scholarly journals PIV of Swirling Flow in a Conical Pipe with Vibrating Wall

2018 ◽  
Vol 10 (02) ◽  
pp. 1850022 ◽  
Author(s):  
Yan Xu ◽  
Yan-Yue Zhang ◽  
Franck C. G. A. Nicolleau ◽  
Zun-Ce Wang
Keyword(s):  
Particle Image ◽  
Swirling Flow ◽  
Water Channel ◽  
Swirling Flows ◽  
Industrial Processes ◽  
Reynolds Stresses ◽  
Pipe Flows ◽  
Velocity Statistics ◽  
Image Velocimetry ◽  
The Mean

Swirling flows in conical pipe can be found in a number of industrial processes, such as hydrocyclone, separator and rotating machinery. It has been found that wall oscillations can reduce the drag in water channel and pipe flows, but there is no study of a swirling flow combined with a vibrating wall in conical pipes, though there are many applications of such combination in engineering processes. A two-dimensional particle image velocimetry (PIV) is used to measure the swirling flow field in a water conical pipe subjected to a periodic vibrating wall for a Reynolds number 3800. The flow velocity statistics are studied under different vibration frequencies corresponding to Strouhal numbers from 60 to 242. The instantaneous axial and vertical velocity in one vibrating period, the mean velocities, and Reynolds stresses were obtained. The results show the existence of an intermediary recirculation cell in the middle of the pipe. They also show that the vibration improves the symmetry for the swirling flow while decreasing dramatically the velocity fluctuation.

Experimental investigation of the influence of the hydraulic performance of an axial blood pump on intraventricular blood flow

2021 ◽  
pp. 039139882110130
Author(s):  
Guang-Mao Liu ◽  
Fu-Qing Jiang ◽  
Xiao-Han Yang ◽  
Run-Jie Wei ◽  
Sheng-Shou Hu
Keyword(s):  
Blood Flow ◽  
Particle Image ◽  
Swirling Flow ◽  
Blood Stasis ◽  
Systemic Circulation ◽  
Operating Conditions ◽  
Blood Pump ◽  
Image Velocimetry ◽  
Ct Data

Blood flow inside the left ventricle (LV) is a concern for blood pump use and contributes to ventricle suction and thromboembolic events. However, few studies have examined blood flow inside the LV after a blood pump was implanted. In this study, in vitro experiments were conducted to emulate the intraventricular blood flow, such as blood flow velocity, the distribution of streamlines, vorticity and the standard deviation of velocity inside the LV during axial blood pump support. A silicone LV reconstructed from computerized tomography (CT) data of a heart failure patient was incorporated into a mock circulatory loop (MCL) to simulate human systemic circulation. Then, the blood flow inside the ventricle was examined by particle image velocimetry (PIV) equipment. The results showed that the operating conditions of the axial blood pump influenced flow patterns within the LV and areas of potential blood stasis, and the intraventricular swirling flow was altered with blood pump support. The presence of vorticity in the LV from the thoracic aorta to the heart apex can provide thorough washing of the LV cavity. The gradually extending stasis region in the central LV with increasing blood pump support is necessary to reduce the thrombosis potential in the LV.

scholarly journals Particle image velocimetry measurements of induced separation at the leading edge of a plate

2016 ◽  
Vol 804 ◽  
pp. 278-297 ◽  
Author(s):  
J. P. J. Stevenson ◽  
K. P. Nolan ◽  
E. J. Walsh
Keyword(s):  
Particle Image Velocimetry ◽  
Shear Layer ◽  
Particle Image ◽  
Reverse Flow ◽  
Leading Edge ◽  
Quadrant Analysis ◽  
Bypass Transition ◽  
Reynolds Stresses ◽  
Free Stream Turbulence ◽  
Image Velocimetry

