Refine your search:     
Report No.
 - 
Search Results: Records 1-6 displayed on this page of 6
  • 1

Presentation/Publication Type

Initialising ...

Refine

Journal/Book Title

Initialising ...

Meeting title

Initialising ...

First Author

Initialising ...

Keyword

Initialising ...

Language

Initialising ...

Publication Year

Initialising ...

Held year of conference

Initialising ...

Save select records

JAEA Reports

Study on convective mixing for thermal striping phenomena; Evaluation on Similarity of DNS for turbulence characteristics of mixing among jets

Kimura, Nobuyuki; Miyake, Yasuhiro*; Nagasawa, Kazuyoshi*; ; Kamide, Hideki; Hishida, Koichi

JNC TN9400 2001-132, 67 Pages, 2002/02

JNC-TN9400-2001-132.pdf:2.79MB

A quantitative evaluation on thermal striping, in which temperature fluctuation due to convective mixing causes high cycle thermal fatigue in structural components, is of importance for reactor safety. In this study, we carried out the velocity/temperature measurement using thermocouples and the particle image velocimetry in a water experiment, which had a parallel tripl-jet configuration, and a direct numerical simulation (DNS) was performed using DINUS-3 code and compared with the experimental result. As for the experimental condition, the discharged velocities of three jets were equally 0.5 m/s and the discharged temperature difference was 5$$^{circ}$$C. The time-averaged temperature/velocity fields obtained from the DNS calculation were in good agreements with the experimental results including the vortex structures between the jets. The DNS calculation overestimated the turbulent quantities in the experiment. The calculated profiles of the probability density function in the velocity fluctuating components, however, were in good agreements with those in the experiment. The predicted joint probability density function between the horizontal and vertical velocity fluctuating components was close to the experimental one. It was shown that the DNS calculation well simulated the convective mixing processes between the jets from the point of view of the turbulent quantities.

JAEA Reports

Applications of ultrasound technique to flow velocity measurement in water experiment of inter-wrapper flow; Comparison with particle image velocimetry

Kimura, Nobuyuki; ; ; ; Kamide, Hideki; Tokuhiro, Akira; Hishida, Koichi

JNC TN9400 2000-057, 60 Pages, 2000/05

JNC-TN9400-2000-057.pdf:2.11MB

ln experimental study for the thermohydraulics of fast reactor, a simple experiment with fine measurement has been desired for understanding of phenomena and for verification of computer code rather than mockup experiments of large scale. For such purposes quality of experimental data must be improved. ln the velocity measurement, instantaneous velocity profile will have great advances for the understanding of phenomena and for the verification of computer code. ln this report two methods of the velocity profile measurement are discussed; one is ultrasound Doppler velocimetry (UDV) and the other is particle image velocimetry (PIV). These methods were applied to water experiments. The UDV was applied to pipe flow, planer jet, and the inter-wrapper flow which is seen in the gap region between subassemblies of fast reactor core. Cross check with laser Doppler velocimetly showed proper measurement of the UDV. Problems including the application to sodium experiments are also discussed. The PIV was also applied to the inter-wrapper flow. For the application to complex flow geometry, noise reduction method was developed to improve the measurement accuracy.

JAEA Reports

Development of flow velocity measurement techniques in visible images; Improvement of particle image velocimetry techniques on image process

Kimura, Nobuyuki; Miyake, Yasuhiro*; ; Kamide, Hideki; Hishida, Koichi

JNC TN9400 99-078, 44 Pages, 1999/10

JNC-TN9400-99-078.pdf:1.91MB

Noise reduction system was developed to improve applicability of Particle Image Velocimetly (PIV) to complicated configure bounded flows. For fast reactor safety and thermal hydraulic studies, experiments are performed in scale models which usually have rather complicated geometry and structures such as fuel subassemblies, heat exchangers, etc. The structures and stuck dusts on the view window of the models obscure the particle image. Thus the image cxcept the moving particles can be regarded as a noise. In the present study, two noise reduction techniques are proposed. The one is the Time-averaged Light Intensity Subtraction method (TIS) which subtracts the the-averaged light intensity of each pixel in the sequential images from the each corresponding pixel. The other one is the Minimum Light Intensity Subtraction method (MIS) which subtracts the minimum light intensity of each pixel in the sequential images from the each corresponding pixel. Both methods are examined on their capabilities of noise reduction. As for the original "bench mark" image, the image made from Large Eddy Simulation was used. To the bench mark image, noises are added which are referred as sample images, Both methods reduce the rate of vector with the error of more than one pixel from 90% to less than 5%. Also, more than 50% of the vectors have the error of less than 0.2 pixel. The analysis of uncertainty shows that these methods enhances the accuracy of vector measurement 3$$sim$$12 times if the image with noise were processed, and the TIS method has 1.1 $$sim$$ 2.1 times accuracy compared to the TIS. Thus the present noise reduction methods are quite efficient to enhance the accuracy of flow velocity fields measured with particle images including structures and deposits on the view window.

