scholarly journals Bubble Sweep-Down of Research Vessels Based on the Coupled Eulerian-Lagrangian Method

2020 ◽  
Vol 8 (12) ◽  
pp. 1040
Author(s):  
Wei Wang ◽  
Guobin Cai ◽  
Yongjie Pang ◽  
Chunyu Guo ◽  
Yang Han ◽  
...  
Keyword(s):  
Pressure Field ◽  
Element Model ◽  
Lagrangian Method ◽  
Discrete Element Model ◽  
Bubble Motion ◽  
Interaction Method ◽  
Movement Characteristics ◽  
Spatial Movement ◽  
Motion Characteristics ◽  
The Impact

To explore the reason for the bubble sweep-down phenomenon of research vessels and its effect on the position of the stern sonar of a research vessel, the use of a fairing was investigated as a defoaming appendage. The separation vortex turbulence model was selected for simulation, and the coupled Eulerian-Lagrangian method was adopted to study the characteristics of the bubble sweep-down motion, captured using a discrete element model. The interaction between the bubbles, water, air, and hull was defined via a multiphase interaction method. The bubble point position and bubble layer were calculated separately. The spatial movement characteristics of the bubbles were extracted from bubble trajectories. It was demonstrated that the bubble sweep-down phenomenon is closely related to the distribution of the bow pressure field and that the bubble motion characteristics is related to the speed and initial bubble position. When the initial bubble position is between the water surface and the ship bottom, the impact on the middle of the ship bottom is greater and increases further with increasing speed. A deflector forces the bubbles to both sides through physical shielding, strengthening the local vortex structure and keeping bubbles away from the middle of the ship bottom.

Fractality of Simulated Fracture

2009 ◽  
Vol 409 ◽  
pp. 154-160 ◽  
Author(s):  
Petr Frantík ◽  
Zbyněk Keršner ◽  
Václav Veselý ◽  
Ladislav Řoutil
Keyword(s):  
Numerical Model ◽  
Elastic Plate ◽  
Model Simulation ◽  
Element Model ◽  
The Other ◽  
Particle Model ◽  
Discrete Element Model ◽  
Fractal Nature ◽  
Discrete Elements ◽  
The Impact

The paper is focussed on numerical simulations of the fracture of a quasi-brittle specimen due to its impact onto a fixed rigid elastic plate. The failure of the specimen after the impact is modelled in two ways based on the physical discretization of continuum: via physical discrete elements and pseudo-particles. Advantages and drawbacks of both used methods are discussed. The size distribution of the fragments of the broken specimen resulting from physical discrete element model simulation follows a power law, which indicates the ability of the numerical model to identify the fractal nature of the fracture. The pseudo-particle model, on the other side, can successfully predict the kinematics of the fragments of the specimen under impact failure.

A Global Simulation Model for Hermetic Reciprocating Compressors

1991 ◽  
Vol 113 (3) ◽  
pp. 395-400 ◽  
Author(s):  
M. A. de los Santos ◽  
S. Cardona ◽  
J. Sa´nchez-Reyes
Keyword(s):  
Theoretical Model ◽  
Simulation Model ◽  
Modal Analysis ◽  
Degrees Of Freedom ◽  
Element Model ◽  
Discrete Element Model ◽  
Lagrange Equations ◽  
The Impact ◽  
Three Degrees Of Freedom ◽  
Elastic Elements

This article presents a simulation model for reciprocating hermetic compressors. The acoustical behavior of both admission and discharge circuits is analyzed by invoking the discrete element model. Cavities are considered as elastic elements and ducts as rigid elements with inertia according to this model. Reed valves are modeled as systems of three degrees of freedom, and are studied by using modal analysis. The percussive version of Lagrange equations is used to describe the impact between valves and stops or seats. Results from the theoretical model are checked with those experimentally obtained for a real compressor.

scholarly journals NUMERICAL INVESTIGATION OF BORE HOLE FILLING VOLUME IN A COASTAL AREA

2018 ◽  
pp. 58
Author(s):  
Feddy Adong ◽  
Anne-Claire Bennis ◽  
Dominique Mouazé
Keyword(s):  
Coastal Area ◽  
Numerical Study ◽  
Flow Direction ◽  
Circulation Model ◽  
Element Model ◽  
Spherical Particles ◽  
Discrete Element Model ◽  
Hole Filling ◽  
Coastal Circulation Model ◽  
The Impact

A numerical study is carried out to determine the parameters controlling the filling of a bore hole in Alderney Race. Our final goal is to identify the configuration minimizing the filling. We performed a one-way coupling between a coastal circulation model and a discrete element model for that purpose. Simulations used spherical particles and a monopile technology. We show that: as long as the distance between the hole and the residuals remains smaller than twenty meters, the flow direction plays a negligible role; interaction between moving particles and bottom roughness leads to a slight increase of the filling; the impact of ambient sediments strongly depends on seabed morphology and current effects.

