Begell House Inc.
Journal of Flow Visualization and Image Processing
JFV
1065-3090
10
1-2
2003
CULTURAL IDENTITY DEVELOPMENT MODEL USING DISCRETE WAVELETS. A STUDY OF LETTERS IN THE AUTOBIOGRAPHY
12
10.1615/JFlowVisImageProc.v10.i12.10
N.
Morohoshi
Shirayuri College, 1-25 Midorigaoka, Tokyo, Japan
H.
Tsuchiya
Shirayuri College, 1-25 Midorigaoka, Tokyo, Japan
Kiyoshi
Horii
Shirayuri College, 1-25 Midorigaoka, Chofu-shi, Tokyo 182-8525, JAPAN
Yoshifuru
Saito
Department of Electrical and Electronic Engineering, College of Technology, Hosei University, Tokyo, Japan
A new objective method for receptivity of cross-cultural values has been developed using discrete wavelets. This method has been applied to 21 letters written by Hart. They were included in her autobiography Once in a Lifetime that recounts her experience before and after the studies in the U.S. The receptivity process of American culture in Yasuko Hart’s heart and mind was visualized as a W-curve. The results also suggested common cross-cultural development models. This is the first attempt to analyze the sentences used in the private letters.
FLOW VISUALIZATION AND FREE CONVECTION HEAT TRANSFER AT THE JUNCTION OF SHORT CYLINDERS MOUNTED ON A HEATED WALL
14
10.1615/JFlowVisImageProc.v10.i12.20
Guillaume
Polidori
Laboratoire de Thermomecanique GRESPI- EA4301, Universite de Reims, 51687 Reims cedex 2, France
Jacques
Padet
Laboratoire de Thermomécanique - UTAP Moulin de la housse, Faculté des Sciences, Université de Reims Champagne Ardenne, B.P. 1039, 51687 Reims cedex 2, France
Unsteady free convection in the vicinity of vertical wall-mounted insulated short cylinders is considered under isoflux thermal conditions used for wall heating. Especially, this study is aimed at analyzing how free convection heat transfer at the wall can be locally modified by the presence of a short protrusion. For this purpose, the idea is to correlate local heat transfer at a given abscissa on the wall with the flow patterns at the junction for a large range of angular cylinder positions a around this abscissa. In contrast to a circular shape, it is shown that the presence of a cylinder with sharp edges embedded in a free-convection boundary layer induces heat transfer enhancement at a given abscissa for a < 50°. It is argued that flow visualization can be a powerful technique in the understanding of the complex local heat transfer process, especially by identifying both the position of the wake separation and the rotational flow features.
NUMERICAL AND EXPERIMENTAL VISUALIZATION OF THE FLOW OVER BLUFF BODIES
22
10.1615/JFlowVisImageProc.v10.i12.30
Gérard J.
Poitras
Faculte d’ingenierie, Université de Moncton, New Brunswick, Canada, E1A 3E9
L.-E.
Brizzi
Laboratoire d’etudes aerodynamiques, UMR 6609 SP2MI, Boulevard Marie et Pierre Curie, Teleport 2 BP 30179 86962, Futuroscope Chasseneuil, France; Université de Poitiers ENSMA, Futuroscope Chasseneuil, France
Y.
Gagnon
Faculte des etudes superieures et de la recherche, Universite de Moncton, Moncton, NB, Canada, E1A 3E9
The flow around several bluff bodies is studied both numerically and experimentally. The flow is simulated using a mixed Eulerian–Lagrangian numerical algorithm based on Vortex Methods. This method allows the study of the unsteady flow dynamics by using instantaneous numerical velocity and vorticity fields. However, only the mean two-dimensional flow is analyzed in this paper. Furthermore, experimental flow visualization using laser light sheet and Particle Image Velocimetry are performed on the same geometries inside a water channel. Several configurations are studied at different Reynolds numbers and a comparison of the numerical results with the experimental results is presented. The numerical results show good agreement with the experimental results and with other studies.
