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.

PIV Measurements in a Two-Pass 90-Deg Ribbed-Wall Parallelogram Channel

2014 ◽  
Author(s):  
Tong-Miin Liou ◽  
Shyy Woei Chang ◽  
Shu-Po Chan ◽  
Yu-Shuai Liu
Keyword(s):  
Secondary Flow ◽  
Separation Bubble ◽  
Turbine Rotor ◽  
Rotor Blades ◽  
Channel Height ◽  
Mean Velocity ◽  
Cross Sectional ◽  
Local Flow ◽  
Sharp Turn ◽  
Cooling Air

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 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 10000 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.

Effect of Rib Angle Orientation on Flow Field in a Two-Pass Parallelogram Channel With 180-Deg Sharp Turn

2015 ◽  
Author(s):  
Tong-Miin Liou ◽  
Shyy-Woei Chang ◽  
Shu-Po Chan ◽  
Yu-Shuai Liu
Keyword(s):  
Secondary Flow ◽  
Flow Characteristics ◽  
Hydraulic Diameter ◽  
Mean Velocity ◽  
Cross Sectional ◽  
Longitudinal Vortices ◽  
Image Velocimetry ◽  
Sharp Turn ◽  
Flow Motion ◽  
Normal Mean

Detailed flow patterns and turbulence parameters, including secondary-flow mean velocity vector, turbulent intensity, Reynolds stress and turbulent kinetic energy, are compared between three different rib orientations (45-deg, −45-deg, and 90-deg) in a two-pass ribbed-wall parallelogram channel with a 180-deg sharp turn. Velocity measurements were performed with Particle Image Velocimetry (PIV). 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-hydraulic diameter ratio and pitch-to-height ratio were 0.1 and 10, respectively. All the measurements were performed at a fixed Reynolds number, characterized by channel hydraulic diameter of 32.17 mm, cross-sectional bulk mean velocity, and fluid property of air at room temperature, of 10,000 and a null rotating number. A correlation between pitchwise variations of the reattachment lengths and rib-edge normal mean velocities is found. In addition, a comparison of the spanwise reattachment loci in the present parallelogram channel with those reported previously in the square channels is made. Overall, the 45-deg ribs and −45-deg or 90-deg ribs augment the secondary flow motion most in the first and second pass, respectively. Among the rib orientations investigated, the 45-deg and −45-deg ribs induce a pair of counter-rotating longitudinal vortices that strengthens the inlet-generated secondary flow in the first pass and the 180-deg sharp turn generated secondary flow in the second pass, respectively. One interesting finding is the noticeable difference in the flow characteristics near the top and bottom walls of the parallelogram channel for all three rib angles examined. On the contrary, previous studies with the square channels revealed almost the same heat transfer distributions on the ±45-deg ribbed top and bottom walls.

Characteristics of a separated flow past a semicircular leading-edge airfoil model under different imposed pressure gradient

2021 ◽  
pp. 095441002110212
Author(s):  
K Anand ◽  
KT Ganesh
Keyword(s):  
Boundary Layer ◽  
Particle Image Velocimetry ◽  
Pressure Gradient ◽  
Particle Image ◽  
Separation Bubble ◽  
Separated Flow ◽  
Leading Edge ◽  
Field Measurements ◽  
Bench Mark ◽  
Image Velocimetry

The effect of pressure gradient on a separated boundary layer past the leading edge of an airfoil model is studied experimentally using electronically scanned pressure (ESP) and particle image velocimetry (PIV) for a Reynolds number ( Re) of 25,000, based on leading-edge diameter ( D). The features of the boundary layer in the region of separation and its development past the reattachment location are examined for three cases of β (−30°, 0°, and +30°). The bubble parameters such as the onset of separation and transition and the reattachment location are identified from the averaged data obtained from pressure and velocity measurements. Surface pressure measurements obtained from ESP show a surge in wall static pressure for β = −30° (flap deflected up), while it goes down for β = +30° (flap deflected down) compared to the fundamental case, β = 0°. Particle image velocimetry results show that the roll up of the shear layer past the onset of separation is early for β = +30°, owing to higher amplification of background disturbances compared to β = 0° and −30°. Downstream to transition location, the instantaneous field measurements reveal a stretched, disoriented, and at instances bigger vortices for β = +30°, whereas a regular, periodically shed vortices, keeping their identity past the reattachment location, is observed for β = 0° and −30°. Above all, this study presents a new insight on the features of a separation bubble receiving a disturbance from the downstream end of the model, and these results may serve as a bench mark for future studies over an airfoil under similar environment.

