Solid Particle Resuspension Model Development for the GASFLOW Code

2010 ◽  
Author(s):  
Zhanjie Xu ◽  
John R. Travis ◽  
Thomas Jordan
Keyword(s):  
Experimental Data ◽  
Model Development ◽  
Three Dimensional ◽  
Solid Particles ◽  
Force Balance ◽  
Dust Particles ◽  
Vacuum Vessel ◽  
Particle Resuspension ◽  
Numerical Predictions ◽  
Accident Scenarios

Safety reports have shown that tons of solid particles would be generated as dusts in the operation of ITER facility. The dust particles include carbon, beryllium and tungsten with diameters ranging from a few to a few hundreds microns. The particles deposit downwards and mostly accumulated on the surfaces of the diverter on the bottom side of the vacuum vessel (VV). In accident scenarios, e.g., loss of vacuum accident (LOVA), the potentially combustible dust particles can be suspended by the air ingress and entrained into the whole volume of the VV, and impose a risk of dust explosions in case of unintentionally ignition to the whole ITER facility. Therefore the mechanism of particle resuspension was investigated theoretically in the work. A force balance approach and numerical fittings have been utilized to develop a semiempirical particle resuspension model based on a group of particle resuspension experimental data. The model has been applied into a three-dimensional computational fluid dynamics code, GASFLOW. The model validation has been done by comparison of the numerical predictions about particle resuspension rates in given incoming flows against the corresponding experimental data. The comparisons have proved the validity of the developed model about particle resuspension.

Numerical simulations of the flow through the inlet and isolator of a Mach 4 dual mode scramjet

2012 ◽  
Vol 116 (1182) ◽  
pp. 833-846 ◽  
Author(s):  
S. Janarthanam ◽  
V. Babu
Keyword(s):  
Experimental Data ◽  
Numerical Simulations ◽  
Three Dimensional ◽  
Pressure Rise ◽  
Dual Mode ◽  
Flow Distortion ◽  
Capture Ratio ◽  
Boundary Interaction ◽  
Numerical Predictions ◽  
Mass Capture

Abstract Results from numerical simulations of the three dimensional flow in the intake-isolator of a dual mode scramjet are presented. The FANS calculations have utilised the SST k -ω turbulence model. The effect of cowl length and cowl convergence angle on the inlet mass capture ratio, flow distortion, shock strength and pressure rise are studied in detail. Three cowl lengths and four or five cowl convergence angles for each cowl length are considered. The predicted values of the dimensionless wall static pressure and inlet mass capture ratio are compared with experimental data reported in the literature. The numerical predictions are shown to agree well with the experimental data. In addition, details of the flow field such as shocks, expansion fans and shock boundary interaction are also captured accurately. Inlet unstart is also demonstrated for one case.

scholarly journals Observation of aerodynamic instability in the flow of a particle stream in a dilute gas

2019 ◽  
Vol 622 ◽  
pp. A151 ◽  
Author(s):  
Holly L. Capelo ◽  
Jan Moláček ◽  
Michiel Lambrechts ◽  
John Lawson ◽  
Anders Johansen ◽  
...  
Keyword(s):  
Local Density ◽  
Mass Density ◽  
Density Ratio ◽  
Three Dimensional ◽  
Particle Number Density ◽  
Solid Particles ◽  
Dust Particles ◽  
Drag Forces ◽  
Velocity Statistics ◽  
The Mean

Forming macroscopic solid bodies in circumstellar discs requires local dust concentration levels significantly higher than the mean. Interactions of the dust particles with the gas must serve to augment local particle densities, and facilitate growth past barriers in the metre size range. Amongst a number of mechanisms that can amplify the local density of solids, aerodynamic streaming instability (SI) is one of the most promising. This work tests the physical assumptions of models that lead to SI in protoplanetary discs (PPDs). We conduct laboratory experiments in which we track the three-dimensional motion of spherical solid particles fluidised in a low-pressure, laminar, incompressible, gas stream. The particle sizes span the Stokes–Epstein drag regime transition and the overall dust-to-gas mass density ratio,ϵ, is close to unity. A recently published study establishes the similarity of the laboratory flow to a simplified PPD model flow. We study velocity statistics and perform time-series analysis of the advected flow to obtain experimental results suggesting an instability due to particle-gas interaction: (i) there exist variations in particle concentration in the direction of the mean relative motion between the gas and the particles, that is the direction of the mean drag forces; (ii) the particles have a tendency to “catch up” to one another when they are in proximity; (iii) particle clumping occurs on very small scales, which implies local enhancements above the backgroundϵby factors of several tens; (iv) the presence of these density enhancements occurs for a meanϵapproaching or greater than 1; (v) we find evidence for collective particle drag reduction when the local particle number density becomes high and when the background gas pressure is high so that the drag is in the continuum regime. The experiments presented here are precedent-setting for observing SI under controlled conditions and may lead to a deeper understanding of how it operates in nature.

