Journal of Visualization - Volume 1, issue 3

Authors: , Yasuki

Article Type: Other

Citation: Journal of Visualization, vol. 1, no. 3, pp. 231-231, 1998

Article Type: Other

Citation: Journal of Visualization, vol. 1, no. 3, pp. 233-238, 1998

Authors: Massonnet, D.

Article Type: Research Article

Abstract: Radar instruments are used to observe the Earth with radio waves. The resulting image reflects both the physical properties of the waves and the technological choices that have to be made to obtain a usable image from the raw data gathered by the instrument. We describe the way a radar image is obtained through computer as a two-fold image. The first part, the amplitude, conveys a similar, but different information than conventional imagery, such as the …geometry of pixel layout on the ground and the estimation of the speed of mobile targets on land or sea. The second part, the phase, cannot be visualized by itself and gains value only through the comparison with the similar part of a companion image. An accurate description of terrain elevation can be obtained from the slight difference of point of view between the images. A much more accurate assessment of terrain displacement, down to millimeters, between the acquisition dates of the images can also be obtained. In addition, otherwise invisible meteorological phenomena can be mapped. We describe examples of the way these various pieces of information are obtained together or separately, as well as ways to combine the results into a singe color image. Show more

Keywords: remote sensing, radar, interferometry, space geodesy, digital elevation models

Citation: Journal of Visualization, vol. 1, no. 3, pp. 239-253, 1998

Authors: Modi, V.J. | Yokomizo, T.

Article Type: Research Article

Abstract: The paper studies effect of momentum injection, accomplished through circular cylindrical rotating elements, on the pressure distribution at the roof of a model house. Extensive wind tunnel tests, complemented by flow visualization, suggest that such Moving Surface Boundary-layer Control (MSBC) effectively delays separation and significantly increases the pressure, both on leeward and windward surfaces. This would assist in protection of the roof against wind storms and snow accumulation.

Keywords: wind-induced roof pressure, boundary-layer control

Citation: Journal of Visualization, vol. 1, no. 3, pp. 255-260, 1998

Authors: Endo, M. | Iwamoto, J.

Article Type: Research Article

Abstract: Noise is generated from a flow field upstream of a shock wave periodically discharged from a pipe end. A vortex ring and an underexpanded jet are periodically formed and diffused downstream. To clarify the mechanism of the noise generation, the flow field was experimentally and numerically studied. The flow field was visualized mainly by the schlieren method and the sound pressure of the noise was measured. The pulsatile flow through the pipe was numerically simulated by …Random-Choice Method and using these results as the boundary condition, the pulsatile jet was simulated by TVD scheme. As a result, a good qualitative agreement was found between the flow field obtained by the calculations and that by the experiments. Furthermore, a relation between the behaviour of the vortex ring and the generation of the noise was discussed. Show more

Keywords: simulation, pulsatile jet, noise generation, TVD scheme, Random-Choice Method

Citation: Journal of Visualization, vol. 1, no. 3, pp. 261-269, 1998

Authors: Nishimura, T. | Kaga, T. | Shirotani, K. | Kadowaki, J.

Article Type: Research Article

Abstract: Vortical and thermal structures of non-premixed propane flame in a bluff-body burner are studied experimentally in the transition from laminar to turbulent flow. In particular, we focus attention on the effect of annular air flow on the flame. The small-scale inner vortices inside the flame is stimulated by the annular air flow, and outside the flame, small eddies due to turbulence rather than the large-scale outer vortices due to thermal buoyancy become dominant with increasing air …velocity. The interrelation between the vortical and thermal structures is analyzed by looking at the frequency spectrum and probability density function of temperature fluctuations. Show more

Keywords: combustion, non-premixed flame, shadowgraph method vortical structure, thermal structure, bluff-body burner

Citation: Journal of Visualization, vol. 1, no. 3, pp. 271-281, 1998

Authors: Yang, Q.D. | Ma, M.S. | Yu, T. | Hu, H.D. | Zhou, N.C. | Zhang, J.X.

Article Type: Research Article

Abstract: Some results of flow visualization are described for an unconventional fuselage with Erickson-like forebody. The experiment includes force measurement, surface oil flow visualization, and laser sheet flow visualization. Some results are also obtained from a CFD code for solving laminar Navier-Stokes equations. Although there are some differences between the model in the experiment and the model in the computation, the location of vortex on the models exhibits good agreements. The investigation in this paper …shows that varying the forebody shape of fuselage can change the flow characteristics greatly and the Erickson-like forebody has potential to improve the lateral-direction stability of the aircraft at high angles of attack. Show more

Keywords: flow visualization, unconventional forebody , high angle of attack

Citation: Journal of Visualization, vol. 1, no. 3, pp. 283-290, 1998

Authors: Hassan, Y.A. | Schmidl, W.D. | Ortiz-Villafuerte, J.

Article Type: Research Article

Abstract: The experimental flow visualization tool, Particle Image Velocimetry (PIV), is being extended to determine the velocity fields in three-dimensional, two-phase fluid flows. In the past few years, the technique has attracted quite a lot of interest. PIV enables fluid velocities across a region of a flow to be measured at a single instant in time in the whole volume (global) of interest. This instantaneous velocity profile of a given flow field is determined by digitally recording …particle (microspheres or bubbles) images within the flow over multiple successive video frames and then conducting flow pattern identification and analysis of the data. This paper presents instantaneous velocity measurements in various three-dimensional, bubbly two-phase flow situations. This information is useful for developing or improving existing computer constitutive models that simulate this type of flow field. It is also useful for understanding the detailed structure of two-phase flows. Show more

Keywords: three-dimensional measurement, particle image velocimetry, bubbly flow, conditional sampling, Reynolds stress

Citation: Journal of Visualization, vol. 1, no. 3, pp. 291-301, 1998

Authors: Kaga, A. | Yamaguchi, K. | Inoue, Y. | Kondo, A.

Article Type: Research Article

Abstract: A new 3-D PIV-technique that is applicable to low velocity airflow in a real space such as indoor airflow is proposed, and its performance is inspected through a simulation and an experimental application. In this technique, two parallel planes separated by short distance are illuminated by a pair of laser light sheets of different colors. The visualized images are separated with optical filters, and recorded on VTRs. The 2-D tracer pattern movement on visualized planes is …tracked with pattern tracking and the movement normal to the visualized planes is calculated from the difference of tracer concentration between two planes. The simulation result showed that the algorithm proposed here can calculate 3-D velocity field adequately, but the experimental result showed that the luminous intensity difference between two visualized planes became the main source of experimental errors. Show more

Keywords: PIV, indoor airflow, pattern tracking, simulation, wind tunnel experiment

Citation: Journal of Visualization, vol. 1, no. 3, pp. 303-312, 1998

Authors: Takehara, K. | Etoh, T.

Article Type: Research Article

Abstract: An algorithm for particle identification in PTV, which is classified in the category .particle mask correlation method,.is presented and tested. A typical brightness pattern of a particle image is referred to as a particle mask. The particle mask is centered on a pixel in the image plane and the cross correlation between the particle mask and a region of the image plane centered on the given pixel is calculated. The particle mask is scanned over the entire …image plane and the cross correlation coefficient is calculated at each pixel location. Small subareas with high correlation coefficients indicate central areas of particle images. Show more

Keywords: particle mask, particle image extraction, particle tracking velocimetry

Citation: Journal of Visualization, vol. 1, no. 3, pp. 313-323, 1998