Sensitivity to tab disturbance of the mean flow structure of nonswirling jet and swirling jet in crossflow

2005 ◽  
Vol 17 (4) ◽  
pp. 045102 ◽  
Author(s):  
Asi Bunyajitradulya ◽  
Sidtipong Sathapornnanon
Keyword(s):  
Flow Structure ◽  
Mean Flow ◽  
Jet In Crossflow ◽  
Swirling Jet ◽  
The Mean

The Ultimate Asymptote and Mean Flow Structure in Toms’ Phenomenon

1970 ◽  
Vol 37 (2) ◽  
pp. 488-493 ◽  
Author(s):  
P. S. Virk ◽  
H. S. Mickley ◽  
K. A. Smith
Keyword(s):  
Velocity Profile ◽  
Drag Reduction ◽  
Flow Structure ◽  
Viscous Sublayer ◽  
Mixing Length ◽  
Mean Flow ◽  
Mean Velocity ◽  
Law Of The Wall ◽  
Length Constant ◽  
The Mean

The maximum drag reduction in turbulent pipe flow of dilute polymer solutions is ultimately limited by a unique asymptote described by the experimental correlation: f−1/2=19.0log10(NRef1/2)−32.4 The semilogarithmic mean velocity profile corresponding to and inferred from this ultimate asymptote has a mixing-length constant of 0.085 and shares a trisection (at y+ ∼ 12) with the Newtonian viscous sublayer and law of the wall. Experimental mean velocity profiles taken during drag reduction lie in the region bounded by the inferred ultimate profile and the Newtonian law of the wall. At low drag reductions the experimental profiles are well correlated by an “effective slip” model but this fails progressively with increasing drag reduction. Based on the foregoing a three-zone scheme is proposed to model the mean flow structure during drag reduction. In this the mean velocity profile segments are (a) a viscous sublayer, akin to Newtonian, (b) an interactive zone, characteristic of drag reduction, in which the ultimate profile is followed, and (c) a turbulent core in which the Newtonian mixing-length constant applies. The proposed model is consistent with experimental observations and reduces satisfactorily to the Taylor-Prandtl scheme and the ultimate profile, respectively, at the limits of zero and maximum drag reductions.

scholarly journals On the impact of swirl on the growth of coherent structures

2014 ◽  
Vol 741 ◽  
pp. 156-199 ◽  
Author(s):  
K. Oberleithner ◽  
C. O. Paschereit ◽  
I. Wygnanski
Keyword(s):  
Stability Analysis ◽  
Coherent Structures ◽  
Large Scale ◽  
Vortex Breakdown ◽  
Shear Mode ◽  
Mean Flow ◽  
Swirling Jet ◽  
The Mean ◽  
The Impact ◽  
Helical Mode

AbstractSpatial linear stability analysis is applied to the mean flow of a turbulent swirling jet at swirl intensities below the onset of vortex breakdown. The aim of this work is to predict the dominant coherent flow structure, their driving instabilities and how they are affected by swirl. At the nozzle exit, the swirling jet promotes shear instabilities and, less unstable, centrifugal instabilities. The latter stabilize shortly downstream of the nozzle, contributing very little to the formation of coherent structures. The shear mode remains unstable throughout generating coherent structures that scale with the axial shear-layer thickness. The most amplified mode in the nearfield is a co-winding double-helical mode rotating slowly in counter-direction to the swirl. This gives rise to the formation of slowly rotating and stationary large-scale coherent structures, which explains the asymmetries in the mean flows often encountered in swirling jet experiments. The co-winding single-helical mode at high rotation rate dominates the farfield of the swirling jet in replacement of the co- and counter-winding bending modes dominating the non-swirling jet. Moreover, swirl is found to significantly affect the streamwise phase velocity of the helical modes rendering this flow as highly dispersive and insensitive to intermodal interactions, which explains the absence of vortex pairing observed in previous investigations. The stability analysis is validated through hot-wire measurements of the flow excited at a single helical mode and of the flow perturbed by a time- and space-discrete pulse. The experimental results confirm the predicted mode selection and corresponding streamwise growth rates and phase velocities.

Observations on turbulent-drag reduction in a dilute suspension of clay in sea-water

1976 ◽  
Vol 75 (1) ◽  
pp. 29-47 ◽  
Author(s):  
Giselher Gust
Keyword(s):  
Drag Reduction ◽  
Clay Mineral ◽  
Flow Structure ◽  
Sea Water ◽  
Streamwise Velocity ◽  
Viscous Sublayer ◽  
Mean Flow ◽  
Turbulent Drag Reduction ◽  
Turbulent Drag ◽  
The Mean

Hot-wire anemometer measurements have been made in a dilute sea-water/claymineral suspension. For fully developed turbulent flows in an open channel with a smooth mud (from the North Sea) bottom, mean streamwise velocity profiles were measured for Reynolds numbers between 5400 and 27 800 (i.e. non-eroding and eroding flow rates) and compared with Newtonian flows under the same experimental conditions. For the clay-mineral suspensions, measurements of the kinematic viscosityv, Kármán's constantkand the mean streamwise velocity$\overline{u}$of the logarithmic layer seemed to verify a Newtonian flow structure. Although the distributions of concentration showed no substantial increase towards the wall, it was found that beneath this Newtonian core there existed a viscous sublayer whose thickness was enhanced by a factor of 2–5. The friction velocityu*determined by the gradient method in the viscous sublayer was reduced by as much as 40 %. The mean flow structure exhibited an additional new layer in the region 10 <y+< 30.The measurements indicate that turbulent-drag reduction occurs for the experimental clay-mineral suspension at non-eroding and also at eroding velocities. Agglomeration of suspended clay-mineral particles is suggested as possible explanation of this phenomenon.

