Visualization Of Vortex Structures In The Near Field Of The Round Jet Formed In Curved Channel By Piv-Method

2016 ◽  
Vol 11 (2) ◽  
pp. 103-107
Author(s):  
Maria Litvinenko ◽  
Yuriy Litvinenko ◽  
Valentin Vikhorev
Keyword(s):  
Velocity Gradient ◽  
Particle Image ◽  
Near Field ◽  
Gradient Field ◽  
Low Velocity ◽  
Round Jet ◽  
Dean Vortices ◽  
Piv Method ◽  
Image Velocimetry ◽  
Vector Velocity Field

The results of experimental investigation of the round jet with Dean vortices (Red = 4 000, De = 1 673) using Particle Image Velocimetry are presented. The measurements were performed with synchronization the phase of acoustic signal and a laser pulse. Instant picture of vorticity field ωz and vector velocity field for the U- and V-components of the jet cross-actions show Dean vortices near the output of the channel in the low velocity gradient field and Kelvin – Helmholtz vortices in the high-velocity gradient field. The presence of Dean vortices distorts two-dimensional vortex ring, which gets an Ω-shaped form, at that the « head» of Ω-vortex outpaces its «legs», as it is in a higher velocity area.

scholarly journals The Fluid Dynamical Performance of the Carpentier-Edwards PERIMOUNT Magna Ease Prosthesis

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Philipp Marx ◽  
Wojciech Kowalczyk ◽  
Aydin Demircioglu ◽  
Gary Neil Brault ◽  
Hermann Wendt ◽  
...  
Keyword(s):  
Velocity Gradient ◽  
Aortic Wall ◽  
Particle Image ◽  
In Vitro Study ◽  
Maximal Velocity ◽  
Flow Parameters ◽  
Velocity Gradients ◽  
Image Velocimetry ◽  
Maximal Strain

The aim of the present in vitro study was the evaluation of the fluid dynamical performance of the Carpentier-Edwards PERIMOUNT Magna Ease depending on the prosthetic size (21, 23, and 25 mm) and the cardiac output (3.6–6.4 L/min). A self-constructed flow channel in combination with particle image velocimetry (PIV) enabled precise results with high reproducibility, focus on maximal and local peek velocities, strain, and velocity gradients. These flow parameters allow insights into the generation of forces that act on blood cells and the aortic wall. The results showed that the 21 and 23 mm valves have a quite similar performance. Maximal velocities were 3.03±0.1 and 2.87±0.13 m/s; maximal strain Exx, 913.81±173.25 and 896.15±88.16 1/s; maximal velocity gradient Eyx, 1203.14±221.84 1/s and 1200.81±61.83 1/s. The 25 mm size revealed significantly lower values: maximal velocity, 2.47±0.15 m/s; maximal strain Exx, 592.98±155.80 1/s; maximal velocity gradient Eyx, 823.71±38.64 1/s. In summary, the 25 mm Magna Ease was able to create a wider, more homogenous flow with lower peak velocities especially for higher flow rates. Despite the wider flow, the velocity values close to the aortic walls did not exceed the level of the smaller valves.

scholarly journals Application of particle image velocimetry (PIV) to measure the displacement of sandy soil in laboratory

2021 ◽  
Vol 63 (3) ◽  
pp. 70-77
Keyword(s):  
Grain Size ◽  
Particle Image Velocimetry ◽  
Sandy Soil ◽  
Laboratory Tests ◽  
Particle Image ◽  
Degree Of Saturation ◽  
Grain Sizes ◽  
Piv Method ◽  
Soil Displacement ◽  
Image Velocimetry

Particle image velocimetry (PIV) has been heavily used to measure the displacement and flow velocity in fluid mechanics. However, applications of this method to determining soil displacement in geotechnical laboratory tests are rare. This paper aims to verify the applicability of this method in determining the displacement of sandy soil under different saturation conditions and soil grain sizes. The results showed that this method could effectively determine soil displacement with an accuracy of 0.13 mm. Furthermore, the degree of saturation of soil did not influence the PIV results whereas the homogeneity of soil, as indicated by grain size distribution, reduced the precision of the PIV method.

Particle Image Velocimetry for Air Flows Behind Permeable Cylinders

2007 ◽  
Author(s):  
Hirotaka Takeuchi ◽  
Yuji Tasaka ◽  
Yuichi Murai ◽  
Yasushi Takeda ◽  
Hideaki Tezuka ◽  
...  
Keyword(s):  
Particle Image Velocimetry ◽  
Particle Image ◽  
Reverse Flow ◽  
Near Field ◽  
Water Mist ◽  
Circular Cylinders ◽  
Spatial Density ◽  
Turbulence Energy ◽  
Solid Cylinder ◽  
Image Velocimetry

Particle image velocimetry is applied to measurement of airflows around three types of permeable circular cylinders. The experimental model of the permeable cylinder is made of squared meshed sheet rolled in circle. Water mist smoke is used as air tracer, which is generated with dry ice in a chamber to produce fine spatial density fluctuation for guaranteeing the PIV quality. Since the flow involves fluctuation in a very wide wavenumber from the cylinder size to mesh-dependent eddies, calculating brightness spectrum quantitatively assesses the smoke image quality. The experiment is carried out in an open type wind tunnel. The following results are obtained when the measurement results are compared to those of a solid cylinder. 1: The flow just behind the cylinder has forward velocity due to the permeability while the solid cylinder has reverse flow in the wake. This feature relaxes near field excitation of Karman vortex shedding. 2: The reattachment point behind the cylinder displaces several times as the solid case. As a result of the above two phenomena, the peak potion of the turbulence energy appears in the far downstream region as the permeability of the cylinder increases.

