Takayuki Nagata

Takayuki Nagata
Tohoku University | Tohokudai · Department of Aerospace Engineering

Doctor of Philosophy (Engineering)

About

77
Publications
7,799
Reads
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406
Citations
Citations since 2016
71 Research Items
405 Citations
2016201720182019202020212022050100150
2016201720182019202020212022050100150
2016201720182019202020212022050100150
2016201720182019202020212022050100150
Additional affiliations
March 2021 - present
Tohoku University
Position
  • Professor (Assistant)
April 2020 - March 2021
Tohoku University
Position
  • PostDoc Position
April 2018 - March 2020
Tohoku University
Position
  • Fellow
Education
April 2017 - March 2020
Tohoku University
Field of study
  • Aerospace Engineering
April 2015 - March 2017
Tokai University
Field of study
  • Aeronautica and Astronautics
April 2011 - March 2015
Tokai University
Field of study
  • Aeronautics and Astronautics

Publications

Publications (77)
Article
Full-text available
Reconstruction of the distribution of ground motion due to an earthquake is one of the key technologies for the prediction of seismic damage to infrastructure. Particularly, the immediate reconstruction of the spatially continuous wavefield is valuable for decision-making of disaster response decisions in the initial phase. For a fast and accurate...
Article
Full-text available
Unsteady drag, unsteady lift and movement of one or two moving particles caused by the passage of a planar shock wave are investigated using particle-resolved simulations of viscous flows. The particle motion analysis is carried out based on particle-resolved simulations for one or two particles under a shock Mach number of 1.22 and a particle Reyn...
Article
Full-text available
We developed and evaluated an anodized-aluminum pressure-sensitive paint (AA-PSP) with new formulations of free-base porphyrin, H2TCPP, as an optical unsteady pressure sensor. The luminophore H2TCPP has quite a short fluorescent lifetime (2.4 ns on the condition of the AA-PSP). The fluorescence spectroscopy result shows that the excitation waveleng...
Article
This study proposes a method for predicting the wind direction against the simple automobile model (Ahmed model) and the surface pressure distributions on it by using data-driven optimized sparse pressure sensors. Positions of sparse pressure sensor pairs on the Ahmed model were selected for estimation of the yaw angle and reconstruction of pressur...
Article
The present study proposed the framework of the spatiotemporal superresolution measurement based on the sparse regression with dimensionality reduction using the proper orthogonal decomposition (POD). The non-time-resolved particle image velocimetry (PIV) and the time-resolved near-field acoustic measurements using microphones were simultaneously p...
Conference Paper
View Video Presentation: https://doi.org/10.2514/6.2022-3606.vid The present study proposes a method for estimating the wind direction against a simple automobile model (Ahmed model) and reconstructing surface pressure distribution on it by the sparse pressure sensors. The sparse pressure sensor placement was optimized by the three algorithms based...
Conference Paper
View Video Presentation: https://doi.org/10.2514/6.2022-3242.vid This study proposes a reservoir computing reduced-order model (RCROM) of the post-stallflow around NACA0015 airfoil based on the time series velocity field, and the estimationaccuracy of RCROM is evaluated compared to that of a linear reduced-order model (LROM).The data is experimenta...
Article
Distributions of the pressure and mass transfer coefficient on rotating blades under low-pressure (low-Reynolds-number) conditions were visualized, whereas the latter is closely related to the skin-friction distribution. Two types of optical measurement techniques, lifetime-based pressure-sensitive paint (PSP) measurements and sublimation visualiza...
Preprint
Full-text available
A seismic wavefield reconstruction framework based on compressed sensing using the data-driven reduced-order model (ROM) is proposed and its characteristics are investigated through numerical experiments. The data-driven ROM is generated from the dataset of the wavefield using the singular value decomposition. The spatially continuous seismic wavef...
Conference Paper
The present study proposes a framework of the superresolution measurement based on the dynamic mode decomposition (DMD) with the Kalman filter and Rauch–Tung–Striebel smoother. The dual-planar particle image velocimetry (PIV) systems were constructed to acquire the paired velocity fields of a Mach 1.1 supersonic jet. The acoustic measurement was si...
Conference Paper
In this study, a pressure distribution inside a two-dimensional rectangular cavity with a ratio L/D = 5.0 of the cavity length L to the depth D over supersonic flow was obtained using anodized-aluminum pressure-sensitivity paint (AA-PSP). The freestream Mach number was M = 1.85 and the frequencies of the dominant cavity modal phenomena called a Ros...
