研究者詳細 - 河内　俊憲

論文 - 河内　俊憲

分割表示 113 件中 1 - 20 件目／全件表示 >>

Spherical shock wave modulation induced by interaction with homogeneous isotropic turbulence

K. Tanaka, T. Watanabe, H. Suzuki, T. Kouchi

Physics of Fluids 2025年2月

CNN Model to Predict Wall Shear Stress From Flow Velocity Data Without Viscous Sub-Layer

Kazuki Naridomi, Toshinori Kouchi, Kento Tanaka

AIAA Scitech2025 2025年1月

Investigation of Instantaneous Velocity-Fields by Schlieren Image Velocimetry Using Ray-Traced Simulated Focusing-Schlieren Images

Toshinori Kouchi, Narumi Kodera, Kento Tanaka, Hiroki Suzuki

AIAA Scitech2025 2025年1月

Numerical Analysis of a Low Reynolds Number Flow in a Non-Contact Air Stage Validated through Time Increment Width Testing 査読

Hiroaki Oka, Hiroki Suzuki, Jun Fujiwara, Toshinori Kouchi

Proceedings of the 12th JFPS International Symposium on Fluid Power P2-21 2024年10月

Attempt to compensate for effects of energy conservation error on static pressure fluctuation using sub-grid scale components with the Reynolds number dependence of isotropic/anisotropic steady turbulence 査読

Makoto Chitose, Hiroki Suzuki, Toshinori Kouchi

Journal of Physics: Conference Series 2793 ( 1 ) 012004 - 012004 2024年7月

掲載種別：研究論文（学術雑誌）出版者・発行元：IOP Publishing

Abstract

This study focuses on the kinetic energy conservation error and the compensation effect by adjusting a model constant. The kinetic energy conservation error is caused by the implicit time integration of the second-order Crank-Nicholson method, and we investigate how much this error affects the RMS of the static pressure fluctuation. Anisotropic and isotropic external force terms are used to generate a steady turbulent flow field, and the numerical analysis employs Large Eddy Simulation (LES) and the Smagorinsky model. Studies have shown that the influence of kinetic energy conservation errors on turbulent kinetic energy is limited, but large-scale turbulent structures are affected by errors in anisotropic turbulent fields with large Re numbers. Ta. Regarding the compensation of the RMS of the static pressure fluctuation, it was shown that the error could be reduced in both isotropic and anisotropic fields by adjusting the model constant, but there was a clear difference for the turbulent kinetic energy. This result shows that the compensation of kinetic energy conservation errors by a model constant is not perfect and that the errors can have different effects on the turbulence statistics.

DOI： 10.1088/1742-6596/2793/1/012004

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その他リンク： https://iopscience.iop.org/article/10.1088/1742-6596/2793/1/012004/pdf

Numerical analysis clarifying non-equilibrated periodic flows generated by dual-scaling Taylor’s analytical solution 査読

Xuanyou Gong, Hiroki Suzuki, Toshinori Kouchi

Journal of Physics: Conference Series 2793 ( 1 ) 012001 - 012001 2024年7月

掲載種別：研究論文（学術雑誌）出版者・発行元：IOP Publishing

Abstract

This study investigates the properties of a flow field derived from the multiplexed Taylor solution, focusing on its impact on established equilibrium relationships. We numerically analyse a multiplexed flow field by introducing a secondary flow with twice the period of the original Taylor solution, hypothesising that this dualisation affects the balance between transient and viscous terms. The visualisation of the flow field and the time evolution of the kinetic energy are investigated. Using second and sixth order central differences and the fractional step method with BiCGStab, we analyse three flow fields with different coefficients in a two-dimensional periodic domain. The study shows that the dualisation of the flow field disturbs the equilibrium between the unsteady and viscous terms. The time-averaged kinetic energy shows that the evolution of the dualised field approaches the kinetic energy distribution of the analytical solution, with variations depending on the coefficient of the quadratic term. The spatial distribution of the kinetic energy in fully developed fields is also compared with the analytical solution.

