Journal of Visualization - Volume 10, issue 1

Authors: Iida, A. | Mizuno, A. | Brown, R. J. | Kato, C.

Article Type: Other

Citation: Journal of Visualization, vol. 10, no. 1, pp. 37-38, 2007

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

Article Type: Research Article

Abstract: Movement of natural sand particles (d=200–300 μm) in a simulated atmospheric boundary layer was visualized using a digital high-speed camera. The consecutive particle images recorded at 2000 fps (frame per second) enabled us to observe the particle transport in detail, especially near the flat sand surface. Various modes of sand saltation were identified. The transverse motion of particles, often ignored in previous studies, was also visualized. In addition, instantaneous velocity fields of saltating particles were obtained …using a particle tracking velocimetry (PTV), and statistical analysis of saltating particle trajectories was performed. The qualitative and quantitative results of the present study will be useful for understanding the basic physics of transport of saltating sand particles. Show more

Keywords: Visualization, High-speed photography, Saltation, PTV, sand particles

Citation: Journal of Visualization, vol. 10, no. 1, pp. 39-46, 2007

Authors: Paik, B. G. | Kim, G. D. | Lee, J. Y. | Lee, S. J.

Article Type: Research Article

Abstract: The inflow ahead of a rotating propeller attached to a container ship model was visualized using a two-frame particle image velocimetry (PIV) technique. For illuminating the inflow region, a transparent window was installed at the stern of the ship model. Ensemble-averaged mean velocity fields were measured at four different blade phases under the design loading condition. The characteristics of the inflow in the upper plane above the propeller axis are quite different from those below the …propeller axis. In the far upstream region above the propeller axis, most of the inflow comes from the hull wake and the axial velocity is very small. As the inflow moves toward the propeller plane, its axial velocity component increases rapidly. In addition, the variation of the inflow characteristics with respect to phase angle becomes apparent. The thick hull boundary layer and out-of-plane motion resulting from the propeller rotation produce a large turbulent kinetic energy around the tip of the propeller blade in the upper inflow region. The axial velocity distribution of the propeller inflow is asymmetric with respect to the vertical center axis, exhibiting different axial velocities on the port and starboard sides. Show more

Keywords: Two-frame PIV, Propeller inflow, Phase-averaging, Tip vortex, Total velocity

Citation: Journal of Visualization, vol. 10, no. 1, pp. 47-55, 2007

Authors: Shao, C. P. | Wang, J. M. | Wei, Q. D.

Article Type: Research Article

Abstract: A narrow strip has been introduced as a control element to suppress vortex shedding from a cylinder. The strip is set parallel to the cylinder axis, and the key parameter of control in this study is the strip position, which is determined by the angle of attack of the strip and the distance between the strip and the cylinder axis. A circular cylinder and a square cylinder were tested respectively. Flow visualization and hot-wire measurement were …performed in a low turbulence wind tunnel in the range of Reynolds number Re=4.0 × 10^3 ∼ 2.0 × 10^4 . Test results show that, vortex shedding from both sides of the cylinder can be effectively suppressed if the strip is located in a certain zone in the wake. The effective zones in circular cylinder wakes at different Reynolds numbers have been found out, and the mechanism of the suppression has been discussed. Show more

Keywords: Visualization, Flow control, Bluff-body, Vortex shedding, High Reynolds number

Citation: Journal of Visualization, vol. 10, no. 1, pp. 57-64, 2007

Authors: Alam, Md. Mahbub | Fu, S. | Zhou, Y.

Article Type: Research Article

Abstract: The wake of a streamwise oscillating cylinder is presently investigated. The Reynolds number investigated is 300, based on the cylinder diameter d. The cylinder oscillates at an amplitude of 0.5 d and a frequency f_e /f_s =1.8, where f_e is the cylinder oscillating frequency and f_s is the natural vortex shedding frequency of a stationary cylinder. Under these conditions the flow is essentially two dimensional. A two-dimensional direct numerical …simulation (DNS) scheme has been developed to calculate the flow. The DNS results display a street of binary vortices, each containing two counter-rotating vortical structures, symmetrical about the centerline, which is in excellent agreement with measurements. The drag and lift on the cylinder have been examined. The time averaged drag and lift are 1.4 and 0, respectively, which are the same as those on a stationary cylinder at the same Re. However, the fluctuating drag was high, about 2.68. It has been found that, being symmetrically formed about the centerline, the binary vortices induce an essentially zero fluctuating lift, which may have a profound implication in flow control and engineering. Show more

Keywords: Binary vortex, Streamwise oscillating cylinder, Vortex formation mechanism

Citation: Journal of Visualization, vol. 10, no. 1, pp. 65-73, 2007

Authors: Ohyama, R. | Aoyagi, K. | Kitahara, Y. | Ohkubo, Y.

Article Type: Research Article

Abstract: Experimental visualization for ionic wind motion originated from DC corona discharges in a needle-plate electrode system has been investigated. A vapor-phase biacetyl tracer with laser-induced phosphorescence emission is used for optically characterizing the ionic wind profile. The ionic wind blows the excited biacetyl molecules away in continuing the visible phosphorescence emission for a long radiative lifetime. The captured image with elapsing time from the excitation presents the shifting location of radiative tracer along …the ionic wind direction. The experimental results show the ionic wind profile enhanced in the electric field direction corresponding to the corona discharge progress. Especially, the ionic wind near an initiating point of corona discharges is focused as an advantage of this optical technique. The ionic wind velocity along the electrode axis can be obtained at the location close enough to the corona discharge initiation point, and the velocity at 0.5 mm from the discharge point is figured out as 9.3 to 19.2 m/s under the condition of the EHD Reynolds number of 0.95 × 10^3 to 2.1 × 10^3 . Show more

Keywords: Ionic wind, Phosphorescence emission, Flow velocity measurement, Corona discharge, Radiative tracer

Citation: Journal of Visualization, vol. 10, no. 1, pp. 75-82, 2007

Authors: Yang, H. C.

