Simulation of Turbulent Flows in River Confluences and Meandering Channels with a Cartesian 3D Free Surface Hydrodynamic Model

2015 ◽  
Vol 12 (06) ◽  
pp. 1550035 ◽  
Author(s):  
C. L. Ramón ◽  
J. Prats ◽  
F. J. Rueda
Keyword(s):  
Free Surface ◽  
Turbulent Flows ◽  
Three Dimensional ◽  
Computational Time ◽  
Natural Environments ◽  
Computational Domain ◽  
Meandering Channels ◽  
Lateral Cavity ◽  
Reasonable Approach ◽  
Simple Flows

Three-dimensional primitive equations (3DPE) become a reasonable approach in hydrodynamics in terms of computational costs when the length of the computational domain and/or computational time scales increases. However, given the simplified set of equations used in the analysis, results with 3DPE-based models are expected to be approximate and before attempting to reproduce complex natural flows they first need to be validated against more simple flows observed in laboratory settings. Here, the validity of Cartesian free-surface hydrodynamic models to reproduce three turbulent flows characteristic of river environments is tested: (1) the development of shallow mixing layers, (2) flow pass a lateral cavity and (3) flow in open channel with mild curvature. Errors between measured and modeled values were generally less than 10%, proving their validity to reproduce such turbulent flows and their potential for simulations in more complex natural environments, such it is the case of the confluence between the Ebro and Segre rivers into Ribarroja reservoir.

Numerical simulations of nonlinear axisymmetric flows with a free surface

1987 ◽  
Vol 178 ◽  
pp. 195-219 ◽  
Author(s):  
Douglas G. Dommermuth ◽  
Dick K. P. Yue
Keyword(s):  
Free Surface ◽  
Numerical Simulations ◽  
Three Dimensional ◽  
Vertical Cylinder ◽  
Free Surface Flows ◽  
Boundary Integral ◽  
The Body ◽  
Special Treatment ◽  
Computational Domain ◽  
Vortex Sheets

A numerical method is developed for nonlinear three-dimensional but axisymmetric free-surface problems using a mixed Eulerian-Lagrangian scheme under the assumption of potential flow. Taking advantage of axisymmetry, Rankine ring sources are used in a Green's theorem boundary-integral formulation to solve the field equation; and the free surface is then updated in time following Lagrangian points. A special treatment of the free surface and body intersection points is generalized to this case which avoids the difficulties associated with the singularity there. To allow for long-time simulations, the nonlinear computational domain is matched to a transient linear wavefield outside. When the matching boundary is placed at a suitable distance (depending on wave amplitude), numerical simulations can, in principle, be continued indefinitely in time. Based on a simple stability argument, a regriding algorithm similar to that of Fink & Soh (1974) for vortex sheets is generalized to free-surface flows, which removes the instabilities experienced by earlier investigators and eliminates the need for artificial smoothing. The resulting scheme is very robust and stable.For illustration, three computational examples are presented: (i) the growth and collapse of a vapour cavity near the free surface; (ii) the heaving of a floating vertical cylinder starting from rest; and (iii) the heaving of an inverted vertical cone. For the cavity problem, there is excellent agreement with available experiments. For the wave-body interaction calculations, we are able to obtain and analyse steady-state (limit-cycle) results for the force and flow field in the vicinity of the body.

scholarly journals MR-WC-MPS: A Multi-Resolution WC-MPS Method for Simulation of Free-Surface Flows

Water ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 1349 ◽  
Author(s):  
Mohammad Amin Nabian ◽  
Leila Farhadi
Keyword(s):  
Free Surface ◽  
Free Surface Flows ◽  
Submarine Landslide ◽  
Particle Methods ◽  
Computational Time ◽  
Computational Domain ◽  
Surface Flows ◽  
Mps Method ◽  
Weakly Compressible ◽  
Moving Particle

A Multi-Resolution Weakly Compressible Moving-Particle Semi-Implicit (MR-WC-MPS) method is presented in this paper for simulation of free-surface flows. To reduce the computational costs, as with the multi-grid schemes used in mesh-based methods, there is also a need in particle methods to efficiently capture the characteristics of different flow regions with different levels of complexity in different spatial resolutions. The proposed MR-WC-MPS method allows the use of particles with different sizes in a computational domain, analogous to multi-resolution grid in grid-based methods. To evaluate the accuracy and efficiency of the proposed method, it is applied to the dam-break and submarine landslide tests. It is shown that the MR-WC-MPS results, while about 15% faster, are in good agreement with the conventional single-resolution MPS results and experimental results. The remarkable ability of the MR-WC-MPS method in providing robust savings in computational time for up to 60% is then shown by applying the method for simulation of extended submarine landslide test.

