Journal of Visualization - Volume 8, issue 3

Article Type: Other

Citation: Journal of Visualization, vol. 8, no. 3, pp. 193-193, 2005

Article Type: Other

Citation: Journal of Visualization, vol. 8, no. 3, pp. 195-200, 2005

Authors: Tesař, V. | Trávníček, Z.

Article Type: Research Article

Abstract: This is the second part of a survey summarizing authors' research over a period of two decades on enhancing impinging jet heat and/or mass transfer by periodic unsteadiness of nozzle flow rate. The first part, Tesař and Trávníček (2004 b), identified the reasons why pulsation does not always improve the transfer rate: the pulses do not reach up to the wall. The authors nevertheless demonstrate a transfer rate improvement, but in flows with inherent instability found …in annular impinging jet. The excitation there causes a topological metamorphosis (reversal of flow character). Also in the extreme case of the synthetic (zero time-mean flow) jets the authors demonstrated a substantial improvement with the annular nozzle. The new approaches presented in the paper offer increased performance of drying and heating/cooling systems, in particular in microdevices with otherwise low or absent levels of natural jet turbulence. Show more

Keywords: Visualization, Unsteady jets, Periodic jet flows, Synthetic jets

Citation: Journal of Visualization, vol. 8, no. 3, pp. 201-208, 2005

Authors: Cieslinski, J. T. | Polewski, J. | Szymczyk, J. A.

Article Type: Research Article

Abstract: A study on flow field measurement around growing and rising vapour bubbles by use of PIV technique is presented. Bubbles were generated from single artificial cavities. Experiments have been conducted with saturated boiling of distilled water at atmospheric pressure. In the experiment fluid velocity field surrounding the bubbles was visualized by use of polyamide tracer particles and a sheet of a YAG pulse laser beam. The images were recorded with a cross-correlation CCD-camera. It has been …shown that for lower heat flux density bubble growths in an almost quiescent bulk of liquid. For higher heat flux density the train of bubbles creates a vapour column with strong wake effect. Maximum liquid velocity recorded is approximately equal to the terminal velocity of bubble rising in a stagnant liquid. Show more

Keywords: Pool boiling, Bubble growth, PIV

Citation: Journal of Visualization, vol. 8, no. 3, pp. 209-216, 2005

Authors: Knapp, Y. | Bertrand, E.

Article Type: Research Article

Abstract: In vitro experiments are often unable to reproduce all the complexities of biological flows observed in vivo. The in vitro models are often rigid, use Newtonian fluids, and/or some ideal geometry tested under ideal physiological parameters. The study presented in this article describes the in vitro assessment of mitral prosthetic heart valves in a setup able to simulate the pulsatile blood flow in a model of the left heart with moving walls. The specific laboratory mockup …built for these experiments consists in a Dual Activation Simulator (DAS) that provides a realistic simulation of the atrial and ventricular flow in anatomically shaped silicone models cavities. This mockup, initially designed for ultrasonic velocity measurements took recently advantage of the use of particle image velocimetry. We present here some aspects of flow visualization and phase averaged two-dimensional PIV measurements which can provide new insight in the interaction between the flow dynamics and the heart valves. Show more

Keywords: Cardiovascular Fluid Flows, PIV, Visualization, Valve dynamics

Citation: Journal of Visualization, vol. 8, no. 3, pp. 217-224, 2005

Authors: Fujimatsu, N. | Tamura, Y. | Fujii, K.

Article Type: Research Article

Abstract: Image processing procedures for noise reduction and image registration in the Pressure Sensitive Paint (PSP) experiments are investigated. A several types of filter are examined for the removal of shot noise. An algorithm to detect a marker cell located on the model surface is proposed and an appropriate marker size is discussed. The digital processing based on the wavelet transform is effective to reduce the shot noise and to enhance the edge of the model. The …algorithm to sharpen the edge of the model using wavelet transforms is developed. The results indicate that the methods developed in this study effectively remove the shot noise and correct the displacement of the model on the images taken during the wind-on. Show more

Keywords: Flow Visualization, Post Image Processing, Pressure Sensitive Paint, Wavelet Transform

Citation: Journal of Visualization, vol. 8, no. 3, pp. 225-233, 2005

Authors: Liu, Zhanping | Moorhead II, Robert J.

