Study of the Turbulent Flow Structure around a Standard Rushton Impeller

2014 ◽  
Vol 35 (1) ◽  
pp. 137-147 ◽  
Author(s):  
Bohuš Kysela ◽  
Jiří Konfršt ◽  
Ivan Fořt ◽  
Michal Kotek ◽  
Zdeněk Chára
Keyword(s):  
Particle Image ◽  
Laser Doppler Anemometry ◽  
Turbulent Jet ◽  
Piv Measurements ◽  
Rushton Turbine ◽  
Image Velocimetry ◽  
Validity Range ◽  
Turbulent Flow Structure ◽  
The Mean ◽  
Rushton Impeller

Abstract The velocity field around the standard Rushton turbine was investigated by the Laser Doppler Anemometry (LDA) and Particle Image Velocimetry (PIV) measurements. The mean ensembleaveraged velocity profiles and root mean square values of fluctuations were evaluated at two different regions. The first one was in the discharge stream in the radial direction from the impeller where the radial flow is dominant and it is commonly modelled as a swirling turbulent jet. The validity range of the turbulent jet model was studied. The second evaluated region is under the impeller where flow seems to be at first sight rather rigorous but obtained results show nonnegligible values of fluctuation velocity.

scholarly journals Characterisation of vortex shedding on a hydrofoil using PIV measurements

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Hervé Bonnard ◽  
Ludovic Chatellier ◽  
Laurent David
Keyword(s):  
Vortex Shedding ◽  
Particle Image ◽  
Statistical Data ◽  
Two Dimensional ◽  
Mean Velocity ◽  
Piv Measurements ◽  
Image Velocimetry ◽  
The Mean ◽  
Flow Configurations

An experimental study of vortex shedding on a hydrofoil Eppler 817 was conducted using two-dimensional two components Particle Image Velocimetry. This foil section’s characteristics are adapted for naval applications but sparsely documented. The characterization of the flow modes was realized based on statistical data such as the mean velocity field and the standard deviation of the vertical velocities. The data were acquired at very low Reynolds number which are not often covered for such hydrofoil and at four angles of attack ranging from 2◦ to 30◦. A map of different characteristic flow modes was made for this space of parameters and was used to identify flow configurations exhibiting particular dynamics.

scholarly journals CFD Simulation of the Discharge Flow from Standard Rushton Impeller

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Bohuš Kysela ◽  
Jiří Konfršt ◽  
Ivan Fořt ◽  
Zdeněk Chára
Keyword(s):  
Large Eddy Simulation ◽  
Cfd Simulation ◽  
Laser Doppler Anemometry ◽  
Rushton Turbine ◽  
Sliding Mesh ◽  
Eddy Simulation ◽  
Large Eddy ◽  
The Mean ◽  
Rushton Impeller ◽  
Good Agreement

The radial discharge jet from the standard Rushton turbine was investigated by the CFD calculations and compared with results from the Laser Doppler Anemometry (LDA) measurements. The Large Eddy Simulation (LES) approach was employed with Sliding Mesh (SM) model of the impeller motion. The obtained velocity profiles of the mean ensemble-averaged velocity and r.m.s. values of the fluctuating velocity were compared in several distances from the impeller blades. The calculated values of mean ensemble-averaged velocities are rather in good agreement with the measured ones as well as the derived power number from calculations. However, the values of fluctuating velocities are obviously lower from LES calculations than from LDA measurements.

PIV Measurements Within the Waves of Wavy and Wavy-Annular Horizontal Two-Phase Flow

2005 ◽  
Author(s):  
R. E. Foster ◽  
T. A. Shedd
Keyword(s):  
Particle Image ◽  
Image Processing Algorithm ◽  
Two Phase ◽  
Piv Measurements ◽  
Post Process ◽  
Image Velocimetry ◽  
Processed Form ◽  
Image Pairs ◽  
Particle Images ◽  
The Waves

A novel technique of microscopic Particle Image Velocimetry (PIV) is presented for two-phase annular, wavy-annular and stratified flow. Seeding of opaque particles in a water/dye flow allows the acquisition of instantaneous film velocity data in the film cross-section at the center of the tube in the form of digital image pairs. An image processing algorithm is also described that allows numerical velocities to be distilled from particle images by commercial PIV software. The approach yields promising results for stratified and wavy-annular flows, however highly bubbly flows remain difficult to image and post-process. Initial data images are presented in raw and processed form.

