Begell House Inc.
Journal of Flow Visualization and Image Processing
JFV
1065-3090
14
1
2007
EVALUATION OF THE RAINBOW VOLUMIC VELOCIMETRY (RVV) PROCESS BY SYNTHETIC IMAGES
1-15
10.1615/JFlowVisImageProc.v14.i1.10
R.
Malfara
Department CREST, Institute FEMTO-ST UMR CNRS 6174, 2 Av. J. Moulin, 90000 Belfort, FRANCE
Yannick
Bailly
FEMTO-ST Institute, Univ. Bourgogne Franche-Comté, CNRS, Belfort, France
Jean-Pierre
Prenel
University of Franche Comte/CNRS 6174, Belfort, France
C.
Cudel
Laboratoire MIPS/Lab.El Université de Haute Alsace, France
The main goal of this paper is to present recent improvements of the original optical method dedicated to 3D flows, named R VV (Rainbow Volumic Velocimetry). The authors propose a new way to evaluate the importance of the image quality in flow visualization. A method for generating synthetic images has been developed in order to simulate the RVV technique. With this approach, some factors can be tested such as image noise, image contrast, and spectrum characteristics. Moreover, the performance of image processing tools specifically developed for RVV applications can be also estimated. The principles of both PTV and PSV have been investigated synthetically.
DISCRETE ELEMENT METHOD FOR MOLECULAR SCALE VISUALIZATION OF MICRO-FLOWS
17-34
10.1615/JFlowVisImageProc.v14.i1.20
A.
Munjiza
School of Engineering and Materials science, Queen Mary University of London, Mile End Road, London E1 4NS, United Kingdom
E.
Rougier
Queen Mary, University of London, Mile End Road E1 4NS, UK
N. W. M.
John
Queen Mary, University of London, Mile End Road E1 4NS, UK
According to the Knudsen number four different types of flow regimes can be identified: continuum, slip, transition, and free-molecular flow. The continuum flow regime is well described by the Navier−Stokes equations. The slip flow can also be described by the Navier−Stokes equations, provided that some special boundary conditions are prescribed. In the transition and the free-molecular flow regimes, the flow is described by the Boltzmann equation, which is a molecular-based model. By using this model, it is possible to solve the high Knudsen number flow problems through molecular-based direct simulation techniques.
However, independent of micro-flow research the particulate-solids research community has developed the so-called Discrete Element Method. In recent years, QMUL and MIT research groups (Munjiza, Williams) have revolutionarized these methods by inventing a set of linear packing-density-independent search algorithms, which have enabled systems comprising billions of particles to be considered on a desktop machine. Recently the QMUL group has applied the method to micro-flows. The most important aspect of this new method is accurate integration of motion of individual molecules including interaction between molecules.
As temporal and spatial constraints make the visualization of micro-flows in experimental research difficult, the new method is an ideal tool for visualization of micro-flows. The power of these new visualization tools is best demonstrated through the so-called "virtual movies" obtained from simulations. Through these movies the observer is given an opportunity to see the motion of individual atoms of a fluid and their interaction with each other and with the boundary.
EFFECT OF AMBIENT PRESSURE, OVERALL INPUT EQUIVALENCE RATIO AND RESIDENCE TIME ON CARBON PARTICULATE FORMATION AND OXIDATION IN A CONFINED SPRAY FLAME
35-52
10.1615/JFlowVisImageProc.v14.i1.30
R. J.
Crookes
Department of Engineering, Queen Mary, University of London, Mile End Road, London E1 4NS, UK
A.
Demosthenous
Department of Engineering, Queen Mary, University of London, UK
The paper uses a modified, rapid compiling, in-home spray-combustion code to calculate soot concentration distribution profiles within the combustion chamber of a high-pressure spray burner. The code is first assessed by comparison with the commercial code STAR-CD for gaseous product species mole fractions. It is then used with three available soot-formation models and two adaptations of a soot-oxidation model to calculate net soot concentration, throughout the combustion chamber, under different operating conditions. Input mixture ratio, combustion pressure and oxygen:nitrogen ratio, in the oxidiser, are varied to produce results at constant pressure, constant equivalence ratio or constant mass flow rate and residence time respectively. The results are presented as property distribution maps relative to the geometry of an experimental high-pressure combustion chamber and results of mean exhaust values are compared with experimental data at the same conditions.
VISUALIZING VORTEX FORMATION IN THE WAKES OF TURBINE BLADES AND OSCILLATING AEROFOILS
53-66
10.1615/JFlowVisImageProc.v14.i1.40
J. P.
Gostelow
Department of Engineering, University of Leicester, UK
M. F.
Platzer
AeroHydro R&T Associates, Pebble Beach, CA, USA
W. E.
Carscallen
Institute for Aerospace Research, National Research Council, 1500 MontreaL Road
Ottawa, ON, K1A 0R6, Canada
Joseph C. S.
Lai
University of New South Wales Canberra, Northcott Dr, Campbell ACT 2600, Australia
Similarities between anomalous vortex shedding from blunt trailing-edged transonic turbine nozzle blades and from oscillating plunging aerofoils were investigated. Whereas under subsonic conditions the turbine nozzle cascade shed vortices in a conventional von Kármán vortex-street wake, under transonic conditions a variety of different shedding configurations were observed with vortices shedding and pairing in different ways. Oscillating aerofoils were investigated in sinusoidal heaving motion in a water tunnel and a similar range of interesting wake vortex configurations was encountered. The established field of vortex-induced vibration has provided a developed classification scheme for the phenomena observed. The paper has brought together three previously unrelated fields of investigation and, by showing that the three are essentially related, has provided the basis for a new synthesis. The experiments were served well by the use of schlieren, including a novel use in conjunction with the hydraulic analogy, by the use of dye in a water tunnel and by computational work used to provide further interpretation of the observations.
