scholarly journals BOUNDARY CONDITIONS FOR LIMITED AREA MODELING

1984 ◽  
Vol 1 (19) ◽  
pp. 58
Author(s):  
Y.P. Sheng ◽  
H. Lee Butler
Keyword(s):  
Boundary Condition ◽  
Gravity Waves ◽  
Real World ◽  
Open Boundary ◽  
Limited Area ◽  
Computational Domain ◽  
Open Boundary Condition ◽  
Open Boundaries ◽  
Engineering Problems ◽  
The Impact

A simple open boundary condition for limiting the computational domain in tidal simulations is presented. In modeling the impact of proposed coastal projects with a limited-area model, problems due to undesired reflection of gravity waves at open boundaries often occur. The boundary condition presented herein eliminates these problems in many instances and can be easily incorporated into a wide variety of models. The adapted procedure permits representation of appropriate forcing conditions while allowing propagation of internally-generated disturbances out of the open boundaries. Applications to real world engineering problems are presented.

scholarly journals AN OPEN BOUNDARY CONDITION FOR APPLICATION IN NUMERICAL COASTAL MODELS

2011 ◽  
Vol 1 (32) ◽  
pp. 30 ◽  
Author(s):  
Peifeng Ma ◽  
Ole Secher Madsen
Keyword(s):  
Boundary Condition ◽  
Phase Speed ◽  
Open Boundary ◽  
Computational Domain ◽  
Open Boundary Conditions ◽  
Flow Conditions ◽  
Open Boundary Condition ◽  
Open Boundaries ◽  
Two Parameters ◽  
Coastal Flow

Open boundaries (OBs) are usually unavoidable in numerical coastal circulation simulations. At OBs, appropriate open boundary conditions (OBCs) are required and a good OBC should be able to let outgoing waves freely pass to the exterior of a computational domain without creating reflections at the OBs. In the present study, a methodology has been developed to predict two parameters, phase speed c_r and decay time T_f, in a standard OBC formulation, so that the OBC is significantly improved compared to commonly used existing OBCs with specified c_r and T_f. For the conditions where wave period is unknown, the OBC with approximated c_r and T_f may be applied and a test reveals that this OBC is able to yield good results in typical coastal flow conditions. In addition, a Swing-Door Boundary Condition (SDBC) is proposed and tested for application at an offshore open boundary where both incoming and outgoing waves exist.

Numerical Simulation of Nonlinear Wave Diffraction by a Vertical Cylinder in a Narrow Flume, Wide Tank, and Infinitely Wide Tank

2003 ◽  
Author(s):  
Alaa M. Mansour ◽  
A. Neil Williams
Keyword(s):  
Boundary Condition ◽  
Boundary Conditions ◽  
Nonlinear Wave ◽  
Wave Diffraction ◽  
Open Boundary ◽  
Computational Domain ◽  
Open Boundary Condition ◽  
Lateral Direction ◽  
Cylinder Diameter ◽  
Side Walls

In this paper, a three dimensional numerical wave tank model has been used to simulate fully nonlinear wave diffraction by a uniform vertical circular cylinder. The cylinder has been placed in a narrow flume of a width equal to four times the cylinder diameter. The runup and the hydrodynamic forces on the cylinder has been compared to the results when a similar cylinder is placed in a similar tank but with a width equal to sixteen times the cylinder diameter. The model has been further extended by applying an open boundary condition to the side-walls to simulate an infinitely wide tank and hence more realistically simulate open sea condition. The proposed open boundary condition in the lateral direction is based on coupling of two prescribed boundary conditions, namely, numerical beach and Orlanski boundary conditions. The use of this coupled boundary condition has been found to be very efficient in eliminating any significant wave reflection from the side-walls back into the computational domain.

TRAFFIC FLOW INFLUENCED BY TRAFFIC LIGHT AND TURNING PROBABILITY FOR A CROSSROAD

2004 ◽  
Vol 18 (17n19) ◽  
pp. 2658-2662 ◽  
Author(s):  
HUILI TAN ◽  
CHAOYING ZHANG ◽  
LINGJIANG KONG ◽  
MUREN LIU
Keyword(s):  
Boundary Condition ◽  
Cellular Automaton ◽  
Traffic Flow ◽  
Cellular Automaton Model ◽  
Open Boundary ◽  
Open Boundary Condition ◽  
Traffic Light ◽  
Cycle Times ◽  
The Road ◽  
The Impact

A cellular automaton model with open boundary condition for a crossroad system controlled by a traffic light is presented. The traffic flow and speed of the first part of the road are quite different from those of the second part behind the crossing. The impact of turning probabilities and the cycle times of traffic light on the flow are investigated.