The Mean Flow Structure Around and Within a Turbulent Junction or Horseshoe Vortex—Part I: The Upstream and Surrounding Three-Dimensional Boundary Layer

1988 ◽  
Vol 110 (4) ◽  
pp. 406-414 ◽  
Author(s):  
J. D. Menna ◽  
F. J. Pierce
Keyword(s):  
Boundary Layer ◽  
Flow Structure ◽  
Vortex Flow ◽  
Three Dimensional ◽  
Horseshoe Vortex ◽  
Mean Flow ◽  
Complex Flow ◽  
Mean Velocity ◽  
Standard Case ◽  
The Mean

The mean flow structure upstream, around, and in a turbulent junction or horseshoe vortex is reported for an incompressible, subsonic flow. This fully documented, unified, comprehensive, and self-consistent data base is offered as a benchmark or standard case for assessing the predictive capabilities of computational codes developed to predict this kind of complex flow. Part I of these papers defines the total flow being documented. The upstream and surrounding three-dimensional turbulent boundary layer-like flow away from separation has been documented with mean velocity field and turbulent kinetic energy field measurements made with hot film anemometry, and local wall shear stress measurements. Data are provided for an initial condition plane well upstream of the junction vortex flow to initiate a boundary layer calculation, and freestream or edge velocity, as well as floor static pressure, are reported to proceed with the solution. Part II of these papers covers the flow through separation and within the junction vortex flow.

The Mean Flow Structure Around and Within a Turbulent Junction or Horseshoe Vortex—Part II. The Separated and Junction Vortex Flow

1988 ◽  
Vol 110 (4) ◽  
pp. 415-423 ◽  
Author(s):  
F. J. Pierce ◽  
M. D. Harsh
Keyword(s):  
Flow Structure ◽  
Vortex Flow ◽  
Static Pressure ◽  
Horseshoe Vortex ◽  
Cylinder Surface ◽  
Pressure Measurements ◽  
Mean Flow ◽  
Vortex System ◽  
Measured Velocity ◽  
The Mean

The mean flow structure upstream, around, and in a turbulent junction or horseshoe vortex are reported for an incompressible, subsonic flow. This fully documented, unified, comprehensive, and self-consistent data base is offered as a benchmark or standard test case for assessing the predictive capabilities of computational codes developed to predict this kind of complex flow. The three-dimensional turbulent boundary layer-like flow upstream and around the separated junction vortex flow is described in a companion paper, Part I. Part II of these papers covers the flow through the separation region and in the vortex system. This portion of the flow has been documented with mean velocity, static pressure, and total pressure measurements using a very carefully calibrated five-hole probe. The streamwise vorticity field is calculated from the measured velocity field. Extensive floor static pressure measurements emphasizing the region of the vortex system, and static pressure measurements on the cylinder surface are also reported. Flow visualizations on the floor and cylinder surface show unusual detail and agree well both qualitatively and quantitatively with the various flow field measurements.

Characterisation of the mean flow of a micro-injector induced swirling jet

2008 ◽  
Vol 5 (1) ◽  
pp. 51-58
Author(s):  
I K Toh ◽  
P O’Neill ◽  
D Honnery ◽  
J Soria
Keyword(s):  
Mean Flow ◽  
Swirling Jet ◽  
The Mean

Simple explicit model of liquid mean flow in region above axial impeller

1985 ◽  
Vol 50 (11) ◽  
pp. 2396-2410
Author(s):  
Miloslav Hošťálek ◽  
Ivan Fořt
Keyword(s):  
Vortex Flow ◽  
Flow Model ◽  
Quantitative Agreement ◽  
Mean Flow ◽  
Flat Bottom ◽  
Proposed Model ◽  
Minimum Number ◽  
The Mean ◽  
Model Equations ◽  
Radial Circulation

The study describes a method of modelling axial-radial circulation in a tank with an axial impeller and radial baffles. The proposed model is based on the analytical solution of the equation for vortex transport in the mean flow of turbulent liquid. The obtained vortex flow model is tested by the results of experiments carried out in a tank of diameter 1 m and with the bottom in the shape of truncated cone as well as by the data published for the vessel of diameter 0.29 m with flat bottom. Though the model equations are expressed in a simple form, good qualitative and even quantitative agreement of the model with reality is stated. Apart from its simplicity, the model has other advantages: minimum number of experimental data necessary for the completion of boundary conditions and integral nature of these data.

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