Conference Paper
A method for estimating time-resolved three-dimensional velocity fields from non-time-resolved particle image velocimetry (PIV) and time-resolved near-field acoustic data is proposed and evaluated on a screeching, underexpanded jet. Multi-time-delay modified linear stochastic estimation (MTD-mLSE) is applied to the reduced-order PIV data and the Fo...
Preprint
Full-text available
The seismic data not only acquired by seismometers but also acquired by vibrometers installed in buildings and infrastructure and accelerometers installed in smartphones will be certainly utilized for seismic research in the near future. Since it is impractical to utilize all the seismic big data in terms of the computational cost, methods which ca...
Article
In this study, a new method that optimizes a measurement condition in a lifetime-based simultaneous measurement of a pressure-sensitive paint (PSP) and a temperature-sensitive paint (TSP) is proposed for the improvement of the accuracy of the pressure measurement. An optimal gate is selected based on a pressure measurement error when calculating th...
Article
View Video Presentation: https://doi.org/10.2514/6.2022-4166.vid The objective of this study is to develop digital signal processing methods that reduce noise caused by atmospheric fluctuation and image sensors and extract signal of fluid phenomena from data obtained by the highly sensitive schlieren measurement in the low-density wind tunnel. Time...
Preprint
Full-text available
This study proposes a method for predicting the wind direction against the simple automobile model (Ahmed model) and the surface pressure distributions on it by using data-driven optimized sparse pressure sensors. Positions of sparse pressure sensor pairs on the Ahmed model were selected for estimation of the yaw angle and reconstruction of pressur...
Preprint
Full-text available
The present study proposed the framework of the spatiotemporal superresolution measurement based on the sparse regression with dimensionality reduction using the proper orthogonal decomposition (POD). The non-time-resolved particle image velocimetry (PIV) and the time-resolved near-field acoustic measurements using microphones were simultaneously p...
Preprint
Full-text available
The present paper proposes a data-driven sensor selection method for a high-dimensional nondynamical system with strongly correlated measurement noise. The proposed method is based on proximal optimization and determines sensor locations by minimizing the trace of the inverse of the Fisher information matrix under a block-sparsity hard constraint....
Preprint
Full-text available
Randomized group-greedy methods for sensor selection problems are proposed. The randomized greedy sensor selection algorithm is straightforwardly applied to the group-greedy method, and a customized method is also considered. In the customized method, a part of the shrunken sensor candidates is selected to be the oversampled sensors by the common g...
Article
The exact dynamic mode decomposition (DMD) was applied to the nonsequential image dataset obtained by the double-pulsed schlieren measurement of a supersonic impinging jet, and the effect of the dataset length on the obtained spatial modes and estimated frequencies of the aeroacoustic fields was investigated. The Mach number of the jet was 2.0, the...
Preprint
Full-text available
In this study, a nondominated-solution-based multiobjective-greedy sensor selection method for the optimal design of experiments is proposed and its performance is investigated. The proposed method simultaneously considers D-, A- and E-optimality and applies the idea of Pareto ranking to select the sensor set. With the proposed method, a new sensor...
Article
Martian conditions present various challenges when designing rotorcraft. Specifically, the thin atmosphere and low sound speed require Martian rotor blades to operate in a low-Reynolds-number (1000–10,000) compressible regime, for which conventional airfoils are not designed. Here, we use PyFR to undertake high-order direct numerical simulations (D...
Article
Signal processing methods that remove noise due to atmospheric fluctuation and image sensors and extract fluid phenomena from schlieren images obtained in the low-density wind tunnel test were developed together with the highly sensitive schlieren measurement setup. Time-series schlieren images of the flow around a triangular airfoil were analyzed,...
Article
Full-text available
We propose a markerless image alignment method for pressure-sensitive paint measurement data replacing the time-consuming conventional alignment method in which the black markers are placed on the model and are detected manually. In the proposed method, feature points are detected by a boundary detection method, in which the PSP boundary is detecte...
Article
Full-text available
In the present study, we organize the existing sparsity-promoting dynamic mode decomposition (DMDsp) in terms of noise robustness, propose faster optimization algorithm for DMDsp, and evaluate its characteristics. Two kinds of DMDsp, namely system-based DMDsp (sDMDsp) and observation-based DMDsp (oDMDsp), combined with three kinds of optimization a...
