Journal of Visualization - Volume 12, issue 4

Article Type: Other

Citation: Journal of Visualization, vol. 12, no. 4, pp. 283-284, 2009

Authors: Voropayev, S. I. | Fernando, H. J. S. | Nath, C.

Article Type: Other

Citation: Journal of Visualization, vol. 12, no. 4, pp. 285-285, 2009

Authors: He, P. | Zhou, Z. | Wang, Z. | Zhou, J. | Cen, K.

Article Type: Other

Citation: Journal of Visualization, vol. 12, no. 4, pp. 286-286, 2009

Authors: Chowdhury, M. R. | Testik, F. Y. | Khan, A. A.

Article Type: Other

Citation: Journal of Visualization, vol. 12, no. 4, pp. 287-287, 2009

Authors: Estruch, D. | Lawson, N. J. | MacManus, D. G. | Garry, K. P. | Stollery, J. L.

Article Type: Other

Citation: Journal of Visualization, vol. 12, no. 4, pp. 289-290, 2009

Authors: Saito, Y. | Ingram, A. | Fan, X. | Seville, J. P. K.

Article Type: Other

Citation: Journal of Visualization, vol. 12, no. 4, pp. 291-292, 2009

Authors: Nosu, K. | Yabuzaki, Y. | Yamanaka, K.

Article Type: Other

Citation: Journal of Visualization, vol. 12, no. 4, pp. 293-294, 2009

Authors: Paeng, D.-G. | Nam, K.-H.

Article Type: Research Article

Abstract: It is well known that the scatter of ultrasound by blood is mainly attributed to red blood cells (RBCs) and RBC aggregation. In the present review, researches of hemodynamic influence on RBC aggregation and ultrasound backscatter from blood were overviewed. A mock flow loop and a cylindrical chamber were employed to produce various blood flows, such as pulsatile, oscillatory, and rotational flow. The "black hole" (BLH), a dark hole at the tube center surrounded by bright …zone in the cross sectional B-mode image and "bright collapsing ring" (BRCR) phenomena, appearance of bright ring at the periphery and collapse of it at the center during a pulsatile cycle, were observed under pulsatile flow. The combined effects of shear rate and flow acceleration on RBC aggregation were suggested as a possible mechanism for these phenomena. The stroke volume-dependence of the "bright ring" phenomenon under oscillatory flow could also be explained by flow acceleration. The enveloped echo images from rotational flow in a compact blood chamber showed the spatial and temporal variations of RBC aggregation, which varied with the mammalian species. In the stenotic model, it was found that the echogenic variation increased locally at a distance of three tube diameters downstream from the stenosis during decelerating period, which was proposed to be mainly due to flow turbulence. The similar "bright ring" was also observed from in vivo human carotid artery in harmonic imaging. Show more

Keywords: Blood echogenicity, Flow turbulence, Flow acceleration, Hemodynamics, Red blood cell aggregation, Shear rate, Ultrasonic visualization

Citation: Journal of Visualization, vol. 12, no. 4, pp. 295-306, 2009

Authors: Auteri, F. | Belan, M. | Cassinelli, C. | Gibertini, G.

Article Type: Research Article

Abstract: The flow around two bluff bodies in tandem is an interesting phenomenon whose nature strongly depends on the distance between the bodies. In this work oil smoke visualizations of the flow around two normal flat plates in tandem configuration are compared with phase averaged Laser Doppler Anemometry measurements of the flow field for a full period. Phase averaging is exploited to resolve the mean time evolution of the flow and the signal from a single constant …temperature hot wire probe is employed as phasing reference. The flow-field information obtained from visualizations agrees well with quantitative indications provided by measures, and the comparison allows to precisely understand what information can be extracted from simple visualizations. As a result, new insight in flow mechanism is obtained from the analysis of the flow data showing that, for the analyzed plate distance, the gap between the two plates behaves substantially as a cavity while the vortex formation process takes place in the wake region behind the aft plate. Show more

Keywords: Flat Plate, Bluff bodies, Wake Interference, Laser Doppler Anemometry, Phase averaging

Citation: Journal of Visualization, vol. 12, no. 4, pp. 307-321, 2009

Authors: Seiler, F. | Pichler, A. | Pfaff, R. | Srulijes, J.

