Journal of the Japanese Society for Experimental Mechanics, 2013
Variation of Velocity Profile around an Automotive Brake Disc arising from Ventilation Duct Kazuh... more Variation of Velocity Profile around an Automotive Brake Disc arising from Ventilation Duct Kazuhiro ITOH, Hiroshige KUMAMARU and Yuji SHIMOGONYA Flow through an air passage of ventilated automotive brake rotor affects the thermal energy dissipation from rotor into atmosphere. In the present work, a velocity profile around a ventilated brake disc was measured using a hot-wire anemometer in order to understand the statistical turbulent property of air passage flow. Three-dimensional velocity components were evaluated at 5 mm outside the disc edge by rotating X-type hot-wire probe. The probe was also tilted corresponding to rotational speed so that it could receive the maximum velocity from disc. The maximum value of both average and fluctuation velocity increased significantly than that of solid disc. The velocity fluctuation profile indicated asymmetric aspect in contrast to the average velocity profile. An empirical one-dimensional model was suggested for evaluation of flow through...
Free surface fluctuations on a high-speed water jet were measured by a laser beam refraction tech... more Free surface fluctuations on a high-speed water jet were measured by a laser beam refraction technique. This method can be used to obtain quantitative time-series data on local surface fluctuations. The developed system employs two pulsed laser diodes, and it uses a high-speed optical sensor to detect the instantaneous positions of the laser beams that are refracted at the free surface. Fluctuations in the slope angle are measured at two locations separated by 1.27 mm. The wave speed of each free surface wave, which is determined by the zero-upcrossing method, is experimentally evaluated by the cross-correlation method. A two-dimensional waveform is obtained by integrating the slope angle data. The local mean wavelength and mean wave steepness are evaluated for average jet velocities up to m/s. Streamwise waveforms of the high-speed water jet at several locations exhibit appreciable asymmetry and have steep profiles.
For the safety design of a Sodium-cooled Fast Reactor, it is strongly required that the molten ma... more For the safety design of a Sodium-cooled Fast Reactor, it is strongly required that the molten material which is released from a core region has to be solidified and cooled down in a reactor vessel by breaking up in the sodium coolant during a Core Disruptive Accident in terms of Post Accident Heat Removal. In this paper, in order to investigate the effects of the surface solidification on the jet breakup, the experimental results using a low melting point alloy and water are reported. The jet breakup behavior is observed with a high speed video camera, the front position of the jet and the jet breakup length are estimated with the visual observation results. In the high injection velocity conditions, it is found that the jet breakup is dominated by fragmentation induced by the surface instability due to the relative velocity even in the surface solidification condition. In addition, it is also found that the tendency of the jet breakup length is close to Epstein's correlation.
The Proceedings of the International Conference on Nuclear Engineering (ICONE), 2007
For the safety design of the Fast Breeder Reactor (FBR), the post accident heat removal (PAHR) of... more For the safety design of the Fast Breeder Reactor (FBR), the post accident heat removal (PAHR) of a hypothetical core disruptive accident (CDA) is an important issue. In the PAHR scenario, an important issue is that the molten core material injected into the sodium coolant is solidified in high boiling point sodium coolant. In the
The relation between the development of the wall boundary layer in a convergent nozzle and free s... more The relation between the development of the wall boundary layer in a convergent nozzle and free surface waves on the emanated liquid jet has been investigated experimentally. In the convergent nozzle, which forms a water jet along a flat back wall, the velocity profiles of the wall boundary layer were measured using a laser Doppler velocimeter with jet average velocities of U 0 = 5, 10 and 15 m/s. The property of free-surface waves and the intermittency factor of free surface fluctuations were also determined by photography and an optical measurement technique, using laser beam refraction on the jet surface. For the lowest velocity case U 0 = 5 m/s, the mean velocity profiles of the boundary layer under the pressure gradient in the convergent nozzle indicated an inverse transition from turbulent to laminar boundary layer, so-called relaminarization. On the other hand, for the higher velocity case U 0 ≥ 10 m/s, the relaminarization in the convergent section became incomplete. For these cases, the turbulent intensity near the wall increased significantly and the nozzle-exit boundary layer was restored quickly to a turbulent profile for a short parallel section immediately upstream of the nozzle exit plane. The increase in the velocity fluctuation near the wall promotes wave generation downstream of the nozzle exit plane. Therefore, the intermittence of the wave packet almost disappeared and the jet free surface was covered with continuous capillary waves when the turbulent boundary layer was separated from the nozzle exit.