The free shear layer that separates from the leading edge of a round-nosed plate has been studied under conditions of low (background) and elevated (grid-generated) free stream turbulence (FST) using high-fidelity particle image velocimetry. Transition occurs after separation in each case, followed by reattachment to the flat surface of the plate downstream. A bubble of reverse flow is thereby formed. First, we find that, under elevated (7 %) FST, the time-mean bubble is almost threefold shorter due to an accelerated transition of the shear layer. Quadrant analysis of the Reynolds stresses reveals the presence of slender, highly coherent fluctuations amid the laminar part of the shear layer that are reminiscent of the boundary-layer streaks seen in bypass transition. Instability and the roll-up of vortices then follow near the crest of the shear layer. These vortices are also present under low FST and in both cases are found to make significant contributions to the production of Reynolds stress over the rear of the bubble. But their role in reattachment, whilst important, is not yet fully clear. Instantaneous flow fields from the low-FST case reveal that the bubble of reverse flow often breaks up into two or more parts, thereby complicating the overall reattachment process. We therefore suggest that the downstream end of the ‘separation isoline’ (the locus of zero absolute streamwise velocity that extends unbroken from the leading edge) be used to define the instantaneous reattachment point. A histogram of this point is found to be bimodal: the upstream peak coincides with the location of roll-up, whereas the downstream mode may suggest a ‘flapping’ motion.

Effects of the Interaction Point of Multi-Passage Swirlers on the Swirling Flow Field

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
Foad Vashahi ◽  
Jeekeun Lee
Keyword(s):  
Geometrical Parameter ◽  
Swirling Flow ◽  
Energy Levels ◽  
Fuel Mixture ◽  
Mean Flow ◽  
Interaction Point ◽  
Stagnation Points ◽  
Image Velocimetry ◽  
The Mean ◽  
Proper Orthogonal

An experimental study is conducted to understand the mean and instantaneous behavior of the swirling flow issued from a triple swirler influenced by a single critical geometrical parameter, termed as the passage length. The investigated geometrical parameter defines the interaction point of the inner axial swirlers with the outer radial swirler, which consequently defines the primary air–fuel mixture characteristics and the resultant combustion state. Experiments were performed under cold flow conditions, and planar particle image velocimetry was employed to measure the velocity field. The mean flow pattern exhibited significant differences in terms of the swirl-jet width and angle and altered the number of stagnation points on the swirler axis. When the passage length was reduced to half, two stagnation points appeared on the swirler axis due to an initially developed smaller recirculation zone at the swirler mouth. Also, the turbulent activity at the vicinity of the swirler increased with as the passage length reduced. Investigations on the relocation of the second stagnation point on the axis through an arbitrary window revealed identical standard deviation in x and y directions. The energetic coherent structures extracted from the proper orthogonal decomposition also identified major differences in terms of the spatial distribution of the modes and their corresponding energy levels. The experimental results indicated that if the passage length is altered, the number of stagnation points on the swirler axis increases, and a breakdown of both the bubble and cone vortex may appear at the same time as different energy levels.

Experimental and computational investigations of flow dynamics in LPP combustor

2017 ◽  
Vol 121 (1240) ◽  
pp. 790-802 ◽  
Author(s):  
Y. W. YAN ◽  
Y. P. Liu ◽  
Y. C. Liu ◽  
J. H. Li
Keyword(s):  
Recirculation Zone ◽  
Swirling Flow ◽  
Mixing Layer ◽  
Experimental Tests ◽  
Flow Dynamics ◽  
Reynolds Stresses ◽  
Lean Combustion ◽  
Low Emission ◽  
Image Velocimetry ◽  
Combustion Technology

ABSTRACTA Lean Premixed Prevaporised (LPP) low-emission combustor with a staged lean combustion technology was developed. In order to study cold-flow dynamics in the LPP combustor, both experimental tests using the particle image velocimetry (PIV) to quantify the flow dynamics and numerical simulation using the commercial software (FLUENT) were conducted, respectively. Numerical results were in good agreement with the experimental data. It is shown from the observation of the results that: there is a Primary Recirculation Zone (PRZ), a Corner Recirculation Zone (CRZ) and a Lip Recirculation Zone (LRZ) in the LPP combustor, and the exchanges of mass, momentum and energy between pilot swirling flow and primary swirling flow are contributed by the velocity gradients, and the shear flow is transformed into a mixing layer exhibiting the higher Reynolds stresses, which suggests the mixing process is strictly affected by the Reynolds stresses.