Article Type: Research Article

Abstract: A unique technique, the Doppler Picture Velocimetry (DPV), for measuring and visualizing velocities especially in hypersonic gas flows is presented. By means of a Michelson interferometer (MI) the Doppler shifted light scattered by tracers is transformed into an image showing Fizeau fringes. The image fringe distribution provides information on the Doppler frequency shift which is related to the velocity of the particles crossing a light sheet plane. To overcome former disadvantages of DPV, the optical set-up …as well as the processing scheme have been improved significantly. Two schemes have been tested in recent times for fringe processing: 1) an alternative process, the Least Square Estimators (LES) and 2) an algorithm based on a technique using Fast Fourier Transformations (FFT) to examine the DPV images in the frequency domain. The new DPV algorithms now allow an automated calculation of the velocity profiles from the Doppler pictures without manual fringe tracing as it had to be done in the past. Both methods are compared by means of Mach 6 flows around a wedge and a sphere produced in the ISL high energy shock tunnel STA. TiO_2 particles are illuminated by a laser light sheet which was perpendicularly arranged to the main flow direction. Light observation via the MI from the side (90° to illumination) informs on the vertically oriented velocity through the DPV images. Show more

Keywords: 2D Doppler velocity measurements, hypersonic flow, light sheet, tracer, velocity visualization, Michelson interferometer, sphere and wedge flow velocity visualization

Citation: Journal of Visualization, vol. 12, no. 4, pp. 323-337, 2009

Authors: Kubota, Y. | Mochizuki, O.

Article Type: Research Article

Abstract: Splashes caused by a spherical body plunging into water were investigated experimentally using a high speed CMOS camera. We categorized types of splash according to impact velocities of the sphere. Three types of splash were found: Type-I is a thin spire-type splash, Type-II is a mushroom-type splash with many droplets, and Type-III is a crown-type splash with many droplets. The reaction to the concave water surface attached to the sinking sphere is a cause of the …Type-I splash. The film flow climbing up the sphere is a dominant cause of the Type-II splash. The velocity of the film flow, which is proportional to the impact velocity of the sphere, affects the fingers of the film flow, detaching of droplets, and maximum height of the Type-II splash. The Type-III crown-type splash is characterized by water jets with many droplets. A bulky air column in water is formed behind the sinking sphere, and longitudinal ridges and ripples on the surface of the air column were observed. Show more

Keywords: Visualization, Water splash, Solid sphere, Film flow, High speed CMOS video camera

Citation: Journal of Visualization, vol. 12, no. 4, pp. 339-346, 2009

Authors: Sohn, C.H. | Ju, M.G. | Gowda, B.H.L.

Article Type: Research Article

Abstract: The vortexing phenomenon that occurs in a cylindrical container is studied using PIV. The influence of the vane-type suppressors which prevent the vortex formation is investigated. An attempt has been made to understand the mechanism that is responsible for vortex suppressing. There is a strong updraft generated due to the suppressors which leads to annihilation of vorticity which appears to be responsible for vortex suppression.

Keywords: Vortexing, Vane-type Suppressors, PIV

Citation: Journal of Visualization, vol. 12, no. 4, pp. 347-360, 2009

Authors: Kantoush, S.A. | Schleiss, A.J.

