Fluid Flow Separation in Down Comer During a Safety Injection Scenario: Quantitative Experimental Results

Volume 4 ◽  
2004 ◽  
Author(s):  
Th. Bichet ◽  
A. Martin ◽  
F. Beaud
Keyword(s):  
Fluid Flow ◽  
Experimental Model ◽  
Flow Separation ◽  
Cold Water ◽  
Numerical Study ◽  
Salt Water ◽  
Numerical Results ◽  
Experimental Results ◽  
Flow Density ◽  
Physical Phenomena

Within the framework of the nuclear power plant lifetime issue, the assessment of the French 900 MWe (3-loops) series Reactor Pressure Vessel (RPV) integrity was performed. A simplified analysis has shown that one of the most severe loading condition is given by the small break loss of coolant accidents (SBLOCA) due to the pressurized injection of cold water (9°C) into the cold leg and down comer of the RPV. Two main physical phenomena, considered important for the RPV cooling transient, were identified during numerical application obtained with EDF CFD tools. These phenomena are the fluid flow separation and the plume oscillations in the down comer. In order to consolidate these numerical results with the EDF home code, called Code_Saturne, an experimental study has been carried out with the new EDF R&D facility. This transparent experimental model is based on the representation at 1/2 scale of a cold leg and a third of down comer including a thermal shield. The experiments were realized by injecting of salt water flow (density effects) in the cold leg according to a similitude study based on Froude number conservation between experiments and reactor scenarios. Firstly, this paper presents the main qualitative experimental results, based essentially on visualizations of different injections of dyed salt water in the cold leg and in the down comer. The physical phenomena observed showed a qualitative good agreement between visualizations and numerical results. Secondly, this paper presents the first experimental results of the assessment of the fluid flow separation in the experimental model obtained with temperature probes inserted in the down comer. We showed, in the experiments analysis, the fluid flow separation and the jet oscillations were detected. The next step will consist to compare these quantitative experiments with numerical study which will be carry out with Code_Saturne.

scholarly journals Numerical Study on Deformation and Interior Flow of a Droplet Suspended in Viscous Liquid under Steady Electric Fields

2014 ◽  
Vol 6 ◽  
pp. 532797 ◽  
Author(s):  
Zhentao Wang ◽  
Qingming Dong ◽  
Yonghui Zhang ◽  
Junfeng Wang ◽  
Jianlong Wen
Keyword(s):  
Electric Fields ◽  
Numerical Study ◽  
Internal Flow ◽  
High Viscosity ◽  
Numerical Results ◽  
Experimental Results ◽  
Fluid Viscosity ◽  
Single Droplet ◽  
Deformation Velocity ◽  
Interior Flow

A model based on the volume of fluid (VOF) method and leaky dielectric theory is established to predict the deformation and internal flow of the droplet suspended in another vicious fluid under the influence of the electric field. Through coupling with hydrodynamics and electrostatics, the rate of deformation and internal flow of the single droplet are simulated and obtained under the different operating parameters. The calculated results show that the direction of deformation and internal flow depends on the physical properties of fluids. The numerical results are compared with Taylor's theory and experimental results by Torza et al. When the rate of deformation is small, the numerical results are consistent with theory and experimental results, and when the rate is large the numerical results are consistent with experimental results but are different from Taylor's theory. In addition, fluid viscosity hardly affects the deformation rate and mainly dominates the deformation velocity. For high viscosity droplet spends more time to attain the steady state. The conductivity ratio and permittivity ratio of two different liquids affect the direction of deformation. When fluid electric properties change, the charge distribution at the interface is various, which leads to the droplet different deformation shapes.