Experimental study of the mean structure and quasi-conical scaling of a swept-compression-ramp interaction at Mach 2

2018 ◽  
Vol 841 ◽  
pp. 1-27 ◽  
Author(s):  
Leon Vanstone ◽  
Mustafa Nail Musta ◽  
Serdar Seckin ◽  
Noel Clemens
Keyword(s):  
Boundary Layer ◽  
Shock Wave ◽  
Particle Image Velocimetry ◽  
Flow Field ◽  
Scaling Laws ◽  
Particle Image ◽  
Separated Flow ◽  
Image Velocimetry ◽  
The Mean ◽  
Wave Boundary

This study investigates the mean flow structure of two shock-wave boundary-layer interactions generated by moderately swept compression ramps in a Mach 2 flow. The ramps have a compression angle of either $19^{\circ }$ or $22.5^{\circ }$ and a sweep angle of $30^{\circ }$. The primary diagnostic methods used for this study are surface-streakline flow visualization and particle image velocimetry. The shock-wave boundary-layer interactions are shown to be quasi-conical, with the intermittent region, separation line and reattachment line all scaling in a self-similar manner outside of the inception region. This is one of the first studies to investigate the flow field of a swept ramp using particle image velocimetry, allowing more sensitive measurements of the velocity flow field than previously possible. It is observed that the streamwise velocity component outside of the separated flow reaches the quasi-conical state at the same time as the bulk surface flow features. However, the streamwise and cross-stream components within the separated flow take longer to recover to the quasi-conical state, which indicates that the inception region for these low-magnitude velocity components is actually larger than was previously assumed. Specific scaling laws reported previously in the literature are also investigated and the results of this study are shown to scale similarly to these related interactions. Certain limiting cases of the scaling laws are explored that have potential implications for the interpretation of cylindrical and quasi-conical scaling.

Particle Image Velocimetry Experiment and Computational Fluid Dynamics Simulation of Flow Around Rigid Cylinder

2018 ◽  
Vol 140 (5) ◽  
Author(s):  
Guangyao Wang ◽  
Ye Tian ◽  
Spyros A. Kinnas
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Particle Image Velocimetry ◽  
Vector Fields ◽  
Particle Image ◽  
Cfd Simulation ◽  
Dynamics Simulation ◽  
Reynolds Stresses ◽  
Rigid Cylinder ◽  
Image Velocimetry

This work focuses on the study of the flow around a rigid cylinder with both particle image velocimetry (PIV) experiment and computational fluid dynamics (CFD) simulation. PIV measurements of the flow field downstream of the cylinder are first presented. The boundary conditions for CFD simulations are measured in the PIV experiment. Then the PIV flow is compared with both Reynolds-averaged Navier–Stokes (RANS) two-dimensional (2D) and large eddy simulation (LES) three-dimensional (3D) simulations performed with ANSYS fluent. The velocity vector fields and time histories of velocity are analyzed. In addition, the time-averaged velocity profiles and Reynolds stresses are analyzed. It is found that, in general, LES (3D) gives a better prediction of flow characteristics than RANS (2D).

