scholarly journals Effects of Nozzle Pressure Ratio and Nozzle-to-Plate Distance to Flowfield Characteristics of an Under-Expanded Jet Impinging on a Flat Surface

Aerospace ◽  
2019 ◽  
Vol 6 (1) ◽  
pp. 4 ◽  
Author(s):  
Duy Thien Nguyen ◽  
Blake Maher ◽  
Yassin Hassan
Keyword(s):  
Vector Fields ◽  
Pressure Ratio ◽  
Flow Characteristics ◽  
Impinging Jets ◽  
Central Plane ◽  
Mean Velocity ◽  
Image Velocimetry ◽  
Nozzle Pressure ◽  
Pod Analysis ◽  
Impingement Surface

The current work experimentally investigates the flowfield characteristics of an under-expanded turbulent jet impinging on a solid surface for various nozzle-to-plate distances 2.46 D j , 1.64 D j , and 0.82 D j ( D j is the jet hydraulic diameter), and nozzle pressure ratios (NPRs) ranging from 2 to 2.77 . Planar particle image velocimetry (PIV) measurements were performed in the central plane of the test nozzle and near the impingement surface. From the obtained PIV velocity vector fields, flow characteristics of under-expanded impinging jets, such as mean velocity, root-mean-square fluctuating velocity, and Reynolds stress profiles, were computed. Comparisons of statistical profiles obtained from PIV velocity measurements were performed to study the effects of the impingement surface, nozzle-to-plate distances, and NPRs to the flow patterns. Finally, proper orthogonal decomposition (POD) analysis was applied to the velocity snapshots to reveal the statistically dominant flow structures in the impinging jet regions.

PIV measurements in a twin-jet STOVL fountain flow

2005 ◽  
Vol 109 (1100) ◽  
pp. 439-449 ◽  
Author(s):  
P. M. Cabrita ◽  
A. J. Saddington ◽  
K. Knowles
Keyword(s):  
Pressure Ratio ◽  
Three Dimensional ◽  
Jet Impingement ◽  
Turbulent Jets ◽  
Spreading Rate ◽  
Nozzle Pressure Ratio ◽  
Mean Velocity ◽  
Fountain Flow ◽  
Image Velocimetry ◽  
Nozzle Pressure

Abstract Mean velocity and first order turbulence measurements were obtained from a three-dimensional upwash fountain flow generated by the impingement of two compressible axisymmetric turbulent jets onto a normal plane. The jet impingement area and fountain formation regions were examined with data obtained through the use of particle image velocimetry. Seven configurations with different nozzle pressure ratios were considered to ascertain the influence of jet compressibility on the fountain development. Results indicate that the mixing of the fountain is dependent on the nozzle pressure ratio, leading to an increase in the fountain spreading rate with increase in nozzle pressure ratio.

Turbulent Flow Measurements and Visualizations of Supersonic Jets Impinging on a Flat Plate and an Inclined Plate

2020 ◽  
Author(s):  
Thien D. Nguyen ◽  
Blake Maher ◽  
Yassin A. Hassan
Keyword(s):  
Kinetic Energy ◽  
Flat Plate ◽  
Pressure Ratio ◽  
Flow Characteristics ◽  
Field Measurements ◽  
Central Plane ◽  
Inclined Plate ◽  
Mean Velocity ◽  
Flow Measurements ◽  
Full Field

Abstract This study experimentally investigates the flow characteristics of a high-pressure air jets impinging on a flat plate and an inclined plate with various nozzle-to-plane gaps of 10 mm, 20 mm, and 30 mm. Full-field measurements of flow characteristics in the central plane of the nozzle and near the impinging surface are performed using two-dimensional two-component (2D2C) particle image velocimetry (PIV) technique. This paper presents results from the nozzle pressure ratio (NPR) of 2.77, approximately yielding the sonic jet with Mach number of 1.2. Flow characteristics obtained from the 2D2C-PIV measurements with various spatial gaps are compared and presented. Results including the first- and second-order flow statistics, such as mean velocity and turbulent kinetic energy, and effects of the impinging surface to the flow patterns are investigated. Finally, proper orthogonal decomposition (POD) analysis is applied to reveal the statistically dominant flow structures that capture the highest amount flow kinetic energy and play important roles to the flow dynamics and heat transfers.