Hydrodynamic Investigation of a Wafer Rinse Process Through Numerical Modeling and Flow Visualization Methods

2018 ◽  
Vol 140 (8) ◽  
Author(s):  
Chia-Yuan Chen ◽  
Bivas Panigrahi ◽  
Kok-Shen Chong ◽  
Wei-Hsien Li ◽  
Yi-Li Liu ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Flow Visualization ◽  
Particle Image ◽  
Original Design ◽  
Major Drawback ◽  
Wafer Cleaning ◽  
Piv Method ◽  
Batch Fabrication ◽  
Image Velocimetry ◽  
Strong Agreement

In the current semiconductor industrial scenario, wafers are rinsed in an overflow rinsing tank while being mounted on several lifters prior to most of its manufacturing processes. However, a major drawback of this overflow rinsing methodology is that some of the processing fluid stagnates due to the generated vortices in the regions between the side and middle lifters which entrap some of the flushed particles that further adhere and deteriorate the surface of the wafers. In this work, the hydrodynamics of the flow field inside the wafer rinsing tank with this original lifter orientation setup was studied and compared through numerical simulation and flow visualization using particle image velocimetry (PIV) method, and a strong agreement was found between them in terms of velocity calculation. A new lifter orientation setup was initiated and it was evidenced by the numerical simulation that with this new setup, the generated vortices which are situated opposite to the lifters tilting direction can be displaced significantly in terms of magnitude and distribution. This work presents a new wafer cleaning concept which shows its great potentials in improvement and implementation to the current in-line wafer batch fabrication process without modifying the original design of the rinsing tank.

Measurement of the Periodic Flow Field in a Radial Diffuser Pump by the PIV-Method

2007 ◽  
Author(s):  
Friedrich-Karl Benra ◽  
Jianjun Feng ◽  
Hans Josef Dohmen
Keyword(s):  
Particle Image ◽  
Flow Measurements ◽  
Piv Method ◽  
Diffuser Flow ◽  
Image Velocimetry ◽  
Impeller Outlet ◽  
Rear Part ◽  
Low Specific Speed ◽  
Specific Speed ◽  
Inflow Conditions

Detailed flow measurements are conducted by two-dimensional Particle Image Velocimetry (PIV) in a low specific speed radial diffuser pump at the design operating point, in order to investigate the impeller-diffuser interaction. The measurements are conducted at midspan for different relative positions between the impeller and diffuser. The measuring region covers a complete impeller channel and also a complete diffuser channel. The analysis of the experimental results shows that a jet-wake structure is observed near the impeller outlet. The presence of the diffuser vanes mainly affects the impeller flow at the rear part near the impeller outlet. The diffuser flow strongly depends on the relative impeller position which provides different inflow conditions for the diffuser.

Influence of Internal Objects in Flow Characteristics of Darrieus Turbine

2011 ◽  
Author(s):  
Kotaro Takeshima ◽  
Yuji Tasaka ◽  
Yuichi Murai
Keyword(s):  
Particle Image ◽  
Angle Of Attack ◽  
Flow Characteristics ◽  
Temporal Variations ◽  
Hot Wire ◽  
Low Velocity ◽  
Image Velocimetry ◽  
Internal Objects ◽  
Low Efficiency ◽  
A New Technique

Since Darrieus turbine is omnidirectional against the wind, it has a great essential advantage in turbulent wind environment. However, a disadvantage on the starting up is known in low velocity conditions of the wind compared with propeller turbines. Darrieus turbine has a low efficiency problem at low tip-speed ratios due to this disadvantage. Some studies have done to overcome this problem, but these have been on the beginning of the way toward the solution. The reason is that the angle of attack for Darrieus blades is changed largely during the rotation relative to the wind direction. In this study, we found a new technique to improve the efficiency. The technique is the providing a large internal cylinder rotating together with the blades, which can control the angle of attack of the blades. We evaluated the influence of cylindrical diameter on the blade performance by the time-averaged velocity distribution and the intensity of the velocity fluctuation comparing between with cylinder and without cylinder. The flow field around the blades is measured with two kinds of instruments. One is Hot Wire Anemometer for analyzing temporal variations of flows, and the other is Particle Image Velocimetry for analyzing the spatial flow structure in detail. Angles of attack and lift coefficients are calculated from the measured relative velocity vector field. As a result, the angles of attack and the lift coefficients are improved in some rotational angles, which are also confirmed by numerical simulations.

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