Experimental and numerical study on water-lubricated rubber bearings

2014 ◽  
Vol 66 (2) ◽  
pp. 282-288 ◽  
Author(s):  
You-Qiang Wang ◽  
Xiu-Jiang Shi ◽  
Li-Jing Zhang
Keyword(s):  
Friction Coefficient ◽  
Numerical Study ◽  
Hydrodynamic Lubrication ◽  
Load Capacity ◽  
Numerical Results ◽  
Experimental Results ◽  
Content Type ◽  
Tribological Behaviors ◽  
Rubber Bearing ◽  
Rubber Bearings

Purpose – Water-lubricated rubber bearing is one of the most appropriate bearings for underwater use. The most popular design used widely today is the straight fluted rubber bearing. The special configuration leads to partial hydrodynamic lubrication and low load capacity. A new bearing bush structure with two cavities which is favorable for constructing continuous hydrodynamic lubrication was designed and studied. The paper aims to discuss these issues. Design/methodology/approach – A new bearing bush structure with two cavities which is favorable for constructing continuous hydrodynamic lubrication was designed. The apparatus for studying the tribological behaviors of the two types of water-lubricated rubber bearings has been devised and established in the paper. The experimental studies on the tribological properties of the rubber bearings have been conducted under different loads and velocities. The eccentricity ratio of the new structure rubber bearing with two cavities was measured in experiment and the load capacity was calculated by numerical simulation. Findings – The experimental results show that the friction coefficient decreases with increasing velocity; the friction coefficient increases sharply with the rising temperature, the friction coefficient increases at first and then decreases with increasing load for fluted rubber bearings. The numerical results were in good agreement with the experimental results. The numerical results show that complete hydrodynamic lubrication can be formed in the new designed rubber bearing with two cavities. The experimental and numerical results all indicate that there is an appropriate bearing clearance which the friction coefficient is minimum and the load capacity is maximum. Originality/value – A new bearing bush structure with two cavities which is beneficial to constructing continuous hydrodynamic lubrication film was designed. A new apparatus for studying the tribological behaviors of the two types of water-lubricated rubber bearings has been devised and established. Experimental and numerical study on the new structure rubber bearing were conducted in the paper.

Numerical and Qualitative Analysis of a Single Particle Behavior in a Shear Driven Flow in Equilateral Triangular Cavity

2013 ◽  
Vol 465-466 ◽  
pp. 557-561
Author(s):  
Muhammad Ammar Nik Mutasim ◽  
Nasir Ali ◽  
M.S. Idris ◽  
Ahmed N. Oumer
Keyword(s):  
Fluid Flow ◽  
Numerical Study ◽  
Flow Speed ◽  
Numerical Results ◽  
Driven Cavity ◽  
The Past ◽  
Particle Flows ◽  
Equivalent Time ◽  
Surrounding Fluid ◽  
Good Agreement

Intesive research works have been done on solid particle flows for the past decades. However, prediction of accurate relationship between the particle and the surrounding fluid is still challenging. This study focuses on the experimental and numerical study of behavior of a particle flow in a lid-driven cavity of equilateral triangular shape. Numerical analysis was done using Finite Difference Method (FDM) with stream function vorticity approach. The center location of the fluid flow was treated assumed to be the particle motion. To check the validaty of the numerical results, experiment was done. The particle and fluid used for the experiment were water and silk, respectively. The particle is considered to be slightly buoyant towards water. In the experiment the fluid flow was based on horizontal translating motion where the particle was initially at rest at the bottom wall of the cavity. The fluid flow speed is set to laminar flow with Reynolds Number, Re = 0 to 1000. It was found that the silk particle moved to the preferential path of the primary vortex at equivalent time of 13 seconds. Generally, the experimetal and numerical results for the streamlines were in good agreement.

Numerical Study on Performance of Surface Piercing Propeller using RANS Approach

2015 ◽  
Author(s):  
Kohei Himei ◽  
Hajime Yamaguchi
Keyword(s):  
Standardized Test ◽  
Numerical Study ◽  
High Reliability ◽  
Experimental Studies ◽  
Performance Estimation ◽  
Experimental Results ◽  
Ventilated Cavitation ◽  
Wide Range ◽  
Physical Phenomena ◽  
Surface Piercing Propeller

