Yuta Ozawa

Yuta Ozawa
Tohoku University | Tohokudai · Department of Aerospace Engineering

Doctor of Philosophy (Engineering)

About

47
Publications
2,743
Reads
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220
Citations
Citations since 2016
46 Research Items
220 Citations
2016201720182019202020212022020406080100
2016201720182019202020212022020406080100
2016201720182019202020212022020406080100
2016201720182019202020212022020406080100
Additional affiliations
March 2021 - March 2022
Tohoku University
Position
  • Professor (Assistant)

Publications

Publications (47)
Article
Full-text available
An experimental study is performed to investigate the feasibility of success in controlling supersonic boundary-layer flows using a device to discharge the jets flapping at several tens of kilohertz (kHz). In the experiments, a shadowgraph image velocimetry (SIV) technique is applied for measuring the velocities in a supersonic boundary-layer flow...
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
In this study, a cylinder with a slanted afterbody was magnetically levitated without support structures by means of a magnetic suspension and balance system (MSBS) with six-degrees-of-freedom (6-DOF) control. The levitation stability during the 6-DOF levitation was first confirmed and accurate to less than 8.9 μm and 18.6 mdeg at 15 m/s freestream...
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/10.2514/6.2022-4132.vid Background-oriented schlieren (BOS) system proposed in this paper realizes high-spatial resolution by applying the single-pixel correlation method for the image pairs obtained in the process of BOS. The backgrounds are projected by a high-speed projector and changed at 900 Hz for calc...
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, the Amiet model, which calculates the steering vector for sound-source localization, was verified with a laser monopole sound source. The laser generates plasma and corresponding sound that does not interfere with the flow in the wind tunnel, and thus, the acoustic data of the monopole sound source can be acquired. First, the laser m...
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...
Article
View Video Presentation: https://doi.org/10.2514/6.2022-4167.vid A test model called slanted cylinder afterbody was magnetically supported by a magnetic suspension and balance system (MSBS) in this wind tunnel test. The stability of the levitation was found to be accurate to less than 8.9 ��m and 18.6 mdeg at 15 m/s freestream. The aerodynamic forc...
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...
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...
Article
In this study, the dynamical behavior of the vortex pair produced in the wake of a cylinder with a slanted afterbody, relevant to cargo aircraft applications, is examined experimentally through time-resolved particle image velocimetry (TR-PIV) and fast-response pressure sensitive paint (PSP). The vortex wandering phenomenon, characterstic of this w...
Article
A high-spatial resolution measurement system by the background-oriented schlieren (BOS) method is proposed in this note. The single-pixel correlation method is applied for the image pairs obtained by the BOS method, and the displacement is calculated. The backgrounds are projected by a high-speed projector and changed at 900 Hz for calculation of t...
Conference Paper
View Video Presentation: https://doi.org/10.2514/6.2021-2254.vid In this study, the propagation time and attenuation rate distributions of each sound source grid point (200 × 200) to a microphone of an arbitrary position across the shear layer, that are required for beamforming, were reconstructed by the reduced-order model with sparse sampling for...
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
Three-dimensional density fields of the twin jets were numerically and experimentally investigated. The present study focused on the comparison of the density distribution for the twin jets. The results obtained by the computational fluid dynamics (CFD) and three-dimensional background-oriented schlieren (3D-BOS) indicate that the periodic density...
Article
Aeroacoustic fields of a supersonic free jet at the Mach and Reynolds numbers of 2.1 and 70 000, respectively, of the transitional conditions are computationally investigated by large-eddy simulations. The supersonic transitional jets of different shear layer thicknesses without disturbances and those of the fixed shear layer thickness with disturb...
Article
Full-text available
In this study, the propagation time and attenuation rate distributions of each sound source grid point (200 × 200) to a microphone of an arbitrary position across the shear layer, which are required for beamforming, were reconstructed by the reduced-order model with sparse sampling for acceleration of the computation. First, the propagation time an...
Article
Full-text available
The wake structure of a freestream-aligned circular cylinder and its aerodynamic characteristics were investigated using a magnetic suspension and balance system (MSBS), which can levitate a model to eliminate support interference. The objectives of the present study were to investigate the flow field around a freestream-aligned circular cylinder a...
Article
