scholarly journals Time-Based Separation for Aircraft Landing Using Danger Value Distribution Flow Model

2012 ◽  
Vol 2012 ◽  
pp. 1-16
Author(s):  
Ta-Chung Wang ◽  
Chih-Hsiang Tsao
Keyword(s):  
Flow Model ◽  
Continuous Distribution ◽  
Value Distribution ◽  
Collision Probability ◽  
Adjustment Method ◽  
Separation Time ◽  
Aircraft Landing ◽  
Proposed Model ◽  
Model Collision ◽  
Peak Value

This study proposes a flow model using a modified Lighthill-Whitham-Richards highway model. The proposed model treats each aircraft on an airway as a continuous distribution of air collision probability, which is called the danger value distribution. With the proposed flow model, collision can be easily predicted by the peak value of the overlap of the danger value distribution of each aircraft. The study further proposes a velocity adjustment method that can be used to resolve the conflict. The proposed method can be applied for aircraft separation during the landing process, in which the separation time is different for different combinations of aircraft types.

Simple explicit model of liquid mean flow in region above axial impeller

1985 ◽  
Vol 50 (11) ◽  
pp. 2396-2410
Author(s):  
Miloslav Hošťálek ◽  
Ivan Fořt
Keyword(s):  
Vortex Flow ◽  
Flow Model ◽  
Quantitative Agreement ◽  
Mean Flow ◽  
Flat Bottom ◽  
Proposed Model ◽  
Minimum Number ◽  
The Mean ◽  
Model Equations ◽  
Radial Circulation

The study describes a method of modelling axial-radial circulation in a tank with an axial impeller and radial baffles. The proposed model is based on the analytical solution of the equation for vortex transport in the mean flow of turbulent liquid. The obtained vortex flow model is tested by the results of experiments carried out in a tank of diameter 1 m and with the bottom in the shape of truncated cone as well as by the data published for the vessel of diameter 0.29 m with flat bottom. Though the model equations are expressed in a simple form, good qualitative and even quantitative agreement of the model with reality is stated. Apart from its simplicity, the model has other advantages: minimum number of experimental data necessary for the completion of boundary conditions and integral nature of these data.

A Physically-Based Anisotropic Discrete Fiber Model for Fibrous Soft Tissues

2010 ◽  
Author(s):  
C. Flynn ◽  
M. B. Rubin ◽  
P. M. F. Nielsen
Keyword(s):  
Soft Tissues ◽  
Mechanical Response ◽  
Continuous Distribution ◽  
Collagen Fibers ◽  
Fiber Bundles ◽  
Parameter Study ◽  
Rabbit Skin ◽  
Pig Skin ◽  
Proposed Model ◽  
Physically Based

Physically-based fibrous soft tissue models often consider the tissue to be a collection of fibers with a continuous distribution function to represent their orientations. This study proposes a simple model for the response of fibrous connective tissues in terms of a discrete number of fiber bundles. The proposed model consists of six weighted fiber bundles orientated such that they pass through opposing vertices of an icosahedron. A novel aspect of the proposed model is the use of a simple analytical function to represent the undulation distribution of the collagen fibers. The mechanical response of the elastin fiber is represented by a neo-Hookean hyperelastic equation. A parameter study was performed to analyze the effect of each parameter on the overall response of the model. The proposed model accurately simulated the uniaxial stretching of pig skin with an 8% error-of-fit for stretch ratios up to 1.8. The model also accurately simulated the biaxial stretching of rabbit skin with a 10% error-of-fit for stretch ratios up to 1.9. The stiffness of the collagen fibers determined by the model was about 100 MPa for the rabbit skin and 900 MPa for the pig skin, which are comparable with values reported in the literature. The stiffness of the elastin fibers in the model was about 2 kPa.

scholarly journals A Macroscopic Traffic Model based on Driver Reaction and Traffic Stimuli

2019 ◽  
Vol 9 (14) ◽  
pp. 2848 ◽  
Author(s):  
Zawar H. Khan ◽  
Waheed Imran ◽  
Sajid Azeem ◽  
Khurram S. Khattak ◽  
T. Aaron Gulliver ◽  
...  
Keyword(s):  
Traffic Flow ◽  
Flow Model ◽  
Traffic Model ◽  
Traffic Flow Model ◽  
Velocity Constant ◽  
Model Based ◽  
Proposed Model ◽  
Macroscopic Traffic Flow ◽  
Macroscopic Traffic Model ◽  
Traffic Behavior

A new macroscopic traffic flow model is proposed, which considers driver presumption based on driver reaction and traffic stimuli. The Payne–Whitham (PW) model characterizes the traffic flow based on a velocity constant C 0 which results in unrealistic density and velocity behavior. Conversely, the proposed model characterizes traffic behavior with velocities based on the distance headway. The performance of the proposed and PW models is evaluated over a 300 m circular road for an inactive bottleneck. The results obtained show that the traffic behavior with the proposed model is more realistic.

