scholarly journals The iFlow Modelling Framework v2.4. A modular idealised process-based model for flow and transport in estuaries

2017 ◽  
Author(s):  
Yoeri M. Dijkstra ◽  
Ronald L. Brouwer ◽  
Henk M. Schuttelaars ◽  
George P. Schramkowski
Keyword(s):  
Equations Of Motion ◽  
Transport Processes ◽  
Computational Grids ◽  
Model Parameters ◽  
Systematic Analysis ◽  
Modelling Framework ◽  
Numerical Solution Methods ◽  
Tidal Rivers ◽  
Solution Methods ◽  
Model Components

Abstract. The iFlow modelling framework allows for a systematic analysis of the water motion and sediment transport processes in estuaries and tidal rivers and the sensitivity of these processes to model parameters. iFlow has a modular structure, making the model easily extendible. This allows one to use iFlow to construct anything from very simple to rather complex models. The iFlow core is designed to make it easy to include, exclude or change model components, called modules. The core automatically ensures modules are called in the correct order, inserting iteration loops over groups of modules that are mutually dependent. The iFlow core also ensures a smooth coupling of modules using analytical and numerical solution methods or modules that use different computational grids. iFlow includes a range of modules for computing the hydrodynamics and suspended sediment dynamics in estuaries and tidal rivers. These modules employ perturbation methods, which allow for distinguishing the effect of individual forcing terms in the equations of motion and transport. Also included are several modules for computing turbulence and salinity. These modules are supported by auxiliary modules, including a module that facilitates sensitivity studies. Additional to an explanation of the model functionality, we present two case studies, demonstrating how iFlow facilitates the analysis of model results, the understanding of the underlying physics and the testing of parameter sensitivity. A comparison of the model results to measurements show a good qualitative agreement.

scholarly journals The iFlow modelling framework v2.4: a modular idealized process-based model for flow and transport in estuaries

2017 ◽  
Vol 10 (7) ◽  
pp. 2691-2713 ◽  
Author(s):  
Yoeri M. Dijkstra ◽  
Ronald L. Brouwer ◽  
Henk M. Schuttelaars ◽  
George P. Schramkowski
Keyword(s):  
Sediment Transport ◽  
Numerical Solution ◽  
Solution Method ◽  
Transport Processes ◽  
Modular Structure ◽  
Model Parameters ◽  
Water Motion ◽  
Modelling Framework ◽  
Numerical Solution Methods ◽  
Solution Methods

Abstract. The iFlow modelling framework is a width-averaged model for the systematic analysis of the water motion and sediment transport processes in estuaries and tidal rivers. The distinctive solution method, a mathematical perturbation method, used in the model allows for identification of the effect of individual physical processes on the water motion and sediment transport and study of the sensitivity of these processes to model parameters. This distinction between processes provides a unique tool for interpreting and explaining hydrodynamic interactions and sediment trapping. iFlow also includes a large number of options to configure the model geometry and multiple choices of turbulence and salinity models. Additionally, the model contains auxiliary components, including one that facilitates easy and fast sensitivity studies. iFlow has a modular structure, which makes it easy to include, exclude or change individual model components, called modules. Depending on the required functionality for the application at hand, modules can be selected to construct anything from very simple quasi-linear models to rather complex models involving multiple non-linear interactions. This way, the model complexity can be adjusted to the application. Once the modules containing the required functionality are selected, the underlying model structure automatically ensures modules are called in the correct order. The model inserts iteration loops over groups of modules that are mutually dependent. iFlow also ensures a smooth coupling of modules using analytical and numerical solution methods. This way the model combines the speed and accuracy of analytical solutions with the versatility of numerical solution methods. In this paper we present the modular structure, solution method and two examples of the use of iFlow. In the examples we present two case studies, of the Yangtze and Scheldt rivers, demonstrating how iFlow facilitates the analysis of model results, the understanding of the underlying physics and the testing of parameter sensitivity. A comparison of the model results to measurements shows a good qualitative agreement. iFlow is written in Python and is available as open source code under the LGPL license.

