Effects of an Initial Gap on the Turbulent Jet Flow over a Curved Wall

1968 ◽  
Vol 72 (685) ◽  
pp. 63-67
Author(s):  
S. C. Paranjpe ◽  
K. Sridhar
Keyword(s):  
Angular Position ◽  
Leading Edge ◽  
Turbulent Jet ◽  
Hysteresis Phenomenon ◽  
Wall Jet ◽  
Exit Velocity ◽  
Free Jet ◽  
Surface Pressure Distribution ◽  
Turbulent Jet Flow ◽  
Gap Effects

Summary The flow in a two-dimensional curved wall jet with different initial gaps between the nozzle exit and the leading edge of the wall was probed at various stations along the jet. The jet slot thickness, the jet exit velocity and the radius of the wall were kept constant. It was found that the region close to the leading edge of the wall behaved like a settling zone. In this zone the type of flow changed from a free jet to a curved wall jet. The length required for settling depended on gap size and was less than that of the plane wall jet. Gap effects on surface pressure distribution and angular position of separation were examined. The hysteresis phenomenon associated with gaps was investigated.

Effects of an Initial Gap on the Flow in a Turbulent Wall Jet

1966 ◽  
Vol 70 (666) ◽  
pp. 669-673 ◽  
Author(s):  
K. Sridhar ◽  
P. K. C. Tu
Keyword(s):  
Power Law ◽  
Nozzle Exit ◽  
Leading Edge ◽  
Wall Jet ◽  
Gap Size ◽  
Two Dimensional ◽  
Free Jet ◽  
Layer Velocity ◽  
Turbulent Wall ◽  
Gap Effects

SummaryThe flow in a two-dimensional plane wall jet with different initial gaps between the nozzle exit and the leading edge of the wall was probed at various stations along the jet. The jet slot thickness and the velocity were kept constant. It was found that the region close to the leading edge of the wall behaved like a transforming region where the type of flow changed from a free jet to a wall jet. The length of this region, which depended directly on the gap size, was so short for small gaps that the gap effects were found to be negligible. In addition, it was found that the inner layer velocity distribution of a wall jet did not follow the classic one-seventh power law.

The Laminar Two-Dimensional Free Jet of an Incompressible Pseudoplastic Fluid

1968 ◽  
Vol 35 (4) ◽  
pp. 810-812 ◽  
Author(s):  
P. F. Lemieux ◽  
T. E. Unny
Keyword(s):  
Boundary Layer ◽  
Exact Solution ◽  
Similarity Solutions ◽  
Turbulent Jet ◽  
Two Dimensional ◽  
Pseudoplastic Fluid ◽  
Free Jet ◽  
Boundary Layer Equations ◽  
Turbulent Jet Flow ◽  
Special Case

Boundary-layer equations have been used to obtain an exact solution for the free outflow of a non-Newtonian pseudoplastic fluid from a two-dimensional orifice into a mass of the same fluid. Existence of similarity solutions has been proved. The results obtained by Schlichting for the Newtonian fluid flow is shown to be the special case of the more general analysis given here. Though further effort is necessary to investigate the turbulent jet flow, the analysis presented here should make a definite contribution in this definition.

A Simple Criterion to Estimate Performance of Pulse Jet Mixed Vessels

2016 ◽  
Author(s):  
Leonard F. Pease ◽  
Judith Ann Bamberger ◽  
Lenna A. Mahoney ◽  
S. Thomas Yokuda ◽  
Michael J. Minette
Keyword(s):  
Jet Flow ◽  
Turbulent Jet ◽  
Processing Plant ◽  
Local Velocity ◽  
Simple Criterion ◽  
Free Jet ◽  
Vertical Extent ◽  
Turbulent Jet Flow ◽  
Fill Level ◽  
Pulse Jet