CFD Multiphase Flow Modelling of Air Porosity Defect Formation During High-Pressure Die-Casting Filling Process

2015 ◽  
Author(s):  
J. Hao ◽  
Y. J. Lin ◽  
Y. Nie
Keyword(s):  
High Pressure ◽  
Multiphase Flow ◽  
High Speed ◽  
Flow Model ◽  
Defect Formation ◽  
Die Casting ◽  
Phase Flow ◽  
Filling Process ◽  
Proposed Model ◽  
Pressure Die Casting

High-Pressure Die-Casting (HPDC) is an important process for manufacturing high-volume and low-cost components. In this process molten metal is injected at high speed under high pressure into the die cavity, which often leads to entrapment of air into the liquid metal. This will cause air porosity after solidification, the main defect in the parts made by HPDC. The aim of this work was to develop a CFD multiphase flow simulation method to numerically study the air porosity defect formation in HPDC. Some numerical models have been developed to predict the air porosity defect in HPDC. However, most of them are limited to one phase flow model which could only simulate the filling process of liquid metal. In this study both the bulk fluid and surrounding air were modeled by a 3D multiphase flow model. The proposed model can describe the entrapment, advection and coalescence of air bubbles within the melt, and thus has the ability to accurately simulate the air porosity defect formation in HPDC. In the present paper, an incompressible-compressible two-phase flow model was developed. The numerical benchmark test of a broken dam problem was used to demonstrate the effectiveness of the proposed model. Then numerical model was applied to simulate a high speed water filling process. Results of the modeling were compared with corresponding experimental data and good agreement has been found.

Macroscopic Model and Its Numerical Solution for Two-Flow Mixed Traffic with Different Speeds and Lengths

2003 ◽  
Vol 1852 (1) ◽  
pp. 209-219 ◽  
Author(s):  
Stéphane Chanut ◽  
Christine Buisson
Keyword(s):  
Traffic Flow ◽  
Flow Model ◽  
Macroscopic Model ◽  
Model Output ◽  
Mixed Traffic ◽  
Traffic Flow Model ◽  
Hyperbolic Conservation ◽  
Flux Function ◽  
First Order ◽  
Proposed Model

A new first-order traffic flow model is introduced that takes into account the fact that various types of vehicles use the roads simultaneously, particularly cars and trucks. The main improvement this model has to offer is that vehicles are differentiated not only by their lengths but also by their speeds in a free-flow regime. Indeed, trucks on European roads are characterized by a lower speed than that of cars. A system of hyperbolic conservation equations is defined. In this system the flux function giving the flow of heavy and light vehicles depends on total and partial densities. This problem is partly solved in the Riemann case in order to establish a Godunov discretization. Some model output is shown stressing that speed differences between the two types of vehicles and congestion propagation are sufficiently reproduced. The limits of the proposed model are highlighted, and potential avenues of research in this domain are suggested.

scholarly journals Diffusion Approximation Model of TCP NewReno Congestion Control Mechanism

2019 ◽  
Vol 1 (1) ◽  
Author(s):  
Adam Domański ◽  
Joanna Domańska ◽  
Tadeusz Czachórski ◽  
Jerzy Klamka ◽  
Jakub Szyguła ◽  
...  
Keyword(s):  
Fluid Flow ◽  
Diffusion Approximation ◽  
Traffic Control ◽  
Flow Model ◽  
Time Jitter ◽  
Mean Values ◽  
New Model ◽  
Proposed Model ◽  
Transmission Quality ◽  
Congestion Control Mechanism

Abstract The aim of the article is to contribute to the modeling and evaluation of TCP/IP traffic control in case of active queue management mechanisms implemented in congestion router. We consider mechanisms based on RED and fractional-order $$PI^\alpha$$PIα controller. A new model based on diffusion approximation is developed and its results are compared with the results of an existing fluid flow model. Both models are used to investigate the influence of AQM control parameters on the flow control. Their numerical results concerning dynamics of congestion widow, loss probability, and traffic changes are quite similar. The advantage of the new model lies in giving more detailed information: the distribution of router queue and the distribution of introduced delay, not only their mean values as it is in case of fluid flow model. The variability of transmission time (jitter) is a factor of transmission quality, and therefore, the proposed model may be useful in further studies on TCP/IP quality of service.

