scholarly journals Improving Water Level Forecast of an Oceanographic Model in Malacca Strait Based on Data-Driven Open Boundary Correction

10.29007/9bfr ◽  
2018 ◽  
Author(s):  
Xuan Wang ◽  
Serene Hui Xin Tay ◽  
Vladan Babovic
Keyword(s):  
Boundary Condition ◽  
Numerical Model ◽  
Open Boundary ◽  
Computational Domain ◽  
Time Step ◽  
Underlying Assumption ◽  
Indispensable Tool ◽  
Data Assimilation Technique ◽  
Oceanographic Model ◽  
Boundary Correction

Numerical model is an indispensable tool for understanding oceanographic phenomena and resolving associated physical processes. However, model error cannot be avoided due to limitations such as underlying assumption, insufficient information of bathymetry or boundary condition and so on. Data assimilation technique thus becomes an effective and essential tool to improve prediction accuracy. Updating of output is an efficient way to correct the model, but it is often carried out locally at specific locations in the model domain where measurement is available. In this study, instead of correcting output of numerical model locally, we propose to combine local correction and input correction to update open boundary of numerical model. The open boundary condition is corrected through spatial interpolation algorithm based on nearby observation in the hindcast period. Then the local forecast at measured location is distributed using the same interpolation scheme to update the boundary in the forecast period. Such boundary correction not only explores the variation in the future time step from the input updating but also allows the backbone physics embedded in numerical model to resolve the hydrodynamics in the entire computational domain.

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.

Towards a General-Purpose Open Boundary Condition for Wave Simulations

2011 ◽  
Author(s):  
Bulent Duz ◽  
Rene H. M. Huijsmans ◽  
Peter R. Wellens ◽  
Mart J. A. Borsboom ◽  
Arthur E. P. Veldman
Keyword(s):  
Boundary Condition ◽  
Three Dimensional ◽  
General Purpose ◽  
Absorbing Boundary Conditions ◽  
Design Stage ◽  
Open Boundary ◽  
Computational Domain ◽  
Absorbing Boundary ◽  
Scaled Model ◽  
Artificial Boundaries

For the design of FPSO’s in harsh environments an accurate assessment of the ability of the platform to survive in extreme sea conditions is of prime importance. Next to scaled model tests on the FPSO in waves also CFD capabilities are at the disposal of the designer. However even with the fastest computers available it is still a challenge to use CFD in the design stage because of the large computational resources they require. In that respect to use a small computational domain will improve the turn around time of the computations, however at the expense of various numerical artifacts, like reflection on artificial boundaries in the computational domain. In order to mitigate the reflection properties new absorbing boundary conditions have been developed. The work in this paper is constructed on the previous study about the generating and absorbing boundary condition (GABC) in the ComFLOW project. We present a method to apply the GABC on all the boundaries in a three dimensional domain. The implementation of the GABC in ComFLOW is explained in detail.

scholarly journals Investigation of Seiche Oscillations in the Adjacent Bays by the Example of the Sevastopol and the Quarantine Bays

2020 ◽  
Vol 27 (3) ◽  
Author(s):  
Yu. V. Manilyuk ◽  
D. I. Lazorenko ◽  
V. V. Fomin ◽  
◽  
◽  
...  
Keyword(s):  
Numerical Model ◽  
Numerical Experiments ◽  
Energy Exchange ◽  
Mutual Influence ◽  
Open Boundary ◽  
Computational Domain ◽  
Sea Level Fluctuations ◽  
Wave Disturbances ◽  
Sevastopol Bay ◽  
Seiche Oscillations

Purpose. The paper is aimed at studying the seiche structure in the adjacent bays' system of real configuration. Methods and Results. The response of the Sevastopol and Quarantine bays (Black Sea) to sea level fluctuations set at the open boundary of the computational domain has been studied. A number of random harmonics within the range of the eigen periods of these bays were used as fluctuations. The ADCIRC numerical model was applied for simulating. The numerical experiments were performed for three ranges obtained from the analytical estimates: 30–52, 8–30 and 1–15 min. The energy-bearing periods of seiche oscillations were revealed for both bays. The mutual influence of these bays was also studied. Conclusions. The above mentioned wave disturbances lead to generation of the seiche oscillations in the bays. For the Sevastopol Bay, their periods are 48, 22, 16, 10 and 6 min, for the Quarantine Bay – 11.4 and 4.8 min. The number of the generated modes is determined by the interval of the wave disturbance periods. The bays have a mutual influence on each other due to the wave energy exchange through their entrances. At that intensity of the eigen modes of the Sevastopol Bay penetrating the Quarantine Bay can exceed intensity of those of the Quarantine Bay. In both bays, the seiches with the largest amplitudes are induced by the disturbances, the periods of which are in the interval 30–52 min.

A Two-Dimensional Numerical Wave Flume—Part 1: Nonlinear Wave Generation, Propagation, and Absorption

2001 ◽  
Vol 123 (2) ◽  
pp. 70-75 ◽  
Author(s):  
S. F. Baudic ◽  
A. N. Williams ◽  
A. Kareem
Keyword(s):  
Numerical Model ◽  
Fluid Motion ◽  
Radiation Condition ◽  
Wave Theory ◽  
Published Data ◽  
Computational Domain ◽  
Two Dimensional ◽  
Time Step ◽  
Numerical Wave Flume ◽  
Wave Flume

A numerical model is developed to simulate fully nonlinear transient waves in a semi-infinite, two-dimensional wave tank. A mixed Eulerian-Lagrangian formulation is adopted and a high-order boundary element method is used to solve for the fluid motion at each time step. Input wave characteristics are specified at the upstream boundary of the computational domain using an appropriate wave theory. At the downstream boundary, a damping region is used in conjunction with a radiation condition to prevent wave reflections back into the computational domain. The convergence characteristics of the numerical model are studied and the numerical results are validated through a comparison with previous published data.

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.

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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