Experimental and Numerical Study of Airflow Dynamics Through an Opening in a Depressurized Enclosure: Application to Nuclear Decommissioning

2017 ◽  
Author(s):  
Salima Kaissoun ◽  
Eric Climent ◽  
Corinne Prevost ◽  
Laurent Ricciardi
Keyword(s):  
Numerical Study ◽  
Turbulent Jet ◽  
Numerical Investigations ◽  
Directional Flow ◽  
Nuclear Decommissioning ◽  
Flow Visualizations

In order to understand airflow dynamics through small openings encountered in containment enclosures used for nuclear decommissioning operations, the results of experimental and numerical investigations are analyzed. The main purposes of this work are to identify the required conditions likely to generate flow inversions at the studied opening which lead to pollutant leakage outside depressurized enclosures, and also to verify the ability of CFD1 simulations to predict these flow inversions by using U-RANS2 and LES3 approaches. All along this work, we tried to reproduce the conditions of leakage occurring at the opening in terms of aerodynamics and openings geometries. Laser flow visualizations and CFD results show that an additional flow, such as a turbulent jet in competition with the directional flow and a disturbed level of pressure inside the enclosure are among the main causes leading to the leakage through the opening.

Experimental and Numerical Study of Mixing in a Hot-Water Storage Tank

2009 ◽  
Vol 131 (1) ◽  
Author(s):  
A. Aviv ◽  
Y. Blyakhman ◽  
O. Beeri ◽  
G. Ziskind ◽  
R. Letan
Keyword(s):  
Numerical Model ◽  
Storage Tank ◽  
Numerical Study ◽  
Tap Water ◽  
Three Dimensional ◽  
Hot Water ◽  
Software Validation ◽  
Water Storage Tank ◽  
Thermal Mixing ◽  
Numerical Investigations

Thermal mixing and stratification are explored numerically and experimentally in a cylindrical tank, which simulates a storage of water heated by a solar collector. The tank is 70cm in height and 24cm in diameter. The inlet and outlet are vertical and located off the centerline of the tank. The study is conducted in a transient mode, namely, the tank is filled with hot water, and as the hot water is being withdrawn, the tap water replaces it in a stratified way or by mixing. The flowrates of 2l∕min, 3l∕min, 5l∕min and 7l∕min, which correspond to superficial velocities of 4.35cm∕min, 6.52cm∕min, 10.87cm∕min, and 15.2cm∕min, are explored. Temperature of hot water ranges within 40–50°C, while the tap water is about 25–27°C. Installation of one and two horizontal baffles above the inlet is examined. Simultaneous experimental and numerical investigations are performed. In the experiment, both flow visualization and temperature measurements are used. Three-dimensional transient numerical simulations are done using the FLUENT 6 software. Validation of the numerical model is achieved by comparison with the experimental results. Then, the numerical model is applied to a study of various possible changes in the system. The results show that at low flowrates, up to a superficial velocity of about 11cm∕min through the tank, the baffles have no effect on tap water mixing with the stored hot water. At higher flowrates, a single horizontal baffle prevents the mixing and preserves the desired stratified temperature distribution in the storage tank.

Numerical study of an axisymmetric turbulent jet-impingement flow

1993 ◽  
Author(s):  
YEU-PIN YEH ◽  
F. CHEUNG ◽  
KENNETH KUO ◽  
THOMAS LITZINGER
Keyword(s):  
Numerical Study ◽  
Jet Impingement ◽  
Turbulent Jet

scholarly journals Numerical study of nanoparticle formation in a free turbulent jet

2016 ◽  
Vol 158 ◽  
pp. 012039
Author(s):  
A K Gilfanov ◽  
W Koch ◽  
S K Zaripov ◽  
O D Rybdylova
Keyword(s):  
Numerical Study ◽  
Turbulent Jet ◽  
Nanoparticle Formation

CFD ANALYSIS OF FLOW THROUGH HORIZONTAL CEILING OPENING DUE TO BUOYANCY AND PRESSURE DIFFERENCE

2013 ◽  
Vol 25 (01) ◽  
pp. 1340022 ◽  
Author(s):  
B. GERA ◽  
P. K. SHARMA ◽  
R. K. SINGH
Keyword(s):  
Critical Pressure ◽  
Numerical Study ◽  
Salt Water ◽  
Density Difference ◽  
Exchange Flow ◽  
Navier Stokes Equation ◽  
Directional Flow ◽  
Flow Through ◽  
Horizontal Vent ◽  
Lower Compartment

The buoyancy driven exchange flow through the large openings in horizontal partitions occurs in many practical situations such as in enclosed regions with a ceiling opening and a heat source such as fire. The density difference between two compartments arises partly due to difference in composition and partly from the difference in temperature. A heavier fluid located on the top of a lighter fluid and separated by a horizontal vent constitutes a gravitationally unstable system. Horizontal vents produce flow, which are unstable with irregular oscillatory behavior. However, when lower compartment is slightly pressurized the flow becomes stable and unidirectional. A numerical study has been performed to characterize the bi-directional flow and transition to unidirectional flow through a horizontal vent in an enclosure, due to differences in pressure and density across the vent. Fresh and salt water has been considered as working fluids to create density difference across the vent with a pressure field imposed in the lower compartment. The pressure in the lower region was increased to find the critical pressure corresponding to transition to unidirectional from bi-directional flow. Unsteady, 2D axisymmetric, incompressible Navier–Stokes equation along with species, turbulence and continuity equation have been solved with finite volume method using the in-house computational fluid dynamics (CFD) code. Several cases were examined to compute the critical pressure for various density differences for low opening aspect ratio. The code has been validated with reported experiments and used to simulate various other practical cases occurred during fire induced flow through such openings.

Experimental and Numerical Investigations of Thermal Ignition of a Phase Changing Energetic Material

2016 ◽  
Vol 66 (3) ◽  
pp. 228
Author(s):  
Priyanka Shukla ◽  
M. Deepu
Keyword(s):  
Energetic Materials ◽  
Numerical Study ◽  
Energetic Material ◽  
Transient Heat Conduction ◽  
Thermal Ignition ◽  
Explosive Material ◽  
Field Function ◽  
Precise Control ◽  
Numerical Investigations ◽  
Commercial Solver

Fortuitous exposure to high temperatures initiates reaction in energetic materials and possibilities of such event are of great concern in terms of the safe and controlled usage of explosive devices. Experimental and numerical investigations on time to explosion and location of ignition of a phase changing polymer bonded explosive material (80 per cent RDX and 20 per cent binder), contained in a metallic confinement subjected to controlled temperature build-up on its surface, are presented. An experimental setup was developed in which the polymer bonded explosive material filled in a cylindrical confinement was provided with a precise control of surface heating rate. Temperature at various radial locations was monitored till ignition. A computational model for solving two dimensional unsteady heat transfer with phase change and heat generation due to multi-step chemical reaction was developed. This model was implemented using a custom field function in the framework of a finite volume method based standard commercial solver. Numerical study could simulate the transient heat conduction, the melting pattern of the explosive within the charge and also the thermal runaway. Computed values of temperature evolution at various radial locations and the time to ignition were closely agreeing with those measured in experiment. Results are helpful both in predicting the possibility of thermal ignition during accidents as well as for the design of safety systems.

Sign in / Sign up

Export Citation Format

Share Document