Study on the Mixing Traffic in a Single-Lane Roundabout with Open Boundary Condition

2014 ◽  
Vol 926-930 ◽  
pp. 3657-3660
Author(s):  
Rui Hong Dong ◽  
Wan Dong Xue ◽  
Chang Sheng Zhu
Keyword(s):  
Boundary Condition ◽  
Traffic Flow ◽  
Average Velocity ◽  
Critical Level ◽  
Open Boundary ◽  
Small Range ◽  
Open Boundary Condition ◽  
Mixed Traffic Flow ◽  
Cellular Automation Model ◽  
The Impact

Based on the Nagel-Schrekenberg (NaSch) model, a cellular automation model is proposed to describe the mixing traffic flow in a single-lane roundabout with open boundary condition. In this model, the impact of the injection probability and the mixed proportion coefficient on the mixed traffic flow is emphatically studied. Simulation results indicate that the injection probability can change the system density, velocity and flow in a certain range for a constant mixed proportion coefficient. Moreover, for a fixed injection probability, when the injection probability is lower than the critical level, the system average velocity will be more affected by the mixed proportion coefficient, By contrast, the system flow will not change by the mixed proportion coefficient; When the injection probability is higher than the critical level, the mixed proportion coefficient can only change the system density, average velocity and flow in a small range.

scholarly journals Simulation of Free-Surface Flow Using the Smoothed Particle Hydrodynamics (SPH) Method with Radiation Open Boundary Conditions

2016 ◽  
Vol 33 (11) ◽  
pp. 2435-2460 ◽  
Author(s):  
Xingye Ni ◽  
Jinyu Sheng ◽  
Weibing Feng
Keyword(s):  
Boundary Condition ◽  
Boundary Conditions ◽  
Circulation Model ◽  
Open Boundary ◽  
Open Boundary Conditions ◽  
Open Boundary Condition ◽  
Sph Method ◽  
Open Boundaries ◽  
Particle Hydrodynamics ◽  
Smoothed Particle

AbstractThe smoothed particle hydrodynamics (SPH) technique is a mesh-free numerical method that has great potential to be used in the development of the next generation of numerical ocean models. The implementation of open and solid boundary conditions in the SPH method, however, is not as straightforward as the mesh-based numerical methods. Two types of open boundary conditions are considered in this study: the adaptive open boundary condition (AOBC) and Flather’s open boundary condition (FOBC). These two open boundary conditions are implemented in the SPH-based shallow-water equation (SWE) circulation model for simulating sea surface elevations and depth-mean currents over a limited area with open boundaries. The performance of these two open boundaries is assessed in four numerical test cases. In comparison with the conventional characteristic open boundary condition, both the AOBC and the FOBC allow perturbations to propagate out more effectively and are easy to implement with the specification of external flow conditions at the model open boundaries. The model results also demonstrate that the AOBC requires an accurate estimation of the phase speed of perturbations and could lead to a small drift in the mean water level. By comparison, the FOBC is computationally more efficient without any model drift. The SPH-based SWE circulation model is also used in simulating the laboratory observations of the 1993 Okushiri Tsunami. The numerical results in this case demonstrate the feasibility and capability of the SPH-based SWE model for simulating free-surface flows in regions with complicated bathymetry and irregular coastline.

scholarly journals An Open Boundary Condition for Numerical Coastal Circulation Models

2011 ◽  
Vol 41 (12) ◽  
pp. 2363-2380 ◽  
Author(s):  
Peifeng Ma ◽  
Ole Secher Madsen
Keyword(s):  
Boundary Condition ◽  
Phase Speed ◽  
Open Boundary ◽  
Computational Domain ◽  
Coastal Circulation ◽  
Open Boundary Condition ◽  
Characteristic Analysis ◽  
Theoretical Derivation ◽  
Predictive Parameters ◽  
Short Period

Abstract Open boundaries (OBs) are usually unavoidable in numerical coastal circulation simulations. At OBs, an appropriate open boundary condition (OBC) is required so that outgoing waves freely pass to the exterior without creating reflections back into the interior of the computational domain. In this paper, the authors derive, based on the shallow-water equations including bottom friction and neglecting Coriolis effect and by means of nonlinear characteristic analysis, an OBC formulation with two predictive parameters, phase speed cr, and decay time Tf. Simple idealized tests are performed to demonstrate the proposed OBC’s excellent skills in elimination of unwanted reflections at OBs when the motion is periodic, as assumed in its theoretical derivation. It turns out that the formulas for the two OBC parameters become independent of period in the limit of small friction and/or short period. This feature is used to derive an OBC applicable when information about the typical period of the motion to be simulated is unavailable. Simple, idealized tests of this period independent OBC demonstrate its ability to afford excellent results, even when the limitations inherent in its derivation are exceeded. Finally, the OBC is applied in more realistic simulations, including Coriolis effects of 2D tidal flows, and is shown to yield excellent results, especially for residual flows.

ANALYSIS OF THE INFLUENCE OF LANE CHANGING ON TRAFFIC-FLOW DYNAMICS BASED ON THE CELLULAR AUTOMATON MODEL

2011 ◽  
Vol 22 (03) ◽  
pp. 271-281 ◽  
Author(s):  
SHINJI KUKIDA ◽  
JUN TANIMOTO ◽  
AYA HAGISHIMA
Keyword(s):  
Boundary Condition ◽  
Cellular Automaton ◽  
Numerical Simulations ◽  
Traffic Flow ◽  
Flow Dynamics ◽  
Open Boundary ◽  
Open Boundary Condition ◽  
Lane Changing ◽  
Basic Characteristics ◽  
Conventional Models

Many cellular automaton models (CA models) have been applied to analyze traffic flow. When analyzing multilane traffic flow, it is important how we define lane-changing rules. However, conventional models have used simple lane-changing rules that are dependent only on the distance from neighboring vehicles. We propose a new lane-changing rule considering velocity differences with neighboring vehicles; in addition, we embed the rules into a variant of the Nagel–Schreckenberg (NaSch) model, called the S-NFS model, by considering an open boundary condition. Using numerical simulations, we clarify the basic characteristics resulting from different assumptions with respect to lane changing.

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