Makoto Oki

Colorful patterns reveal the structures in fluids

Analytical methods based on color visualization are widely used today not only in the physical sciences but also in the rapidly expanding arena of life sciences. In addition to visualizing fluid flows, we have now added color imaging of dehydrated drops of biological liquids(blood serum, bile, tear, gastric juice), which are used in medical applications. The foundations of these prospective diagnostic methods are now being discussed along with some impressive examples of color visualization . This Journal contains papers from two different sources. One consists of papers extended from talks presented at the 11th Biannual Conference on Fluxes and Structures in Fluids. This conference was held at the Institute for Problems in Mechanics of the Russian Academy of Science on June 20-22, 2001. More than one hundred research scientists presented almost one hundred talks during the 3-day conference. The principal objective of the conference was discussing ways to construct closed models of environmental processes. The topic of flow imaging has come to play an important role in the journey toward achieving this goal. Recently, large sets of regular and chaotic structures in traditional and modern experimental studies can now be revealed by visualization techniques. The detailed structures of boundary layers and internal boundary currents in stratified and/or rotating fluids are now being studied under laboratory conditions. The most impressive applications of color flow visualization have been selected by the chairpersons of the various sessions for presentation in this Journal. However, it is beyond the scope of the Journal to present all the selected papers in a single issue. Therefore, papers not included in this issue will appear in subsequent issues. Parts of other presented papers are slated for publication in various Russian and International Journals. The other source of material is invited papers from researchers all over the world who wish to submit papers to the Journal of Visualization. We are grateful to all the authors for the effort to adapt their manuscripts to the Journal of Visualization’s style and standards. We are especially grateful to the chairpersons of the Conference Sessions who screened and recommended these papers out of the large number of presentations, and who have been involved in the preliminary peer review process. We’re very much looking forward to your participation at the next conference “Fluxes and Structures in Fluids”, scheduled to be held June 23-26, 2003 in St. Petersburg, Russia.

Effect of the Number of Grooves on Flow Characteristics around a Circular Cylinder with Triangular Grooves

In the flow around a circular cylinder, a sudden decrease in the mean drag coefficient occurs at a high Reynolds number, but the same phenomenon occurs at a lower Reynolds number in the case where there exist grooves or roughness on the cylinder surface. In this paper, in order to make clear the flow characteristics around a cylinder with 20, 26 and 32 triangular grooves, the mean drag coefficient, pressure distribution, velocity distribution and turbulence intensity distribution were measured. Moreover, the flow around the cylinder was analyzed by applying the RNGk − ɛ turbulent model, and the surface flow pattern was investigated using the oil-film technique. From these results, it was found that a sudden decrease in the mean drag coefficient of a cylinder with 32 triangular grooves occurs at a lower Reynolds number compared with 20 and 26 triangular grooves.

Effect of Groove Shape on Flow Characteristics around a Circular Cylinder with Grooves

In the flow around a circular cylinder, a sudden decrease in the drag force occurs at a high Reynolds number, but the same phenomenon occurs at a lower Reynolds number in the case where there exist grooves or roughness on the circular cylinder surface. In this paper, in order to make clear the flow characteristics around a circular cylinder in the case of changing the shapes of grooves, the drag coefficient, pressure distribution, velocity distribution and turbulent distribution were measured. Moreover the flow around the cylinder was analyzed by applying the RNGk · ∈ turbulent model, and the surface flow pattern was investigated using the oil-film technique. From these results, it is clear that the drag coefficient of a circular cylinder with triangular grooves decreases by about 15% compared with that of a circular cylinder with arc grooves.

Numerical Simulation of Flow around a Circular Cylinder with Curved Sectional Grooves

In a circular cylinder with uniform flow, a sudden decrease in the drag force occurs at a high Reynolds numbers; however, it is known that the same phenomenon occurs at a lower Reynolds number in the case where there exist grooves or roughness on the circular cylinder surface. To clarify the flow characteristics around a circular cylinder in the case of changing the shape of grooves we analyzed the drag coefficient, lift coefficient, turbulent kinetic energy, vorticity and pressure by applying the RNGk-ε turbulent model. The shapes of the grooves were arced, triangulated and curved. The results showed that the separation point for a circular cylinder with curved sectional grooves shifts to the most downstream side and the drag coefficient becomes the smallest among circular cylinders with grooves.

Jomon Pottery Observed from the Point of View of Fluid Mechanics: Did Jomon People Discover Twin and Kármán Vortices?

It is said that the Jomon period began about 12,000 years ago and continued till about 2,500 years ago. The potteries of that age are known as Jomon pottery. Among them, a pottery discovered from the Umataka ruin in Niigata Prefecture in 1931 has an excellent shape. It is said that this pottery was made about 4,500 years ago. Jomon potteries of similar artistic styles have been discovered in various parts in Japan. These potteries have very nice shapes, but the pottery discovered from the Umataka ruin excels other potteries in its excellent proportion. From the shape of lip, it was named “Kaen pottery” meaning “Flame potter”. However, from the patterns of its lip and side wall, it is more appropriate to consider that they are related to water flow. In this report, this hypothesis is made clear by a visualization method using the pollen of cedar and pine trees, and computer simulation.