Article Type: Research Article

Abstract: Existing texture-based 3D flow visualization techniques, e.g., volume Line Integral Convolution (LIC), are either limited to steady flows or dependent on special-purpose graphics cards. In this paper we present a texture-based hardware-independent technique for time-varying volume flow visualization. It is based on our Accelerated Unsteady Flow LIC (AUFLIC) algorithm (Liu and Moorhead, 2005), which uses a flow-driven seeding strategy and a dynamic seeding controller to reuse pathlines in the value scattering process …to achieve fast time-dependent flow visualization with high temporal-spatial coherence. We extend AUFLIC to 3D scenarios for accelerated generation of volume flow textures. To address occlusion, lack of depth cuing, and poor perception of flow directions within a dense volume, we employ magnitude-based transfer functions and cutting planes in volume rendering to clearly show the flow structure and the flow evolution. Show more

Keywords: Texture-based flow visualization, Unsteady 3D flow, LIC, UFLIC, Volume rendering

Citation: Journal of Visualization, vol. 8, no. 3, pp. 235-244, 2005

Authors: Hwang, T. G. | Doh, D. H. | Okamoto, K.

Article Type: Research Article

Abstract: 4D-PTV system was constructed. The measurement system consists of three high-speed high-definition cameras (1k × 1k, 2000 fps), Nd-Yag laser (2000 Hz) and a host computer. The GA-3D-PTV algorithm was used for completing the measurement system. The 4D-PTV is capable of probing the spatial distribution of velocity vectors of the flow field overcoming the temporal resolution of the characteristic turbulence length scales of the measured flow fields. A horizontal impinged jet flow (H/D=7) was measured. The …Reynolds number is about 33,000. Spatial temporal evolution of the jet flow was examined and physical properties such as spatial distributions of vorticity and turbulent kinetic energy were obtained with the constructed system. Show more

Keywords: 4D-PTV, GA-3D-PTV algorithm, Impinged Jet, Vortex Ring

Citation: Journal of Visualization, vol. 8, no. 3, pp. 245-252, 2005

Authors: Espa, S. | Cenedese, A.

Article Type: Research Article

Abstract: One of the main consequences of chaos is that transport is enhanced with respect to the fluid at rest, where only molecular diffusion is present. Considering long times and spatial scales much larger than the length scale of the velocity field, particles typically diffuse with a diffusion constant, usually much bigger than the molecular one. Nevertheless there are some important physical systems in which the particle motion is not a normal diffusive process: in such a …case one speaks of anomalous diffusion. In this paper, anomalous diffusion is experimentally studied in an oscillating two-dimensional vortex system. In particular, scalar enhanced diffusion due to the synchronization between different characteristic frequencies of the investigated flow (i.e., resonance) is investigated. The flow has been generated by applying an electromagnetic forcing on a thin layer of an electrolyte solution and measurements are made through image analysis. In particular, by using the Feature Tracking (FT) technique, we are able to obtain a large amount of Lagrangian data (i.e., the seeding density can be very high and trajectories can be followed for large time intervals) and transport can be characterized by analyzing the growth of the variance of particle displacements versus time and the dependence of the diffusion coefficient on the flow characteristic frequencies. Show more

Keywords: Anomalous diffusion, Lagrangian chaos, Resonance, Lagrangian statistics, Particle tracking

Citation: Journal of Visualization, vol. 8, no. 3, pp. 253-260, 2005

Authors: Lawson, N. J. | Finnis, M. V. | Tatum, J. A. | Harrison, G. M.

Article Type: Research Article

Abstract: The flow fields for a sphere sedimenting through a Newtonian and two non-Newtonian liquids near a wall in a square tank are investigated using 3-D stereoscopic particle image velocimetry (PIV) and line integral convolution (LIC) methods. The PIV data were taken using an angular stereoscopic configuration with tilt and shift arrangements for the Scheimpflug condition and a pair of liquid correction prisms. Data were recorded from planes perpendicular and parallel to the wall for each fluid …case over a range of distances from the wall. The PIV and LIC results highlight significant differences in the wake structure for all three cases. Out of plane flow was also found to persist up to two sphere diameters downstream in the wake for all cases. Show more

Keywords: Visualization, Stereoscopic PIV, LIC, Non-Newtonian

Citation: Journal of Visualization, vol. 8, no. 3, pp. 261-268, 2005