Ct (Computer Tomography) Measurement of 3d Density Distributions of Flame: Obtaining Vertical Gradient Schlieren Brightness From Horizontal Gradient for Image-Noise Reduction

Nazari, A.; Ishino, Yuji; Yamada, Ryoya; Motohiro, Takanori; Fumiya, Ito; Kondo, Haruumi; Miyazato, Yoshiaki; Nakao, Shinichiro

doi:10.1615/tfec2019.cbf.027746

Cited by 2 publications

(6 citation statements)

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“…Figure 3 shows a conceptual framework for the formation of a projection image (density thickness) in the proposed schlieren 3D-CT system. Detailed descriptions of the various sections of Figures 3(a)-(k), along with the supporting formula, are provided in the previous reports [2]- [8] and many other references cited therein. Here, for brevity, the main points of Figure 3 are explained as follows.…”

Section: Image Processingmentioning

confidence: 99%

“…In fluid dynamics, the schlieren imaging technique is a common tool to illustrate detailed descriptions of air flows, shock waves, compressions, and expansion fans in supersonic jet flows for use in aerodynamical studies [1]. In previous works, a non-scanning three-dimensional computerized tomography (3D-CT) technique using a delicate multi-directional quantitative schlieren optical system with a flashlight source was developed and employed to measure instantaneous density distributions of several types of flames in laminar and turbulent flows [2] [3] [4] [5] [6]; in addition, some new techniques have been introduced [7] [8].…”

Section: Introductionmentioning

confidence: 99%

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Multi-Schlieren CT Measurements of Supersonic Microjets from Circular and Square Micro Nozzles

Nazari¹,

Ishino²,

Ishiko³

et al. 2020

JFCMV

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Instantaneous three-dimensional (3D) density distributions of a shock-cell structure of perfectly and imperfectly expanded supersonic microjets escaping into an ambient space are measured. For the 3D observation of supersonic microjets, non-scanning 3D computerized tomography (CT) technique using a 20-directional quantitative schlieren optical system with flashlight source is employed for simultaneous schlieren photography. The 3D density distributions data of the microjets are obtained by 3D-CT reconstruction of the projection's images using maximum likelihood-expectation maximization. Axisymmetric convergent-divergent (Laval) circular and square micro nozzles with operating nozzle pressure ratio 5.0, 4.5, 4.0, 3.67, and 3.5 have been studied. This study examines perfectly expanded, overexpanded, and underexpanded supersonic microjets issued from micro nozzles with fully expanded jet Mach numbers M j ranging from 1.47 -1.71, where the design Mach number is M d = 1.5. A complex phenomenon for free square microjets called axis switching is clearly observed with two types "upright" and "diagonal" of "cross-shaped". The initial axis-switching is 45˚ within the first shock-cell range. In addition, from the symmetry and diagonal views of square microjets for the first shock-cells, two different patterns of shock waves are viewed. The shock-cell spacing and supersonic core length for all nozzle pressure ratios are investigated and reported.

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Section: Image Processingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Multi-Schlieren CT Measurements of Supersonic Microjets from Circular and Square Micro Nozzles

Nazari¹,

Ishino²,

Ishiko³

et al. 2020

JFCMV

Self Cite

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“…Density thickness images are used for CT-reconstruction by maximum likelihood-expectation maximization (ML-EM) [15] an appropriate CT algorithm to obtain the 3D reconstruction of density distribution, the ML-EM method [2]- [9] is employed for CT-reconstruction. The CT procedure is carried out in each horizontal plane of z-axis for the reconstruction of deviation density distribution Δρ(x,y) from a linear data set of density thickness Dt'(X(θ)) (Figure 4(j)).…”

Section: Ct-reconstructionmentioning

confidence: 99%

“…In the present report, two new techniques are introduced based on a novel concept of complex brightness gradient in the quantitative schlieren images, "inverse process" and "multi-path integration" for image-noise reduction. The new techniques partially are presented in international conferences [8] [9], in detail and entirely will be discussed here. Furthermore, it will be shown an important ability of complex schlieren brightness gradient, which is independence on the path and starting point in the integration process.…”

Section: Introductionmentioning

confidence: 99%

“…Figure4shows a conceptual framework for the formation of a projection image (density thickness) in the proposed schlieren 3D-CT system. Detailed descriptions of the various sections of Figures4(a)-(k), along with the supporting formula, are given in the previous reports[2]-[9] and many other references cited therein. Here, for brevity, the main points of Figure4are explained as follows.The first goal is obtaining the density thickness of deviation density (Dt* (X(θ))) which shown in Figure4(d) with a unit of (kg/m 3 )(m).…”

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confidence: 99%

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Quantitative Schlieren Image-Noise Reduction Using Inverse Process and Multi-Path Integration

Nazari¹,

Ishino²,

Ito³

et al. 2020

JFCMV

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This report deals with introducing two new techniques based on a novel concept of complex brightness gradient in quantitative schlieren images, "inverse process" and "multi-path integration" for image-noise reduction. Noise in schlieren images affects the projections (density thickness) images of computerized tomography (CT). One spot noise in the schlieren image appears in a line shape in the density thickness image. Noise effect like an infectious disease spreads from a noisy pixel to the next pixel in the direction of single-path integration. On the one hand, the noise in the schlieren image reduces the quality of the image and quantitative analysis and is undesirable; on the other it is unavoidable. Therefore, the importance of proper noise reduction techniques seems essential and tangible. In the present report, a novel technique "multi-path integration" is proposed for noise reduction in projections images of CT. Multi-path integration is required the schlieren brightness gradient in two orthogonal directions. The 20-directional quantitative schlieren optical system presents only images of schlieren brightness in the horizontal gradient and another 20-directional optical system seems necessary to obtain vertical schlieren brightness gradient, simultaneously. Using the "inverse process", a new technique enables us to obtain vertical schlieren brightness gradient from horizontal experimental data without the necessity of a new optical system and can be used for obtaining any optional directions of schlieren brightness gradient.

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Ct (Computer Tomography) Measurement of 3d Density Distributions of Flame: Obtaining Vertical Gradient Schlieren Brightness From Horizontal Gradient for Image-Noise Reduction

Cited by 2 publications

References 0 publications

Multi-Schlieren CT Measurements of Supersonic Microjets from Circular and Square Micro Nozzles

Multi-Schlieren CT Measurements of Supersonic Microjets from Circular and Square Micro Nozzles

Quantitative Schlieren Image-Noise Reduction Using Inverse Process and Multi-Path Integration

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