scholarly journals Complex Flow Generation and Development in a Full-Scale Turbofan Inlet

2018 ◽  
Vol 140 (8) ◽  
Author(s):  
Tamara Guimarães ◽  
K. Todd Lowe ◽  
Walter F. O'Brien
Keyword(s):  
Secondary Flow ◽  
Full Scale ◽  
Stereoscopic Particle Image Velocimetry ◽  
Complex Flow ◽  
Mean Velocity ◽  
Ground Testing ◽  
Turbofan Engines ◽  
Flow Generation ◽  
Image Velocimetry ◽  
The Mean

The future of aviation relies on the integration of airframe and propulsion systems to improve aerodynamic performance and efficiency of aircraft, bringing design challenges, such as the ingestion of nonuniform flows by turbofan engines. In this work, we describe the behavior of a complex distorted inflow in a full-scale engine rig. The distortion, as in engines on a hybrid wing body (HWB) type of aircraft, is generated by a 21-in diameter StreamVane, an array of vanes that produce prescribed secondary flow distributions. Data are acquired using stereoscopic particle image velocimetry (PIV) at three measurement planes along the inlet of the research engine (Reynolds number of 2.4 × 106). A vortex dynamics-based model, named StreamFlow, is used to predict the mean secondary flow development based on the experimental data. The mean velocity profiles show that, as flow develops axially, the vortex present in the profile migrates clockwise, opposite to the rotation of the fan, and toward the spinner of the engine. The turbulent stresses indicate that the center of the vortex meanders around a preferred location, which tightens as flow gets closer to the fan, yielding a smaller radius mean vortex near the fan. Signature features of the distortion device are observed in the velocity gradients, showing the wakes generated by the distortion screen vanes in the flow. The results obtained shed light onto the aerodynamics of swirling flows representative of distorted turbofan inlets, while further advancing the understanding of the complex vane technology presented herein for advanced ground testing.

Complex Flow Generation and Development in a Full-Scale Turbofan Inlet

2017 ◽  
Author(s):  
Tamara Guimarães ◽  
K. Todd Lowe ◽  
Walter F. O’Brien
Keyword(s):  
Fuel Efficiency ◽  
Full Scale ◽  
Complex Flow ◽  
Body Type ◽  
Mean Velocity ◽  
Ground Testing ◽  
Turbofan Engines ◽  
Velocity Gradients ◽  
Flow Generation ◽  
Image Velocimetry

The future of aviation relies on the integration of airframe and propulsion systems to increase fuel efficiency and improve the aerodynamic performance of aircraft. This need brings design challenges, such as the ingestion of non-uniform flows by turbofan engines. In this work, we seek to understand the behavior of a complex distorted inflow in a full-scale engine rig. A 21-inch diameter distortion screen previously designed is used to mimic the behavior of an adverse inlet flow encountered by a hybrid wing body type of aircraft. Three measurement planes along the inlet of the research engine are selected for the acquisition of data using particle image velocimetry at a duct diameter Reynolds number of 2.6 million. The resulting mean velocity profiles, velocity gradients and turbulent stresses are analyzed in order to describe the evolution of the flow along the inlet of the turbofan engine and as it approaches the fan face. As flow develops downstream, the vortex present in the profile migrates clockwise, opposite to the rotation of the fan, and towards the spinner of the engine. The turbulent stresses indicate that the center of the vortex meanders around a preferred location, and that location tightens as flow gets closer to the fan, yielding a smaller radius mean vortex near the fan. An analysis of velocity gradients shows the influence of the distortion screen in the flow, mainly in the streamwise direction, where signature features of the distortion device are observed, as an effect from the wakes of the vanes. The results obtained shed light onto the aerodynamics of swirling flows representative of distorted turbofan inlets, while further advancing the understanding of the complex vane technology presented herein for advanced ground testing of swirling inflows.

Stereo-PIV Measurements of Turbulent Swirling Flow Inside a Pipe

2020 ◽  
Author(s):  
Ayesha Almheiri ◽  
Lyes Khezzar ◽  
Mohamed Alshehhi ◽  
Saqib Salam ◽  
Afshin Goharzadeh
Keyword(s):  
Swirling Flow ◽  
Reverse Flow ◽  
Tangential Velocity ◽  
Circular Disk ◽  
Pipe Diameter ◽  
Working Fluid ◽  
Complex Flow ◽  
Mean Velocity ◽  
Radial Profiles ◽  
The Mean

Abstract Stereo-PIV is used to map turbulent strongly swirling flow inside a pipe connected to a closed recirculating system with a transparent test section of 0.6 m in length and a pipe diameter of 0.041 m. The Perspex pipe was immersed inside a water trough to reduce the effects of refraction. The working fluid was water and the Reynolds number based on the bulk average velocity inside the pipe and pipe diameter was equal to 14,450. The turbulent flow proceeds in the downstream direction and interacts with a circular disk. The measurements include instantaneous velocity vector fields and radial profiles of the mean axial, radial and tangential components of the velocity in the regions between the swirler exit and circular disk and around this later. The results for mean axial velocity show a symmetric behavior with a minimum reverse flow velocity along the centerline. As the flow developed along the pipe’s length, the intensity of the reversed flow was reduced and the intensity of the swirl decays. The mean tangential velocity exhibits a Rankine-vortex distribution and reached its maximum around half of the pipe’s radius. As the flow approaches the disk, the flow reaches stagnation and a complex flow pattern of vortices is formed. The PIV results are contrasted with LDV measurements of mean axial and tangential velocity. Good agreement is shown over the mean velocity profiles.

