Experimental Study of Three-Dimensional Laminar Wall Jets of Non-Newtonian Fluid

2009 ◽  
Author(s):  
Kofi K. Adane ◽  
Mark F. Tachie
Keyword(s):  
Newtonian Fluid ◽  
Open Channel ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Jet Flows ◽  
Wall Jet ◽  
Particle Image Velocimetry Technique ◽  
Piv Measurements ◽  
Image Velocimetry ◽  
Shear Thinning Fluid

A particle image velocimetry technique was employed to study three-dimensional laminar wall jet flows of a non-Newtonian shear-thinning fluid. The wall jet was created using a circular pipe of diameter 7 mm and flows into an open channel. The Reynolds numbers based on the pipe diameter and jet exit velocity were varied from 250 to 800. The PIV measurements were performed in various streamwise-transverse and streamwise-spanwise planes. From these measurements, the velocity profiles, jet growth rate and spread rates were obtained to study the characteristics of three-dimensional wall jet flows of a non-Newtonian fluid.

PIV Study of Three-Dimensional Wall Jet Over Smooth and Rough Surfaces

2007 ◽  
Author(s):  
Martin Agelinchaab ◽  
Mark F. Tachie
Keyword(s):  
Open Channel ◽  
Rough Surfaces ◽  
Reynolds Shear Stress ◽  
Three Dimensional ◽  
Jet Flows ◽  
Wall Jet ◽  
Image Velocimetry ◽  
The Mean ◽  
Turbulent Wall ◽  
Insight Into

This paper reports experimental study of three-dimensional turbulent wall jet over smooth and rough surfaces. The wall jet was created using a square nozzle of size 6 mm and flow into an open channel. The experiments were performed at a Reynolds number based on the nozzle size and jet exit velocity of 4800. A particle image velocimetry was used to conduct detailed measurements over the smooth and rough surfaces at various streamwise-transverse and streamwise-spanwise planes. From these measurements, mean velocities and turbulent quantities were extracted at selected locations. The distributions of the mean velocities, turbulent intensities and Reynolds shear stress were used to provide insight into the characteristics of three-dimensional wall jet flows over smooth and rough surface.

PIV Study of Laminar Wall Jets of Non-Newtonian Fluids

2010 ◽  
Vol 132 (7) ◽  
Author(s):  
K. F. K. Adane ◽  
M. F. Tachie
Keyword(s):  
Reynolds Number ◽  
Three Dimensional ◽  
Maximum Velocity ◽  
Reynolds Numbers ◽  
Newtonian Fluids ◽  
Jet Flows ◽  
Wall Jet ◽  
Fluid Type ◽  
Particle Image Velocimetry Technique ◽  
Velocity Decay

Three-dimensional laminar wall jet flows of shear-thinning non-Newtonian fluids have been studied using a particle image velocimetry technique. The non-Newtonian fluids were prepared from xanthan gum solutions of various concentrations. The velocity measurements were performed in various streamwise-transverse and streamwise-spanwise planes at various inlet Reynolds numbers. From these measurements, the maximum velocity decay, jet half-widths, and velocity profiles were obtained to study the effects of Reynolds number and fluid type on the characteristics of the wall jet flows. It was observed that the maximum velocity decay and jet half-widths depend on inlet Reynolds number and fluid but the similarity velocities profiles are independent of both Reynolds number and specific fluid type.

Experimental and Numerical Study of Laminar Round Jet Flows Along a Wall

2010 ◽  
Vol 132 (10) ◽  
Author(s):  
K. F. K. Adane ◽  
M. F. Tachie
Keyword(s):  
Numerical Study ◽  
Three Dimensional ◽  
Open Water ◽  
Reynolds Numbers ◽  
Navier Stokes ◽  
Jet Flows ◽  
Wall Jet ◽  
Water Tank ◽  
Navier Stokes Equation ◽  
Image Velocimetry

In the present study, both experimental and numerical techniques were employed to study three-dimensional laminar wall jet flows. The wall jet was created using a circular pipe of diameter 7×10−3 m and flows into an open water tank. The inlet Reynolds numbers based on the pipe diameter and jet exit velocity were 310 and 800. A particle image velocimetry (PIV) was used to conduct detailed measurements at various streamwise-transverse and streamwise-spanwise planes. The complete nonlinear incompressible Navier–Stokes equation was also solved using a collocated finite volume based in-house computational fluid dynamics (CFD) code. The computation was performed for three inlet Reynolds numbers, namely, 310, 420, and 800. From the PIV measurements and CFD results, velocity profiles and jet half-widths were extracted at selected downstream locations. It was observed that the numerical results are in reasonable agreement with the experimental data. The distributions of the velocities, jet spread rates, and vorticity were used to provide insight into the characteristics of three-dimensional laminar wall jet flows.

