate how climate and catchment characteristics interact to produce observed hydrologic response. The model uses topographic, geomorphologic, soil and vegetation information at the catchment scale and conditions parameter values using readily available data on precipitation, temperature and streamflow. It is applicable to a wide range of catchments in different climate settings. We have developed a step-by-step procedure to analyze the observed hydrologic response and to assign parameter values related to specific components of the model. We applied this procedure to 12 catchments across a climate gradient east of the Rocky Mountains, USA. We show that the model is capable of reproducing the observed hydrologic behavior measured through hydrologic signatures chosen at different temporal scales. Next, we analyze the dominant time scales of catchment response and their dimensionless ratios with respect to climate and observable landscape features in an attempt to explain hydrologic partitioning. We find that only a limited number of model parameters can be related to observable landscape features. However, several climate-model time scales, and the associated dimensionless numbers, show scaling relationships with respect to the investigated hydrological signatures (runoff coefficient, baseflow index, and slope of the flow duration curve). Moreover, some dimensionless numbers vary systematically across the climate gradient, possibly as a result of systematic co-variation of climate, vegetation and soil related time scales. If such co-variation can be shown to be robust across many catchments along different climate gradients, it opens perspective for model parameterization in ungauged catchments as well as prediction of hydrologic response in a rapidly changing environment.

Analysis and Design of Segmented Dampers for Rotor Dynamic Control

1982 ◽  
Vol 104 (1) ◽  
pp. 84-90 ◽  
Author(s):  
D. L. Taylor ◽  
V. S. Fehr
Keyword(s):  
Pressure Distribution ◽  
Dynamic Control ◽  
Design Procedure ◽  
Operating Conditions ◽  
Squeeze Film ◽  
Fluid Viscosity ◽  
Damping Force ◽  
Analysis And Design ◽  
Wide Range ◽  
Parameter Values

Dampers have become of increasing importance in the control of shaft vibration of rotating equipment which must operate through one or more critical speeds. This paper presents the analytical results for the study of a new class of damper, the segmented film damper. A series of isolated segments of fluid are used rather than a continuous film as in the traditional squeeze film damper. This configuration provides energy dissipation through fluid viscosity within the film segments and through oriface flow in the supply and exit ports for each segment. The pressure distribution within an individual segment is developed on the basis of Reynolds equation with appropriate boundary conditions. The effects of various parameters are discussed in terms of this pressure distribution. The geometric effects of multiple segments are derived for both input, how shaft motion excites each segment, and output, how the segments’ pressure distributions combine to provide a net force. The damping force is shown to be linear for a wide range of operating conditions, speed and unbalance, and thus validly expressed in terms of a damping coefficient. Additionally, this class of damper is shown to have no radial stiffness. The limitations and implications for the designer are discussed in detail. A structured design procedure is given for the selection of parameter values, and a design example with numerical values is included.

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