DOI： 10.1088/1742-6596/2793/1/012001

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その他リンク： https://iopscience.iop.org/article/10.1088/1742-6596/2793/1/012001/pdf

LES Analysis on the Impact of Mass Conservation Uncertainty on the Static Pressure Fluctuation in Spatially Periodic Steady Turbulence 査読

Xuanyou Gong, Hiroki Suzuki, Mikio Nakahama, Toshinori Kouchi

2023 2nd International Conference on Automation, Robotics and Computer Engineering (ICARCE) 1 - 5 2024年4月

CTA Measurement on the Frequency Response of a Grid Turbulence Fluctuation Measurement with a Focus on Bispectrum 査読

Hiroto Yamaguchi, Hiroki Suzuki, Kyosuke Fujita, Toshinori Kouchi

2023 2nd International Conference on Automation, Robotics and Computer Engineering (ICARCE) 1 1 - 6 2024年4月

Non-linear response of kinetic energy in an inviscid Taylor-Green flow obtained by OpenFOAM-LES with respect to time increments 査読

Akira Ono, Hiroki Suzuki, Toshinori Kouchi

Journal of Physics: Conference Series 2701 ( 1 ) 012054 - 012054 2024年2月

掲載種別：研究論文（学術雑誌）出版者・発行元：IOP Publishing

Abstract

This study investigates the conservation error of kinetic energy with respect to time increment using OpenFOAM LES. The energy conservation error is verified using an inviscid Taylor-Green vortex and the effect on energy conservation is checked by varying the time increment by a factor of 30. Differences in the response of turbulent energy conservation between large and small time increments are also verified. Higher order accuracy for time increments is expected when the kinetic energy conservation accuracy is high, however the actual behaviour in OpenFOAM needs to be investigated: as the implicit time integration method is used in OpenFOAM, a non-linear response is expected. As a result, it is evident that kinetic energy is not fully conserved in the inviscid flow of OpenFOAM. The kinetic energy distribution is similar for different time increments, with a different relationship between the conservation error observed in the range of large and small time increments.

DOI： 10.1088/1742-6596/2701/1/012054

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その他リンク： https://iopscience.iop.org/article/10.1088/1742-6596/2701/1/012054/pdf

Energy conservation uncertainly due to the use of an implicit time integration method clarified by a multiplexed TGV inviscid flow 査読

Makoto Chitose, Hiroki Suzuki, Toshinori Kouchi

Journal of Physics: Conference Series 2701 ( 1 ) 012059 - 012059 2024年2月

掲載種別：研究論文（学術雑誌）出版者・発行元：IOP Publishing

Abstract

This study attempts to elucidate the conservation errors induced by the implicit time integration method within a multiscale flow. Using the multiplexed Taylor analytical solution as the initial field, three distinct multiscale turbulence fields were formulated, each characterised by different wavenumber attributes. A two-dimensional inviscid flow field, replicated in a computational domain with a side of 2π and subject to periodic boundary conditions, was used to illuminate kinetic energy conservation errors. The implicit time integration method - specifically the second-order accurate Crank-Nicolson method - was compared with explicit methods, such as the second-order accurate Adams-Bashforth and third-order accurate Runge-Kutta methods. The study also examines the differences between the analytical Taylor solution and a random flow field, particularly in their satisfaction of the Navier-Stokes equations and wavenumber composition, while highlighting the need for preliminary analysis for random flow fields prior to validation calculations.

DOI： 10.1088/1742-6596/2701/1/012059

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その他リンク： https://iopscience.iop.org/article/10.1088/1742-6596/2701/1/012059/pdf

Multiscaled inviscid Taylor-Green vortex flow for examining energy conservation error in incompressible flows 査読