Journal of the Japanese Society for Experimental Mechanics, 2013
Variation of Velocity Profile around an Automotive Brake Disc arising from Ventilation Duct Kazuh... more Variation of Velocity Profile around an Automotive Brake Disc arising from Ventilation Duct Kazuhiro ITOH, Hiroshige KUMAMARU and Yuji SHIMOGONYA Flow through an air passage of ventilated automotive brake rotor affects the thermal energy dissipation from rotor into atmosphere. In the present work, a velocity profile around a ventilated brake disc was measured using a hot-wire anemometer in order to understand the statistical turbulent property of air passage flow. Three-dimensional velocity components were evaluated at 5 mm outside the disc edge by rotating X-type hot-wire probe. The probe was also tilted corresponding to rotational speed so that it could receive the maximum velocity from disc. The maximum value of both average and fluctuation velocity increased significantly than that of solid disc. The velocity fluctuation profile indicated asymmetric aspect in contrast to the average velocity profile. An empirical one-dimensional model was suggested for evaluation of flow through...
Free surface fluctuations on a high-speed water jet were measured by a laser beam refraction tech... more Free surface fluctuations on a high-speed water jet were measured by a laser beam refraction technique. This method can be used to obtain quantitative time-series data on local surface fluctuations. The developed system employs two pulsed laser diodes, and it uses a high-speed optical sensor to detect the instantaneous positions of the laser beams that are refracted at the free surface. Fluctuations in the slope angle are measured at two locations separated by 1.27 mm. The wave speed of each free surface wave, which is determined by the zero-upcrossing method, is experimentally evaluated by the cross-correlation method. A two-dimensional waveform is obtained by integrating the slope angle data. The local mean wavelength and mean wave steepness are evaluated for average jet velocities up to m/s. Streamwise waveforms of the high-speed water jet at several locations exhibit appreciable asymmetry and have steep profiles.
For the safety design of a Sodium-cooled Fast Reactor, it is strongly required that the molten ma... more For the safety design of a Sodium-cooled Fast Reactor, it is strongly required that the molten material which is released from a core region has to be solidified and cooled down in a reactor vessel by breaking up in the sodium coolant during a Core Disruptive Accident in terms of Post Accident Heat Removal. In this paper, in order to investigate the effects of the surface solidification on the jet breakup, the experimental results using a low melting point alloy and water are reported. The jet breakup behavior is observed with a high speed video camera, the front position of the jet and the jet breakup length are estimated with the visual observation results. In the high injection velocity conditions, it is found that the jet breakup is dominated by fragmentation induced by the surface instability due to the relative velocity even in the surface solidification condition. In addition, it is also found that the tendency of the jet breakup length is close to Epstein's correlation.
The Proceedings of the International Conference on Nuclear Engineering (ICONE), 2007
For the safety design of the Fast Breeder Reactor (FBR), the post accident heat removal (PAHR) of... more For the safety design of the Fast Breeder Reactor (FBR), the post accident heat removal (PAHR) of a hypothetical core disruptive accident (CDA) is an important issue. In the PAHR scenario, an important issue is that the molten core material injected into the sodium coolant is solidified in high boiling point sodium coolant. In the
The relation between the development of the wall boundary layer in a convergent nozzle and free s... more The relation between the development of the wall boundary layer in a convergent nozzle and free surface waves on the emanated liquid jet has been investigated experimentally. In the convergent nozzle, which forms a water jet along a flat back wall, the velocity profiles of the wall boundary layer were measured using a laser Doppler velocimeter with jet average velocities of U 0 = 5, 10 and 15 m/s. The property of free-surface waves and the intermittency factor of free surface fluctuations were also determined by photography and an optical measurement technique, using laser beam refraction on the jet surface. For the lowest velocity case U 0 = 5 m/s, the mean velocity profiles of the boundary layer under the pressure gradient in the convergent nozzle indicated an inverse transition from turbulent to laminar boundary layer, so-called relaminarization. On the other hand, for the higher velocity case U 0 ≥ 10 m/s, the relaminarization in the convergent section became incomplete. For these cases, the turbulent intensity near the wall increased significantly and the nozzle-exit boundary layer was restored quickly to a turbulent profile for a short parallel section immediately upstream of the nozzle exit plane. The increase in the velocity fluctuation near the wall promotes wave generation downstream of the nozzle exit plane. Therefore, the intermittence of the wave packet almost disappeared and the jet free surface was covered with continuous capillary waves when the turbulent boundary layer was separated from the nozzle exit.
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Papers by Kazuhiro Itoh