Multibody Dynamics Versus Fluid Dynamics: Two Perspectives on the Dynamics of Granular Flows

2020 ◽  
Vol 15 (9) ◽  
Author(s):  
Milad Rakhsha ◽  
Conlain Kelly ◽  
Nic Olsen ◽  
Radu Serban ◽  
Dan Negrut
Keyword(s):  
Fluid Dynamics ◽  
Granular Material ◽  
Equations Of Motion ◽  
Dam Break ◽  
Granular System ◽  
Processing Unit ◽  
Static Case ◽  
Granular Dynamics ◽  
Numerical Solution Methods ◽  
Solution Methods

Abstract Considering that granular material is second only to water in how often it is handled in practical applications, characterizing its dynamics represents a ubiquitous problem. However, studying the motion of granular material poses stiff computational challenges. The underlying question in this contribution is whether a continuum representation of the granular material, established in the framework of the smoothed particle hydrodynamics (SPH) method, can provide a good proxy for the fully resolved granular dynamics solution. To this end, two approaches described herein were implemented to run on graphics processing unit (GPU) cards to solve the three-dimensional (3D) dynamics of the granular material via two solution methods: a discrete one, and a continuum one. The study concentrates on the case when the granular material is packed but shows fluid-like behavior under large strains. On the one hand, we solve the Newton–Euler equations of motion to fully resolve the motion of the granular system. On the other hand, we solve the Navier–Stokes equations to describe the evolution of the granular material when treated as a homogenized continuum. To demonstrate the similarities and differences between the multibody and fluid dynamics, we consider three representative problems: (i) a compressibility test (highlighting a static case); (ii) the classical dam break problem (highlighting high transients); and (iii) the dam break simulation with an obstacle (highlighting impact). These experiments provide insights into conditions under which one can expect similar macroscale behavior from multibody and fluid dynamics systems governed by manifestly different equations of motion and solved by vastly different numerical solution methods. The models and simulation platform used are publicly available and part of an open source code called Chrono. Timing results are reported to gauge the efficiency gains associated with treating the granular material as a continuum.

Model of vortex flow of charge in a vessel with turbine impeller

1987 ◽  
Vol 52 (8) ◽  
pp. 1888-1904
Author(s):  
Miloslav Hošťálek ◽  
Ivan Fořt
Keyword(s):  
Boundary Conditions ◽  
Equations Of Motion ◽  
Theoretical Data ◽  
Eddy Diffusion ◽  
Quantitative Agreement ◽  
Creeping Flow ◽  
Model Parameters ◽  
Mean Flow ◽  
Two Dimensional Flow ◽  
Vorticity Transport

A theoretical model is described of the mean two-dimensional flow of homogeneous charge in a flat-bottomed cylindrical tank with radial baffles and six-blade turbine disc impeller. The model starts from the concept of vorticity transport in the bulk of vortex liquid flow through the mechanism of eddy diffusion characterized by a constant value of turbulent (eddy) viscosity. The result of solution of the equation which is analogous to the Stokes simplification of equations of motion for creeping flow is the description of field of the stream function and of the axial and radial velocity components of mean flow in the whole charge. The results of modelling are compared with the experimental and theoretical data published by different authors, a good qualitative and quantitative agreement being stated. Advantage of the model proposed is a very simple schematization of the system volume necessary to introduce the boundary conditions (only the parts above the impeller plane of symmetry and below it are distinguished), the explicit character of the model with respect to the model parameters (model lucidity, low demands on the capacity of computer), and, in the end, the possibility to modify the given model by changing boundary conditions even for another agitating set-up with radially-axial character of flow.