Article
The present paper proposes a data-driven sensor selection method for a high-dimensional nondynamical system with strongly correlated measurement noise. The proposed method is based on proximal optimization and determines sensor locations by minimizing the trace of the inverse of the Fisher information matrix under a block-sparsity hard constraint....
Conference Paper
View Video Presentation: https://doi.org/10.2514/6.2021-2217.vid Applicability of exact dynamic mode decomposition (DMD) for the evaluation of the aeroacoustic field was investigated on the nonsequential data obtained by the double-pulsed schlieren measurement of the supersonic impinging jet. The Mach number of the jet was 2.0, the Reynolds number...
Conference Paper
View Video Presentation: https://doi.org/10.2514/6.2021-2106.vid Supersonic jets of M=1.35 and 2.0 were measured by time-resolved near-field acoustic measurement and non-time-resolved particle image velocimetry (PIV). The multi-time-delay modified linear stochastic estimation (MTD-mLSE) was applied to the reduced-order acoustic and velocity field d...
Article
A comprehensive review of all relevant experimental data was completed, including recent data for the drag coefficient for a sphere in supersonic and hypersonic flows. The primary characterization parameter included the relative Mach, Knudsen, and Reynolds numbers based on the relative velocity, the sphere diameter, and other parameters. This revie...
Article
Full-text available
The characteristics of fast-response pressure-sensitive paints (PSPs) in low-pressure conditions were evaluated. Three representative porous binders were investigated: polymer-ceramic PSP (PC-PSP), anodized-aluminum PSP (AA-PSP), and thin-layer chromatography PSP (TLC-PSP). For each PSP, two types of luminophores, Pt(II) meso-tetra (pentafluorophen...
Article
Full-text available
In this paper, the sparse sensor placement problem for least-squares estimation is considered, and the previous novel approach of the sparse sensor selection algorithm is extended. The maximization of the determinant of the matrix which appears in pseudo-inverse matrix operations is employed as an objective function of the problem in the present ex...
Article
The present study proposes a sensor selection method based on the proximal splitting algorithm and the A-optimal design of experiment using the alternating direction method of multipliers (ADMM) algorithm. The performance of the proposed method was evaluated with a random sensor problem and compared with previously proposed methods, such as the gre...
Article
Full-text available
This study aims to isolate and evaluate the influence of a corrugation on flow structures and aerodynamics under compressible low Reynolds number conditions, and to compare it to simpler but well-known model: the flat plate. The simplified corrugated model was made by a flat surface with only two corrugations on the leading edge. The models only di...
Article
Full-text available
The problem of selecting an optimal set of sensors estimating a high-dimensional data is considered. Objective functions based on D-, A-, and E-optimality criteria of optimal design are adopted to greedy methods, that maximize the determinant, minimize the trace of the inverse, and maximize the minimum eigenvalue of the Fisher information matrix, r...
Article
Full-text available
The effects of the oxygen mole fraction on the static properties of pressure-sensitive paint (PSP) were investigated. Sample coupon tests using a calibration chamber were conducted for poly(hexafluoroisopropyl methacrylate)-based PSP (PHFIPM-PSP), polymer/ceramic PSP (PC-PSP), and anodized aluminum PSP (AA-PSP). The oxygen mole fraction was set to...
Article
Flow over a flat plate with a 5% thickness ratio is investigated by schlieren visualization in compressible low-Reynolds-number conditions. The results show that flow separates at the leading-edge and laminar separation-bubble forms. The position of the maximum root mean square of the schlieren image which is related to the position of the vortex s...
Article
Urolithiasis is a disease in which calcium oxalate crystallizes in the urinary tract, and has a high recurrence rate. It is necessary to consider the burden on the body by surgical treatment, therefore, treatment methods that effectively promote spontaneous stone passage are required. In this study, we verified the results of the drainage orbit vis...
Preprint
Full-text available
The effects of oxygen mole fraction on the static properties of pressure-sensitive paint (PSP) were investigated. Sample coupon tests using a calibration chamber were conducted for polymer-based PSP (PHFIPM-PSP), polymer/ceramic PSP (PC-PSP), and anodized-aluminium PSP (AA-PSP). The oxygen mole fraction was set to be between 0.1-100% and the ambien...
Article
Full-text available
In the present study, compressible low-Reynolds-number flow past a stationary isolated sphere was investigated by direct numerical simulations of the Navier–Stokes equations using a body-fitted grid with high-order schemes. The Reynolds number based on free-stream quantities and the diameter of the sphere was set to be between 250 and 1000, and the...