PSL—An Economical Approach to the Numerical Analysis of Near-Wall, Elliptic Flow

1984 ◽  
Vol 106 (2) ◽  
pp. 241-242 ◽  
Author(s):  
H. Iacovides ◽  
B. E. Launder
Keyword(s):  
Numerical Analysis ◽  
Numerical Computation ◽  
Turbulent Flows ◽  
Three Dimensional ◽  
Elliptic Flow ◽  
Computational Time ◽  
Three Dimensional Flow ◽  
Fine Grid ◽  
Dimensional Flow ◽  
Grid Analysis

The paper points out that, in the numerical computation of elliptic or three-dimensional turbulent flows, the neglect of pressure-variations across the very thin viscosity affected region near the wall allows a fine-grid analysis of this sublayer without prohibitive penalties in core or computational time. The scheme has been successfully applied to the three-dimensional flow around a U-bend.

An Approximate Three-Dimensional Solution for Melting or Freezing Around a Buried Pipe Beneath a Free Surface

1986 ◽  
Vol 108 (4) ◽  
pp. 900-906 ◽  
Author(s):  
G.-P. Zhang ◽  
S. Weinbaum ◽  
L. M. Jiji
Keyword(s):  
Approximate Solution ◽  
Free Surface ◽  
Phase Change ◽  
Initial Conditions ◽  
Three Dimensional ◽  
Three Dimensions ◽  
Computational Time ◽  
Buried Pipe ◽  
Dimensional Solution ◽  
Pipe Surface

This paper presents a quasi-steady-state approximate solution for small Stefan number for the three-dimensional melting or freezing around a fluid-carrying pipe buried in a semi-infinite phase change medium (PCM). The two-dimensional quasi-steady approximate solution method, the virtual free surface technique [18], has been extended to three dimensions where axial thermal interaction between the moving fluid and the PCM is considered. Of particular interest in the motion of the phase change interface and the time variation of the axial temperature distribution in the fluid. Due to the singularities of the differential equations along the pipe surface, an axisymmetric analytic solution is provided for the region near the pipe wall. Solutions are presented for several representative dimensionless pipe burial depths and initial conditions. The computational time to predict the three-dimensional interface location up to 10 years is several minutes on an IBM 4341 computer.

scholarly journals Parallelization technologies and grid data structures for solving three-dimensional boundary value problems in complex domains on quasistructured grids

2018 ◽  
pp. 496-506
Author(s):  
В.Д. Корнеев ◽  
В.М. Свешников
Keyword(s):  
Boundary Value Problems ◽  
Data Structures ◽  
Complex Geometry ◽  
Boundary Value ◽  
Three Dimensional ◽  
Computational Time ◽  
Computational Domain ◽  
Grid Data ◽  
Dimensional Boundary ◽  
Stored Information

При распараллеливании решения трехмерных краевых задач, особенно в областях со сложной геометрией, важными являются технологии проведения вычислений и структуры данных. От них зависит объем хранимой информации и время решения. В статье предлагаются технологии распараллеливания метода декомпозиции расчетной области на подобласти, сопрягаемые без наложения, на квазиструктурированных сетках. Разработаны параллельные сеточные структуры данных, ориентированные преимущественно на работу со структурированными массивами данных. Приведен иллюстративный пример, показывающий основные положения предлагаемого подхода. When parallelizing the solution of three-dimensional boundary value problems, especially in domains with complex geometry, the сomputational technologies and data structureы are important. The amount of stored information and the computational time depend on them. In this paper we propose the technologies for parallelizing the method of decomposition of the computational domain into subdomains conjugated without overlapping on a quasistructured grid. Parallel grid data structures oriented mainly to work with structured data arrays are developed. An illustrative example clarifying the fundamentals of the proposed approach is discussed.

