Begell House Inc.
Journal of Flow Visualization and Image Processing
JFV
1065-3090
2
1
1995
VISUALIZATION OF DEVELOPING SECONDARY FLOW PATTERNS IN THE HYDRODYNAMIC ENTRANCE REGION OF A CURVED PIPE
1-13
10.1615/JFlowVisImageProc.v2.i1.10
K. C.
Cheng
Department of Mechanical Engineering, University of Alberta Edmonton, Canada
Masao
Takuma
Department of Mechanical Engineering, University of Alberta, Edmonton, Alberta, Canada T6G 2G8
Yoshiyuki
Kamiya
Department of Mechanical Engineering, University of Alberta, Edmonton, Alberta, Canada T6G 2G8
Photographic results obtained by smoke injection method are presented for developing secondary flow patterns in the hydrodynamic entrance region of a curved pipe (pipe inside diameter d = 25.4 mm, radius of curvature R = 127 mm, and curvature ratio d/2R = 0.1) with fully developed parabolic entry velocity profile for the bend angles φ = 0, 15, 30, 45, 60, 90, 120, 135, and 180°. The Dean number and Reynolds number ranges are K = 91−653 and Re = 287−2,064, respectively. The characteristic features of the developing secondary flow patterns and some discrepancies between flow visualization results and the existing theoretical predictions are pointed out. Secondary flow separation phenomena near the inner wall are disclosed clearly by flow visualization. The present flow visualization study complements theoretical study.
FLOW VISUALIZATION INVESTIGATION AROUND HELICOPTER ROTOR BLADE TIPS IN HOVERING FLIGHT
15-27
10.1615/JFlowVisImageProc.v2.i1.20
E.
Berton
Institut de Mécanique des Fluides, Université d'Aix-Marseille II, UM-34 du C.N.R.S., 13009 Marseille, France
D.
Favier
Institut de Mécanique des Fluides, Université d'Aix-Marseille II, UM-34 du C.N.R.S., 13009 Marseille, France
C.
Maresca
Institut de Mécanique des Fluides, Université d'Aix-Marseille II, UM-34 du C.N.R.S., 13009 Marseille, France
M. Nsi
Mba
Institut de Mécanique des Fluides, Université d'Aix-Marseille II, UM-34 du C.N.R.S., 13009 Marseille, France
Rotor tip vortex formation and roll-up have been investigated using a flow visualization method coupled with a digital image processing technique. Emphasis is placed on the effect of the blade tip shape on the vortex structure and stability along its path. Particular attention is given to the influence of the tip geometry modification on the flowfield generated around the blade and its wake. For each blade configuration, the experiments include visualizations of the vortical structures generated by the blade tip and measurements of the tip vortex path. When compared to the rectangular tips, the evolutive tips are shown significantly to modify the wake geometry and to generate a dual vortex structure that produces a stronger instability of the tip vortex path. This vortex instability significantly affects the airloads distribution along the blade span.
MEASUREMENT OF ACTUAL GAS VELOCITY IN TWO-PHASE FLOW USING HIGH SPEED VIDEO AND IMAGE PROCESSING
29-38
10.1615/JFlowVisImageProc.v2.i1.30
Kamiel S.
Rezkallah
Microgravify Research Group, College of Engineering, University of Saskatchewan, Saskatoon, Mechanical Engineering Dept. University of Manitoba, Winnipeg, Canada
Pieter
de Jong
Microgravity Research Group, Mechanical Engineering Department, University of Saskatchewan, Saskatoon, SK, S7N-0W0, Canada
For many years, the modelling of two-phase, gas-liquid flows has been severely hindered by actual measurements of phase velocities and interfacial parameters (e.g., interfacial area, interfacial shear). Such information is crucial for the development of reliable two-phase flow codes and correlations. Recent advances in high speed photography and video imaging, coupled with significant development of image processing techniques and software, have opened new opportunities in flow visualization and measurement techniques. This report represents the results of measured gas-phase velocity in two-phase flow. The measurements were obtained using high speed video images and several image processing software. The results agreed within 20−25% with the values using the "no-slip" velocity approach.
DIGITAL VISUALIZATION OF THE BEHAVIOR OF PERIODIC UNSTEADY BOUNDARY LAYER TRANSITION ALONG A CURVED PLATE AT ZERO LONGITUDINAL PRESSURE GRADIENT
39-59
10.1615/JFlowVisImageProc.v2.i1.40
Meinhard Taher
Schobeiri
Turbomachinery Performance Laboratory, Texas A&M University, College Station, Texas 77843-3123
R. E.
Radke
Turbomachinery Performance Laboratory, Texas A&M University, College Station, Texas 77843-3123
Digital visualization of complex boundary layer transition along the concave side of a curved plate under a periodic unsteady flow condition and zero longitudinal pressure gradient is presented in this report. The concave side simulates the pressure surface of a turbine blade with zero degree of reaction. Experimental investigations were carried out on an unsteady flow research facility using a rotating cascade of rods positioned upstream of the curved plate with a zero longitudinal pressure gradient. A specially designed traversing system and hot-wire probe enabled detailed boundary layer measurements that were analyzed by the ensemble-averaging technique. The results presented in the temporal-spatial domain allow clear visualization of the transition phenomenon and further development of the boundary layer, specifically the ensemble-averaged velocity and turbulence intensity. Furthermore, they contribute to better understanding the transition phenomenon, which is essential for development of a comprehensive boundary layer transition model.