Aerodynamic Particle Resuspension due to Human and Model Foot Motions

2010 ◽  
Author(s):  
Yoshihiro Kubota ◽  
Hiroshi Higuchi
Keyword(s):  
Flow Visualization ◽  
Particle Concentration ◽  
Three Dimensional ◽  
Wall Jet ◽  
Piv Measurements ◽  
Particle Resuspension ◽  
Human Foot ◽  
Image Velocimetry ◽  
Foot Motion ◽  
Foot Tapping

Human foot motions such as walking and foot tapping detach the particulate matter on the floor and redistribute it, increasing the particle concentration in air. The objective of this paper is to experimentally investigate the mechanism of particle resuspension and redistribution due to human foot motion. In particular, generation and deformation of vortex produced by the foot motion and how they are affected by the shape of sole have been examined. The experiments were carried out by particle flow visualization and the Particle Image Velocimetry (PIV) measurements in air, and dye flow visualization in water. The flow visualizations with human foot tapping and stomping were also carried out in order to elucidate the particle resuspension in real situations. In a laboratory experiment, the foot was modeled either as an elongated plate or a foot wearing a slipper, moving normal to the ground downward or upward. To focus on the aerodynamic effect, the model foot was stopped immediately above the floor before contacting the floor. The results indicated that the particles were resuspended both in downward motion and in upward motion of the foot. The particle resuspension and redistribution were associated with the wall jet between the foot and floor and the vortex dynamics. With an elongated plate, three-dimensional vortex structure strongly affected the particle redistribution.

Three-Dimensional Laminar Wall Jet Flows

2009 ◽  
Author(s):  
Kofi K. Adane ◽  
Mark F. Tachie
Keyword(s):  
Numerical Study ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Secondary Flows ◽  
Navier Stokes ◽  
Jet Flows ◽  
Wall Jet ◽  
Navier Stokes Equation ◽  
Flow Geometry

The present article reports on both experimental and numerical study of three-dimensional laminar wall jet flows. The wall jet was created using a circular pipe of diameter 7 mm and flows into an open channel. The Reynolds numbers based on the pipe diameter and jet exit velocity were varied from 310 to 1300. A particle image velocimetry (PIV) was used to conduct detailed velocity measurements at various streamwise-transverse and streamwise-spanwise planes. A complete nonlinear incompressible Navier-Stokes equation was also solved using a co-located finite volume based in-house computational fluid dynamic (CFD) code. This code was used to compute the experimental flow geometry. From the PIV measurements and CFD results, velocities profiles and jet-half-widths were extracted at selected locations. It was observed that the numerical results are in reasonable agreement with the experimental data. The distributions of the velocities, jet-half-widths and visualisation of the secondary flows were used to provide insight into the characteristics of three-dimensional wall jet flows.

PIV Measurements of the Turbulent Secondary Flow in a Three-Dimensional Wall Jet

2010 ◽  
Author(s):  
Lhendup Namgyal ◽  
Joseph W. Hall
Keyword(s):  
Secondary Flow ◽  
Reynolds Shear Stress ◽  
Three Dimensional ◽  
Secondary Flows ◽  
Half Width ◽  
Wall Jet ◽  
Normal Stresses ◽  
Reynolds Stresses ◽  
Piv Measurements ◽  
Image Velocimetry

The lateral half width of the turbulent three-dimensional wall jet is typically five to eight times larger than the vertical half width normal to the wall. Although, the reason for this behavior is not fully understood, it is known to be caused by strong secondary flows that develop in the jet due to presence of the wall. The source of the secondary flow in the jet has been attributed previously with both mean vorticity reorientation and to anisotropy in the Reynolds normal stresses, but until now there have been no measurements of these quantities in this flow. Particle Image Velocimetry (PIV) measurements are used herein to measure the Reynolds stresses that contribute to the secondary flow in a turbulent three-dimensional wall jet formed using a circular contoured nozzle with exit Reynolds number of 250,000. In particular, the Reynolds shear stress, vw was found to be significantly smaller throughout the jet than the differences in the Reynolds normal stresses (v2 − w2).

scholarly journals Fish larvae exploit edge vortices along their dorsal and ventral fin folds to propel themselves

2016 ◽  
Vol 13 (116) ◽  
pp. 20160068 ◽  
Author(s):  
Gen Li ◽  
Ulrike K. Müller ◽  
Johan L. van Leeuwen ◽  
Hao Liu
Keyword(s):  
Larval Fish ◽  
Fish Larvae ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Bony Fish ◽  
The Body ◽  
Functional Explanation ◽  
Image Velocimetry ◽  
Median Fins