Prediction of Ship Motions Via a Three-Dimensional Time-Domain Method Following a Quad-Tree Adaptive Mesh Technique

2020 ◽  
Vol 27 (1) ◽  
pp. 29-38
Author(s):  
Teng Zhang ◽  
Junsheng Ren ◽  
Lu Liu
Keyword(s):  
Free Surface ◽  
Incident Wave ◽  
Time Domain ◽  
Three Dimensional ◽  
Adaptive Mesh ◽  
Wave Profile ◽  
Time Domain Method ◽  
Ship Motions ◽  
Quad Tree ◽  
Mesh Technique

AbstractA three-dimensional (3D) time-domain method is developed to predict ship motions in waves. To evaluate the Froude-Krylov (F-K) forces and hydrostatic forces under the instantaneous incident wave profile, an adaptive mesh technique based on a quad-tree subdivision is adopted to generate instantaneous wet meshes for ship. For quadrilateral panels under both mean free surface and instantaneous incident wave profiles, Froude-Krylov forces and hydrostatic forces are computed by analytical exact pressure integration expressions, allowing for considerably coarse meshes without loss of accuracy. And for quadrilateral panels interacting with the wave profile, F-K and hydrostatic forces are evaluated following a quad-tree subdivision. The transient free surface Green function (TFSGF) is essential to evaluate radiation and diffraction forces based on linear theory. To reduce the numerical error due to unclear partition, a precise integration method is applied to solve the TFSGF in the partition computation time domain. Computations are carried out for a Wigley hull form and S175 container ship, and the results show good agreement with both experimental results and published results.

scholarly journals A Proof-of-Concept Algorithm for the Retrieval of Total Column Amount of Trace Gases in a Multi-Dimensional Atmosphere

2021 ◽  
Vol 13 (2) ◽  
pp. 270
Author(s):  
Adrian Doicu ◽  
Dmitry S. Efremenko ◽  
Thomas Trautmann
Keyword(s):  
Trace Gases ◽  
Three Dimensional ◽  
Principal Component ◽  
Radiative Transfer Model ◽  
Computational Time ◽  
Transfer Model ◽  
Proof Of Concept ◽  
Discrete Ordinate ◽  
Distribution Method ◽  
Total Column

An algorithm for the retrieval of total column amount of trace gases in a multi-dimensional atmosphere is designed. The algorithm uses (i) certain differential radiance models with internal and external closures as inversion models, (ii) the iteratively regularized Gauss–Newton method as a regularization tool, and (iii) the spherical harmonics discrete ordinate method (SHDOM) as linearized radiative transfer model. For efficiency reasons, SHDOM is equipped with a spectral acceleration approach that combines the correlated k-distribution method with the principal component analysis. The algorithm is used to retrieve the total column amount of nitrogen for two- and three-dimensional cloudy scenes. Although for three-dimensional geometries, the computational time is high, the main concepts of the algorithm are correct and the retrieval results are accurate.

scholarly journals Free-surface behaviour of shallow turbulent flows

2021 ◽  
Vol 59 (1) ◽  
pp. 1-20
Author(s):  
Fabio Muraro ◽  
Giulio Dolcetti ◽  
Andrew Nichols ◽  
Simon J. Tait ◽  
Kirill V. Horoshenkov
Keyword(s):  
Free Surface ◽  
Turbulent Flows

scholarly journals Simulation of Thermal and Electric Field Distribution in Packaged Sausages Heated in a Stationary Versus a Rotating Microwave Oven

Foods ◽  
2021 ◽  
Vol 10 (7) ◽  
pp. 1622
Author(s):  
Wipawee Tepnatim ◽  
Witchuda Daud ◽  
Pitiya Kamonpatana
Keyword(s):  
Temperature Distribution ◽  
Electric Field ◽  
Three Dimensional ◽  
Development Stage ◽  
Microwave Oven ◽  
Computational Time ◽  
Plastic Package ◽  
Heating Uniformity ◽  
The Cost ◽  
Good Agreement

The microwave oven has become a standard appliance to reheat or cook meals in households and convenience stores. However, the main problem of microwave heating is the non-uniform temperature distribution, which may affect food quality and health safety. A three-dimensional mathematical model was developed to simulate the temperature distribution of four ready-to-eat sausages in a plastic package in a stationary versus a rotating microwave oven, and the model was validated experimentally. COMSOL software was applied to predict sausage temperatures at different orientations for the stationary microwave model, whereas COMSOL and COMSOL in combination with MATLAB software were used for a rotating microwave model. A sausage orientation at 135° with the waveguide was similar to that using the rotating microwave model regarding uniform thermal and electric field distributions. Both rotating models provided good agreement between the predicted and actual values and had greater precision than the stationary model. In addition, the computational time using COMSOL in combination with MATLAB was reduced by 60% compared to COMSOL alone. Consequently, the models could assist food producers and associations in designing packaging materials to prevent leakage of the packaging compound, developing new products and applications to improve product heating uniformity, and reducing the cost and time of the research and development stage.

Sign in / Sign up

Export Citation Format

Share Document