scholarly journals Closure to “Discussion of ‘The Mean Flow Structure on the Symmetry Plane of a Turbulent Junction Vortex’” (1990, ASME J. Fluids Eng., 112, p. 527)

1990 ◽  
Vol 112 (4) ◽  
pp. 527-528
Author(s):  
F. J. Pierce ◽  
I. K. Tree
Keyword(s):  
Flow Structure ◽  
Symmetry Plane ◽  
Mean Flow ◽  
The Mean

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.

Three-dimensional structure and momentum transfer in a turbulent cylinder wake

1999 ◽  
Vol 394 ◽  
pp. 303-337 ◽  
Author(s):  
A. VERNET ◽  
G. A. KOPP ◽  
J. A. FERRÉ ◽  
FRANCESC GIRALT
Keyword(s):  
Velocity Field ◽  
Saddle Point ◽  
Three Dimensional ◽  
Symmetry Plane ◽  
Half Width ◽  
Small Scale ◽  
Spanwise Direction ◽  
Mean Flow ◽  
Mean Velocity ◽  
The Mean

Simultaneous velocity and temperature measurements were made with rakes of sensors that sliced a slightly heated turbulent wake in the spanwise direction, at different lateral positions 150 diameters downstream of the cylinder. A pattern recognition analysis of hotter-to-colder transitions was performed on temperature data measured at the mean velocity half-width. The velocity data from the different ‘slices’ was then conditionally averaged based on the identified temperature events. This procedure yielded the topology of the average three-dimensional large-scale structure which was visualized with iso-surfaces of negative values of the second eigenvector of [S2+Ω2]. The results indicate that the average structure of the velocity fluctuations (using a triple decomposition of the velocity field) is found to be a shear-aligned ring-shaped vortex. This vortex ring has strong outward lateral velocities in its symmetry plane which are like Grant's mixing jets. The mixing jet region extends outside the ring-like vortex and is bounded by two foci separated in the spanwise direction and an upstream saddle point. The two foci correspond to what has been previously identified in the literature as the double rollers.The ring vortex extracts energy from the mean flow by stretching in the mixing jet region just upstream of the ring boundary. The production of the small-scale (incoherent) turbulence by the coherent field and one-component energy dissipation rate occur just downstream of the saddle point within the mixing jet region. Incoherent turbulence energy is extracted from the mean flow just outside the mixing jet region, but within the core of the structure. These processes are highly three-dimensional with a spanwise extent equal to the mean velocity half-width.When a double decomposition is used, the coherent structure is found to be a tube-shaped vortex with a spanwise extent of about 2.5l0. The double roller motions are integral to this vortex in spite of its shape. Spatial averages of the coherent velocity field indicate that the mixing jet region causes a deficit of mean streamwise momentum, while the region outside the foci of the double rollers has a relatively small excess of streamwise momentum.

Characteristics of Turbulent Three-Dimensional Offset Jets

2011 ◽  
Vol 133 (5) ◽  
Author(s):  
M. Agelin-Chaab ◽  
M. F. Tachie
Keyword(s):  
Three Dimensional ◽  
Symmetry Plane ◽  
Outer Region ◽  
Decay Rates ◽  
Wall Region ◽  
Mean Flow ◽  
Particle Image Velocimetry Technique ◽  
Similar Region ◽  
The Mean ◽  
Turbulence Transport

Three-dimensional turbulent offset jets were investigated using a particle image velocimetry technique. Three jet exit Reynolds numbers, Rej = 5000, 10,000, and 20,000, and four offset heights, h/d = 0.5, 1.0, 2.0, and 4.0, were studied. The mean flow and turbulence statistics were studied over larger downstream distances than in previous studies. The decay and spread rates were found to be nearly independent of Reynolds number and offset height at certain exit diameters (x = 73d) downstream and h/d ≤ 2. The decay rates of 1.18 ± 0.03 and spread rates of 0.055 ± 0.001 and 0.250 ± 0.005 in the wall-normal and lateral directions were obtained, respectively. The reattachment lengths are also independent of Rej but increase with offset height. The locations of the maximum mean velocities increased linearly with streamwise distance in the self-similar region. It was observed that profiles of the mean velocities, turbulence intensities, and Reynolds shears stresses are nearly independent of Rej and h/d far downstream. The triple products in the symmetry plane indicated turbulence transport from the outer region of the jet towards the wall region.

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.

The Mean Flow Structure on the Symmetry Plane of a Turbulent Junction Vortex

1990 ◽  
Vol 112 (1) ◽  
pp. 16-22 ◽  
Author(s):  
F. J. Pierce ◽  
I. K. Tree
Keyword(s):  
Velocity Field ◽  
Vortex Structure ◽  
Symmetry Plane ◽  
Leading Edge ◽  
Surface Flow ◽  
The Body ◽  
Mean Flow ◽  
Velocity Measurements ◽  
Vortex System ◽  
The Mean

The mean flow structure on the symmetry plane of a turbulent junction vortex is documented. A two-channel, two-color LDV system allowed nonintrusive measurements of the two velocity components on the symmetry plane. Extensive measurements were made in and around the separation point and within the junction vortex system, both very close to the floor and to the leading edge of the body generating the vortex system. Real-time smoke visualizations confirmed a region of strongly time-variant flow with large changes in the scale and position of the principal vortex structure. The extensive velocity field data are correlated with high quality surface visualizations and surface pressure measurements. The mean velocity measurements show one large well-defined vortex structure and one singular saddle point of separation on the symmetry plane. The transverse vorticity field computed from the extensive velocity field suggests a very strong but small second, counter rotating vortex located in the extreme corner formed by the floor and leading edge of the body. The surface flow visualization suggests only one clear separation line. The single pair of counter rotating vortices revealed by these detailed LDV velocity measurements is in agreement with two independent studies which used multiple orifice pressure probes. This measured two vortex model is not in agreement with the frequently pictured four vortex flow model, inferred from surface flow visualizations, showing two pairs of counter rotating vortices.

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