Ultrasound Vector Flow Imaging – could be a new tool in evaluation of arteriovenous fistulas for hemodialysis?

2017 ◽  
Vol 18 (4) ◽  
pp. 284-289 ◽  
Author(s):  
Ilaria Fiorina ◽  
Maria Vittoria Raciti ◽  
Alfredo Goddi ◽  
Vito Cantisani ◽  
Chandra Bortolotto ◽  
...  
Keyword(s):  
Venous Aneurysm ◽  
Flow Imaging ◽  
Angular Deviation ◽  
Complex Flow ◽  
Mean Velocity ◽  
Ultrasound Technique ◽  
Arteriovenous Fistulas ◽  
The Mean ◽  
Vessel Walls ◽  
Ultrasound Scanner

Introduction We report the use of a new ultrasound technique to evaluate the axial and lateral components of a complex flow in the arteriovenous fistula (AVF). Vector Flow Imaging (VFI) allows to identify different components of the flow in every direction, even orthogonal to the flow streamline, represented by many single vectors. VFI could help to identify flow alterations in AVF, probably responsible for its malfunction. Methods From February to June 2016, 14 consecutive patients with upper-limb AVF were examined with a Resona 7 (Mindray, Shenzhen, China) ultrasound scanner equipped with VFI. An analysis of mean velocity, angular direction and mean number of vectors impacting the vessel wall was carried out. We also identified main flow patterns present in the arterial side, into the venous aneurysm and in correspondence of significant stenosis. Results A disturbed flow with the presence of vectors directed against the vessel walls was found in 9/14 patients (64.28%): in correspondence of the iuxta-anastomotic venous side (4/9; 44.4%), into the venous aneurysmal tracts (3/9; 33.3%) and in concomitance of stenosis (2/9; 22.2%). The mean velocity of the vectors was around 20-25 cm/s, except in presence of stenosis, where the velocities were much higher (45-50 cm/s). The vectors directed against the vessel walls presented high angle attack (from 45° to 90°, with a median angular deviation 65°). Conclusions VFI was confirmed to be an innovative and intuitive imaging technology to study the flow complexity in the arteriovenous fistulas.

A Batchelor Vortex Model for Mean Velocity of Turbulent Swirling Flow in a Macroscale Multi-Inlet Vortex Reactor

2015 ◽  
Vol 137 (4) ◽  
Author(s):  
Zhenping Liu ◽  
Rodney O. Fox ◽  
James C. Hill ◽  
Michael G. Olsen
Keyword(s):  
Reynolds Number ◽  
Simple Model ◽  
Velocity Field ◽  
Swirling Flow ◽  
Stereoscopic Particle Image Velocimetry ◽  
Mean Velocity ◽  
Vortex Model ◽  
Nonlinear Curve Fitting ◽  
Image Velocimetry ◽  
Vortex Reactor

The velocity field in a macroscale multi-inlet vortex reactor (MIVR) used in “flash nanoprecipitation (FNP)” process for producing functional nanoparticles was investigated using stereoscopic particle image velocimetry (SPIV). Based on the experimental data, a simple model was proposed to describe the average velocity field within the reactor. In the model, the axial and azimuthal velocities could be well described by the combination of two coflowing Batchelor vortices. In this model, six dimensionless coefficients are identified by nonlinear curve fitting, and their dependence on Reynolds number can be linearly described. This simple model is able to accurately predict the mean velocity field within the confined turbulent swirling flow based purely on Reynolds number.

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.

Separated and Reattached Flow Over Square, Rectangular and Semi-Circular Blocks

2007 ◽  
Author(s):  
M. Agelinchaab ◽  
M. F. Tachie
Keyword(s):  
Boundary Layer ◽  
Cross Sections ◽  
Recirculation Region ◽  
Reynolds Stresses ◽  
Mean Velocity ◽  
Block Height ◽  
Turbulent Statistics ◽  
Image Velocimetry ◽  
The Mean ◽  
Separated And Reattached Flow

A particle image velocimetry is used to study the characteristics of separated and reattached turbulent flow over two-dimensional transverse blocks of square, rectangular and semi-circular cross-sections fixed to the bottom wall of an open channel. The ratio of upstream boundary layer thickness to block height is considerably higher than in prior studies. The results show that the mean and turbulent statistics in the recirculation region and downstream of reattachment are significantly different from the upstream boundary layer. The variation of the Reynolds stresses along the separating streamlines is discussed within the context of vortex stretching, longitudinal strain rate and wall damping. It appears wall damping is a more dominant mechanism in the vicinity of reattachment. The levels of turbulence diffusion and production by the normal stresses are significantly higher than in classical turbulent boundary layers. The bulk of turbulence production occurs in mid-layer and transported into the inner and outer layers. The results also reveal that the curvature of separating streamline, separating bubble beneath it as well as the mean velocity and turbulent quantities depend strongly on block geometry.

