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.

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.

scholarly journals STARDUST experimental campaign and numerical simulations: influence of obstacles and temperature on dust resuspension in a vacuum vessel under LOVA

2011 ◽  
Vol 51 (5) ◽  
pp. 053017 ◽  
Author(s):  
C. Bellecci ◽  
P. Gaudio ◽  
I. Lupelli ◽  
A. Malizia ◽  
M.T. Porfiri ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Vacuum Vessel ◽  
Experimental Campaign ◽  
Dust Resuspension

CFD Modelling of Loss of Vacuum Accident (LOVA) for CFETR

2018 ◽  
Author(s):  
Youyou Xu ◽  
Songlin Liu ◽  
Xiaoman Cheng ◽  
Xuebin Ma
Keyword(s):  
High Speed ◽  
Reverse Flow ◽  
Fluid Dynamic ◽  
Fusion Energy ◽  
Normal Operation ◽  
Vacuum Vessel ◽  
Cfd Modelling ◽  
Ansys Cfx ◽  
Section Area ◽  
Break Area

Chinese Fusion Engineering Testing Reactor (CFETR) is a tokamak-type machine and next device in the roadmap for the realization of fusion energy in China, which aims to bridge the gaps between the International Thermonuclear Experimental Reactor (ITER) and the demonstration reactor (DEMO) [1]. The accident sequence starting from loss of vacuum accident (LOVA) is an important issue concerning the performance of CFETR. During LOVA, air will leak into the vacuum vessel (VV) causing fast pressurization of VV. At the same time, the high speed airflow jet will result in migration and re-suspension of the large quantity of tungsten dust produced and deposited in the lower part of plasma chamber, causing possibilities of radioactive dust leakage into the workshop and environment. In order to conduct a comprehensive analysis of the accident sequence, firstly, the airflow characteristics of LOVA should be studied. In this article, a postulated rupture of different section area is assumed due to a failed component at the equatorial port level. The computational fluid dynamic (CFD) modelling of LOVA was conducted by ANSYS CFX. The results show that the break area has significant influences on the characteristics of the airflow. Two swirling airflows are formed in the upper and lower part of the torus. The airflow characteristics are quite different when the LOVA happens during maintenance or during normal operation. A reverse flow occurs when the LOVA happens during normal operation. Yet can not be observed when LOVA occurs during maintenance. The results are the basis to the further safety study of CFETR such as the re-suspension, migration and explosion of dust.

Investigation of Air Ingress Into a Vacuum Vessel Related to Particle Re-Suspension and Distribution for Dust Issues in ITER

2017 ◽  
Author(s):  
Emmanuel Porcheron ◽  
Pascal Lemaitre
Keyword(s):  
Large Scale ◽  
Low Pressure ◽  
Normal Operation ◽  
Vacuum Vessel ◽  
Physical Processes ◽  
Time Resolved ◽  
Loss Of Coolant Accident ◽  
Image Velocimetry ◽  
Loss Of Coolant ◽  
Air Ingress

During normal operation of the ITER tokamak, few hundred kilograms of dust containing beryllium (Be) and tungsten (W) will be produced due to the erosion of the walls of the vacuum chamber by the plasma. During a loss of coolant accident (LOCA) or a loss of vacuum accident by air ingress (LOVA), hydrogen could be produced by dust oxidation with steam. Evaluation of the risk of dust and hydrogen explosion, that may lead to a loss of containment, requires studying the physical processes involved in the dust re-suspension and its distribution in the tokamak chamber. This experimental study is conducted by the Institut de Radioprotection et de Sûreté Nucléaire (IRSN) to simulate dust re-suspension phenomena induced by high velocity jet under low pressure conditions. Tests are conducted in a large scale facility (TOSQAN, 7 m3) able to reproduce primary vacuum conditions (1 mbar). Optical diagnostics such as PIV technique (Particles Image Velocimetry) are implemented on the facility to provide time resolved measurements of the dust re-suspension in terms of phenomenology and velocity. We present in this paper the TOSQAN facility with its configuration for studying dust re-suspension under low pressure conditions and underway experiments showing the mechanism of dust re-suspension by sonic and supersonic flows.

scholarly journals Safety Analysis in Large Volume Vacuum Systems Like Tokamak: Experiments and Numerical Simulation to Analyze Vacuum Ruptures Consequences

2014 ◽  
Vol 2014 ◽  
pp. 1-29 ◽  
Author(s):  
A. Malizia ◽  
I. Lupelli ◽  
M. Richetta ◽  
M. Gelfusa ◽  
C. Bellecci ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Numerical Model ◽  
Large Volume ◽  
Safety Issue ◽  
Numerical Code ◽  
Vacuum Vessel ◽  
Experimental Facility ◽  
Industrial Operations ◽  
Dust Resuspension ◽  
Vacuum Systems

