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Kato, Naoto
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Experimental Study of Aerodynamic Drag Control on Bluff Body using Synthetic Jets

Utsunomiya University-Naoto Kato, Shunsuke Watanabe, Hiroaki Hasegawa
  • Technical Paper
  • 2019-32-0538
Published 2020-01-24 by Society of Automotive Engineers of Japan in Japan
Since flow separation causes increase of the drag on bluff bodies, its control method has been studied for many years. Active control methods are currently focused as an alternative to passive ones because they impose a larger drag penalty under certain conditions. Although the effectiveness of a steady jet using suction, blowing or pulsed jets has been demonstrated, it is difficult to obtain an effect commensurate with weight increase because the mechanism is complicated.One method of solving this problem is a synthetic jet. Synthetic jets are produced by periodic ejection and suction of fluid from an orifice induced by oscillation of a diaphragm inside a cavity. Small engine powered vehicles demand less drag, a compact package and light weight because the drivers expect fuel efficiency, load capacity and economy. Synthetic jets can supply them because they contribute drag reduction and require only simple components.In this study, the influence of synthetic jets on the drag of a simple bluff body representing a road vehicle is measured. Drag measurement was performed by varying synthetic jet parameters: jet…
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Numerical Analysis of Turbulent Flow in a Square Duct with Periodically Arranged Ribs by an Algebraic Reynolds Stress Model

Japan Atomic Energy Agency-Ryutaro Hino
Utsunomiya Univ.-Yuria Okagaki, Hitoshi Sugiyama, Naoto Kato
  • Technical Paper
  • 2012-08-0198
Published 2012-05-23 by Society of Automotive Engineers of Japan in Japan
Numerical analysis has been performed for turbulent flow in a square duct with periodically arranged ribs on bottom wall by using an algebraic Reynolds stress model and boundary fitted coordinate system which is one of coordinate transformation method. Calculated results are compared in detail with the experiment in order to confirm the validity of the presented model. This kind of turbulent flow is characterized by separated flow which is one of difficult flows to predict. It has been found that the calculation can reproduce reasonably the reattachment point of separated flow including secondary flow vectors. As for Reynolds stresses, although prediction of Reynolds stresses is not perfect, typical features are able to reproduce by an algebraic Reynolds stress model.
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Numerical Analysis of Turbulent Flow in a 90-Degree Bend Pipe With a Half-Trip

Utsunomiya Univ.-Hitoshi Sugiyama, Tomoki Kakuko, Yuria Okagaki, Naoto Kato
Yamada-Taichi Imai
  • Technical Paper
  • 2011-08-0199
Published 2011-10-12 by Society of Automotive Engineers of Japan in Japan
Numerical analysis has been performed for turbulent flow in a 90-degree bend pipe with half-trip ribs by using an algebraic Reynolds stress model and boundary fitted coordinate system. Calculated results are compared with the experiment in order to confirm the validity of the presented model and clarify the mechanism of drag reduction. It has been found that the calculation can reproduce reasonably the measured velocity profiles including secondary flow vectors. Besides, calculated results suggest that drag reduction must be caused by the secondary flow of the second kind which is produced by anisotropic turbulence through half-trip rib.
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Numerical Analysis of Turbulent Flow With Heat Transfer in a Square Duct With 45 Degree Ribs

Utsunomiya Univ.-Yuria Okagaki, Hitoshi Sugiyama, Naoto Kato
  • Technical Paper
  • 2009-08-0592
Published 2009-10-07 by Society of Automotive Engineers of Japan in Japan
Numerical analysis has been performed for turbulent flow with heat transfer in a square duct with 45 degree ribs by using an algebraic Reynolds stress and turbulent heat flux models. Calculated results are compared with the experiment in order to confirm the validity of the presented model. It has been found that the calculation can reproduce reasonably the measured velocity profiles including secondary flow vectors. Besides, two kinds of turbulent models are applied to temperature field and the difference between turbulent heat flux model and constant turbulent Prandtl number model are described by showing the distributions of Nusselt number.
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Development of a New Model Based Air-Fuel Ratio Control System

SAE International Journal of Engines

Toyota Motor Corporation-Shuntaro Okazaki, Naoto Kato, Junichi Kako, Akira Ohata
  • Journal Article
  • 2009-01-0585
Published 2009-04-20 by SAE International in United States
The second-generation air-fuel ratio control method has been developed to reduce exhaust gas emissions in accordance with the improvements in catalysts. The control system consists of a feedforward control using a fuel behavior model, a feedback control using an universal exhaust gas oxygen (UEGO) sensor and a feedback control utilizing the heated exhaust gas oxygen (HEGO) sensor. This significantly improves air-fuel ratio tracking performance by feedforward control derived from the models that express the dynamic phenomena and the disturbance attenuation by UEGO feedback controller which compensates for the long dead-time characteristics by the state predictive control. The tracking performance and the disturbance attenuation can be achieved independently by a two-degree-of-freedom structure presented in this paper. The exhaust air-fuel ratio downstream of the catalyst precisely converges to stoichiometry, which maximizes the conversion efficiency of the catalyst. Experimental results on actual vehicles show the effectiveness of presented method.
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Numerical Analysis of Turbulent Flow in a HVAC Unit with Heat Transfer and Sharp 90-Degree Turn

Utsunomiya Univ.-Hitoshi Sugiyama, Takayuki Sekiya, Naoto Kato
  • Technical Paper
  • 2008-08-0534
Published 2008-10-22 by Society of Automotive Engineers of Japan in Japan
Numerical analysis has been performed for turbulent flow in a HVAC (Heating, Ventilating and Air Conditioning) unit with heat transfer and sharp 90-degree turn by using an algebraic Reynolds stress and turbulent heat flux models. Besides, the other calculation has been done for temperature fields assuming turbulent Prandtl's number is constant. In calculation, heating core is treated as porous media and condition of constant heat flux is imposed on the wall as boundary condition of temperature. As a result of this analysis, it is found that the presented turbulent model predicts reasonably the secondary flow of the second kind in straight duct which is produced by anisotropic turbulence. The calculated results of temperature suggest that both turbulent heat flux model and turbulent Prandtl's number model with constant value are able to reproduce characteristic features of temperature but the difference between both models is recognized in profile of contour map and values.