Application of Particle Image Velocimetry Technique to Study the Turbulent Structure of Cavitating Flows Around a Cascade of NACA0015 Series Hydrofoils

2011 ◽  
Vol 6 (4) ◽  
pp. 70-81
Author(s):  
Vladimir Dulin ◽  
Aleksandra Kravtsova ◽  
Dmitriy Markovich ◽  
Konstantin Pervunin ◽  
Mikhail Timoshevskiy
Keyword(s):  
Liquid Velocity ◽  
Turbulent Structure ◽  
Cavitating Flows ◽  
Particle Image Velocimetry Technique ◽  
Mean Velocity ◽  
Piv Technique ◽  
Image Velocimetry ◽  
Quantitative Characteristics ◽  
Mean Pressure ◽  
The Mean

The results of the application of PIV technique to study the turbulent structure of cavitating flows around a cascade of NACA0015 series hydrofoils are presented. Based on instantaneous velocity fields measured, spatial distributions of the mean velocity were calculated as well as the second-order statistical moments of liquid velocity fluctuations. Quantitative characteristics of the flows around the cascade and a solitary profile were demonstrated to be considerably different due mainly to discrepancies in distributions of the mean pressure and mutual impact of cavitation clouds

Particle Image Velocimetry Measurements in a Two-Pass 90 Degree Ribbed-Wall Parallelogram Channel

2015 ◽  
Vol 137 (4) ◽  
Author(s):  
Tong-Miin Liou ◽  
Shyy-Woei Chang ◽  
Shu-Po Chan ◽  
Yu-Shuai Liu
Keyword(s):  
Particle Image Velocimetry ◽  
Secondary Flow ◽  
Particle Image ◽  
Separation Bubble ◽  
Channel Height ◽  
Mean Velocity ◽  
Cross Sectional ◽  
Local Flow ◽  
Image Velocimetry ◽  
Sharp Turn

A parallelogram channel has drawn very little or no attention in the open literature although it appears as a cross-sectional configuration of some gas turbine rotor blades. Particle image velocimetry (PIV) is presented of local flow structure in a two-pass 90 deg ribbed-wall parallelogram channel with a 180 deg sharp turn. The channel has a cross-sectional equal length, 45.5 mm, of adjacent sides and two pairs of opposite angles are 45 deg and 135 deg. The rib height to channel height ratio is 0.1. All the measurements were performed at a fixed Reynolds number, characterized by channel hydraulic diameter of 32.17 mm and cross-sectional bulk mean velocity, of 10,000 and a null rotating number. Results are discussed in terms of the distributions of streamwise and secondary-flow mean velocity vector, turbulent intensity, Reynolds stress, and turbulent kinetic energy of the cooling air. It is found that the flow is not periodically fully developed in pitchwise direction through the inline 90 deg ribbed straight inlet and outlet leg. Pitchwise variation of reattachment length is revealed, and comparison with reported values in square channels is made. Whether the 180 deg sharp turn induced separation bubble exists in the ribbed parallelogram channel is also documented. Moreover, the measured secondary flow results inside the turn are successively used to explain previous heat transfer trends.

Near-surface particle image velocimetry measurements in a transitionally rough-wall atmospheric boundary layer

2007 ◽  
Vol 580 ◽  
pp. 319-338 ◽  
Author(s):  
SCOTT C. MORRIS ◽  
SCOTT R. STOLPA ◽  
PAUL E. SLABOCH ◽  
JOSEPH C. KLEWICKI
Keyword(s):  
Reynolds Number ◽  
Particle Image Velocimetry ◽  
Environmental Science ◽  
Particle Image ◽  
Shear Velocity ◽  
Mean Flow ◽  
Mean Velocity ◽  
Near Surface ◽  
Image Velocimetry ◽  
The Mean

The Reynolds number dependence of the structure and statistics of wall-layer turbulence remains an open topic of research. This issue is considered in the present work using two-component planar particle image velocimetry (PIV) measurements acquired at the Surface Layer Turbulence and Environmental Science Test (SLTEST) facility in western Utah. The Reynolds number (δuτ/ν) was of the order 106. The surface was flat with an equivalent sand grain roughness k+ = 18. The domain of the measurements was 500 < yuτ/ν < 3000 in viscous units, 0.00081 < y/δ < 0.005 in outer units, with a streamwise extent of 6000ν/uτ. The mean velocity was fitted by a logarithmic equation with a von Kármán constant of 0.41. The profile of u′v′ indicated that the entire measurement domain was within a region of essentially constant stress, from which the wall shear velocity was estimated. The stochastic measurements discussed include mean and RMS profiles as well as two-point velocity correlations. Examination of the instantaneous vector maps indicated that approximately 60% of the realizations could be characterized as having a nearly uniform velocity. The remaining 40% of the images indicated two regions of nearly uniform momentum separated by a thin region of high shear. This shear layer was typically found to be inclined to the mean flow, with an average positive angle of 14.9°.

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