Surface Piercing Propeller (SPP) can achieve high propulsive efficiency on high-speed vessels planing to reduce the frictional resistance of hull. It has the characteristic blade section and works partially submerged condition. The blades repeat entry to and exit from the water free surface and the suction sides and trailing edge of blades are exposed to ventilated cavitation while they are under the water. And interface near SPP is severely deformed by the high rotating blades. This working condition of SPP, therefore, makes it hard that propeller open characteristics are estimated with high reliability. Because SPP is unusual propeller having above difficulty of the performance estimation, the studies for SPP are few compared with large sized propellers for merchant ships. Although the various model tests had been carried out to understand the physical phenomena around various SPPs and their effects on propeller performances, they were not universal approach with standardized test conditions and propeller shape, as mentioned in 23th ITTC report and recommendation (2002). In applying the conventional calculation based on potential theory to SPP, there are many difficulties to model the physical phenomena theoretically. In calculations by Furuya (1984, 1985), thickness of blade and ventilated cavitation were non-consideration, and it was assumed that the suction side of the blade was fully ventilated in the water. In calculations by Young and Kinnas (2001), the interface deformation near SPP was not modeled theoretically. Therefore, they attributed the difference from experimental results to the effect of incompleteness of numerical modeling. On the other hand, CFD analysis can treat the effects of physical phenomena including thick ventilated cavitation and the sharp deformation of interface around SPP. In addition, the characteristic blade shape is modeled accurately without the geometric limitation in CFD. In this paper, typical SPP with experimental results open to the public is analyzed by CFD-RANS approach using Volume of Fluid (VOF) method based on interface-capturing algorithm at wide range of propeller advance coefficient J. Regarding propeller open characteristics, the 6-component force/moment fluctuations by blade rotations, and ventilation patterns, analyses results are compared with measured values. Moreover, the results of simulations in various Froude numbers and Weber numbers are evaluated whether their effects were negligible when they are sufficiently high, in the same manner as the results found by the other’s experimental studies (Shiba, 1953; Brandt, 1973).

A Parametric Numerical Study of Fluid Flow and Heat Transfer in a Computer Chassis

2015 ◽  
Vol 9 (3) ◽  
pp. 242 ◽  
Author(s):  
Efstathios Kaloudis ◽  
Dimitris Siachos ◽  
Konstantinos Stefanos Nikas
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Numerical Study ◽  
Flow And Heat Transfer

Using Ansys for Design and Numerical Study of a Specific Fixed Wing UAV

2018 ◽  
Vol 55 (4) ◽  
pp. 652-657 ◽  
Author(s):  
Gabriel Murariu ◽  
Razvan Adrian Mahu ◽  
Adrian Gabriel Murariu ◽  
Mihai Daniel Dragu ◽  
Lucian P. Georgescu ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Unmanned Aerial Vehicle ◽  
Numerical Study ◽  
Flight Time ◽  
Cluster System ◽  
Numerical Results ◽  
Operational Performance ◽  
Gliding Flight ◽  
Aerial Vehicle ◽  
Constant Altitude

This article presents the design of a specific unmanned aerial vehicle UAV prototype own building. Our UAV is a flying wing type and is able to take off with a little boost. This system happily combines some major advantages taken from planes namely the ability to fly horizontal, at a constant altitude and of course, the great advantage of a long flight-time. The aerodynamic models presented in this paper are optimized to improve the operational performance of this aerial vehicle, especially in terms of stability and the possibility of a long gliding flight-time. Both aspects are very important for the increasing of the goals� efficiency and for the getting work jobs. The presented simulations were obtained using ANSYS 13 installed on our university� cluster system. In a next step the numerical results will be compared with those during experimental flights. This paper presents the main results obtained from numerical simulations and the obtained magnitudes of the main flight coefficients.

Non-Newtonian Casson pulsatile fluid flow influenced by Lorentz force in a porous channel with multiple constrictions: A numerical study

2021 ◽  
Vol 33 (1) ◽  
pp. 79-90 ◽  
Author(s):  
Amjad Ali ◽  
Attia Fatima ◽  
Zainab Bukhari ◽  
Hamayun Farooq ◽  
Zaheer Abbas
Keyword(s):  
Fluid Flow ◽  
Lorentz Force ◽  
Numerical Study ◽  
Porous Channel
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