scholarly journals SIMULATION MODEL OF THE BRUSH CUTTER ROTOR WITH SIX BLADES

2021 ◽  
Vol 11 (3) ◽  
pp. 121-129
Author(s):  
Mikhail Drapalyuk ◽  
Leonid Bukhtoyarov ◽  
A. Pridvorova
Keyword(s):  
Cutting Forces ◽  
Computer Experiment ◽  
Forest Plantations ◽  
Drive Power ◽  
Virtual Sensors ◽  
Movement Characteristics ◽  
Motion Characteristics ◽  
Working Bodies ◽  
Input Motion ◽  
The Impact

Brush cutters are used in forestry for the care of forest plantations in operations for cutting unwanted tree and shrub vegetation (TSV). Rotors can be used as working bodies. The rotor we are considering is a flywheel, on the outer sides of which the blades are hinged. When cutting DKR with blades, a cutting moment arises, which is transmitted through the knife to the axis of its rotation and then to the shaft driving the flywheel. When designing a brush cutter structure, the impact from the cutting forces of the DKR is decisive for the choice of drive power and rotor parameters. We designed the brush cutter rotor in CAD Solidworks to study the cutting process of the DKR. Its geometric and mass parameters were set; the kinematic links of the links were established. The input motion characteristics were set in the Motion Solidworks module and the cutting moment was applied to the knives. Virtual sensors were installed on the model to record movement characteristics. As a result of a computer experiment for three options, which differ in cutting force and the presence of a damper, the trajectories of the knives and the power consumption of the drive were established

scholarly journals Discrete element model for general polyhedra

2021 ◽  
Author(s):  
Alfredo Gay Neto ◽  
Peter Wriggers
Keyword(s):  
Frictional Contact ◽  
Virtual Work ◽  
Particle Surface ◽  
Element Model ◽  
Discrete Element ◽  
Discrete Element Model ◽  
Principle Of Virtual Work ◽  
Dynamics Model ◽  
Railway Ballast ◽  
Multibody Dynamics Model

AbstractWe present a version of the Discrete Element Method considering the particles as rigid polyhedra. The Principle of Virtual Work is employed as basis for a multibody dynamics model. Each particle surface is split into sub-regions, which are tracked for contact with other sub-regions of neighboring particles. Contact interactions are modeled pointwise, considering vertex-face, edge-edge, vertex-edge and vertex-vertex interactions. General polyhedra with triangular faces are considered as particles, permitting multiple pointwise interactions which are automatically detected along the model evolution. We propose a combined interface law composed of a penalty and a barrier approach, to fulfill the contact constraints. Numerical examples demonstrate that the model can handle normal and frictional contact effects in a robust manner. These include simulations of convex and non-convex particles, showing the potential of applicability to materials with complex shaped particles such as sand and railway ballast.

scholarly journals MFIX-Exa: A path toward exascale CFD-DEM simulations

2021 ◽  
pp. 109434202110092
Author(s):  
Jordan Musser ◽  
Ann S Almgren ◽  
William D Fullmer ◽  
Oscar Antepara ◽  
John B Bell ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Element Model ◽  
Discrete Element Model ◽  
Software Framework ◽  
Chemical Reactors ◽  
Software Infrastructure ◽  
Fundamental Physics ◽  
Dem Simulations ◽  
Algorithmic Approaches

MFIX-Exa is a computational fluid dynamics–discrete element model (CFD-DEM) code designed to run efficiently on current and next-generation supercomputing architectures. MFIX-Exa combines the CFD-DEM expertise embodied in the MFIX code—which was developed at NETL and is used widely in academia and industry—with the modern software framework, AMReX, developed at LBNL. The fundamental physics models follow those of the original MFIX, but the combination of new algorithmic approaches and a new software infrastructure will enable MFIX-Exa to leverage future exascale machines to optimize the modeling and design of multiphase chemical reactors.

Investigation on the shaft voltage generation of large synchronous turboalternators

2020 ◽  
Vol 39 (5) ◽  
pp. 1145-1156
Author(s):  
Kevin Darques ◽  
Abdelmounaïm Tounzi ◽  
Yvonnick Le-menach ◽  
Karim Beddek
Keyword(s):  
Finite Element ◽  
Design Methodology ◽  
Short Circuit ◽  
Element Model ◽  
Stator Winding ◽  
Content Type ◽  
Voltage Generation ◽  
The Impact ◽  
Investigation Process ◽  
Circulating Currents

Purpose This paper aims to go deeper on the analysis of the shaft voltage of large turbogenerators. The main interest of this study is the investigation process developed. Design/methodology/approach The analysis of the shaft voltage because of several defects is based on a two-dimensional (2D) finite element modeling. This 2D finite element model is used to determine the shaft voltage because of eccentricities or rotor short-circuit. Findings Dynamic eccentricities and rotor short circuit do not have an inherent impact on the shaft voltage. Circulating currents in the stator winding because of defects impact the shaft voltage. Originality/value The original value of this paper is the investigation process developed. This study proposes to quantify the impact of a smooth stator and then to explore the contribution of the real stator winding on the shaft voltage.

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