Near-field mixing in turbulent free jets issuing from triangular orifices with different apex angles

2012 ◽  
Author(s):  
Mohammad Azad ◽  
Willie Quinn ◽  
Dominic Groulx
Keyword(s):  
Near Field ◽  
Free Jets

An experimental study of underexpanded sonic, coaxial, swirl jets

2004 ◽  
Vol 218 (1) ◽  
pp. 93-103 ◽  
Author(s):  
K-H Lee ◽  
T Setoguchi ◽  
S Matsuo ◽  
H-D Kim
Keyword(s):  
Static Pressure ◽  
Near Field ◽  
Flow Structures ◽  
Experimental Investigations ◽  
Pressure Measurements ◽  
Annular Nozzle ◽  
Free Jets ◽  
Underexpanded Jets ◽  
Secondary Stream ◽  
The Impact

The present study addresses experimental investigations of the near-field flow structures of an underexpanded sonic, dual, coaxial, swirl jet. The swirl stream is discharged from the secondary annular nozzle and the primary inner nozzle provides the underexpanded free jets. The interactions between the secondary swirl and primary underexpanded jets are quantified by a fine pitot impact and static pressure measurements and are visualized using a shadowgraph optical method. The pressure ratios of the secondary swirl and primary underexpanded jets are varied below 7.0. Experiments are conducted to investigate the effects of the secondary swirl stream on the primary underexpanded jets, compared with the secondary stream of no swirl. The results show that the presence of an annular swirl stream causes the Mach disc to move further downstream, with an increased diameter, and remarkably reduces the fluctuations of the impact pressures in the underexpanded sonic dual coaxial jet, compared with the case of the secondary annular stream with no swirl.

1701 Experiments in the Near-field Structures of Circular Free Jets Issued from Various Shaped Nozzles(1)

2006 ◽  
Vol 2006 (0) ◽  
pp. _1701-a_
Author(s):  
Yoshihiro INOUE ◽  
Yoshimasa YAMADA ◽  
Shintaro YAMASHITA
Keyword(s):  
Near Field ◽  
Free Jets

Vortex dynamics and entrainment in rectangular free jets

2001 ◽  
Vol 437 ◽  
pp. 69-101 ◽  
Author(s):  
FERNANDO F. GRINSTEIN
Keyword(s):  
Aspect Ratio ◽  
Turbulent Flows ◽  
Vortex Dynamics ◽  
Near Field ◽  
Vortex Sheet ◽  
Free Jets ◽  
Flow Equations ◽  
Low Aspect Ratio ◽  
Eddy Simulation ◽  
Axis Switching

Simulations of low-aspect-ratio, rectangular free jets are presented. The investigations focus on the entrainment and transitional vortex dynamics in compressible (subsonic) jets initialized with laminar conditions, a thin vortex sheet with slightly rounded-off corner regions, and uniform initial momentum thickness. A monotonically integrated large-eddy simulation approach based on the solution of the unsteady flow equations with high-resolution monotone algorithms is used. Inherent uncertainties in the jet entrainment measurement process are addressed using the database from laboratory experiments and simulations. Vorticity geometries characterizing the near flow field of low aspect-ratio (A) rectangular jets are demonstrated, involving: (i) self-deforming and (ii) splitting vortex rings; interacting ring and braid (rib) vortices including (iii) single ribs aligned with corner regions (A [ges ] 2) and (iv) rib pairs aligned with the corners (A = 1); (v) a more disorganized flow regime in the far jet downstream, where the rotational-fluid volume is occupied by a relatively weak vorticity background with strong, slender tube-like filament vortices filling a small fraction of the domain – as observed in fully developed turbulent flows. The near field entrainment properties of low-A rectangular jets are shown to be largely determined by the characteristic A-dependent coupling geometry of interacting rib and ring vortices and by vortex-ring axis-switching times.

Predictions of Impacting Sonic and Supersonic Jets

1997 ◽  
Vol 119 (1) ◽  
pp. 83-89 ◽  
Author(s):  
P. S. Cumber ◽  
M. Fairweather ◽  
S. A. E. G. Falle ◽  
J. R. Giddings
Keyword(s):  
Near Field ◽  
Supersonic Jets ◽  
Wall Jet ◽  
Pressure Oscillations ◽  
Free Jets ◽  
Underexpanded Jets ◽  
Free Jet ◽  
Model Predictions ◽  
Periodic Pressure ◽  
Spatially Periodic

A mathematical model of sonic and supersonic jets, validated previously by the present authors for the prediction of moderately and highly underexpanded free jets, is used to simulate the near field structure of jets which impact a flat surface orthogonally, and its accuracy assessed by comparing model predictions with experimental data available in the literature. For impacting, moderately underexpanded jets, results derived from the model are found to be in close agreement with data on the location of both free jet shocks, and the stand-off shock formed adjacent to the impacted surface. In addition, the model provides reasonable estimates of density within the free jet and stagnation regions of such flows, with the existence, or otherwise, of bubbles being successfully predicted. Measurements of pressure occurring on the surface of the impacted plate, produced by the impingement of both sonic and supersonic jets, are also predicted with reasonable accuracy, although the decaying amplitude of spatially periodic pressure oscillations within the wall jet region of these flows is slightly over predicted in some cases.

1701 Experiments in the Near-field Structures of Circular Free Jets Issued from Various Shaped Nozzles(2)

2006 ◽  
Vol 2006 (0) ◽  
pp. _1701-1_-_1701-4_
Author(s):  
Yoshihiro INOUE ◽  
Yoshimasa YAMADA ◽  
Shintaro YAMASHITA
Keyword(s):  
Near Field ◽  
Free Jets

Near-field scanning optical microscopy

1986 ◽  
Vol 44 ◽  
pp. 642-643
Author(s):  
E. Betzig ◽  
A. Harootunian ◽  
M. Isaacson ◽  
A. Lewis
Keyword(s):  
Near Field ◽  
Optical Microscope ◽  
Visible Radiation ◽  
Field Methods ◽  
Optical Elements ◽  
Optical Region ◽  
Order Of Magnitude ◽  
Nondestructive Imaging ◽  
Scanning Optical Microscopy ◽  
Near Field Scanning

In general, conventional methods of optical imaging are limited in spatial resolution by either the wavelength of the radiation used or by the aberrations of the optical elements. This is true whether one uses a scanning probe or a fixed beam method. The reason for the wavelength limit of resolution is due to the far field methods of producing or detecting the radiation. If one resorts to restricting our probes to the near field optical region, then the possibility exists of obtaining spatial resolutions more than an order of magnitude smaller than the optical wavelength of the radiation used. In this paper, we will describe the principles underlying such "near field" imaging and present some preliminary results from a near field scanning optical microscope (NS0M) that uses visible radiation and is capable of resolutions comparable to an SEM. The advantage of such a technique is the possibility of completely nondestructive imaging in air at spatial resolutions of about 50nm.

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