Rotating Effect on Fluid Flow in Two Smooth Ducts Connected by a 180-Degree Bend

2003 ◽  
Vol 125 (1) ◽  
pp. 138-148 ◽  
Author(s):  
Tong-Miin Liou ◽  
Chung-Chu Chen ◽  
Meng-Yu Chen
Keyword(s):  
Heat Transfer ◽  
Kinetic Energy ◽  
Secondary Flow ◽  
Turbulent Kinetic Energy ◽  
Separation Bubble ◽  
Turbine Blades ◽  
Outer Part ◽  
Intensity Level ◽  
Mean Velocity ◽  
Sharp Turn

Laser Doppler velocimetry (LDV) measurements are presented of turbulent flow in a two-pass square-sectioned smooth duct simulating the coolant passages employed in gas turbine blades under rotating and nonrotating conditions. For all cases studied, the Reynolds number characterized by duct hydraulic diameter and bulk mean velocity was fixed at 1×104. The rotation number Ro was varied from 0 to 0.2. It is found that as Ro is increased, both the skewness (SK) of streamwise mean velocity and magnitude of secondary-flow velocity increase linearly, SK=2.3 Ro and U2+V2¯/Uh=2.3 Ro+0.4, and the magnitude of turbulence intensity level increases exponentially. As Ro is increased, the curvature induced symmetric Dean vortices in the turn for Ro=0 is gradually dominated by a single vortex most of which impinges directly on the outer part of leading wall. The high turbulent kinetic energy is closely related to the dominant vortex prevailing inside the 180-deg sharp turn. The size of separation bubble immediately after the turn is found to diminish to null as Ro is increased from 0 to 0.2. A simple correlation is developed between the bubble size and Ro. A critical range of Ro responsible for the switch of faster moving flow from near the outer wall to the inner wall is identified. For both rotating and nonrotating cases, the direction and strength of the secondary flow with respect to the wall are the most important fluid dynamic factors affecting local the heat transfer distributions inside a 180-deg sharp turn. The role of the turbulent kinetic energy in the overall enhancement of heat transfer is well addressed.

Investigation of Cross-Sectional Velocity Field Near the Inducer Plane of a Turbocharger Compressor Using 2D Particle Image Velocimetry

2019 ◽  
Author(s):  
Deb Banerjee ◽  
Rick Dehner ◽  
Ahmet Selamet ◽  
Keith Miazgowicz ◽  
Todd Brewer ◽  
...  
Keyword(s):  
Particle Image Velocimetry ◽  
Velocity Field ◽  
Flow Field ◽  
Mass Flow ◽  
Particle Image ◽  
Tangential Velocity ◽  
Cross Sectional ◽  
Flow Rates ◽  
Blade Passage ◽  
Image Velocimetry

Abstract Understanding the velocity field at the inlet of an automotive turbocharger is critical in order to suppress the instabilities encountered by the compressor, extend its map and improve the impeller design. In the present study, two-dimensional particle image velocimetry experiments are carried out on a turbocharger compressor without any recirculating channel to investigate the planar flow structures on a cross-sectional plane right in front of the inducer at a rotational speed of 80 krpm. The objective of the study is to investigate the flow field in front of a compressor blade passage and quantify the velocity distributions along the blade span for different mass flow rates ranging from choke (77 g/s) to deep surge (13.6 g/s). It is observed that the flow field does not change substantially from choke to about 55 g/s, where flow reversal is known to start at this speed from earlier measurements. While the tangential velocity is less than 8 m/s, the radial velocity increases along the span to 17–20 m/s near the tip at high flow rates (55–77 g/s). As the mass flow rate is reduced below 55 g/s, the radial component starts decreasing and the tangential velocity increases rapidly. From about 5 m/s at 55 g/s, the tangential velocity at the blade tip exceeds 50 m/s at 50 g/s and reaches a maximum of about 135 m/s near surge. These time-averaged distributions are similar for different angular locations in front of the blade passage and do not exhibit any substantial azimuthal variation.

An Experimental Investigation of Turbulent Drag Reduction in Concentric Annulus Using Particle Image Velocimetry Technique

2013 ◽  
Author(s):  
Fabio Ernesto Rodriguez Corredor ◽  
Majid Bizhani ◽  
Ergun Kuru
Keyword(s):  
Particle Image Velocimetry ◽  
Turbulent Flow ◽  
Drag Reduction ◽  
Particle Image ◽  
Reynolds Shear Stress ◽  
Polymer Concentration ◽  
Mean Flow ◽  
Flow Loop ◽  
Mean Velocity ◽  
Image Velocimetry