Article Type: Research Article

Abstract: Shallow depth flow fields and low velocity magnitudes are often challenges for traditional velocity measuring instruments. As such, new techniques have been developed that provide more reliable velocity measurements under these circumstances. In the present study, the two-dimensional (2D) surface velocity field of shallow basins is assessed by means of Large-Scale Particle Image Velocimetry (LSPIV). The measurements are carried out at the water surface, which means that a laser light sheet is not needed. Depending on …the time scales of the flow and the camera characteristics, it is even possible to work with a constant light source. An experimental application of this method is presented to analyze the effects of shallow basin geometry on flow characteristics in reservoirs where large coherent two-dimensional flow structures in the mixing layer dominate the flow characteristics. The flow and boundary conditions that give rise to asymmetric flow are presented. Asymmetric flow structures were observed starting from basin shape ratios that are less than or equal to 0.96. By decreasing the basin length and increasing the shape ratio to greater than 0.96, the flow structure generally tends towards a symmetric pattern. Show more

Keywords: Visualization, LSPIV, Flow in shallow basins, Basin geometry, Flow patterns

Citation: Journal of Visualization, vol. 12, no. 4, pp. 361-373, 2009

Authors: Kang, J.H. | Lee, S.J.

Article Type: Research Article

Abstract: The ventilation flow in a heating, ventilation and air conditioning (HVAC) module of a passenger car was investigated experimentally. Three different ventilation modes with varying temperature mode were tested to study the effect of ventilation mode on the velocity field inside the HVAC module. For each mode, more than 450 instantaneous velocity fields were measured using a particle image velocimetry (PIV) velocity field measurement technique. The instantaneous velocity fields were ensemble averaged to obtain the spatial …distribution of mean velocity and spanwise vorticity. The present work highlights the usefulness of the PIV technique for the analysis of the flow inside an HVAC module. The experimental results can be used not only to understand and improve the ventilation flow of an HVAC module but also to validate numerical predictions. Show more

Keywords: HVAC, PIV, ventilation mode, temperature mode, flow visualization

Citation: Journal of Visualization, vol. 12, no. 4, pp. 375-382, 2009

Authors: Ueda, Y. | Kurata, M. | Kida, T. | Iguchi, M.

Article Type: Research Article

Abstract: Flow past a square prism with cut-corners at the front-edge is numerically and experimentally visualized to investigate a mechanism of drag reduction. An adaptive numerical scheme based on the vortex method is implemented for two values of the Reynolds number between 200 and 1,250, and the results are compared with experiments. Experimental visualization techniques include the hydrogen-bubble technique at Re=4,000 and the oil-flow technique at Re=10,000 for a global wake formation, and the aluminum-flake …technique for transient flow at the early stage of motion at Re=1,250. A similar reattachment flow pattern is shown in a wide range of the Reynolds number between 200 and 10,000, which implies a possibility of the drag reduction in the Reynolds number being approximately lower than 8,000 unlike the previous findings. Show more

Keywords: Drag Reduction, Square Prism, Vortex Method, Hydrogen-Bubble Technique, Aluminum-Flake Technique, Oil-Flow Technique

Citation: Journal of Visualization, vol. 12, no. 4, pp. 383-391, 2009

Authors: Kitagawa, K. | Sakakibara, M. | Yasuhara, M.

Article Type: Research Article

Abstract: Investigation of flapping wings of insect are focused on low Reynolds number effect and the unsteady aerodynamic properties. Interaction between flapping wing of insects and the air flow became one of important and fundamental research topics in micro air vehicle. The present work is aim to investigate the flow behavior of flapping wings of tethered scarab beetle. The generation mechanisms of velocity field and vortex formation are visualized with smoke-wire method. Tethered flight of the drone …beetle shows the motion with elastic deformation of flapping wing. Measured flapping frequency is about 71 Hz and its frequency is higher than for dragonfly and butterfly. Beetle decreases negative lift by feathering motion in the upstroke process and increase positive lift by effect of wake capture in the downstroke process. Show more

Keywords: insect flight, drone beetle, flow visualization, biofluid mechanics, micro air vehicle

Citation: Journal of Visualization, vol. 12, no. 4, pp. 393-400, 2009

Article Type: Other

Citation: Journal of Visualization, vol. 12, no. 4, pp. 401-404, 2009