Pulse jet mixed process vessels comprise a key element of the U.S. Department of Energy’s strategy to process millions of gallons of legacy nuclear waste slurries. Slurry suctioned into a pulse jet mixer (PJM) tube at the end of one pulse is pneumatically driven from the PJM toward the bottom of the vessel at the beginning of the next pulse, forming a jet. The jet front traverses the distance from nozzle outlet to the bottom of the vessel and spreads out radially. Varying numbers of PJMs are typically arranged in a ring configuration within the vessel at a selected radius and operated concurrently. Centrally directed radial flows from neighboring jets collide to create a central upwell that elevates the solids in the center of the vessel when the PJM tubes expel their contents. An essential goal of PJM operation is to elevate solids to the liquid surface to minimize stratification. Solids stratification may adversely affect throughput of the waste processing plant. Unacceptably high slurry densities at the base of the vessel may plug the pipeline through which the slurry exits the vessel. Additionally, chemical reactions required for processing may not achieve complete conversion. To avoid these conditions, a means of predicting the elevation to which the solids rise in the central upwell that can be used during vessel design remains essential. In this paper we present a simple criterion to evaluate the extent of solids elevation achieved by a turbulent upwell jet. The criterion asserts that at any location in the central upwell the local velocity must be in excess of a cutoff velocity to remain turbulent. We find that local velocities in excess of 0.6 m/s are necessary for turbulent jet flow through both Newtonian and yield stress slurries. By coupling this criterion with the free jet velocity equation relating the local velocity to elevation in the central upwell, we estimate the elevation at which turbulence fails, and consequently the elevation at which the upwell fails to further lift the slurry. Comparing this elevation to the vessel fill level predicts whether the jet flow will achieve the full vertical extent of the vessel at the center. This simple local-velocity criterion determines a minimum PJM nozzle velocity at which the full vertical extent of the central upwell in PJM vessels will be turbulent. The criterion determines a minimum because flow in regions peripheral to the central upwelling jet may not be turbulent, even when the center of the vessel in the upwell is turbulent, if the jet pulse duration is too short. The local-velocity criterion ensures only that there is sufficient wherewithal for the turbulent jet flow to drive solids to the surface in the center of the vessel in the central upwell.

Numerical Study of the Mean and Filtered Characteristics of Turbulent Jets Impinging on Convex and Flat Surfaces Using LES

2012 ◽  
Author(s):  
Adra Benhacine ◽  
Zoubir Nemouchi ◽  
Lyes Khezzar ◽  
Nabil Kharoua
Keyword(s):  
Convex Surface ◽  
Numerical Study ◽  
Three Dimensional ◽  
Turbulent Jets ◽  
Scale Model ◽  
Wall Jet ◽  
Potential Core ◽  
Flat Surfaces ◽  
Free Jet ◽  
Eddy Simulation

A numerical study of a turbulent plane jet impinging on a convex surface and on a flat surface is presented, using the large eddy simulation approach and the Smagorinski-Lilly sub-grid-scale model. The effects of the wall curvature on the unsteady filtered, and the steady mean, parameters characterizing the dynamics of the wall jet are addressed in particular. In the free jet upstream of the impingement region, significant and fairly ordered velocity fluctuations, that are not turbulent in nature, are observed inside the potential core. Kelvin-Helmholtz instabilities in the shear layer between the jet and the surrounding air are detected in the form of wavy sheets of vorticity. Rolled up vortices are detached from these sheets in a more or less periodic manner, evolving into distorted three dimensional structures. Along the wall jet the Coanda effect causes a marked suction along the convex surface compared with the flat one. As a result, relatively important tangential velocities and a stretching of sporadic streamwise vortices are observed, leading to friction coefficient values on the curved wall higher than those on the flat wall.

Experimental investigation of the effect of active flow control on the wake of a wind turbine blade

2021 ◽  
pp. 095440622110089
Author(s):  
GholamHossein Maleki ◽  
Ali Reza Davari ◽  
Mohammad Reza Soltani
Keyword(s):  
Experimental Investigation ◽  
Wind Turbine ◽  
Turbine Blade ◽  
Active Flow Control ◽  
Leading Edge ◽  
Wind Turbine Blade ◽  
Plasma Actuators ◽  
Plasma Actuation ◽  
Surface Pressure Distribution ◽  
Stall Angle

An extensive experimental investigation was conducted to study the effects of Dielectric Barrier Discharge (DBD), on the flow field of an airfoil at low Reynolds number. The DBD was mounted near the leading edge of a section of a wind turbine blade. It is believed that DBD can postpone the separation point on the airfoil by injecting momentum to the flow. The effects of steady actuations on the velocity profiles in the wake region have been investigated. The tests were performed at α = 4 to 36 degrees i.e. from low to deep stall angles of attack regions. Both surface pressure distribution and wake profile show remarkable improvement at high angles of attack, beyond the static stall angle of the airfoil when the plasma actuation was implemented. The drag calculated from the wake momentum deficit has further shown the favorable role of the plasma actuators to control the flow over the airfoil at incidences beyond the static stall angle of attack of this airfoil. The results demonstrated that DBD has been able to postpone the stall onset significantly. It has been observed that the best performance for the plasma actuation for this airfoil is in the deep stall angles of attack range. However, below and near the static stall angles of attack, plasma augmentation was pointed out to have a negligible improvement in the aerodynamic behavior.