Preprint
Full-text available
The present study proposes a sensor selection method based on the proximal splitting algorithm and the A-optimal design of experiment using the alternating direction method of multipliers (ADMM) algorithm. The performance of the proposed method was evaluated with a random sensor problem and compared with the previously proposed methods such as the...
Preprint
Full-text available
The selection problem of an optimal set of sensors estimating the snapshot of high-dimensional data is considered. The objective functions based on various criteria of optimal design are adopted to the greedy method: D-optimality, A-optimality, and E-optimality, which maximizes the determinant, minimize the trace of inverse, and maximize the minimu...
Article
In the present study, a compressible low-Reynolds-number flow over a circular cylinder was investigated using a low-density wind tunnel with time-resolved schlieren visualizations and pressure and force measurements. The Reynolds number (Re) based on freestream quantities and the diameter of a circular cylinder was set to be between 1000 and 5000,...
Article
Full-text available
A temperature-sensitive paint (TSP) using a chameleon luminophore [ Tb 0 . 99 Eu 0 . 01 ( hfa ) 3 ( dpbp ) ] n is proposed. The chameleon luminophore was dispersed in isobutyl methacrylate polymer in a toluene solvent to fix it on a sample coupon. Temperature and pressure sensitivities of the chameleon luminophore-based TSP were measured using a sp...
Article
In the present study, new performance evaluation parameters for pressure-sensitive paint (PSP) were proposed, and the effects of the ambient pressure on the characteristics of the PSP were evaluated. The proposed parameters allow us to determine the optimal pressure range on the basis of the following quantities: (1) the Stern--Volmer coefficient,...
Article
Full-text available
In this study, free-flight tests of a sphere for Reynolds numbers between 3.9 × 10³ and 3.8 × 10⁵ and free-flight Mach numbers between 0.9 and 1.6 were conducted using a ballistic range, and compressible low-Reynolds-number flows over an isolated sphere were investigated with the schlieren technique. The flow visualization was carried out under low...
Article
Full-text available
In the present study, we proposed a simple collision algorithm, which can be handled arbitrarily shaped objects, for flow solvers using the immersed boundary method (IBM) based on the level set and ghost cell methods. The proposed algorithm can handle the collision of the arbitrarily shaped object with little additional computational costs for the...
Conference Paper
In this study, a compressible low-Reynolds number flow over a circular cylinder was investigated by schlieren visualization and the force measurement. A Reynolds number based on freestream quantities and a diameter of a cylinder is set to be 1000 ≤ Re ≤ 5000 and a Mach number is set to be 0.1 ≤ M ≤ 0.5 by using the low-pressure wind tunnel. From th...
Conference Paper
In this study, flow over a pair of vane-type vortex generator is investigated by solving the Navier–Stokes equation. A pair of the vane-type vortex generator implemented on a slip wall in laminar flow is considered so that the problem setting could be simple. The Reynolds number based on freestream quantities and the height of the vanes is set to b...
Conference Paper
In this study, free-flight tests of a sphere at a Reynolds number between 5.7 × 10³ and 3.1 × 10⁵ under transonic to supersonic condition is conducted using ballistic range and investigate the flow over a sphere under compressible low-Reynolds number conditions. The flow visualization is carried out by the schlieren technique. A free-flight Reynold...
Conference Paper
Urinary stones are calcium oxalate stones in the urinary tract. According to the 2005 national survey, the lifetime prevalence of urinary stones is 15.1% for Japanese men and 6.8% for women. In addition, 96% of the whole are upper urinary tract stones such as kidney stones. Small stones are excreted in the urine without feeling great pain in the pr...
Article
In this study, direct numerical simulation of the flow around a rotating sphere at high Mach and low Reynolds numbers is conducted to investigate the effects of rotation rate and Mach number upon aerodynamic force coefficients and wake structures. The simulation is carried out by solving the three-dimensional compressible Navier–Stokes equations. A...
Conference Paper
In this study, flow around a circular cylinder with a Reynolds number between 1.4x103 and 1.4x104, and a Mach number between 0.1 and 0.4 was visualized by the Schlieren method to investigate Reynolds and Mach numbers effects on the flow dynamics. The position of occurrence of the Karman vortex is changed depending on the flow conditions. By perform...
Article
Full-text available
Abstract In this study, an analysis of the flow properties around an isolated sphere under isothermal conditions for flows with high Mach numbers and low Reynolds numbers is conducted via direct numerical simulation (DNS) of the three-dimensional compressible Navier–Stokes equations. The calculations are performed with a boundary-fitted coordinate...