The Memorial Year for the Journal of Visualization

It is our great pleasure to present the Journal of Visualization Volume 10, Number 4 to worldwide readers. JOV had many events in this year of the 10th anniversary. First, the e-Journal of JOV was published from Vol.10 No.1. This system can see the PDF files of each paper by access to the Web page of JOV (http://www.jov.jp/). To access this, it is necessary to use ID and Password, and to pay for the subscription fee. The subscription only e-Journal is not set under present situation. We would like to subscribe in many readers. Furthermore, adjusting to publication of this e-Journal, also Webpage made renewal. In June, it was announced that the impact factor for the year of 2006 became 0.806. This has shown that JOV is highly appraised from the researchers of the world. The 10th Anniversary Ceremony for JOV was held in Tokyo on July 24 during the 35th Symposium on Visualization in Japan and the JOV Award was presented to the Editorial Staffs who made the marvelous editorial contributions. For mainly Foreign Staffs, the same Award was presented at 9th ASV (Hong Kong, China) in June and 9th FLUCOME (Tallahassee, USA) in September. We heartily appreciate to the persons who have supported the publication of JOV and expect the further development of JOV in future. In the present issue, six portfolios, three short papers, six regular papers and a report are presented. The authors spread all over the world such as Korea, China, Germany, France, United Kingdom, Russia, U.S.A. and Japan. Visualization techniques of PIV are applied to measurement of the flow and its vibration of Japanese traditional bamboo flute and to experimental investigations of the unsteady behavior of a confined slot jet impinging on a flat plate. The radial diffuser pump is visualized by PIV method and CFD calculation. Spatially varying surface temperature oscillations in a nominally steady reattaching slot jet are analyzed using Proper Orthogonal Decomposition (POD) for two nozzle-tosurface spacings. The transitional flow patterns at mid-span between shrouded co-rotating disks are visualized using olive oil particles with a laser sheet and CCD camera, and near-wake behind a sphere were investigated using a smoke-wire visualization method. Lastly, we would like to thank all contributing authors, reviewers and related people who were involved with the publication of this issue.

Fluid Flow around a Circular Cylinder with Grooves of Curved Sectional Shape

In the case of a cylinder in uniform flow, a sudden decrease in the drag force occurs at a high Reynolds number, but it is known that the same phenomenon occurs at a lower Reynolds number in the case where there exist grooves or roughness on the cylinder surface. Such a drag reduction phenomenon can be applied to a vessel, an airplane, an electricity line, etc. for improving energy efficiency, or reducing the wind load. The purpose of this study is to investigate the mechanism underlying the flow of some kinds of cylinders with grooves of arc, triangular and curved sectional shape in the vertical direction. From these results, it was found that the separation point of the circular cylinder with grooves of curved sectional shape shifts to the most downstream side and the drag coefficient becomes the smallest.

Application of the Visualization in Information Processing Education

In recent years, in a class of a university, the Web teaching materials came to be used widely. We have developed the teaching materials applied visualization in the information processing education. From them, we report about the example of visualization of the sorting algorithm and the operation procedure of software. The visualization of the sorting algorithm was taken up four kinds of fundamental sorting algorithm (selection sort, bubble sort, insertion sort and quick sort) in the algorithm of computer science, and the visualization which can understand the difference in the technique of each algorithm by two kinds of methods was performed using the animation by Java. The visualization of the operation procedure of software was performed by making Flash movie captured the screen of operation of application software.

Verification of Healing Effect using Hanging Type Water Veil

A very thin water veil like a transparent thin sheet of vinyl has been produced by shaping a double-disk nozzle in such a way to accelerate the water flow inside the nozzle. Comparison of the simulated shape of the water veil with that of the experiment shows that they are almost identical. Human mind can be refreshed and relaxed by being inside of this water veil. In this paper, the application of water veil to healing of mind and body is examined. The analysis of the brain wave data using the emotion spectrum analysis method (ESAM) elicited that the water veil is very useful to recover the freshness and effective to healing of mind and body.

Analysis of New Type Water-Veil and Verification of its Healing Effect

A very thin water veil like a transparent thin sheet of vinyl has been produced by shaping a double-disk nozzle in such a way to accelerate the water flow inside the nozzle. A double-disk nozzle that hangs from upper side was newly developed. Comparison of the simulated shape of the water veil with that of the experiment shows that they are almost identical. Human mind can be refreshed and relaxed by being inside of this water veil. In this paper, the application of water veil to healing of mind and body is examined. The analysis of the brain wave data using the emotion spectrum analysis method (ESAM) elicited that the water veil is very useful to recover freshness and effective in healing mind and body.