Ryuta Imai

The University of Tokyo

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108 Radiated noise simulated from a full-scale multi-stage centrifugal pump

The Proceedings of the Symposium on Environmental Engineering (2005)

Yasushi Takano Yu Jiang Shinobu Yoshimura Ryuta Imai Kanako Nemoto

We present a one-way coupled simulation of fluid flow, structural vibration and acoustical radiation analyses that we applied to predict noise radiating from a 5-stage centrifugal pump. A large eddy simulation was performed to compute pressure fluctuations on the internal surface of the pump. The computed fluctuations were then used in a structural analysis that was based on the explicit dynamic finite element method that computed the elastic wave propagating in the solid. The resulting external surface vibration was then used in a acoustical analysis that was based on the boundary element method that used the normal derivative form of the Helmholtz integral equation. The computed internal pressure fluctuations, vibration velocities on the external surface and the radiated sound pressure level of the pump were compared with the measured equivalents, and reasonably good agreement between computed and measured results were obtained. The proposed method thus shows promise as a tool for the prediction and reduction of flow-induced noise generated from hydraulic turbomachinery.

Turbomachinery

Helmholtz free energy

Large-Eddy Simulation

10.1299/jsmeenv.2005.15.23

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Citations (2)

Development of TOUGH-FrontISTR, a Numerical Simulator for Environmental Impact Assessment of CO2 Geological Storage

Energy Procedia (2013)

Ryosuke Aoyagi Ryuta Imai Jonny Rutqvist Hiroyuki Kobayashi Osamu Kitamura

This paper summarizes the development of a new numerical simulator for environmental impact assessment of CO2 geological storage and the results of case studies. The simulator is developed by coupling the multiphase fluid flow simulator TOUGH2 and an open-source FEM code FrontISTR. Case studies for In Salah CO2 storage project are conducted to assess the validity of the developed simulator. Then, sensitivity analyses for physical parameters corresponding to pore space and rock rigidity are conducted. Results are consistent with measured data and suggest the validity of the simulator.

Rigidity (electromagnetism)

10.1016/j.egypro.2013.06.259

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Citations (4)

Simulation of the Flow-Induced Acoustic Vibration and Noise Generation in a Multi-Stage Centrifugal Pump

TRANSACTIONS OF THE JAPAN SOCIETY OF MECHANICAL ENGINEERS Series C (2006)

Yu Jiang Shinobu Yoshimura Ryuta Imai Hiroyuki Katsura T. Yoshida

This article reports a full-scale structural simulation of flow-induced mechanical noise in a 5-stage centrifugal pump. An interior flow field is simulated by a LES-based CFD code individually, which can be found elsewhere. This paper focuses on data interface, and a structural vibration analysis. We developed a data interface tool to enable mesh match as well as data interpolation between fluid and structure meshes. The vibration of a structural portion is simulated using a parallel explicit dynamic FE code, providing the time series of fluctuating pressure on internal surface as force boundary conditions. The calculated vibration of outer surface of the structure agrees reasonably well with measured one. By Fourier transformation, the vibration modes at the blade passing frequencies were extracted and visualized. The simulation clarified the mechanisms of resonant noise generation and propagation.

Interpolation

Internal flow

10.1299/kikaic.72.2065

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Estimation of Dielectric Constant Distribution Utilizing Subsurface Objects Based on Radar Image Focusing

IGARSS 2022 - 2022 IEEE International Geoscience and Remote Sensing Symposium (2023)

Ryuta Imai Ryo Natsuaki Akira Hirose

We propose a non-destructive method to estimate dielectric constant distribution based on radar image focusing. Water leaks from pipes and deterioration of materials in buildings have a significant impact on building users. However, they are often covered with materials, and periodic inspection is time-consuming. Electromagnetic radar is capable of detecting material changes since the dielectric constant significantly changes where the material is deteriorated or flooded. Several methods have been proposed to estimate a uniform dielectric constant of materials by using electromagnetic radar. In this paper, we obtain spatially-changing constant distribution by using buried objects such as pipes and rebars in such a manner that their radar image obtain a better focus, which means that the objects are clearly visualized.

Constant (computer programming)

10.1109/igarss52108.2023.10281938

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The Corona Type Decomposition of Hardy-Orlicz Spaces

Journal of mathematical sciences (2003)

Ryuta Imai

The H p -corona type problem in several complex variables has been solved affirmatively by Amar (1), Andersson (2), Andersson-Carlesson (3, 4), Krantz-Li (11) and others. In particular, Andersson-Carlsson (4) proved the H p -norm estimates of the corona solutions which are constructed by a concrete integral representation formula. In this paper, we give some Orlicz space versions for in- terpolation theorems of Marcinkiewicz type and prove the Hφ-norm estimates of the corona solutions for φ ∈ ∆2 ∩∇ 2. Moreover we also show that the ∆2-condition is necessary in some interesting cases.

Corona (planetary geology)

Source

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Proposal of Detection of Subsurface Objects with Model-Based Homogeneity to Extend Compressed Sensing

IGARSS 2022 - 2022 IEEE International Geoscience and Remote Sensing Symposium (2022)

Ryuta Imai Yicheng Song Ryo Natsuaki Akira Hirose

This paper proposes model-based homogeneity (MBH) to extend compressed sensing (CS) for detection of subsurface objects. The scattered waves at landmines have features spe-cific to their material and structure. The features spread over a landmine, showing its shape. We calculate the MBH value from spatial distribution of scattering feature vectors by using a model having the landmine shape. We can utilize CS with MBH because the result of MBH calculation is sparse in general. This method eliminates clutter and reduces mea-surement points. Experiments demonstrate that this method makes the time for detection one-twentieth of that in a conventional method.

Feature (linguistics)

10.1109/igarss46834.2022.9883786

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Citations (1)

Target-Phase-Focused Feature Synthesis and Extraction for Weakly Scattering Objects in Ground Penetrating Radar

IGARSS 2022 - 2022 IEEE International Geoscience and Remote Sensing Symposium (2023)

Ryuta Imai Ryo Natsuaki Akira Hirose

We propose a feature synthesis and extraction method by focusing on target phase for weakly scattering objects. This method is capable of distinguishing weakly scattering landmines from clutter. Landmines left in various regions in the world have been a serious problem, and mine detection for their clearance is an important issue. Along with techniques for detecting buried objects, determining whether a detected object is a landmine or not is also crucial for efficient clearance. Various methods for distinction of landmines have been proposed, but it has been a difficult task. In this paper, we propose a method to extract features of weakly scattering buried objects such as plastic landmines by synthesizing complex-valued scattering information and excluding phase rotation due to propagation.

Feature (linguistics)

Ground-Penetrating Radar

10.1109/igarss52108.2023.10282317

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Citations (0)

Toeplitz Type Operators on the Hardy-Orlicz Space

Complex Variables Theory and Application An International Journal (2003)

Ryuta Imai

In this article, we consider Toeplitz type operators and Hankel type operators in the Hardy-Orlicz space Hφ (Ω) and find a condition for the symbol so that they behave well on Hφ (Ω). Furthermore, we will show that Gleason's problem is solved affirmatively in some Hardy-Orlicz spaces.

Symbol (formal)

10.1080/0278107031000108796

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The corona type decomposition of Hardy-Orlicz spaces (Harmonic, Analytic function spaces and Linear Operators, II)

数理解析研究所講究録 (2002)

Ryuta Imai

Birnbaum–Orlicz space

Subharmonic function

Function space

Harmonic

Source