Begell House Inc.
Journal of Flow Visualization and Image Processing
JFV
1065-3090
16
1
2009
PIV MEASUREMENTS OF SURFACE FLOWS IN LABORATORY WAVE BASINS
1-18
10.1615/JFlowVisImageProc.v16.i1.10
Liang
He
Halcrow HPA, 22 Cortlandt Street, New York, NY 10007, USA
Jack A.
Puleo
Center for Applied Coastal Research, Department of Civil and Environmental Engineering, University of Delaware, Newark, DE 19716, USA
Geo-referenced imagery and particle image velocimetry (PIV) are used to quantify surface flow fields in a laboratory wave basin. An application of the technique for topographically controlled rip currents is described. Exact comparisons between PIV data on an undulating free surface and groundtruth velocity data are difficult to perform owing to adverse effects of fixed objects in PIV imagery and the necessary placement of current meters below wave trough level. However, mean PIV velocity magnitudes compared favorably with acoustic Doppler current meter data from roughly 0.05 m below the still water level with root-mean-square differences of 0.077 m·s−1 in the cross-shore and 0.059 m·s−1 in the alongshore directions.
GLOBAL SKIN FRICTION DIAGNOSTICS IN SEPARATED FLOWS USING LUMINESCENT OIL
19-39
10.1615/JFlowVisImageProc.v16.i1.20
Tianshu
Liu
Department of Mechanical and Aeronautical Engineering, G-220, Parkview Campus, Western Michigan University, Kalamazoo, MI 49008
S.
Woodiga
Department of Mechanical and Aeronautical Engineering, G-220, Parkview Campus, Western Michigan University, Kalamazoo, MI 49008
J.
Montefort
Department of Mechanical and Aeronautical Engineering, G-220, Parkview Campus, Western Michigan University, Kalamazoo, MI 49008
K. J.
Conn
Department of Mechanical and Aeronautical Engineering, G-220, Parkview Campus, Western Michigan University, Kalamazoo, MI 49008
Lixin
Shen
Department of Mathematics, Syracuse University, Syracuse, NY 13244
Quantitative skin friction diagnostics in complex separated flows is achieved by using a global luminescent oil-film skin-friction meter. This technique is based on the variational solution for the projected thin-oil-film equation on the image plane. Normalized skin friction fields are obtained in junction flows and flows over surface roughness elements, a double-delta wing, and a low-aspect-ratio rectangular wing. The results show the detailed topological structures of skin friction fields in these flows.
DETERMINATION OF THE THRESHOLD VALUE OF THE QUANTITY CHOSEN FOR VORTEX REPRESENTATION IN TURBULENT FLOW
41-49
10.1615/JFlowVisImageProc.v16.i1.30
Leonardo
Primavera
Fluid Dynamics Laboratory, Universita della Calabria, Via P. Bucci, Cubo 42b, 87036 Rende (Cosenza), Italy
Giancarlo
Alfonsi
Fluid Dynamics Laboratory, Universita della Calabria, Via P. Bucci 42b, 87036 Rende (Cosenza), Italy
In recent times much work has been devoted to the issue of vortex definition in turbulence. Several criteria for vortex identification have been devised and techniques for defining the correspondence between different criteria have been found, leading to the possibility of representing nearly-equally intense vortical structures using different identification methods. The issue remains open of calculating a threshold value of the quantity chosen for vortex eduction, being able to give a physically based representation of the vortical structure at hand. For this purpose we present a direct method based on some statistics of the velocity field, applied in particular to the issue of representing a hairpin vortex in the wall region of turbulent channel flow.
LIQUID CRYSTAL SHEAR STRESS SENSOR FOR BLOOD AND OTHER OPAQUE VISCOUS FLUIDS
51-71
10.1615/JFlowVisImageProc.v16.i1.40
R. K.
Gottlieb
University of Pittsburgh, Departments of Bioengineering and Surgery, Pittsburgh, PA
F.
Shu
University of Pittsburgh, Departments of Bioengineering and Surgery, Pittsburgh, PA
M. V.
Kameneva
University of Pittsburgh, Departments of Bioengineering and Surgery, Pittsburgh, PA
J. F.
Antaki
Carnegie Mellon University, Pittsburgh, PA, University of Pittsburgh, Departments of Bioengineering and Surgery, Pittsburgh, PA
Z. J.
Wu
University of Pittsburgh, Departments of Bioengineering and Surgery, Pittsburgh, PA, University of Maryland, Baltimore, MD
G. W.
Burgreen
University of Pittsburgh, Departments of Bioengineering and Surgery, Pittsburgh, PA, Mississippi State University, Starkville, Mississippi
A liquid crystal-based photochromic coating was formulated to enable direct visualization of shear stress in flowing blood. The coating was comprised of a low durometer silicone rubber elastomer combined with a cholesteric liquid crystal to expand the functional shearsensing range and improve its durability when exposed to viscous flow. The coating was evaluated with black and red opaque viscous fluids as well as blood for spatial resolution and sensitivity. Experiments were conducted in rectangular channels and a cylindrical Taylor-Couette device with shear stress up to 300 dyne/cm2 in blood, and 3000 dyne/cm2 in glycerol. The results illustrated the feasibility of a liquid crystal based shear stress sensor for visualizing the spatial distribution of biologically relevant shear stress.
FLOW VISUALIZATION IN X-SHAPED MICRO-INTERSECTING CHANNELS BY MEANS OF MICRO-PIV
73-83
10.1615/JFlowVisImageProc.v16.i1.50
A Cassegrain system-assisted PIV technique is employed to perform flow visualization experiments to investigate mixing characteristics of the left and right channel flows subsequent to their convergence. Two series of experiments are conducted. One has water supplied to both the left and right channels and the other has water supplied to the left channel and hexane to the right channel. Conditions for generating zebra-stripe flow patterns are determined together with their flow characteristics. Results obtained from the study may be utilized in developing micro reactors.
DEVELOPMENT AND FLOW VISUALIZATION OF FLUID CURTAINS
85-103
10.1615/JFlowVisImageProc.v16.i1.60
An experimental study is performed on a composite flow network consisting of a diamond-shaped cylinder bundle and two (one above and the other below) slit flows in parallel arrangement. Flow velocity and vorticity in the effluent flow field of the composite unit are measured by means of Particle Image Velocimetry (PIV) method and flow visualization of the effluent jet streams is conducted using smoke as the tracer. It is disclosed that by utilizing the effect of shearing action at the mixed flow interfaces, the effluent flow passage from the composite flow network may be elongated and flow rotationality may be controlled by suppressing the reduction of effluent flow velocity. Basic experimental data are obtained for the design of fluid curtains which may be employed in foods preservation.