Xuanyou Gong, Hiroki Suzuki, Toshinori Kouchi

Journal of Physics: Conference Series 2701 ( 1 ) 012052 - 012052 2024年2月

掲載種別：研究論文（学術雑誌）出版者・発行元：IOP Publishing

Abstract

This study investigates kinetic energy conservation errors in incompressible flows using multiplexed inviscid Taylor-Green vortices. Fourth-order precision Runge-Kutta methods, specifically five- and six-step methods, were employed and an inviscid two-dimensional periodic flow field was used as a test case. This method allows the energy conservation error to be suppressed to a very low level. Recent previous studies have dealt with turbulence generation using a multi-scale turbulence grid. In this study, the Taylor-Green vortex of the analytical solution is multiplexed to generate a flow field with a number of wavenumbers. Visualisation results of the initial field and the energy distribution over time were obtained. It was observed that the errors in the time evolution of the fluid energy were extremely small, and that the errors actually increased with time. However, the influence of the time step range was limited and the analytical and numerical solutions were in general agreement. As a result, it was confirmed that the inviscid Taylor-Green vortex is effective in examining the energy conservation error for incompressible flows.

DOI： 10.1088/1742-6596/2701/1/012052

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その他リンク： https://iopscience.iop.org/article/10.1088/1742-6596/2701/1/012052/pdf

Experimental validation on a calibration position of a hot-wire anemometer for measuring multi-scale grid-generated turbulence 査読

Hiroto Yamaguchi, Hiroki Suzuki, Toshinori Kouchi

Journal of Physics: Conference Series 2701 ( 1 ) 012056 - 012056 2024年2月

掲載種別：研究論文（学術雑誌）出版者・発行元：IOP Publishing

Abstract

This study aims to experimentally examine conditions that should be satisfied by a calibration position of a constant-temperature hot-wire anemometer. Specifically, this study addresses an appropriate measurement point when this calibration is performed downstream of a turbulent field generated by a multi-scale turbulence grid. The hot-wire measurement in this study is based on an I-type probe with a standard 5 μm tungsten wire. The hot-wire anemometer in this study is small and can be attached to a probe support. In this study, uncertainty in the calibration curve of the hot-wire measurement is first checked. Here, Pitot tube velocimetry to obtain the calibration curves is carried out using two bell-type micro-differential pressure gauges. Then, the characteristics of the obtained velocity fluctuations and turbulence will be examined. Based on this relative velocity fluctuation RMS value, the effects of the obtained streamwise velocity fluctuation on output voltage are obtained by asymptotically expanding a calibration curve. Using these results, the intensity of the free-stream turbulence, which has a negligible effect on output voltage giving a calibration curve, is clarified.

DOI： 10.1088/1742-6596/2701/1/012056

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その他リンク： https://iopscience.iop.org/article/10.1088/1742-6596/2701/1/012056/pdf

LES analysis of local isotropic turbulence depending on the spatial scale of the external forcing field 査読

Koki Minami, Hiroki Suzuki, Toshinori Kouchi

Journal of Physics: Conference Series 2701 ( 1 ) 012055 - 012055 2024年2月

掲載種別：研究論文（学術雑誌）出版者・発行元：IOP Publishing

Abstract

The study investigates the effect of the parameterisation of an external force scheme based on trigonometric functions on turbulence. In particular, the dependence of the generated turbulence on the Reynolds number and the influence of its spatial parameters are investigated. The turbulence used is generated by a large-eddy simulation based on a high-precision finite volume method, and the turbulence energy and isotropy of the turbulence are also investigated. The parameter of the external force field used in this study characterises the wavelength of the trigonometric function, and the influence of this parameter on the spatial scale is studied in detail. As a result, steady turbulent fields are generated and isotropic turbulence is observed at different spatial scales of the external force field with M=2, 3 and 4. The property of increasing turbulence energy with increasing Reynolds number is confirmed.