Simulation and Experimental Study on the Impact of Breadth of Back Blade on Axial Force Balance

2011 ◽  
Vol 130-134 ◽  
pp. 1568-1572
Author(s):  
Hui Wang ◽  
Jie Gang Mu ◽  
Miao Yin Su ◽  
Shui Hua Zheng ◽  
Jin Jing Zhao ◽  
...  
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Experimental Study ◽  
Axial Force ◽  
Three Dimensional ◽  
Force Balance ◽  
Simulation And Experiment ◽  
Simulation Results ◽  
The Impact ◽  
The Relationship

The paper studies the relationship between axial force and breadth of back blade by numerical simulation and experiment. On the basis of the RNG k-ε turbulence model and technology of compact local grids and regional computing, three dimensional numerical simulations to 100HZ165-250 centrifugal pump with various breadths were carried out. Through comparing and analyzing of the flow field, it can be seen that the axial force reduces with the increase of the back blade breadth. After that, the simulation results were verified by the experimental data got from different test devices, and it shows that the conclusions are reliable.

Comparison of Single and Two-Phase Models for the Study of Mixed Convection Flows With Nanofluids

2010 ◽  
Author(s):  
Mahmood Akbari ◽  
Amin Behzadmehr ◽  
Nicolas Galanis
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Mixed Convection ◽  
Single Phase ◽  
Volume Fraction ◽  
Solid Particles ◽  
Two Phase ◽  
Prediction Ability ◽  
Numerical Predictions ◽  
Phase Models

The single phase and three different two phase models (Volume of fluid, Mixture and Eulerian) are used to analyse laminar mixed convection flow of Al2O3-water nanofluids in a horizontal tube, in order to evaluate their prediction ability. The flow is considered steady and developing. The fluid’s physical properties are temperature dependent whereas those of the solid particles are constant. A uniform heat flux is applied at the fluid-solid interface. Two different Reynolds numbers and three different volume fractions have been considered. The governing three-dimensional partial differential equations are elliptical in all directions and coupled. Predicted convective heat transfer coefficients, velocity, and temperature profiles, as well as secondary flow’s velocity vectors and temperature contours are compared at different axial positions. To validate the comparisons and verify the accuracy of the results, the numerical predictions are compared with corresponding experimental data. There are essentially no differences between the predictions of the two-phase models; however their results are significantly different from those of the single-phase approach. Two-phase model results are closer to the experimental data, but they show an unrealistic increase in heat transfer for small changes of the particle volume fraction. Hydrodynamically, the two-phase and single-phase approaches perform almost the same but their thermal predictions are quite different.

scholarly journals A numerical investigation of horizontal viscous gravity currents

2009 ◽  
Vol 630 ◽  
pp. 71-91 ◽  
Author(s):  
YANNICK HALLEZ ◽  
JACQUES MAGNAUDET
Keyword(s):  
Numerical Technique ◽  
Three Dimensional ◽  
Gravity Currents ◽  
Immiscible Fluids ◽  
Force Balance ◽  
Transition Time ◽  
Slip Boundary ◽  
Numerical Predictions ◽  
Front Position ◽  
Reservoir Solution