Experimental and Computational Studies on Flow Characteristics of Single Expansion Nozzle

2021 ◽  
Author(s):  
Dakshina Murthy Inturi ◽  
Lovaraju Pinnam ◽  
Ramachandra Raju Vegesna
Keyword(s):  
Mach Number ◽  
Flow Field ◽  
Pressure Ratio ◽  
Flow Characteristics ◽  
Oblique Shock ◽  
Solid Boundary ◽  
Computational Studies ◽  
Nozzle Pressure Ratio ◽  
Nozzle Pressure ◽  
Flow Field Characteristics

Abstract The present investigation aims to study the flow field characteristics of a single expansion nozzle (SEN). The flow field characteristics of conventional convergent-divergent (C-D) nozzle are also investigated for comparison. The experimental and computational studies were carried out for nozzle pressure ratios of 1.45, 1.55, 1.75, 2, 3, 4 and 5. The studies reveal that, for the single expansion nozzle the oblique shock moves towards the solid boundary with the increase of nozzle pressure ratio, which makes the flow to accelerate continuously in the majority of the divergent portion. The single expansion nozzle delivers the flow with higher Mach number than the C-D nozzle at the exit of the nozzle.

Turbulence Characteristics in a Rushton Stirring Vessel: A Numerical Investigation

2006 ◽  
Author(s):  
V. N. Vlachakis ◽  
M. R. Brady ◽  
R. H. Yoon ◽  
D. P. Telionis ◽  
P. P. Vlachos
Keyword(s):  
Vector Fields ◽  
Particle Image ◽  
Flow Characteristics ◽  
Mixing Process ◽  
Time Resolved ◽  
Turbulent Dissipation ◽  
Image Velocimetry ◽  
Contour Plots ◽  
Turbulent Models ◽  
Future Work

Results from simulations using FLUENT (a commercial CFD package) are compared with Time Resolved Digital Particle Image Velocimetry (DPIV) for baseline configurations in order to validate and verify the fidelity of the computations. Different turbulent models are used in this study in order to determine which one is the most appropriate. Subsequently a parametric analysis of the flow characteristics as a function of the clearance height of the impeller from the vessel floor is performed. Results are presented along planes normal and parallel to the impeller axis, displaying velocity vector fields and contour plots of vorticity turbulent dissipation and others. Special attention is focused in the neighborhood of the impeller region and the radial jet generated there. The present results provide useful information for the design of the mixing process as well as for more accurate estimations in future work.

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.

Numerical Study of Counter Jet Formed by Impinging Jets in Cross-Flow and its Effect on Mixing

2017 ◽  
Author(s):  
Thomas A. Epalle ◽  
Fabien Gaugain ◽  
Vincent Melot ◽  
Nasser Darabiha ◽  
Olivier Gicquel
Keyword(s):  
Numerical Study ◽  
Velocity Ratio ◽  
Flow Characteristics ◽  
Cross Flow ◽  
Passive Scalar ◽  
Impinging Jets ◽  
Mean Velocity ◽  
Plane Flow ◽  
Flow Mixing ◽  
Mixing Chambers

In this paper we will numerically analyse flow mixing in multiple jets in a crossflow. The system comprises a row of six radially-distributed injectors around the main pipe. The configuration represents mixing zones in industrial systems where a counter jet can be formed in the injection plane. Flow mixing can be modified as a result of geometry and injection velocities. We propose a simple model to describe the counter jet length as a function of injection flow characteristics. We also develop empirical laws to help engineers design practical test facilities. We then vary the velocity ratio to obtain both impinging and non-impinging jets in the injection plane. The focus is mainly on flow characteristics around the radial injection plane in the case of impinging jets, examining the mixing quality and efficiency by introducing a passive scalar discharge in a nitrogen flow. The mean velocity and width of the counter jet are finally analyzed by changing the injection velocities. These results are compared to those of non-impinging jets. It is found that the non-impinging jet configurations are convenient for short length mixing chambers, while the impinging ones should be considered in the case of longer mixing chambers.

THE FEASIBILITY OF FLUORESCENT NANO-PARTICLE FOR BIOLOGICAL FLOW ANALYSIS IN A MICROCHANNEL

2006 ◽  
Vol 20 (25n27) ◽  
pp. 4505-4510 ◽  
Author(s):  
CHEOL WOO PARK ◽  
GYU MAN KIM ◽  
DONG KYUN KIM ◽  
SANG JOON LEE
Keyword(s):  
Blood Flow ◽  
Flow Analysis ◽  
Flow Characteristics ◽  
Nano Particle ◽  
Mean Velocity ◽  
Reynolds Number Flow ◽  
Micro Particle Image Velocimetry ◽  
Micro Piv ◽  
Image Velocimetry ◽  
Number Flow

The biological flow characteristics inside a microchannel were investigated experimentally using a micro-particle image velocimetry (micro-PIV) method. The main objectives of this study were to understand the blood flow in micro-domain blood vessels and to identify the feasibility of nano-scale fluorescent particles for velocity measurement. The flow field was analyzed with a spatial resolution of 1 K ×1 K pixels at low Reynolds number flow. To obtain the spatial distributions of mean velocity, 100 instantaneous velocity fields were captured and ensemble-averaged. As a result, for the case of blood flow, there were substantial velocity variations in the central region of micro-channel due to the presence of blood cells in the blood flow.