Time-Resolved Particle Image Velocimetry (PIV) Measurements in a Radial Diffuser Pump

2009 ◽  
Author(s):  
Jianjun Feng ◽  
Friedrich-Karl Benra ◽  
Hans Josef Dohmen
Keyword(s):  
Particle Image Velocimetry ◽  
Particle Image ◽  
Time Resolved ◽  
Piv Measurements ◽  
Part Load ◽  
Channel Characteristic ◽  
Image Velocimetry ◽  
Pump Stage ◽  
Low Specific Speed ◽  
Load Conditions

The truly time-variant unsteady flow in a low specific speed radial diffuser pump stage has been investigated by time-resolved Particle Image Velocimetry (PIV) measurements. The measurements are conducted at the midspan of the blades for the design condition and also for some severe part-load conditions. The instantaneous flow fields among different impeller channels are analyzed and compared in detail, and more attention has been paid to flow separations at part-load conditions. The analysis of the measured results shows that the flow separations at two adjacent impeller channels are quite different at some part-load conditions. The separations generally exhibit a two-channel characteristic.

Experimental and Numerical Flow Visualization in Patient Specific Pre Operative Human Airway Geometry

2011 ◽  
Author(s):  
Mathias Vermeulen ◽  
Cedric Van Holsbeke ◽  
Tom Claessens ◽  
Jan De Backer ◽  
Peter Van Ransbeeck ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Particle Image ◽  
Patient Specific ◽  
Lung Volume Reduction ◽  
Cfd Simulations ◽  
Piv Measurements ◽  
Image Velocimetry ◽  
Specific Geometry ◽  
Computational Fluid Dynamics Cfd ◽  
Human Airways

An experimental and numerical platform was developed to investigate the fluidodynamics in human airways. A pre operative patient specific geometry was used to create an identical experimental and numerical model. The experimental results obtained from Particle Image Velocimetry (PIV) measurements were compared to Computational Fluid Dynamics (CFD) simulations under stationary and pulsatile flow regimes. Together these results constitute the first step in predicting the clinical outcome of patients after lung surgeries such as Lung Volume Reduction.

Vortices' Characteristics to Explain the Flange Height Effects on the Aerodynamic Performances of a Diffuser Augmented Wind Turbine

2016 ◽  
Vol 138 (6) ◽  
Author(s):  
Rym Chaker ◽  
Mouldi Kardous ◽  
Mahmoud Chouchen ◽  
Fethi Aloui ◽  
Sassi Ben Nasrallah
Keyword(s):  
Wind Velocity ◽  
Particle Image ◽  
Flow Direction ◽  
Pressure Coefficient ◽  
Inlet Section ◽  
Wind Tunnel Experiments ◽  
Piv Measurements ◽  
Velocity Increase ◽  
Image Velocimetry ◽  
Aerodynamic Performances

Flange height is between the geometric features that contribute efficiently to improve the diffuser aerodynamic performances. Results obtained from wind tunnel experiments, particle image velocimetry (PIV) measurements, and numerical simulations reveal that at the diffuser inlet section, the wind velocity increases as the flange height increases. Nevertheless, there is an optimal ratio (flange height/inlet section diameter, Hopt/Da ≈ 0.15) beyond it, the flange height effect on the velocity increase diminishes. This behavior can be explained by both the positions of the two contra-rotating vortices generated downstream of the diffuser and the pressure coefficient at their centers. Indeed, it was found that, as the flange height increases, the two vortices move away from each other in the flow direction and since the flange height exceeds (Hopt/Da), they became too distant from each other and from the flange. While the pressure coefficients at the vortices' centers increase with (H/Da), attain a maximum when (Hopt/Da) is reached, and then decrease. This suggests that the wind velocity increase depends on the pressure coefficient at the vortices' centers. Therefore, it depends on the vortices' locations which are in turn controlled by the flange height. In practice, this means that the diffuser could be more efficient if equipped with a control system able to hold the vortices too near from the flange.

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.

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.

Turbulence Measurements Within a Cyclic Flow and Analysis in the Momentum Equation

2002 ◽  
Author(s):  
Eugene Suk ◽  
Daniel K. Fetter ◽  
Pierre E. Sullivan
Keyword(s):  
Particle Image ◽  
Equations Of Motion ◽  
Ccd Camera ◽  
Momentum Equation ◽  
Piv Measurements ◽  
Cyclic Flow ◽  
Image Velocimetry ◽  
Crank Angle Degree ◽  
Crank Angle ◽  
Averaging Techniques

Particle Image Velocimetry (PIV) measurements were performed within an optical water analog engine. A unique triggering and data collection system was developed to allow a CCD camera to acquire two consecutive image frames at predetermined crank angles. The water analog engine operated at 15 RPM and had a square cross-section with two circular valved inlets. Measurements were made throughout an entire cycle to determine mean and turbulence statistics and results at 60 crank angle degree are discussed in this paper. Different averaging techniques were used and results between the techniques were compared to provide a number of statistical quantities having large discrepancies in scales and distributions. A study of the equations of motion showed that different averaging techniques results in differing physical interpretations of the flow.

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