The large volume vacuum systems are used in many industrial operations and research laboratories. Accidents in these systems should have a relevant economical and safety impact. A loss of vacuum accident (LOVA) due to a failure of the main vacuum vessel can result in a fast pressurization of the vessel and consequent mobilization dispersion of hazardous internal material through the braches. It is clear that the influence of flow fields, consequence of accidents like LOVA, on dust resuspension is a key safety issue. In order to develop this analysis an experimental facility is been developed: STARDUST. This last facility has been used to improve the knowledge about LOVA to replicate a condition more similar to appropriate operative condition like to kamaks. By the experimental data the boundary conditions have been extrapolated to give the proper input for the 2D thermofluid-dynamics numerical simulations, developed by the commercial CFD numerical code. The benchmark of numerical simulation results with the experimental ones has been used to validate and tune the 2D thermofluid-dynamics numerical model that has been developed by the authors to replicate the LOVA conditions inside STARDUST. In present work, the facility, materials, numerical model, and relevant results will be presented.

Effect of Air Flow on Dust Particles Resuspension From Common Flooring

2010 ◽  
Author(s):  
Iman Goldasteh ◽  
Goodarz Ahmadi ◽  
Andrea Ferro
Keyword(s):  
Dust Particle ◽  
Indoor Air ◽  
High Speed ◽  
Indoor Air Pollution ◽  
Dust Particles ◽  
Particle Detachment ◽  
Particle Resuspension ◽  
Wind Tunnel Study ◽  
Wide Size Distribution

Particle resuspension from flooring in connection with increased indoor air pollution was studied. Earlier efforts hypothesized that during the gait cycle, high speed airflow is generated at the floor level that would lead to particle resuspension. The details of the mechanism of the particle resuspension, however, are not well understood. Earlier models were mainly developed for spherical particle detachment from smooth surfaces, but in reality, dust particles are irregular in shape and have a wide size distribution. The resuspension of dust particles thus depends on their shape and size and the nature of their contact with the surface. In this work, a wind tunnel study of dust particle resuspension from common flooring was performed and the critical air velocities for particle detachment were measured. The main goal of the present experimental work is to understand the main mechanism of dust particle resuspension under real conditions by systematically investigating a range of airflow speeds. The other goal of the study is to provide information on the role of the airflow on dust particle detachment from common floorings.

An Experimental Investigation of the Flowfield and Dust Resuspension Due to Idealized Human Walking

2009 ◽  
Vol 131 (8) ◽  
Author(s):  
Yoshihiro Kubota ◽  
Joseph W. Hall ◽  
Hiroshi Higuchi
Keyword(s):  
Flow Visualization ◽  
Large Scale ◽  
Outer Edge ◽  
Human Walking ◽  
Ring Vortex ◽  
Particle Resuspension ◽  
Human Foot ◽  
Image Velocimetry ◽  
Walking Motion ◽  
Dust Resuspension

In order to address how human foot movement causes particles to be resuspended from the floor, particle flow visualization and particle image velocimetry (PIV) measurements were performed on a simplified model of the human walking motion; a disk moving normal to the floor. Flow visualization of particles, seeded initially on the ground, indicates that particles are resuspended by both the downward and upward motions of the walking process. On both the upstep and the downstep, particle resuspension occurs due to a high velocity wall jet, forming between the wall and the disk in general accord with the mechanism for particle resuspension put forth by Khalifa and Elhadidi (2007, “Particle Levitation Due to a Uniformly Descending Flat Object,” Aerosol Sci. Technol., 41, pp. 33–42). Large-scale ring vortex structures were formed on both the downstep and the upstep, and did not cause particle resuspension, but were extremely effective at quickly moving the already resuspended particles away from the wall. By varying the seeding of the particles, it was determined that only particles underneath and toward the outer edge of the disk are resuspended.

An Experimental Investigation of the Flowfield and Dust Resuspension Due to Idealized Human Walking: Disk Model

2007 ◽  
Author(s):  
Yoshihiro Kubota ◽  
Joseph W. Hall ◽  
Hiroshi Higuchi
Keyword(s):  
Experimental Investigation ◽  
Flow Visualization ◽  
Large Scale ◽  
Human Movement ◽  
Human Walking ◽  
Wall Jet ◽  
Disk Model ◽  
Piv Measurements ◽  
Particle Resuspension ◽  
Dust Resuspension

To better understand how human movement causes particles to be resuspended from the ground, we performed flow visualization and PIV measurements on idealized human walking, a disk moved normal to the ground. The flow visualization indicates that particles are resuspended on both the down step and the up step of the walking process by a purely aerodynamic mechanism. The results suggest that a wall jet formed beneath the disk is responsible for particle resuspension, whereas large scale vortices created in the wake of the disk are responsible for the rapid redistribution of the resuspended particles.

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