FLOW VISUALIZATION METHODS FOR INVESTIGATING AN INDUCED FLOW EJECTOR
61-74
10.1615/JFlowVisImageProc.v2.i1.50
Philippe
Desevaux
Institut FEMTO-ST-UMR 6174, Département Energie, Université de Franche-Comté, Parc Technologique, Belfort, France
Jean-Pierre
Prenel
University of Franche Comte/CNRS 6174, Belfort, France
G.
Hostache
Institut de Génie Energétique, Université de Franche-Comté Parc Technologique, 90000 Belfort, France
This report presents an optical diagnosis of the interaction of two coflowing streams inside an air ejector operating in a mixed flow condition. The visualization techniques used are based on Rayleigh and Mie scatterings. They differ from each other by the kind of the illumination source (pulsed or continuous laser), the polarization state of the incident light, and the nature of the seeding. Each method permits the visualization of specific phenomena, and by combining together all these techniques, it is possible to visualize the primary pseudo-shock structure, the nonmixing region, and the instantaneous turbulent structures of the flow. Issues related to the effects of various operating conditions on the flow pattern are addressed by these visualization methods.
APPLICATION OF IMAGE PROCESSING MEASUREMENT TO A RELATIVE FLOW IN A PUMP-TURBINE RUNNER
75-82
10.1615/JFlowVisImageProc.v2.i1.60
Hiroshi
Hayami
Institute of Advanced Material Study, Kyushu University, Kyushu, Japan
Dexin
Chen
North China Institute of Water Conservancy and Hydroelectric Power, China
Toru
Koso
Institute of Advanced Material Study, Kyushu University, Kyushu, Japan
Fluid flow in a small model of a Francis-type pump turbine was visualized by means of a tracer method and was imaged using a video camera rotating with the runner. The relative velocity vectors of the fluid flow were analyzed from the video images using a digital image processing technique based on the correlation method. The flow patterns are discussed in relation to the characteristics of the pump turbine. At a zero incidence inflow condition, the reverse flow zone on the suction surface of the blade is much less than that at a shockless inflow condition. Unsteady flow patterns at a low flow rate are also demonstrated. The problems that occur in the image processing measurement and the countermeasures are discussed.
DIGITAL IMAGE ANALYSIS FOR THE INCOHERENT MEDIUM DENSITY PIV
83-91
10.1615/JFlowVisImageProc.v2.i1.70
Tomomasa
Uemura
Faculty of Engineering, Kansai University, 3-3-35 Yamate, Suita-shi, Osaka, 564 Japan
Manabu
Iguchi
Faculty of Engineering, Osaka University, 2-1 Yamada-oka, Suita-shi, Osaka, 565, Japan
Zen-Ichiro
Morita
Department of Materials Science and Processing Osaka University, Osaka, Japan
A new algorithm for the particle tracking velocimetry is proposed. The algorithm aims to accelerate the analysis of particle imaging velocimetry (PIV) pictures in which particles distribute densely and frequently overlap or touch each other. It is based on PTV algorithms, a modified velocity vector histogram method and the binary-image correlation method. The modified method is used to detect directions of tracers and then, the binary-image method determines displacements of tracers. The new algorithm is examined using simulated pictures during a development procedure and is then applied to actual pictures of moving particles. The processing time, although not shorter than that of the binary-image correlation is far less than that of the popular correlation analysis.
VISUALIZATION OF INTERACTING PILOT AND MAIN DIESEL-TYPE SPRAYS IN AN ENGINE
93-112
10.1615/JFlowVisImageProc.v2.i1.80
K. M.
Sinko
GM Electro-Motive Division, LaGrange, Illinois, USA
D.
Pushka
UIC Engine Laboratory, Department of Mechanical Engineering, University of Illinois, Chicago, Illinois 60680
B.
Chehroudi
Department of Mechanical Engineering, University of Illinois at Chicago, Chicago, Illinois, USA
An optically accessible research engine, image acquisition, and a control system are designed to acquire two-dimensional images of a pilot and main diesel fuel sprays. The ultimate objective is to study the nature of interactions between two fuel sprays and to develop a knowledge base on this interaction to augment the on-going research on possible nitric oxide emission reduction by pilot injection. This report presents the engine-based apparatus, image acquisition techniques, and preliminary results of analysis performed upon interacting diesel fuel sprays. The engine is a single-cylinder, compression-ignition two-stroke with optically accessible head mounted on a high-speed cooperative fuel research (CFR) engine crankcase. It is equipped with a special dual-injection system for production of in-cylinder interacting sprays (main and pilot) with a high degree of adjustability with regard to the sprays' fuel quantities and injection timings. The engine construction permits illumination of the sprays by a thin sheet of laser light from a pulsed Nd:YAG laser frequency doubled to operate at the visible wavelength of 532 nm. Light scattered from the droplets passes through a top-mounted viewing window on a diode array camera, yielding a digital image that defines the boundary of the spray plumes. This permitted spatially resolved images of the interacting sprays. Personal computer-based programs control injector activation times, synchronize operation of the laser illumination system, and acquire/process and display of the spray plume images. Two-dimensional images are presented and discussed for a selected condition.