TIME-RESOLVED STEREO PIV MEASUREMENT OF PULSATILE FLOW IN AN ARTERY MODEL
67-84
10.1615/JFlowVisImageProc.v14.i1.50
M.
Oishi
Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-Ku, Tokyo, 153-8505, Japan
M.
Oshima
Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-Ku, Tokyo, 153-8505, Japan
Y.
Bando
Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-Ku, Tokyo, 153-8505, Japan
T.
Kobayashi
University of Tokyo; and Japan Automobile Research Institute, 2530 Karima, Tsukuba-city, Ibaraki, 305-0822, Japan
This study investigated the behavior of pulsatile blood flow in a curved pipe that simulates the internal carotid artery (ICA), which is a common location for an aneurysm. Since complex secondary flow arises due to the curvature of artery, particle image velocimetry (PIV) was applied to obtain detailed flow information from in vitro experiments. However, blood flow in arteries is pulsatile and time-resolution of conventional PIV is not adequate for capturing the transient behavior of pulsatile flow. Thus, time-resolved PIV, which consists of high-speed cameras and high repetition rate lasers, was applied to measure unsteady flow. This new measurement method can provide superior resolution in space and in time.
Here, we demonstrate an improvement in resolution in space from a two-dimensional PIV system as compared to a stereo PIV system. To perform stereo calibration within a narrow and complex measurement area, we developed a non-invasive stereo calibration technique using lasers.
Stereo time-resolved PIV measurement allows the observation of two-dimensional, three-component transient flow structure. Pairs of secondary-flow vortices have different momentum and affect one other significantly. Flow characteristics at the systole phase are drastically different from those at the diastole phase, even with a similar Reynolds number.
SHEAR-LAYER INSTABILITY IN A ROTATING SYSTEM
85-105
10.1615/JFlowVisImageProc.v14.i1.60
Sebastien
Poncet
Laboratoire M2P2, UMR CNRS 7340 Aix-Marseille Universite / CNRS 38, rue Frederic Joliot-Curie 13451 MARSEILLE Cedex 13; Université de Sherbrooke, Faculté de génie, Département de génie mécanique, 2500 Boulevard de l'Université, Sherbrooke, QC J1K 2R1, Canada
Marie-Pierre
Chauve
Institut de Recherche sur les Phénomènes Hors Equilibre (IRPHE), UMR CNRS 6594, Technopôle Château Gombert, 49 rue F. Joliot-Curie, B.P.146, 13384 Marseille Cedex 13 − France
The shear-layer instability in the flow over a rotating disk with a free surface is investigated experimentally by flow visualizations for a large range of the flow control parameters: the aspect ratio G of the cavity, the rotationnal Reynolds number Re, and the radius ratio s between the inner and outer radii of the rotating disk. This instability develops along the cylindrical shroud as sharp-corner polygonal patterns characterized by the number of vortices m. This number m can be scaled by considering an Ekman number based on the water depth, which confirms that the shroud boundary layer is of Stewartson type. The appearance threshold of the first polygonal mode is constant by considering the mixed Reynolds number introduced by Niino and Misawa [1] based on both the water depth at rest and the rotating disk radius. For large values of s, the instability patterns appear along the hub as small stationary cells.
A MASS CONSERVATIVE STREAMLINE TRACKING METHOD FOR THREE-DIMENSIONAL CFD VELOCITY FIELDS
107-120
10.1615/JFlowVisImageProc.v14.i1.70
Roslyn Preetika
Singh
School of Computing, Information and Mathematical Sciences, The University of the South Pacific, SUVA, FIJI ISLAND
Zhenquan
Li
School of Computing and Mathematics, Charles Sturt University, Thurgoona, NSW2640, Australia
Mass conservation is a key issue for constructing accurate streamlines of flow fields. We consider the CFD velocity fields without further data available such as the measured velocity fields. This paper presents a mass conservative streamline tracking method for such CFD velocity fields. Linear interpolation is used to approximate velocity fields and the exact tangent curve for linear vector fields is used to draw the streamlines. Demonstration examples in the last section show that the method is accurate.
STEREOSCOPIC IMAGING OF TRANSVERSE DETONATIONS IN DIFFRACTION
121-142
10.1615/JFlowVisImageProc.v14.i1.80
F.
Pintgen
Energy and Propulsion Technologies Laboratory General Electric Global Research Center, Niskayuna 12308, NY, USA
J. E.
Shepherd
Graduate Aeronautical Laboratory California Institute of Technology, Pasadena 91125, CA, USA
Diffraction of gaseous detonations has received considerable attention for many years, yet there is limited understanding of the failure and initiation phenomena due to the complex coupling between the combustion and the fluid dynamics. A variety of optical techniques such as streak imaging, open shutter photography, high-speed schlieren imaging, and, more recently, planar laser induced fluorescence (PLIF) has been used to visualize the diffraction process in detonations. To overcome the integrating nature of visualization techniques and also allow for sooted foil records, many diffraction experiments in the past were carried out in narrow channels, studying detonation transition from planar to cylindrical geometry. The experimental investigation on spherically diffracting detonations described in this paper uses stereoscopic image reconstruction of the transverse detonations. The aim is to obtain further insight into the transverse detonations, which are the re-coupling phenomena identified to occur in the critical diffraction regime following a re-initiation event. The 3D reconstruction technique visualizes the transverse detonation as defined by the volume in space with high luminosity. The reconstruction technique is based on gradients, in contrast to those techniques based on target points as used, for example, in 3D particle image velocimetry. Together with a simultaneously obtained schlieren image, the location of the transverse detonation could be determined to be just below the shock surface.