Larvae of bony fish swim in the intermediate Reynolds number ( Re ) regime, using body- and caudal-fin undulation to propel themselves. They share a median fin fold that transforms into separate median fins as they grow into juveniles. The fin fold was suggested to be an adaption for locomotion in the intermediate Reynolds regime, but its fluid-dynamic role is still enigmatic. Using three-dimensional fluid-dynamic computations, we quantified the swimming trajectory from body-shape changes during cyclic swimming of larval fish. We predicted unsteady vortices around the upper and lower edges of the fin fold, and identified similar vortices around real larvae with particle image velocimetry. We show that thrust contributions on the body peak adjacent to the upper and lower edges of the fin fold where large left–right pressure differences occur in concert with the periodical generation and shedding of edge vortices. The fin fold enhances effective flow separation and drag-based thrust. Along the body, net thrust is generated in multiple zones posterior to the centre of mass. Counterfactual simulations exploring the effect of having a fin fold across a range of Reynolds numbers show that the fin fold helps larvae achieve high swimming speeds, yet requires high power. We conclude that propulsion in larval fish partly relies on unsteady high-intensity vortices along the upper and lower edges of the fin fold, providing a functional explanation for the omnipresence of the fin fold in bony-fish larvae.

PIV Measurements in Diffuser of the Radial Pump

2015 ◽  
Author(s):  
Sung Yong Jung ◽  
Young Uk Min ◽  
Kyung Lok Lee
Keyword(s):  
High Speed ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Operating Conditions ◽  
Internal Flows ◽  
Piv Measurements ◽  
Image Velocimetry ◽  
Acquisition Device ◽  
Field Information ◽  
Radial Pump

The performance characteristics of the radial pump commonly used as a multistage (8 or 10 stage) pump have been investigated experimentally. Due to the complex three-dimensional geometries, the hydraulic performance of multistage pumps is closely related to the internal flows in diffuser and return vanes. In order to investigate the flow characteristics in these regions by Particle Image Velocimetry (PIV) technique, a transparent pump is designed. A 532 nm continuous laser and a high-speed camera are used as a light source and an image acquisition device, respectively. The velocity field information in a diffuser of the radial pump is successfully obtained by two-dimensional PIV measurements at various operating conditions.

PIV Investigation of an Open Channel Flow Over a Forward Facing Step

2007 ◽  
Author(s):  
M. K. Shah ◽  
M. F. Tachie
Keyword(s):  
Open Channel ◽  
Particle Image ◽  
Open Channel Flow ◽  
Reynolds Stresses ◽  
Velocity Measurements ◽  
Particle Image Velocimetry Technique ◽  
Mean Velocity ◽  
Freestream Velocity ◽  
Image Velocimetry ◽  
Forward Facing Step

The characteristics of an open channel turbulent flow over a forward facing step (FFS) are investigated in the present study. Two step heights, h = 6 and 9 mm, at Reynolds number, Reh, (based on the approach freestream velocity, U0, and step height, h) of 1900 and 2800 respectively were studied. Particle image velocimetry technique (PIV) was used to obtain detailed velocity measurements upstream of the FFS, in the reattachment region (x/h = 0, 1, 2) and in the redevelopment region (x/h = 4, 10, 15 and 50). The boundary layer integral parameters, mean velocity profiles and Reynolds stresses obtained in the reattachment and redevelopment region are used to document some of the salient features of the flow.

scholarly journals Evolution of Turbulent Horseshoe Vortex System in Front of a Vertical Circular Cylinder in Open Channel

Water ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 2079 ◽  
Author(s):  
Chen ◽  
Yang ◽  
Wu
Keyword(s):  
Open Channel ◽  
Evolutionary Process ◽  
Reynolds Numbers ◽  
Horseshoe Vortex ◽  
Local Scour ◽  
Time Resolved ◽  
Vortex Interactions ◽  
Initial Stage ◽  
Image Velocimetry ◽  
Underlying Mechanisms

A turbulent horseshoe vortex (HV) system around a wall-mounted cylinder in open channel is characterized by random variations in vortex features and an abundance of vortex interactions. The turbulent HV system is responsible for initiating the local scour process in front of the cylinder. The evolution of the turbulent HV system is investigated statistically and quantitatively with time-resolved particle image velocimetry. The cylinder Reynolds numbers of the flow are 8600, 10,200, and 13,600, respectively. A novel vortex tracking method was proposed to obtain the variations in position, size, and strength of the primary HV (PHV) which dominates the system most of the time. Relationships between the various features of the PHV during its evolutionary process were obtained through correlation analyses. Results show that the dimensionless mean lifespan of the PHV is about 5.0. Statistically, the downstream movement of the PHV toward the cylinder is accompanied with its bed-approaching movement and decreasing in size, and the opposite is true. The circulation strength of the PHV decreases and increases dramatically in the region downstream of its time-averaged position when the PHV approaches and departs from the cylinder, respectively. Meanwhile, mechanisms responsible for the generation, movement, variation, and disappearance of the PHV are re-investigated and enriched based on its interactions with vortices in the separation region and structures in the incoming flow. The obtained change trends of the features of the PHV and the underlying mechanisms for its evolution are valuable for predicting and controlling the initial stage of the local scour in front of cylinders.

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