Polymer drag reduction is investigated using the Particle Image Velocimetry (PIV) technique in fully developed turbulent flow through a horizontal flow loop with concentric annular geometry (inner to outer pipe radius ratio = 0.4). The polymer used was a commercially available partially hydrolyzed polyacrylamide (PHPA). The polymer concentration was varied from 0.07 to 0.12% V/V. The drag reduction is enhanced by increasing polymer concentration until the concentration reaches an optimum value. After that, the drag reduction is decreased with the increasing polymer concentration. Optimum concentration value of PHPA was found to be around 0.1% V/V. Experiments were conducted at solvent Reynolds numbers of 38700, 46700 and 56400. The percent drag reduction was found to be increasing with the increasing Reynolds number. The study was also focused on analyzing the mean flow and turbulence statistics for fully-turbulent flow using the velocity measurements acquired by PIV. Axial mean velocity profile was found to be following the universal wall law close to the wall (i.e., y+ <10), but it deviated from log law results with an increased slope in the logarithmic zone (i.e., y+ >30). In all cases of polymer application, the viscous sublayer (i.e., y+ <10) thickness was found to be higher than that of the water flow. Reynolds shear stress in the core flow region was found to be decreasing with the increase in polymer concentration.

Different Modes of Gas Entrainment Through Bottom Discharge Branch by Using Three Dimensional Particle Image Velocimetry System

2007 ◽  
Author(s):  
Wael Fairouz Saleh ◽  
Ibrahim Galal Hassan
Keyword(s):  
Particle Image Velocimetry ◽  
Flow Structure ◽  
Particle Image ◽  
Three Dimensional ◽  
Industrial Applications ◽  
Particle Image Velocimetry System ◽  
Three Dimension ◽  
Two Phase ◽  
Mean Velocity ◽  
Image Velocimetry

The discharge of two-phase flow from a stratified region through single or multiple branches is an important process in many industrial applications including the pumping of fluid from storage tanks, shell-and-tube heat exchangers, and the fluid flow through small breaks in cooling channels of nuclear reactors during loss-of-coolant accidents (LOCA). Knowledge of the flow phenomena involved along with the quality and mass flow rate of the discharging stream(s) is necessary to adequately predict the different phenomena associated with the process. Particle Image Velocimetry (PIV) in three dimension was used to provide detailed measurements of the flow patterns involving distributions of mean velocity, vorticity field, and flow structure. The experimental investigation was carried out to simulate two phase discharge from a stratified region through branches located on a semi-circular wall configuration during LOCA scenarios. The semi-circular test section is in close dimensional resemblance with that of a CANDU header-feeder system, with branches mounted at orientation angles of zero, 45 and 90 degrees from the horizontal. The experimental data for the phase development (mean velocity, flow structure, etc.) was done during single discharge through the bottom branch from an air/water stratified region over a three selected Froude numbers. These measurements were used to describe the effect of outlet flow conditions on phase redistribution in headers and understand the entrainment phenomena.

125 Measurement of Secondary Flow in a Low Solidity Circular Cascade Diffuser by a Particle Image Velocimetry

2014 ◽  
Vol 2014.67 (0) ◽  
pp. _125-1_-_125-2_
Author(s):  
Kanata MIZOKOSHI ◽  
Takuma EIDA ◽  
Xiangyu ZHANG ◽  
Daisaku SAKAGUCHI
Keyword(s):  
Particle Image Velocimetry ◽  
Secondary Flow ◽  
Particle Image ◽  
Image Velocimetry

High Resolution Particle Image Velocimetry and CH-PLIF Measurements and Analysis of a Shear Layer Stabilized Flame

2015 ◽  
Vol 138 (3) ◽  
Author(s):  
C. W. Foley ◽  
I. Chterev ◽  
J. Seitzman ◽  
T. Lieuwen
Keyword(s):  
Particle Image Velocimetry ◽  
High Resolution ◽  
Shear Layer ◽  
Flow Velocity ◽  
Particle Image ◽  
Flame Stabilization ◽  
Flow Conditions ◽  
Local Flow ◽  
Image Velocimetry ◽  
Flow Velocities

Understanding the mechanisms and physics of flame stabilization and blowoff of premixed flames is critical toward the design of high velocity combustion devices. In the high bulk flow velocity situation typical of practical combustors, the flame anchors in shear layers where the local flow velocities are much lower. Within the shear layer, fluid strain deformation rates are very high and the flame can be subjected to significant stretch levels. The main goal of this work was to characterize the flow and stretch conditions that a premixed flame experiences in a practical combustor geometry and to compare these values to calculated extinction values. High resolution, simultaneous particle image velocimetry (PIV) and planar laser induced fluorescence of CH radicals (CH-PLIF) measurements are used to capture the flame edge and near-field stabilization region. When approaching lean limit extinction conditions, we note characteristic changes in the stretch and flow conditions experienced by the flame. Most notably, the flame becomes less critically stretched when fuel/air ratio is decreased. However, at these lean conditions, the flame is subject to higher mean flow velocities at the edge, suggesting less favorable flow conditions are present at the attachment point of the flame as blowoff is approached. These measurements suggest that blowoff of the flame from the shear layer is not directly stretch extinction induced, but rather the result of an imbalance between the speed of the flame edge and local tangential flow velocity.

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