DOI： 10.1088/1742-6596/2701/1/012055

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その他リンク： https://iopscience.iop.org/article/10.1088/1742-6596/2701/1/012055/pdf

Locally Broken Shock Wave Detection with One-Dimensional Convolutional Neural Network in Shock Turbulence Interaction

Kento Tanaka, Toshinori Kouchi, Hiroki Suzuki, Koichi Takeuchi

AIAA SCITECH 2024 Forum 2024-2340 2024年1月

Phase-lock Analysis of Two-Dimensional Transonic Shock Buffet by Using Machine Learning

Tsubasa Kikuchi, Toshinori Kouchi, Kento Tanaka, Koichi Takeuchi

AIAA SCITECH 2024 Forum 2024-0905 2024年1月

Assessing OpenFOAM-based Large-eddy Simulation Using Decay Characteristics of An Isotropic Taylor-green Vortex 査読

Akira Ono, Makoto Chitose, Hiroki Suzuki, Toshinori Kouchi

Journal of Physics: Conference Series 2694 ( 1 ) 012004 - 012004 2024年1月

掲載種別：研究論文（学術雑誌）出版者・発行元：IOP Publishing

Abstract

The aim of this study is to investigate OpenFOAM using isotropic TGV flows. The main focus is on the establishment of energy conservation laws, in particular using inviscid fields to assess energy constancy; Large-Eddy Simulation (LES) is applied and the results are compared with those obtained using spectral methods; unlike previous studies of OpenFOAM, this study uses an unsteady turbulent TGV flow. The computational methods used are a central difference method, a PISO algorithm and a Smagorinsky model. The study revealed errors in the conservation of kinetic energy in the OpenFOAM analysis. In particular, the energy decay was significant at high spatial resolution, confirming the different turbulence energy decay characteristics of DNS and OpenFOAM. However, when the model constant was 0.6, the decay characteristics were shown to be in good agreement with DNS.

DOI： 10.1088/1742-6596/2694/1/012004

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その他リンク： https://iopscience.iop.org/article/10.1088/1742-6596/2694/1/012004/pdf

Comparative Testing the Uncertainty of A/D Converters in A Hot-Wire Anemometer Measurement Using Grid-Generated Turbulence 査読

Hiroto Yamaguchi, Hiroki Suzuki, Toshinori Kouchi

Journal of Physics: Conference Series 2694 ( 1 ) 012003 - 012003 2024年1月

掲載種別：研究論文（学術雑誌）出版者・発行元：IOP Publishing

Abstract

This study investigates the uncertainty of the A/D converter when measuring multi-scale turbulence fluctuations using a hot-wire anemometer. The flow is generated in a low-speed wind tunnel, the turbulence is generated by a turbulence grid and the fluctuations are measured. A compact hot-wire anemometer was used and a high accuracy A/D converter was introduced for the measurements. Methods to minimise the influence of noise were also incorporated and measurements were carried out in two situations, one with and one without turbulence. The experimental results showed that measurements under a specific condition (Case 1 in this study) had the sufficienty reproducibility of turbulence fluctuations and the least effect of noise. The results showed that the high frequency characteristics of the turbulence could also be accurately measured under this condition. In conclusion, it is clear that the choice of a suitable A/D converter and the optimisation of the measurement environment are critical for turbulence measurements with a hot-wire anemometer.

DOI： 10.1088/1742-6596/2694/1/012003

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その他リンク： https://iopscience.iop.org/article/10.1088/1742-6596/2694/1/012003/pdf

Fundamental numerical analysis clarifying the response of incompressible turbulence fields to the uncertainty of kinetic energy conservation 査読

Makoto Chitose, Hiroki Suzuki, Kento Tanaka, Toshinori Kouchi

Proceedings of the International Conference on Power Engineering 2023 (ICOPE-2023) ICOPE-2023-1274 2023年5月

Examination of multi-scale generated decaying turbulence validated for the influence of wind tunnel blockage 査読

Hiroto Yamaguchi, Hiroki Suzuki, Kento Tanaka, Toshinori Kouchi

Proceedings of the International Conference on Power Engineering 2023 (ICOPE-2023) ICOPE-2023-1268 2023年5月

Dynamic Mode Decomposition of Simultaneous Dual-layer Focusing Schlieren and Unsteady Pressure-Sensitive Paint Measurements for Transonic Buffet on a Swept Wing

Shota Fukumoto, Toshinori Kouchi, Yosuke Sugioka, Shunsuke Koike

AIAA SCITECH 2023 Forum 2023-1180 2023年1月

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