Flow visualization

About: Flow visualization is a research topic. Over the lifetime, 12988 publications have been published within this topic receiving 268455 citations.

Low-Speed Wind Tunnel Testing

Abstract: Wind Tunnels Wind Tunnel Design Pressure, Flow, and Shear Stress Measurements Flow Visualization Calibration of the Test Section Forces and Moments from Balance Measurements Use of Wind Tunnel Data: Scale Effects Boundary Corrections I: Basics and Two- Dimensional Cases Boundary Corrections II: Three-Dimensional Flow Boundary Corrections III: Additional Applications Additional Considerations for Aerodynamic Experiments Aircraft and Aircraft Components Ground Vehicles Marine Vehicles Wind Engineering Small Wind Tunnels Dynamic Tests Appendices Index

An Album of Fluid Motion

Abstract: Keywords: visualisation de l'ecoulement ; tourbillon ; dynamique des : fluides ; aubes ; cylindre ; instabilite ; ecoulement : secondaire Note: moult photos Reference Record created on 2005-11-18, modified on 2016-08-08

Blood flow in arteries

Abstract: Blood flow in arteries is dominated by unsteady flow phenomena. The cardiovascular system is an internal flow loop with multiple branches in which a complex liquid circulates. A nondimensional frequency parameter, the Womersley number, governs the relationship between the unsteady and viscous forces. Normal arterial flow is laminar with secondary flows generated at curves and branches. The arteries are living organs that can adapt to and change with the varying hemodynamic conditions. In certain circumstances, unusual hemodynamic conditions create an abnormal biological response. Velocity profile skewing can create pockets in which the direction of the wall shear stress oscillates. Atherosclerotic disease tends to be localized in these sites and results in a narrowing of the artery lumen—a stenosis. The stenosis can cause turbulence and reduce flow by means of viscous head losses and flow choking. Very high shear stresses near the throat of the stenosis can activate platelets and thereby induce thrombosis, which can totally block blood flow to the heart or brain. Detection and quantification of stenosis serve as the basis for surgical intervention. In the future, the study of arterial blood flow will lead to the prediction of individual hemodynamic flows in any patient, the development of diagnostic tools to quantify disease, and the design of devices that mimic or alter blood flow. This field is rich with challenging problems in fluid mechanics involving three-dimensional, pulsatile flows at the edge of turbulence.

Passive mixing in a three-dimensional serpentine microchannel

Abstract: A three-dimensional serpentine microchannel design with a "C shaped" repeating unit is presented in this paper as a means of implementing chaotic advection to passively enhance fluid mixing. The device is fabricated in a silicon wafer using a double-sided KOH wet-etching technique to realize a three-dimensional channel geometry. Experiments using phenolphthalein and sodium hydroxide solutions demonstrate the ability of flow in this channel to mix faster and more uniformly than either pure molecular diffusion or flow in a "square-wave" channel for Reynolds numbers from 6 to 70. The mixing capability of the channel increases with increasing Reynolds number. At least 98% of the maximum intensity of reacted phenolphthalein is observed in the channel after five mixing segments for Reynolds numbers greater than 25. At a Reynolds number of 70, the serpentine channel produces 16 times more reacted phenolphthalein than a straight channel and 1.6 times more than the square-wave channel. Mixing rates in the serpentine channel at the higher Reynolds numbers are consistent with the occurrence of chaotic advection. Visualization of the interface formed in the channel between streams of water and ethyl alcohol indicates that the mixing is due to both diffusion and fluid stirring.

Visualization for the analysis of fluid motion

Abstract: In the present issue, Vol. 8 / No. 1 of the Journal of Visualization, seven technical papers are presented. In many of them, visualization plays key role for the analysis of fluid motions. The authors spread all over the world such as the countries, China, Hong-Kong, Denmark, Turkey, Korea, U. S. A., Jordan and Japan, which indicates JOV is becoming popular journal in the world. On behalf of the Editorial Board, the editors of the present issue acknowledge all the authors, referees and the people that contributed to the publication of this issue. Fluid Motions are nonlinear in their nature. As a result, very different features of fluid motions appear when key parameters are changed. The key parameters in fluid dynamics are, for instance, Reynolds number, Mach number, Prandtl number, and else. Key parameters also lie in body geometries and their configurations immersed in fluid motion. There is infinite choice of the parameters for the problem settings. There are many methods for the approach to research of fluid motion. Theoretical, experimental and computational methods are the basic three. Fortunately, new measurement techniques especially using visualized allow us to carry out experiments for any flow configuration. Same is true for computational techniques. Now, there is a lot of good software available and progressed computer performance allowed us to carry out sophisticated simulations using PC’s. Based on the flow parameters, geometry parameters and the method of approach, we may prepare any number of technical papers by changing the key parameters. It may be necessary to do so for good understanding of nonlinear nature of fluid motions. When looking at the papers in this issue, we notice that it actually happens. They handle compressible flows/incompressible flows. Their approaches are experimental/computational. Their applications are so wide. There is an old publication “Journal of the Aeronautical Research Institute, Tokyo Imperial University”. The “Aeronautical Research Institute” now is the Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (ISAS/JAXA) for which one of the editors of the present issue works. As a No. 65 of this old journal published in January 1930, there appeared the lecture given by Prof. L. Prandtl in October 1929. Within 23 pages of this journal (which would be only four or five pages of JOV), he explained all about boundary layer theory, flow instability, mixing-length (turbulence models) and effect of compressibility (Prandtl-Glauert law). As fluid motion is nonlinear and the research became so difficult, deep analysis in a very narrow research area is required and we, researchers have fallen into such narrow region of fluid dynamics. When I saw the paper by Prof. Prandlt, I felt that we may need to stop and think what we are doing and how we are contributing to the research field of “Fluid Dynamics” from the global viewpoint. Visualization is a very good tool not only to understand the details of fluid motion but also to understand key feature of fluid motion. With this tool, we may be able to make much higher contributions to Fluid Dynamics.