We study numerically the viscous phase of horizontal gravity currents of immiscible fluids in the lock-exchange configuration. A numerical technique capable of dealing with stiff density gradients is used, allowing us to mimic high-Schmidt-number situations similar to those encountered in most laboratory experiments. Plane two-dimensional computations with no-slip boundary conditions are run so as to compare numerical predictions with the ‘short reservoir’ solution of Huppert (J. Fluid Mech., vol. 121, 1982, pp. 43–58), which predicts the front position lf to evolve as t1/5, and the ‘long reservoir’ solution of Gratton & Minotti (J. Fluid Mech., vol. 210, 1990, pp. 155–182) which predicts a diffusive evolution of the distance travelled by the front xf ~ t1/2. In line with dimensional arguments, computations indicate that the self-similar power law governing the front position is selected by the flow Reynolds number and the initial volume of the released heavy fluid. We derive and validate a criterion predicting which type of viscous regime immediately succeeds the slumping phase. The computations also reveal that, under certain conditions, two different viscous regimes may appear successively during the life of a given current. Effects of sidewalls are examined through three-dimensional computations and are found to affect the transition time between the slumping phase and the viscous regime. In the various situations we consider, we make use of a force balance to estimate the transition time at which the viscous regime sets in and show that the corresponding prediction compares well with the computational results.

Hardness of Thin-Film Media: Scratch Experiments and Finite Element Simulations

1996 ◽  
Vol 118 (1) ◽  
pp. 1-11 ◽  
Author(s):  
E. R. Kral ◽  
K. Komvopoulos ◽  
D. B. Bogy
Keyword(s):  
Thin Film ◽  
Experimental Data ◽  
Finite Element ◽  
Surface Layer ◽  
Layered Medium ◽  
Three Dimensional ◽  
Finite Element Simulations ◽  
Force Balance ◽  
Balance Model ◽  
Elastic Plastic

Experiments and finite element simulations are presented pertaining to the effective hardness and the mechanics of indentation and sliding contact on elastic-plastic layered media. Hardness measurements obtained from scratch experiments are presented for thin-film rigid disks with 30 nm carbon overcoats. Reproducible results are obtained for residual scratch depths greater than approximately 8 nm. A simple force balance model is used to calculate the effective hardness of the layered medium. Hardness values for the surface layer are calculated by fitting a relationship between the hardness, scratch geometry, and layer thickness to the experimental data. The experimental results are compared with three-dimensional finite element simulations of a rigid spherical indenter sliding over a half-space with a stiffer and harder surface layer. The finite element results are used to verify the hardness model applied to the experimental data and to provide insight into the observed experimental behavior in the context of the associated elastic-plastic deformation characteristics of the layered medium.

Implementation of a Particle Resuspension Model in a CFD Code: Application to an Air Ingress Scenario in a Vacuum Toroidal Vessel

2020 ◽  
Author(s):  
Thomas Gelain ◽  
Laurent Ricciardi ◽  
François Gensdarmes
Keyword(s):  
Initial Pressure ◽  
Dust Particles ◽  
Vacuum Vessel ◽  
Particle Resuspension ◽  
Ansys Cfx ◽  
Constant Friction ◽  
Airborne Concentration ◽  
Airborne Contamination ◽  
Dust Resuspension ◽  
Air Ingress

Abstract During a loss of vacuum accident (LOVA), dust particles that will be present in the future tokamak ITER are likely to be resuspended, inducing a risk for explosion and airborne contamination. Evaluating the particle resuspension/deposition and resulting airborne concentration in case of a LOVA is therefore a major issue and it can be investigated by using a CFD code. To this end, this article presents the implementation of a resuspension model in a CFD code (ANSYS CFX) and its application to an air ingress in a vacuum toroidal vessel with a volume comparable to ITER one. In the first part of the article, the Rock’n Roll model and its operational version with the Biasi’s correlation is presented. The second part of the article will be devoted to the implementation of the Rock’n’Roll model in ANSYS CFX for constant friction velocities and its adaptation to non-constant friction velocities. Finally, the paper presents the simulations obtained on the particle resuspension for an air ingress scenario in a large vacuum vessel. This case is particularly interesting and non-intuitive because as the initial pressure is reduced, the particle behavior is different from that at atmospheric pressure. Further, a competition between airflow forces and gravitational force occurs, due to the low pressure environment, potentially restricting the resuspension, and the pressure influence also has to be taken into account in the particle transport and deposition (Nerisson, 2011). Three particle diameters were studied allowing to show the evolution of the resuspension with this parameter and to calculate dust resuspension rates and airborne fractions during the air ingress.