MECHANISM OF FLOW THROUGH LOUVER-FINNED SURFACES
18
10.1615/JFlowVisImageProc.v10.i12.40
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 to determine the mechanism of flow through louver-finned surfaces by means of flow visualization and laser Doppler velocimetry (LDV). The louver angle and flow velocities are varied. Results are obtained for the velocity vector, turbulence intensity, Reynolds stress, and power spectrum together with images of flow patterns in both the fin and louver spaces. It is disclosed that an increase in the louver angle promotes enhancement in mixing performance but the appearance of a separation bubble in the vicinity of louver-fin connection bend limits the louver angle. Large longitudinal vortices are induced in flow through all louvered fins. The uniqueness of the louver-finned system is its arched geometry which serves as a curvature producing the centrifugal force for the enhance mixing performance. Applications of such a system are abundant in compact heat exchange devices most well known in automotive radiators.
ANALYSIS OF TIME-DEPENDENT VORTEX SHEDDING BY MEANS OF STREAMFUNCTIONS' STRICTLY ROTATIONAL COMPONENT
38
10.1615/JFlowVisImageProc.v10.i12.50
Giancarlo
Alfonsi
Fluid Dynamics Laboratory, Universita della Calabria, Via P. Bucci 42b, 87036 Rende (Cosenza), Italy
A computational analysis is performed on the two-dimensional time-dependent Navier–Stokes equations in their streamfunction–vorticity transport form, for a numerical investigation on vortex shedding past a circular cylinder. The numerical technique is a mixed spectral-finite analytic scheme in which the flow fields are expanded in the Fourier series along the azimuthal direction and the convolutions arising from the convective terms of the vorticity transport equation are calculated by means of Fast Fourier Transform algorithms; the time advancement is performed by using a fourth-order Runge–Kutta scheme (first four iterations) and a Predictor–Corrector algorithm (subsequent iterations). The flow of a viscous incompressible fluid around an impulsively started circular cylinder at Reynolds number Re = 1000 (based on free stream velocity and cylinder diameter) is examined with particular concern to the mechanism of vortex shedding and more particularly to the shedding of the viscous part of the flow field, when separated from the inviscid. The nonsymmetric configuration of the wake is promoted by imposing at the nondimensional time t = 0 an initial perturbation to the initially irrotational flow. The perturbation consists in a slightly rotational field implemented into the computational code by means of an appropriate perturbation function; six different perturbations are tested. The results are presented for several time steps of integration, in terms of streamlines generated by the strictly rotational component of the streamfunction. The mutual interaction of the primary vortices in the near wake as a fundamental mechanism of the "viscous" vortex shedding, is demonstrated; moreover, different perturbations induce vortex shedding phenomena with different characteristics.
ON THE BEHAVIOR OF POD MODES OF THE FLOW PAST A PERFORATED PLATE
14
10.1615/JFlowVisImageProc.v10.i12.60
Giancarlo
Alfonsi
Fluid Dynamics Laboratory, Universita della Calabria, Via P. Bucci 42b, 87036 Rende (Cosenza), Italy
Leonardo
Primavera
Fluid Dynamics Laboratory, Universita della Calabria, Via P. Bucci, Cubo 42b, 87036 Rende (Cosenza), Italy
Riccardo
Felisari
Dipartimento di Ingegneria Idraulica, Politecnico di Milano Piazza L. da Vinci 32, 20133 Milano, Italy
The temporal behavior of coherent structures of turbulence in the case of a multiple interacting turbulent jet flow developing downstream from a perforated plate is investigated. The Proper Orthogonal Decomposition (POD) is applied to extract the coherent motions from a turbulent flow database of numerical nature obtained with the use of a finite-element computational code for the numerical integration of the Navier–Stokes equations at Re = 13300; for turbulence modeling the Large Eddy Simulation (LES) approach is followed and the Smagorinsky Sub Grid-Scale model (SGS) is used. The three-dimensional time-dependent velocity field past the perforated plate is computed and 400 time steps of the turbulent statistically steady state are considered for the decomposition of the flow field onto two appropriate computational subdomains. "Reduced" velocity fields, each reflecting the contribution of the first four most energetic POD modes containing up to 96.24% and 95.82% of the turbulent kinetic energy of the originary flow field, respectively, are reconstructed. Results are presented in terms of temporal evolution of the turbulent kinetic energy of the four most energetic eigenmodes of each subdomain, showing, in both cases, a rather regular temporal dynamics of the coherent structures (the POD modes) through different phases of the turbulent activity.
