Direct measurement of fluid velocity in an electrospinning jet using particle image velocimetry

2007 ◽  
Vol 102 (9) ◽  
pp. 094308 ◽  
Author(s):  
Leon M. Bellan ◽  
Harold G. Craighead ◽  
Juan P. Hinestroza
Keyword(s):  
Particle Image Velocimetry ◽  
Direct Measurement ◽  
Particle Image ◽  
Fluid Velocity ◽  
Image Velocimetry

Experimental Measurements of Forces on Loose Particle in Motion Over Rough Bed Under Waves Using Oblique Particle Image Velocimetry

2016 ◽  
Vol 138 (6) ◽  
Author(s):  
Sanjay N. Havaldar ◽  
Francis C. K. Ting
Keyword(s):  
Particle Image Velocimetry ◽  
Particle Image ◽  
Fluid Layer ◽  
Fluid Velocity ◽  
Particle Diameter ◽  
Single Layer ◽  
Wave Direction ◽  
Loose Sediment ◽  
Image Velocimetry ◽  
Rough Bed

Magnitude and phase of major forces that act on a loose non-cohesive particle (sediment) on single layer fixed rough bed (longitudinal slope 2%) were determined from experiments in a laboratory flume under waves. The loose particles were glass spheres of diameter 1.58 ± 0.1 mm and specific gravity 2.5. The range of wave-height-to-water-depth (H/h) ratio in the experiments was 0.366 < H/h < 0.521. The measurement plane was parallel to the bed and located at a height of ½ loose particle diameter (ds) above the rough bed. Grayscale morphological image processing methods were used to separate the fluid and loose sediment phases from the same oblique particle image velocimetry (OPIV) image based on their signature sizes. The OPIV calibration method is presented and validated with conventional particle image velocimetry (PIV) method. Loose particle velocity and accelerations along with the associated fluid velocity and fluid total accelerations in the wave direction were determined simultaneously by processing OPIV used to compute magnitude and phase of major forces that act on the loose sediment particle. It was observed that for same wave period (T), an increase in H/h ratio has a dominant effect on sediment displacements onshore. The phase along with magnitude of the major driving force (drag and fluid accelerations) plays an important role at initiation of loose sediment from its rest position. It is suspected that the loose particle overcomes a critical bed friction force with higher H/h ratio as magnitude of drag force is higher. The resultant force then displaces the sediment onshore which experiences sliding and or rolling motions very close to bed, in a thin fluid layer over maximum protrusion of bed sediments. At the instance, the gravitational force plus bed frictions overcomes the lift force the loose particle attains a new position onshore.

Locomotor forces on a swimming fish: three-dimensional vortex wake dynamics quantified using digital particle image velocimetry

1999 ◽  
Vol 202 (18) ◽  
pp. 2393-2412 ◽  
Author(s):  
E.G. Drucker ◽  
G.V. Lauder
Keyword(s):  
Particle Image Velocimetry ◽  
Swimming Speed ◽  
Particle Image ◽  
Fluid Velocity ◽  
Lepomis Macrochirus ◽  
Three Dimensional ◽  
Digital Particle Image Velocimetry ◽  
Force Balance ◽  
Vortex Rings ◽  
Image Velocimetry

Quantifying the locomotor forces experienced by swimming fishes represents a significant challenge because direct measurements of force applied to the aquatic medium are not feasible. However, using the technique of digital particle image velocimetry (DPIV), it is possible to quantify the effect of fish fins on water movement and hence to estimate momentum transfer from the animal to the fluid. We used DPIV to visualize water flow in the wake of the pectoral fins of bluegill sunfish (Lepomis macrochirus) swimming at speeds of 0.5-1.5 L s(−)(1), where L is total body length. Velocity fields quantified in three perpendicular planes in the wake of the fins allowed three-dimensional reconstruction of downstream vortex structures. At low swimming speed (0.5 L s(−)(1)), vorticity is shed by each fin during the downstroke and stroke reversal to generate discrete, roughly symmetrical, vortex rings of near-uniform circulation with a central jet of high-velocity flow. At and above the maximum sustainable labriform swimming speed of 1.0 L s(−)(1), additional vorticity appears on the upstroke, indicating the production of linked pairs of rings by each fin. Fluid velocity measured in the vicinity of the fin indicates that substantial spanwise flow during the downstroke may occur as vortex rings are formed. The forces exerted by the fins on the water in three dimensions were calculated from vortex ring orientation and momentum. Mean wake-derived thrust (11.1 mN) and lift (3.2 mN) forces produced by both fins per stride at 0.5 L s(−)(1) were found to match closely empirically determined counter-forces of body drag and weight. Medially directed reaction forces were unexpectedly large, averaging 125 % of the thrust force for each fin. Such large inward forces and a deep body that isolates left- and right-side vortex rings are predicted to aid maneuverability. The observed force balance indicates that DPIV can be used to measure accurately large-scale vorticity in the wake of swimming fishes and is therefore a valuable means of studying unsteady flows produced by animals moving through fluids.

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