Design and Implementation of Control-Theory-Based Microscopic Traffic Flow Model

2002 ◽  
Vol 1802 (1) ◽  
pp. 214-224
Author(s):  
Huajing Shi ◽  
Athanasios K. Ziliaskopoulos
Keyword(s):  
Control Theory ◽  
Traffic Flow ◽  
Flow Model ◽  
Constant Time ◽  
Flow Density ◽  
Traffic Flow Model ◽  
Time Headway ◽  
Proposed Model ◽  
Vehicle Acceleration ◽  
The Stability

A microscopic traffic flow model based on the constant-time-headway policy and McRuer’s man-machine crossover model was designed. Automatic control theory concepts were employed in the model formulation. The constant-time-headway policy was used to generate the command model of a human driver’s decision for vehicle acceleration or deceleration. This command is the input signal fed into the driver-vehicle dynamics suggested by the crossover model. The proposed model was mathematically formulated, designed, implemented, and numerically simulated. The stability properties and validity of the proposed model were analyzed on the basis of the simulation results. It was demonstrated that the proposed model can reproduce well-known traffic phenomena such as shock waves, intersection starting and stopping waves, and loop structures of flow-density and speed-density plots.

Dynamic congested traffic states of lattice hydrodynamic model with an on-ramp and its immediate upstream off-ramp

2018 ◽  
Vol 32 (29) ◽  
pp. 1850325 ◽  
Author(s):  
Tao Wang ◽  
Jing Zhang ◽  
Shubin Li ◽  
Haoming Du ◽  
Ge Gao
Keyword(s):  
Traffic Flow ◽  
Flow Model ◽  
Lane Change ◽  
Lattice Hydrodynamic Model ◽  
Traffic Patterns ◽  
Traffic Flow Model ◽  
Congested Traffic ◽  
Stop And Go ◽  
Proposed Model ◽  
Simulation Results

This paper investigates the features of congested traffic flow near the combination of off-ramp and on-ramp. Firstly, the stochastic off-ramp and on-ramp are designed. Then, a two-lane lattice hydrodynamic traffic flow model coupled with a combination bottleneck is proposed to reproduce the empirical phenomena. In the simulation, the asymmetric-lane change rules were adopted, and many congested traffic flow patterns were observed near the combination bottlenecks, such as homogeneous synchronized traffic (HST), moving localized cluster (MLC), triggered stop-and-go traffic (TSG), oscillating congested traffic (OCT), pinned localized cluster (PLC), and homogeneous congested traffic (HCT). The obtained simulation results suggest that the proposed model is good and can produce the observed congestion spatiotemporal traffic patterns well.

Numerical Simulation of 2D Hydraulic Jump Flow in a Vertical Plane

2012 ◽  
Vol 482-484 ◽  
pp. 16-20
Author(s):  
Wen Li Wei ◽  
X.J Zhao ◽  
Y. L Liu
Keyword(s):  
Free Surface ◽  
Hydraulic Jump ◽  
Flow Model ◽  
Vertical Plane ◽  
Surface Profile ◽  
Governing Equations ◽  
Proposed Model ◽  
2D Flow ◽  
Time Changes ◽  
Volume Method

This paper was concerned with a vertical two-dimensional (2D) flow model with free surface. The water governing equations were discretized with finite difference method. The function of volume method was employed to track the moving free surface. The model was used to predict the characteristics of hydraulic jump flow in a 2D vertical plane. The surface profile and time averaged velocity were calculated, which shows the proposed model can be capable of capturing sharp water and gas interface configuration as time changes.

MAS-Based Supply Chain Dynamic Collaboration Resource Sharing

2011 ◽  
Vol 282-283 ◽  
pp. 474-477
Author(s):  
Wei Jin Jiang ◽  
Luo Zhong ◽  
Qing Feng Li ◽  
Xiao Qing Deng
Keyword(s):  
Supply Chain ◽  
Resource Sharing ◽  
Flow Model ◽  
Complex Adaptive System ◽  
Supply Chain System ◽  
Proposed Model ◽  
Complex Adaptive ◽  
Chain Dynamic ◽  
Dynamic Collaboration ◽  
Operating Points

In order to study the law of emergence and its internal attributable causes according to the resources owned by agents that interacts with each other in the complex adaptive system about the supply chain, at the beginning the resources which the agents in the supply chain draw are defined as followings: the resources outside system, the resources in the system, the resources that other else agents own, and the dynamic resources the agent itself own, the multi-compartment agent of resources. The operating points of eight resources owned by agents interact with each other are controlled through eight random numbers, the direction, degree, speed and stability of resources flow during interaction among agents are described respectively by matching capability, matching speed and matching time; Furthermore, the evolution process about the resources among agents interacting is described by rules of GEF(Global Evaluate Function) and LEF(Local Evaluate Function), resources flow model of complex system about the supply chain is established; Eventually, through simulating respectively in the Swarm platform both the proposed model and the simple model that doesn’t cunsder the multi-compartment agent but the linear sum of all resources, it is found that the former describes the change rule of the resource more accurately in the supply chain system. It means that syncretizing eight resources, which interact and inter-constrain in the system, to an indiscerptible one is the attributable cause of the emergence.

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