Flow Characteristics and Structure of 3D Turbulent Offset Jets

2014 ◽  
Author(s):  
B. Nyantekyi-Kwakye ◽  
S. Clark ◽  
M. F. Tachie ◽  
J. Malenchak ◽  
G. Muluye
Keyword(s):  
Reynolds Shear Stress ◽  
Three Dimensional ◽  
Symmetry Plane ◽  
Flow Characteristics ◽  
Velocity Measurements ◽  
Height Ratio ◽  
Mean Velocity ◽  
Image Velocimetry ◽  
Velocity Decay ◽  
Contour Plots

Three-dimensional turbulent offset jets were investigated with a particle image velocimetry (PIV) technique. Detailed velocity measurements for the flow were performed at an exit Reynolds number ranging from 8080–12080 for three offset height ratios of 0, 2 and 4. Profiles of the maximum mean velocity decay and wall-normal spread rates were observed to be sensitive to offset height ratio. Contour plots of mean velocity and turbulence kinetic energy exhibited dependence on offset height ratio. The reattachment lengths of the turbulent three-dimensional offset jets were observed to increase with offset height ratio. The results within the symmetry plane revealed that the production of Reynolds shear stress was not significantly enhanced by offset height ratio further downstream.

PIV Measurements of Jet Flow Mixing in the Vicinity of Rod Bundles Using Matched-Index of Refraction

2008 ◽  
Author(s):  
Noushin Amini ◽  
Elvis E. Dominguez-Ontiveros ◽  
Carlos E. Estrada-Perez ◽  
Stephen D. Fortenberry ◽  
Yassin A. Hassan
Keyword(s):  
Particle Image ◽  
Flow Characteristics ◽  
Impinging Jets ◽  
Index Of Refraction ◽  
Velocity Measurements ◽  
Rod Bundles ◽  
Piv Measurements ◽  
Rod Bundle ◽  
Flow Mixing ◽  
Image Velocimetry

In this study, the velocity field of impinging jets within a rod bundle was developed. Velocity measurements were accomplished using Particle Image Velocimetry (PIV). Additionally, Matched-Index of Refraction (MIR) techniques were implemented to allow the visualization of flow characteristics within interior areas of the rod bundle which would typically be obstructed. Such measurements are of importance and essential to the development of new models to predict the systems’ hydraulic behavior.

Experimental investigation on the momentumless wake using trailing edge blowing

2008 ◽  
Vol 222 (8) ◽  
pp. 1477-1486 ◽  
Author(s):  
Y Wu ◽  
X Zhu ◽  
Z Du
Keyword(s):  
Three Dimensional ◽  
Velocity Profiles ◽  
Axial Fan ◽  
Trailing Edge ◽  
Mean Velocity ◽  
Piv Measurement ◽  
Image Velocimetry ◽  
Velocity Spectra ◽  
Momentumless Wake ◽  
Wake Characteristics

A developed plate stator model with and without trailing edge blowing (TEB) is studied using experimental methods. Wake characteristics of flow over the stator in the three-dimensional wake regimes are studied using hot-wire anemometry (HWA) and particle image velocimetry (PIV) techniques. First, the mean velocity profiles have been measured in the wake of the stator using HWA. Four wake characteristics have been obtained through momentum thickness judgments: pure wake, weak wake, momentumless wake, and jet. These velocity profiles show some differences in momentum deficit for the four cases. Then, the velocity spectra of the pure wake and momentumless wake obtained through the HWA measurements showed that TEB can eliminate the shedding vortex of the stator. Characteristic length scales based on the wake turbulent intensity profiles showed that the momentumless wake can reduce the wake width and depth. PIV measurement is carried out to measure the flow field of the four wakes. Finally, the application of TEB approaching momentumless wake status is used on an industrial ventilation low-pressure axial fan to assess noise reduction. The results show that TEB can make the outlet of the stator uniform, reduce velocity fluctuation, destroy the vorticity structure downstream of the stator, and reduce interaction noise level of the stator and rotor.

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