An Investigation Into the Compliance of SCARA Robots. Part II: Experimental and Numerical Validation

1988 ◽  
Vol 110 (1) ◽  
pp. 23-30 ◽  
Author(s):  
H. A. ElMaraghy ◽  
B. Johns
Keyword(s):  
Elastic Compliance ◽  
Servo Control ◽  
Compliance Matrix ◽  
End Effector ◽  
Prismatic Parts ◽  
Numerical Solution Methods ◽  
Solution Methods ◽  
Using Data ◽  
Assembly Performance ◽  
Robot Configurations

A model of inherent elastic compliance was developed for general position-controlled SCARA, with conventional joint feedback control, for both rotational and prismatic part insertion (Part I). The developed model was applied to the SKILAM and ADEPT I robots for validation. Experimental procedures and numerical solution methods are described. It was found that the ADEPT I robot employs a coupled control strategy between joints one and two which produces a constant, decoupled end effector compliance. The applicable compliance matrix, in this case, is presented and the experimental results are discussed. The model may be used to develop compliance maps that define the amount of end effector compliance, as a function of the joints compliance, as well as its variation for different robot configurations. This is illustrated using data for the SKILAM SCARA robot. Results are plotted and discussed. The most appropriate robot postures for assembly were found for both rotational and prismatic parts. The conditions necessary to achieve compliance or semicompliance centers with the SKILAM robot were examined. The results and methods demonstrated in these examples may be used to select appropriate robots for given applications. They can also guide robot designers in selecting joint servo-control gains to obtain the desired joints compliance ratio and improve assembly performance.

Hysteretic Poisson INGARCH model for integer-valued time series

2017 ◽  
Vol 17 (6) ◽  
pp. 401-422 ◽  
Author(s):  
Buu-Chau Truong ◽  
Cathy WS Chen ◽  
Songsak Sriboonchitta
Keyword(s):  
Time Series ◽  
Model Comparison ◽  
Monte Carlo Sampling ◽  
Information Criteria ◽  
Model Parameters ◽  
Modelling Framework ◽  
South Wales ◽  
Proposed Model ◽  
Over Dispersion ◽  
Ingarch Model

This study proposes a new model for integer-valued time series—the hysteretic Poisson integer-valued generalized autoregressive conditionally heteroskedastic (INGARCH) model—which has an integrated hysteresis zone in the switching mechanism of the conditional expectation. Our modelling framework provides a parsimonious representation of the salient features of integer-valued time series, such as discreteness, over-dispersion, asymmetry and structural change. We adopt Bayesian methods with a Markov chain Monte Carlo sampling scheme to estimate model parameters and utilize the Bayesian information criteria for model comparison. We then apply the proposed model to five real time series of criminal incidents recorded by the New South Wales Police Force in Australia. Simulation results and empirical analysis highlight the better performance of hysteresis in modelling the integer-valued time series.

Nonequilibrium Continuum Traffic Flow Model with Frozen Sound Wave Speed

2003 ◽  
Vol 1852 (1) ◽  
pp. 183-192
Author(s):  
W. L. Jin ◽  
H. M. Zhang
Keyword(s):  
Traffic Flow ◽  
Sound Speed ◽  
Flow Model ◽  
Wave Model ◽  
Homogeneous System ◽  
Traffic Flow Model ◽  
Traffic Conditions ◽  
Numerical Solution Methods ◽  
Stable Conditions ◽  
Solution Methods

Results are presented from a recent study on a variation of a new non-equilibrium continuum traffic flow model in which traffic sound speed is constant. Hence this model is called the frozen-wave model. This model resembles the Payne–Whitham model but avoids the “back-traveling” of the latter. For this frozen-wave model, the Riemann problem is analyzed for its homogeneous system, two numerical solution methods are developed to solve it, and numerical simulations are carried out under both stable and unstable traffic conditions. These results show that under stable conditions, the model behaves similarly to the Payne–Whitham model. However, under unstable traffic conditions, it has nonphysical solutions or no solutions when a vacuum problem occurs. This study, on the one hand, provides a more complete picture of the properties of this frozen-wave model and reduces the risk of improper applications of it. On the other hand, it also highlights the need to adopt a density-dependent sound speed.

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