Study on the Characteristics of Turbulent Flow of Viscoelastic Fluid Through a Planar Sudden Expansion by PIV System

2015 ◽  
Author(s):  
Lu Wang ◽  
Jia-Qi Bao ◽  
Tong-Zhou Wei ◽  
Wei-Hua Cai ◽  
Feng-Chen Li
Keyword(s):  
Turbulent Flow ◽  
Particle Image ◽  
Reynolds Shear Stress ◽  
Streamwise Velocity ◽  
Velocity Fields ◽  
Sudden Expansion ◽  
Image Velocimetry ◽  
The Mean ◽  
Cetyltrimethyl Ammonium ◽  
Component Particle

The influences of drag-reducing surfactant additives on the characteristics of a turbulent flow over a planar sudden expansion with expansion ration R = D/d = 3 and aspect ratio A = w/h = 30 were experimentally investigated by a 2D-2C (two dimensional-two component) particle image velocimetry (PIV) system. The 2D-2C velocity fields in the streamwise-wall-normal planes (x-y planes) at three spanwise locations are measured for the flows of water and 50ppm aqueous solution of CTAC/NaSal (CTAC: cetyltrimethyl ammonium chloride; NaSal: sodium salicylate) under the Reynolds number of 1.85 × 104. From the streamline in the x-y plane, it is observed that the reattachment lengths of the vortices in CTAC/NaSal solution are longer. Then the mean streamwise velocity fields and the apparent flow rate at three spanwise locations show that the flow fields in the other two x-y planes are practically symmetrical about the x-y centreplane in CTAC/NaSal solution, as compared with that in water flow. Finally, it is perceived that the Reynolds shear stress for three spanwise locations in CTAC/NaSal solution are obviously decreased.

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.

Experimental Investigation of Flow Blurring Atomizer at Near Field Using Particle Image Velocimetry

2019 ◽  
Author(s):  
Raju Murugan ◽  
Dhanalakshmi Sellan ◽  
Pankaj S. Kolhe
Keyword(s):  
Particle Image Velocimetry ◽  
Flow Rate ◽  
Liquid Flow ◽  
Particle Image ◽  
Liquid Flow Rate ◽  
Diagnostic Technique ◽  
Reynolds Stresses ◽  
Full Field ◽  
Image Velocimetry ◽  
Spray Droplets

Abstract Two-fluid flow blurring atomization is characterized by the backflow recirculation of the air phase in the liquid pipe by bifurcation of the liquid and airflow. Most of the primary spray process is completed in the injector due to the penetration of air into the liquid tube. Thus, the majority of the liquid ligaments are converted into a fine spray at the outlet of the nozzle. Experiments were performed with two different air to liquid ratios (0.6 and 1) by mass, where water is considered as the liquid and airflow was kept constant (0.2 g/s). To change the ALR, the liquid flow rate was changed. Particle image velocimetry (PIV) diagnostic technique provides the full-field velocity of the spray droplets (discrete phase). It may be noted that sprays are self-seeded and PIV measurements reflect the droplet velocities instead of air velocity. To understand the effect of the spatial resolution of PIV on spray droplet velocity; experiments were conducted at three different spatial resolutions (11.8, 16.4 and 23.22 μm/pixel) for each ALR. As the ALR is increased, the mass of the liquid in the spray decreases, resulting in finer atomization and velocity of the spray droplets. This means that finer droplets are generated for the same mass of air at a lower liquid flow rate as compared to higher liquid flow rate. Note that Reynolds stresses provide an indication of the turbulent breakup of the droplet and larger magnitudes observed for higher ALR indicate finer atomization.

Particle Image Velocimetry Measurements of the Mean Flow Characteristics in a Bubble Plume

2007 ◽  
Vol 133 (6) ◽  
pp. 665-676 ◽  
Author(s):  
Dong-Guan Seol ◽  
Tirtharaj Bhaumik ◽  
Christian Bergmann ◽  
Scott A. Socolofsky
Keyword(s):  
Particle Image Velocimetry ◽  
Particle Image ◽  
Flow Characteristics ◽  
Bubble Plume ◽  
Mean Flow ◽  
Image Velocimetry ◽  
The Mean
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