The aeroacoustic fields of twin jets and the equivalent single jet were experimentally investigated using particle image velocimetry (PIV), schlieren visualization, and acoustic measurement. The present study focuses on the aeroacoustic fields of the twin jets, and the effect of the interaction between each jet was investigated using various nozzle...
Conference Paper
In acoustic wind tunnel testing, strut noise can be a great nuisance if it dominates the sound field. A magnetic model support would be a solution to this problem, as it supersedes the need for mechanical struts. A magnetic support is however likely to interfere with the microphone signals in acoustic wind tunnel testing, if the microphones are not...
Article
Full-text available
A single-pixel ensemble correlation method was applied to the schlieren and shadowgraph image velocimetry (SIV) and a velocimetry method that can obtain the convection velocity distribution of high spatial resolution without an expensive pulsed laser system being achieved for a laboratory-scale supersonic jet flow. A cold axisymmetric supersonic je...
Article
The Reynolds number effect on the aeroacoustic fields of a supersonic jet was experimentally investigated via particle image velocimetry (PIV), schlieren visualization, and near-field acoustic measurements. Cold supersonic jets under ideally expanded conditions at a Mach number of 2.0 were produced with the Reynolds number, based on the diameter of...
Article
In the single-pixel particle image velocimetry (PIV) method, the idea of the conventional method to calculate the variation is introduced and the extension of this method to the case in which the ideal particle image is not obtained is addressed. The extended method is based on the previous method which assumes the correlation distribution as a pro...
Article
Full-text available
The effects of jet temperature on acoustic waves generated by a supersonic jet are investigated using large eddy simulation (LES) based on a high-fidelity computational code. The sixth-order compact scheme and the fourth-order Runge–Kutta scheme are employed for spatial derivatives and time integration, respectively. First, a verification and valid...
Article
We proposed applying the cross-spectrum analysis to the unsteady pressure-sensitive paint (PSP) images to eliminate the electronic shot noise component from the pressure fluctuation spectrum. The data of surface pressure fluctuation behind a square cylinder which measured by means of the polymer/ceramic PSP with a frequency response of approximatel...
Conference Paper
In this study, the wake structure around freestream-aligned cylinder is investigated and its aerodynamic characteristics are discussed. A magnetic suspension and balance system (MSBS) was used to support a model without interference from a mechanical support device. Seven models with the fineness ratio (length to diameter, L/D) of 0.5, 1.0, 1.25, 1...
Article
Full-text available
The thermal inertia of sensors drastically limits the measurement of the temperature fluctuations in the high-frequency range. This issue is often addressed using cold wire techniques with dedicated corrections. In this study, three methods are employed to compensate high-frequency attenuation, and the correction of the end losses, are evaluated fo...
Article
Full-text available
The effect of Reynolds number on flow behaviors and pressure drag around axisymmetric conical boattails was experimentally investigated at low-speed conditions. Four conical boattails with slant angles of 12°, 16°, 20°, and 22° were studied. The Reynolds number ranged from 4.34 × 10⁴ to 8.89 × 10⁴ based on the model diameter. The global-luminescent...
Article
Full-text available
In this study, a linear reduced-order model of flow fields around a NACA0015 is constructed based on time-resolved particle image velocimetry (PIV) data. The PIV data were obtained at the chord Reynolds number of 6.4 × 10⁴, and angles of attack from 11° to 20°. Proper orthogonal decomposition (POD) analysis is employed for the PIV data and the degr...
Article
The visualization techniques for the aeroacoustics field of a supersonic jet flow are introduced and its capability is discussed by comparing with the characteristics of aeroacoustics fields acquired by computations. Aeroacoustics fields of supersonic jets (Re=10⁵, 10⁶) were visualized by means of the particle image velocimetry (PIV) and the schlie...
Article
Strong acoustic waves emitted from rocket plume might damage to rocket payloads because rocket payloads consist of fragile structure. Therefore, it is important to predict acoustic directivity and reduce its intensity level. In this study, we conduct experiments of supersonic jet flows and investigate an influence of the nozzle geometry on acoustic...
Article
The objective of this study was to understand the sound generation of flapping wings. In particular, the structural properties of the wings were varied to assess the effects of wing flexibility on the sound generation of flapping wings. A four-wing, hummingbird-inspired flapping wing micro air vehicle (FMAV) was considered. The half wing span was a...
Article
The effects of nozzle geometry on the acoustic waves from Mach 1.9 supersonic jet are experimentally investigated. PIV and microphone measurements are conducted to analyze the relationship between flows and acoustic waves. In this study, three different nozzles of conical nozzle, convergent-divergent nozzle (C-D) nozzle, and tab C-D nozzle in which...

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