Journal of Visualization - Volume 9, issue 1

Article Type: Other

Citation: Journal of Visualization, vol. 9, no. 1, pp. 1-1, 2006

Article Type: Other

Citation: Journal of Visualization, vol. 9, no. 1, pp. 3-8, 2006

Authors: Meegama, R. G. N. | Rajapakse, J. C.

Article Type: Other

Citation: Journal of Visualization, vol. 9, no. 1, pp. 9-11, 2006

Authors: Yang, C. J. | Lee, Y. H.

Article Type: Research Article

Abstract: It is known that an oscillating foil can produce a thrust force through the generation of a reverse Kármán vortex street and this can be expected to be a new highly effective propulsion system. A heaving foil model was made and it was operated within a circulating water channel. The wake formation behind the heaving foil was visualized using PIV method and a dynamic thrust force was measured using a mini 6-axis force sensor based on …force and moment detectors. We examined various conditions such as reduced frequency and amplitude in NACA 0010 profile. The vortical patterns in the wake were classified according to the wake mode and force data. Show more

Keywords: Unsteady flow, Heaving foil, Strouhal Number, Dye Visualization, PIV, Reverse Kármán vortex street

Citation: Journal of Visualization, vol. 9, no. 1, pp. 13-21, 2006

Authors: Ramesh, G. | Venkatakrishnan, L. | Prabhu, A.

Article Type: Research Article

Abstract: The near flow field of small aspect ratio elliptic turbulent free jets (issuing from nozzle and orifice) was experimentally studied using a 2D PIV. Two point velocity correlations in these jets revealed the extent and orientation of the large scale structures in the major and minor planes. The spatial filtering of the instantaneous velocity field using Gaussian convolution kernel shows that while a single large vortex ring circumscribing the jet seems to be present at the …exit of nozzle, the orifice jet exhibited a number of smaller vortex ring pairs close to jet exit. The smaller length scale observed in the case of the orifice jet is representative of the smaller azimuthal vortex rings that generate exial vortex field as they are convected. This results in the axis switching in the case of orifice jet and may have a mechanism different from the self induction process as observed in the case of contoured nozzle jet flow. Show more

Keywords: PIV, Elliptic jet, Axis switching, Spatial filtering, Two point correlation

Citation: Journal of Visualization, vol. 9, no. 1, pp. 23-30, 2006

Authors: Affeld, K. | Affeld, F. | Debaene, P. | Goubergrits, L.

Article Type: Research Article

Abstract: Some civil engineering projects require the injection of granular matter such as sand into the ground. However, granular matter resists pumping through tubes and thus it is difficult to inject such matter into the ground. With the help of several methods forces and movements of grains were visualized. Force chains and arches in a two dimensional granular matter model were visualized with polarized light and photo-elastic material. The movement of sand grains was visualized on a …glass plate in a half-space ground model. With the particle image velocimetry (PIV) method the vector field of the movement and the field of the resulting shear rate were assessed. In this way a new method for the injection of granular material, such as, sand into the ground was devised. The method appears to be applicable to lift a building to counter subsidence. Show more

Keywords: Force chains, Injection of sand, Granular matter Flow, PIV, Subsidence

Citation: Journal of Visualization, vol. 9, no. 1, pp. 31-38, 2006

Authors: Lee, W. J. | Kawahashi, M. | Hirahara, H.

Article Type: Research Article

Abstract: Mechanical ventilations for artificial respiration have been developed to improve the medical treatment of the patients showing respiratory disorder. In various types of ventilation, High Frequency Oscillatory Ventilation (HFOV) is one of the most effective techniques of medical care for pulmonary disease patients, especially, infants or premature infants. HFOV is a ventilation technique with high breathing rate in comparison with the normal breathing rate. Some successful studies have focused on the effect of treatment …using HFOV. However, the mechanism of gas exchange in bronchial tube under the medical treatment by HFOV has not been clarified. In this study, the oscillatory flow in a micro-channel model of bronchial with single bifurcation in HFOV mode has been investigated experimentally with micro Particle Image Velocimetry (micro PIV) technique. The phase averaged velocity profiles changing with the driving frequency of HFOV have been investigated. Show more

Keywords: Respiration, Bronchial tube, Oscillatory flow, Micro channel, Micro PIV

Citation: Journal of Visualization, vol. 9, no. 1, pp. 39-47, 2006

Authors: Fouras, A. | Hourigan, K. | Kawahashi, M. | Hirahara, H.

Article Type: Research Article

Abstract: Current techniques of water wave visualization such as shadowgraphy and stereo photography are widely used but are deficient in many aspects. Refraction based visualization observes the bending of light as it traverses across a liquid-air interface. This work describes the continued development of techniques to measure the surface height of a liquid free surface. The method, Reference Image Topography, utilizes refraction of light at the free surface as a function of the local angle of that …surface. Particle Image Velocimetry (PIV) software is used to evaluate apparent dislocations of the target image viewed through the free surface, which are approximately proportional to the surface angle. High-resolution images are presented of the dynamic surface topography for a point source and the shallow water flow around a vertical cylinder. Show more

Keywords: Visualization, Free Surface, Topography, PIV

Citation: Journal of Visualization, vol. 9, no. 1, pp. 49-56, 2006

Authors: Khan, M. I. | Simons, R. R. | Grass, A. J.

Article Type: Research Article

Abstract: Skimming, wake interference and isolated roughness flow regimes were investigated in the cavity formed between 2-d roughness elements in a laboratory water flume. The flow direction was aligned perpendicular to the roughness elements. Flow visualization and laser Doppler velocimetry were used to confirm the flow pattern and corresponding turbulence characteristics of the flow. Influence of the flow regimes on Reynolds stresses and turbulent diffusion coefficient was investigated at roof level of the cavity. Sweep …events towards the wall were significantly affected by the rough bed. A relatively wider cavity demonstrated significant influence on ejection and sweep stresses because of vortex activity at upstream and downstream positions within the cavity. The turbulent diffusion coefficient increased for isolated roughness flow in comparison to skimming flow regime. Show more

Keywords: Turbulence diffusion, Mixing length scale, Bed roughness, Flow pattern

Citation: Journal of Visualization, vol. 9, no. 1, pp. 57-68, 2006

Authors: Ohtsuki, S. | Tanaka, M.

Article Type: Research Article

Abstract: In order to observe and estimate the flow of fluid in three-dimensional space, the pulsed Doppler method has been used widely. However, the velocity information acquired is only the velocity component in the beam direction of the wave even if an observation plane is formed by beam scanning. Accordingly, it is difficult to know the velocity distribution in the observation plane in tree-dimensional flow. In this paper, the new idea for processing the velocity distribution in …the beam direction on an observation plane for transposing to flux distribution (flow function method) has been introduced. Further, the flow in an observation domain is divided into two kinds of flows, viz., the base flow which indicates the directivity of the flow in the observation domain and the vortex which is considered a two-dimensional flow. By applying the theory of a stream function to the two-dimensional flow, and by using the physical feature of a streamline to the base flow, the velocity component v which intersects perpendicularly to the beam direction is estimated. The flow velocity distribution in a scanning plane (observation plane) can be known from these two components of velocity, viz., beam direction component u and perpendicular component to the beam direction v. The principle was explained by an example of the blood flow measurement in normal and abnormal heart chamber, by the ultrasonic Doppler method. Show more

Keywords: Pulsed Doppler technique, Ultrasonic Doppler method, Flow function, C-mode flow, Flow velocity distribution, Stream function, Streamline

Citation: Journal of Visualization, vol. 9, no. 1, pp. 69-82, 2006