Begell House Inc.
Journal of Flow Visualization and Image Processing
JFV
1065-3090
15
1
2008
NEAR-BED PARTICLE MOTION DUE TO TURBULENT FLOW USING IMAGE-PROCESSING TECHNIQUE
1-15
B. S.
Mazumder
Fluvial Mechanics Laboratory Physics and Applied Mathematics Unit Indian Statistical Institute Kolkata - 700108, India
Anindita
Bhattacharyya
Fluvial Mechanics Laboratory, Physics and Applied Mathematics Unit, Indian Statistical Institute, Kolkata 700108, India
Satya P.
Ojha
Fluvial Mechanics Laboratory Physics and Applied Mathematics Unit Indian Statistical Institute Kolkata - 700108, India
The objective of this paper is to examine the behavior of particle movement due to near-bed turbulence over the rough bed surface in an open channel flow. The fluid velocity components with fluctuations are measured by 3D Micro-acoustic Doppler velocimeter (ADV) and subsequently, under given flow conditions images of released moving particles are recorded using a High-Speed Motion-Scope (HSMS) at the Fluvial Mechanics Laboratory of the Indian Statistical Institute, Calcutta. The recorded images are analyzed in the light of particle motions, trajectories, saltation heights and lengths of individual particles, angles of orientation and their interactions with the boundary using a digital image processing technique. The statistical distributions of the physical parameters of turbulence and particle motion have been discussed. The particle motion analysis at the near-bed turbulence using the image processing technique is a new emerging tool to the sediment sorting process.
AN ADAPTIVE TWO-DIMENSIONAL MESH REFINEMENT METHOD BASED ON THE LAW OF MASS CONSERVATION
17-33
Zhenquan
Li
School of Computing and Mathematics, Charles Sturt University, Thurgoona, NSW2640, Australia
Mesh generation is one of key issues in Computational Fluid Dynamics. This paper presents an adaptive two-dimensional mesh refinement method based on the law of mass conservation. The method can be applied to a governing system that includes the law of mass conservation (continuity equation) for incompressible or compressible steady flows. Users can choose how many refinements they want to perform on the original mesh. The more the number of refinements, the less the error of calculations is. The refined meshes can identify the accurate locations of asymptotes and singular points and draw accurate closed streamlines if the number of refinements is big enough. We show two examples that demonstrate the claims.
COMPOSITE FLOW NETWORKS FOR STRETCHING/STABILIZING EFFLUX FLUID FILMS
35-45
Wen-Jei
Yang
Department of Mechanical Engineering and Applied Mechanics University of Michigan, Ann Arbor, Michigan 48109-2125, U.S.A.
An experimental study is performed on various types of composite flow networks to determine the optimum one which produces the best — longest and stable — efflux jet stream. The composite flow networks being investigated consist of diamond-shaped cylinder bundles and slit-flow channels being arranged in series, parallel and/or combination with slit-flow channel. The diamond-shaped cylinder bundle is the principal unit in the composite flow network which is characterized by self-excited flip-flop flow oscillation with uniform flow-rate jet streams. Experimental results are obtained for the PIV (particle image velocimetry) images at strategic flow cross sections, the visualized images of efflux jet-stream, streak line patterns and vorticity contour distribution, and the velocity contour distribution. The following conclusions have been derived: (i) It is possible to produce multi-phase inter-facial phenomena induced by a combination of the intersecting flow (within a diamond-shaped cylinder bundle) as the main stream, the flip-flop flow containing a longitudinal vortex coexisting in parallel with the slit-flows having vortex shearing direction varying with the contacting phase, (ii) By utilizing composite fluids having the flip-flop flows coexisting with the slit flows, the stretching and formation of stable fluid films can be expected, (iii) Applications become feasible in air curtain and various kinds of environmental security devices together with development of their design guidelines.
FLOW VISUALIZATION AND HEAT TRANSFER IN FREE CONVECTION OVER SLIGHTLY INCLINED SURFACE-MOUNTED PRISMS
47-57
A.
Korichi
Laboratoire des Phénomènes de Transferts, USTHB, Algiers, Algeria
Lounes
Oufer
Laboratoire des Phénomènes de Transferts, Faculty of Mechanical and Process Engineering, University of Sciences and Technology, Houari Boumediene, B.P. 32 El-Alia Bab Ezzouar, 16110 Algiers, Algeria
S.
Fohanno
Laboratoire de Thermomécanique, Faculté des Sciences, Reims, France
Guillaume
Polidori
Laboratoire de Thermomecanique GRESPI- EA4301, Universite de Reims, 51687 Reims cedex 2, France
This experimental study deals with convective heat transfer and flow features in the vicinity of an array of 3D short insulated surface-mounted square cylinders along an inclined plate and under uniform heat-flux density conditions. The experiments were conducted in water with the use of poor conductivity prisms so that both conduction and radiation effects could be neglected. Experiments on the flow and heat transfer were performed for slight inclination angles varying clockwise in the range −20° to +20° around the vertical position. Flow visualizations were carried out with particle-streak and dye-emission techniques to examine the flow field around the protrusions. The experimental analysis highlighted the strong influence of the plate inclination angle on the formation of rotational flows, 3D transverse flows, and separation phenomena in open cavities. Moreover, the positions that best enhanced heat transfer were found to be those corresponding to the positive angle range where 3D transverse flows occupy all open cavities.
ANALYSIS OF TWO-DIMENSIONAL LIQUID SPRAY IMAGES: THE SURFACE-BASED SCALE DISTRIBUTION
59-83
Christophe
Dumouchel
Université et INSA de Rouen
France
Jean
Cousin
UMR 6614-CORIA, Technopole du Madrillet, B.P. 12 Avenue de l'Université 76801 Saint-Etienne du Rouvray Cedex, France
Sebastien
Grout
UMR 6614-CORIA, Technopole du Madrillet, B.P. 12 Avenue de l'Université 76801 Saint-Etienne du Rouvray Cedex, France
The drop-size distribution is a very important characteristic of liquid sprays. From a mathematical point of view these distributions are defined for spherical drops. Furthermore, the experimental diagnostics widely used to measure spray drop-size distribution characterize the droplets by a single length-scale equivalent to a diameter. However, more recent techniques based on spray image processing clearly show that a high proportion of liquid droplets are barely spherical, especially those issued from primary atomization processes. In the present paper, a new description of 2D liquid spray images is presented: the surface-based scale distribution. This distribution and its series of mean scales are functions of the shape of the particles. In the first part of the paper, this description is applied for theoretical sets of objects with controlled shape and size. Characteristic features of the surface-based scale distribution and of the corresponding mean scale series are emphasized from these applications. These features are of practical interest for the determination of the scale distribution characteristics of real 2D liquid spray images presented in the second part of the paper. Among other results, it is found that the ratios of the mean-scales to the traditional mean-diameters, which quantify the deformation of the objects, appear to be mainly a characteristic of the atomization mechanism. Finally, although it has not been explored here, an interesting aspect of this scale distribution is that it can be applied on atomizing liquid flows, opening new fields of investigation.