The Numerical Prediction of Developing Turbulent Flow in Rectangular Ducts

1981 ◽  
Vol 103 (3) ◽  
pp. 445-453 ◽  
Author(s):  
F. B. Gessner ◽  
A. F. Emery
Keyword(s):  
Experimental Data ◽  
Turbulent Flow ◽  
Three Dimensional ◽  
Computational Procedure ◽  
Momentum Equation ◽  
Scale Model ◽  
Length Scale ◽  
Basic Technique ◽  
Numerical Predictions ◽  
Iterative Procedures

Comparisons are made between experimental data and numerical predictions based on a three-dimensional length-scale model applicable to developing turbulent flow in rectangular ducts of arbitrary aspect ratio. The numerical method utilizes an explicit (Dufort-Frankel) differencing scheme for the axial momentum equation and involves no iterative procedures. Although the basic technique has been applied previously to another class of three-dimensional flows, it has not been applied until now to slender shear flows dominated by secondary flow of the second kind. The merits of the length-scale model and the computational procedure are assessed by means of comparisons with results referred to both k–ε and full Reynolds stress closure models which have been applied in recent years.

scholarly journals Finite Element Simulation of Multipass Welding: Full Three-Dimensional Versus Generalized Plane Strain or Axisymmetric Models

2005 ◽  
Vol 40 (6) ◽  
pp. 587-597 ◽  
Author(s):  
W Jiang ◽  
K Yahiaoui ◽  
F R Hall ◽  
T Laoui
Keyword(s):  
Experimental Data ◽  
Finite Element ◽  
Plane Strain ◽  
Three Dimensional ◽  
Welding Process ◽  
Fe Model ◽  
Multipass Welding ◽  
Numerical Predictions ◽  
Material Deposition ◽  
Generalized Plane Strain

A full three-dimensional (3D) thermo-mechanical finite element (FE) model has been developed to simulate the step-by-step multipass welding process. Non-linearities associated with welding, such as a moving heat source, material deposition, temperature-dependent material properties, latent heat, and large deformations, were taken into account. The model was applied to multipass butt-welded mild steel plate and girth butt-welded stainless steel pipe for validation. The simulation results were compared with independently obtained experimental data and numerical predictions from two-dimensional (2D) generalized plane strain and axisymmetric models. Good agreements between the 3D predictions and experimental data have been obtained. The computational model has the potential to be applied to multipass welded complex geometries for residual stress prediction.

scholarly journals The Impact of Swirls on Slurry Flows in Horizontal Pipelines

2021 ◽  
Vol 9 (11) ◽  
pp. 1201
Author(s):  
Hongbo Shi ◽  
Jianping Yuan ◽  
Yalin Li
Keyword(s):  
Swirling Flow ◽  
Three Dimensional ◽  
Internal Flow ◽  
Deep Ocean ◽  
Swirl Flow ◽  
Solid Particles ◽  
Ansys Fluent ◽  
Solid Mixture ◽  
Numerical Predictions ◽  
The Impact

In deep ocean transportation pipeline, the swirling internal flow has a significant impact on the marine minerals transportation efficiency and safety. Therefore, the present work investigates various swirl flow motions for the slurry transport characteristics of the multi-sized particulate flow in a horizontal pipeline. Since the internal flow is a liquid-solid-solid mixture, a steady-state three-dimensional Eulerian-Eulerian multiphase approach in conjunction with the k-ω SST turbulence model is implemented for numerical simulation in the commercial CFD software ANSYS FLUENT 17.0. Numerical predictions of the mixture solid concentration distributions are generally in good conformance with experimental measurements. It is clearly revealed the transition of flow regime from heterogeneous to pseudo-homogeneous with the increasing level of swirl intensity at inlet. Compared to non-swirling flow, the swirling flow is of benefit to the multi-sized solid suspension capacity and the transportation efficiency. Moreover, the intense swirling vortex results in a strong influence on the characteristics of the lubrication layer formed by fine solid particles near the bottom of the pipe. These results provide valuable insights regarding the influence of swirl flow on the transport process for deep ocean mining.

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