Article Type: Research Article

Abstract: Motionless mixers have found a large range of applications, including blending, reaction, dispersion, heat transfer and mass transfer. Understanding the mixing processes that occur in these diverse systems is essential for predicting many aspects of practical importance. The objective of this study is to perform the experimental investigations of mixing characteristics for three different motionless mixers. The red color dye tracer was mixed in the main stream of green hair styling gel, and then the mixing …efficiency was quantified by calculating the percentage area concentration of red color at the outlet cross section using a digital image processing technique. In the Sulzer SMX and YHC mixer, a single element mixes the fluid nearly in two dimensions, and three-dimensional mixing is accomplished by the next elements aligned at 90° to their former one. In the Sulzer SMX mixer, the flow appears to be globally well mixed after 5 elements, while in the YHC and YNU mixers, it is necessary to globally well mix more than 1 and 2 elements. Show more

Keywords: Motionless Mixer, Mixing Element, Mixing Characteristics, Visualization, Digital Image Processing Technique

Citation: Journal of Visualization, vol. 10, no. 1, pp. 83-89, 2007

Authors: Mizukaki, T.

Article Type: Research Article

Abstract: In order to investigate the developing characteristics of a high temperature supersonic impulse jet under an atmospheric ambient condition, we generate jets induced by an incident shock wave at Mach number 2.89, emerging from the open end of a high enthalpy blast wave simulator (HEBS). Developing high temperature supersonic impulse jets were visualized by the direction-indicating color schlieren method and analyzed by numerical calculations. A comparison of the experimental results with literature shows …that the unsteady boundary area generated by the HEBS, starts to grow in half the time that the unsteady boundary area needs after the incident shock wave emerges in the literature. Show more

Keywords: Flow visualization, Supersonic jet, Vortex, Blast wave, Shock tube

Citation: Journal of Visualization, vol. 10, no. 1, pp. 91-98, 2007

Authors: Reungoat, D. | Rivière, N. | Fauré, J. P.

Article Type: Research Article

Abstract: The present work focuses on the measurements of instantaneous concentration fields of a passive scalar due to an impinging round jet injection into a liquid filled rectangular tank. Simultaneous measurements of velocity and passive scalar concentration fields have been conducted by using Particle Image Velocimetry (planar 2C and 3C PIV) and Planar Laser Induced Fluorescence (PLIF) techniques. The mixing injection behavior is analyzed for several injection values of depth and flow rate. Results showed the classical …developing and self-similar regions of the jet, the mixing layer and the coupled concentration and velocity fields due to impingement. Finally, 3C PIV reveals a 3D flow jet structure which seems to be a swirl that does not disturb 2D analysis. Show more

Keywords: Impinging jet, Turbulent, SPIV, PLIF

Citation: Journal of Visualization, vol. 10, no. 1, pp. 99-110, 2007

Authors: Ng, K.-W. | Wong, Y.-P.

Article Type: Research Article

Abstract: In this paper, we propose four different geometric measures to identify appropriate triangles to be simplified in 3D complex model. Each measure yields different weight on the same surface and produces a unique simplified model that worth to be analyzed. The proposed measures involve consideration on the resulting of the surfaces collapse, the high peak and low peak of the triangles mesh, the irregular triangle shape, the capacity and boundary view on the triangles mesh. The …chosen triangle is to be collapsed based criterion on Half-edge Collapse Transformation method. From the empirical results, one of the proposed measures presents almost excellence in all the criteria mentioned above. The empirical results include the quality of the surface models (visualization purpose), the efficiency of the measures and the overall appearance preservation of the simplified models. The proposed measures are then to be compared to three existing measures. From the analyzed results, we combine the measures to adapt to the user's response for generating the user-desired simplified models. Show more

Keywords: Visualization, Computer Graphics, Level of Details, Virtual Reality

Citation: Journal of Visualization, vol. 10, no. 1, pp. 111-121, 2007

Authors: Kompenhans, J.

Article Type: Research Article

Abstract: The 12th International Symposium on Flow Visualization (ISFV12) was held at Göttingen, Germany, September 10–14, 2006. The symposium attracted 360 participants from 31 countries. The symposium was organized in 75 sessions, including one poster session, and seven invited lectures. Five special sessions focused on areas of current interest in flow visualization. Two awards: the Asanuma Award and the Leonardo Da Vinci Award have been presented to two experts in recognition of their excellent contributions to the …field of flow visualization. Three awards have been provided for young scientists to acknowledge their scientific work and oral presentation at the symposium. The symposium was accompanied by a public lecture and an exhibition of vendors of equipment for flow visualization. Show more

Keywords: Aerodynamics, Art, Biological Flows, CFD, Cylinder Flows, Data Analysis and Presentation, Tomography, Density, DGV, Engines, Combustion and Turbines, Experimental Studies, Flames, Flow Control, Polymer Flows, Interferometry, Jet Flows, Technical Flows, LIF, Life Sciences, Liquid Crystals, Liquid Films, Liquid Metals, Micro Flows, Multiphase Flows, PIV (Methods, Turbulence, Applications, MAVs and Low Reynolds Number Flows), Propellers/Convective Flows, PSP/TSP, Quantitative Visualization Methods, Shock Waves, Smoke/Dye, Thermography, Tracking, Vehicle Flows, Vortical Flows

Citation: Journal of Visualization, vol. 10, no. 1, pp. 123-128, 2007