Plane Turbulent Free Jet and Wall Jet

1967 ◽  
Vol 71 (680) ◽  
pp. 585-587 ◽  
Author(s):  
N. Rajaratnam ◽  
K. Subramanya
Keyword(s):  
Velocity Distribution ◽  
Smooth Boundary ◽  
Wall Jet ◽  
Length Scales ◽  
Ambient Environment ◽  
Free Jet ◽  
Turbulent Wall

The aim of this note is to compare the plane turbulent free jet diffusing in an infinite stagnant ambient environment with the corresponding plane turbulent wall jet on a smooth boundary regarding the three important characteristics, namely the velocity distribution and the variation of the velocity and length scales, in the region of developed flow.

scholarly journals The Turbulent Jet from a Series of Holes in Line

1964 ◽  
Vol 15 (1) ◽  
pp. 1-28 ◽  
Author(s):  
R. Knystautas
Keyword(s):  
Jet Flow ◽  
Turbulent Jet ◽  
Two Dimensional ◽  
Turbulent Jet Flow ◽  
Similar Density

SummaryThe possibility of obtaining two-dimensional turbulent jet flow from a series of closely-spaced uniform holes in line has been investigated both theoretically and experimentally. The case studied was that of a jet discharging into still fluid of similar density at incompressible speeds. Such a quasi-two-dimensional jet is a particular example of a multiple-interfering jet group.

scholarly journals Comparative study on combustion characteristics of lean premixed CH4/air mixtures in RCM using spark ignition and turbulent jet ignition in terms of orifices angular position change

2019 ◽  
Vol 176 (1) ◽  
pp. 36-41 ◽  
Author(s):  
Wojciech BUESCHKE ◽  
Maciej SKOWRON ◽  
Krzysztof WISŁOCKI ◽  
Filip SZWAJCA
Keyword(s):  
Internal Combustion Engines ◽  
Positive Impact ◽  
Angular Position ◽  
Turbulent Jet ◽  
Combustion Stability ◽  
Optical Observations ◽  
Charge Movement ◽  
Position Change ◽  
Lean Burn ◽  
The Impact

The increase in ignitability consist a main aim of implementation of the turbulent jet ignition (TJI) in relation to the combustion of diluted charges. Such an ignition system has been introduced to the lean-burn CNG engine in the scope of GasOn-Project (Gas Only Internal Combustion Engines). In this study the impact of TJI application on the main combustion indexes has been investigated using RCM and analyzed on the bases of the indicating and optical observations data. The images have been recorded using LaVision HSS5 camera and post-processed with Davis software. Second part of the study based on indicating measurements consist the analysis of combustion regarding the variation in the geometry of pre-chamber nozzles. It has been noted, that combustion with TJI indicates signi- ficantly bigger flame luminescence and simultaneously – faster flame front development, than the combustion initiated with conventional SI. The positive impact of nozzles angular position on engine operational data has been found in the static charge movement conditions, regarding the combustion stability.

scholarly journals NUMERICAL AND EXPERIMENTAL MODELING OF INTERACTION BETWEEN A TURBULENT JET FLOW AND AN INLET

2000 ◽  
Vol 22 (1) ◽  
pp. 29-38
Author(s):  
H. D. Lien ◽  
I. S. Antonov
Keyword(s):  
Convective Flow ◽  
Integral Method ◽  
Natural Experiment ◽  
Present Model ◽  
Turbulent Jet ◽  
Sources Of Pollution ◽  
Two Component ◽  
Local Sources ◽  
Turbulent Jet Flow ◽  
Harmful Substances

In ventilation devices to get rid of harmful substances out of workingplaces, we use sucking devices. The local sources of pollution are evacuated by them. Abasic element when creating the model of sucking device is: the source of harmful substancesis discussed as a rising convective flow, which is ejected out of sucking spectrum,created by a sucking apparatus. In the present work, the flow is a whole one with variablequantity of motion and kinetic energy along it's length. The change in those twoparameters is caused by and is in dependent function of the inlet spectrum. There hasbeen discussed a two-component flow of air and gas in ventilation devices. A two-velocityscheme of flow is used to realise the numerical method. An integral method of investigationis used, based on the conditions of conservation of mass contents, quantity of motion andkinetic energy. It's been accepted that quantity of motion and energy change in functionof inlet action. A comparison of numerical results and natural experiment are made fortwo conditions: full suck and not full suck. Conclusion is that the present model is preciseand can be unset for engineering calculations.

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