EXPERIMENTAL STUDY OF IMPINGING HEAT TRANSFER OF INLINE AND STAGGERED JET ARRAYS BY TRANSIENT LIQUID CRYSTAL TECHNIQUE
24
10.1615/JFlowVisImageProc.v10.i12.70
W. M.
Yan
Department of Mechanical Engineering, Hua Fan University Shih-Ting, Taipei, 22305, Taiwan, ROC
H. C.
Liu
Department of Mechanical Engineering, Hua Fan University Shih-Ting, Taipei, 22305, Taiwan, ROC
Chyi-Yeou
Soong
Department of Aeronautical Engineering, Feng Chia University Seatwen, Taichung 40745, Taiwan, ROC
The objective of the present experimental work is the study of local heat transfer performance over a target plate under impingement of inline and staggered jet arrays by a liquid crystal thermograph technique. Three jet-to-target spacings Z (= z/d) of 3, 6, and 9 with inline and staggered jet arrays were considered at jet Reynolds numbers Re = 1500, 3000, and 4500 in three different exit-flow orientations. The results show that the local heat transfer rates are characterized by obvious periodic-type variation of Nusselt number distributions. The downstream peaks are diminished with increasing cross-flow effect. The best heat transfer performance is obtained with the cross flow exiting from both ends of the impingement channel. The inline jet array produces relatively higher local and overall heat transfer rates than those of the staggered jet array. Additionally, in the present results of 3 Ј Z Ј 9, higher heat transfer rates are found for the system with a smaller jet-to-plate spacing.
ADMIXTURE EFFECT OF LANCE ARRANGEMENT ON PULVERIZED COAL INJECTION
12
10.1615/JFlowVisImageProc.v10.i12.80
The dye injection method is employed to visualize two-dimensional admixture and diffusion of pulverized coal injected into the blowpipe in the blast furnace. Both the single lance and the double lances are studied. Water is used as working fluid. The velocity ratio and the lance inlet are varied. The lance inlet-angle is fixed as 13°. The jet-width growth rates and the trajectories of jets are not obviously influenced by the velocity ratio in the range 0.1 Ј v/U Ј 0.18. For the double lances, much faster jet-width growth rates than those for the single lance under the same test conditions were disclosed, but the flows gradually move away from the center of the blowpipe after impinging. In contrast, the eccentric double lances, two lances arranged asymmetrically to avoid impingement of two coal flows and obtain excellent jet-width growth rates, are suggested in the study for pulverized coal injection.
EVALUATION OF RADIAL VELOCITY FLUCTUATIONS IN TURBULENT PIPE FLOW BY MEANS OF AN ULTRASONIC DOPPLER VELOCIMETER
7
10.1615/JFlowVisImageProc.v10.i12.90
Giancarlo
Alfonsi
Fluid Dynamics Laboratory, Universita della Calabria, Via P. Bucci 42b, 87036 Rende (Cosenza), Italy
A still controversial issue in the open literature is that of the level of the kurtosis of the normal velocity fluctuations in the near-wall region of a turbulent shear flow. Numerical simulations often report values of the kurtosis considerably higher than experimental results and this fact is attributed by some authors to the different accuracy of the statistics computed from experimental series of data with respect to the numerical databases [1]. A question to be clarified is whether the high kurtosis values result from numerical artifacts of the computations or they are the manifestation of processes of physical nature related to the evolution of the turbulent flow structures near the wall [2]. In this work, experimental data of radial velocity fluctuations in turbulent pipe flow gathered with an Ultrasonic Doppler Velocimeter (UDV) are analyzed. One of the series of measurements shows a strong "sweep" of the radial velocity fluctuations and the evaluation of the related kurtosis gives a value considerably close to that reported by numerical simulations. This circumstance actually shows the occurrence of turbulent events near the wall and demonstrates the reliability of the Ultrasonic Doppler Velocimeter for turbulence measurements in fluid flows.