JAEA Reports

Flow visualization on a natural circulation inter-wrapper row; Experimental and numerical results under a geometric condition of button type spacer pads

Yasuda, Akihiro; ; Hayashi, Kenji; ; Kamide, Hideki; Hishida, Koichi

JNC TN9400 99-072, 70 Pages, 1999/04

JNC-TN9400-99-072.pdf:7.29MB

Investigations on the inter-wrapper flow (IWF) in a liquid metal cooled fast breeder reactor core have been carried out. The IWF is a natural circulation flow between wrapper tubes in the core barrel where cold fluid is coming from a direct heat exchanger (DHX) in the upper plenum. It was shown by the sodium experiment using 7-subassembly core model that the IWF can cool the subassemblies. To clarify thermal-hydraulic characteristics of the IWF in the core, the water experiment was performed using the flow visualization technique. The test rig for IWF (TRIF) has the core simulating the fuel subassemblies and radial reflectors. The subassemblies are constructed featuring transparent heater to enable both Joule heating and flow visualization. The transparent heater was made of glass with thin conductor film coating of tin oxide, and the glass heater was embedded on the wall of modeled wrapper tube made of acrylic plexiglass. In the present experiment, influences of peripheral geometric parameters such as flow holes of core formers on the thermal-hydraulic field were investigated with the button type spacer pads of the wrapper tube. Through the water tests, flow patterns of the IWF were revealed and velocity fields were quantitatively measured with a particle image velocimetry (PIV). Also, no substantial influence of peripheral geometry was found on the temperature field of the IWF, as far as the button type spacer pad was applied. Numerical simulation was applied to the experimental analysis of IWF by using multi-dimensional code with porous body model. The numerical results reproduced the flow patterns within TRIF and agreed well to experimental temperature distributions, showing capability of predicting IWF with porous body model.

JAEA Reports

Implementation of a Particle Image Velocimetry (PIV) system; An example application of PIV to wake-flows behind objects

Tokuhiro, Akira; Hishida, Koichi; Oki, Yoshihisa

PNC TN9410 96-275, 59 Pages, 1996/10

PNC-TN9410-96-275.pdf:1.66MB

Particle Image Velocimetry (PIV) describes a velocity measurement technique for gas and liquid flows whereby, as the name implies, movement of tracer particles in motion with the flow are recorded as images. The particles are framr-to-frame "tracked by one of several correlation techniques from which a 2D vector field can be generated. A 3D vector field is also possible. The measurement method takes advantage of current computer, CCD camera and laser light technologies for its image processing needs. A laser light sheet is typically used to illuminate the tracer particles in the flow field of interest and when implemented accentuates the constrast between the particle and the transparent medium. One can also apply Laser Induced Fluorescence (LIF) in order to further distinguish the tracer particles, the transparent, continuous medium and any light reflecting surfaces in the flow field such as the interface of a gas bubble rising in a liquid. It is also possible to deduce the temperature field from LIF images. In the present work an introduction to PIV is given by way of an example. The selected flow configuration is that of wake-flow behind a bubble and its solid equivalent. By solid equivalent we mean a solid model with approximately the equivalent bubble breadth and volume. This two-component, two-phase flow aptly demonstrates the applicability of PIV to spatio-temporal flows. Use was additionally made of an Infrared Shadow Technique (IST) in order to capture the unlit image (shadow) of the bubble or solid within the flow field. By triggering both the laser and infrared light sources with the CCD camera, the shape of the object as well as the flow field was simultaneously recorded. Besides the 2D vector field, calculations of the vorticity, Reynolds stress and turbulent kinetic energy ($$tke$$) distributions were made. The results indicate that for counter-current flow (U$$_{avg}$$sim$0.245 m/s) of water in a square channel (100 mm) with a single air bubble of ...

Journal Articles

None

Tokuhiro, Akira; Hishida, Koichi; *

CD-LOM ISB, , 

None

6 (Records 1-6 displayed on this page)
  • 1