Structures of Confined Vortex Breakdown in Constant Diameter Pipe Flow

2009 ◽  
Vol 21 (3) ◽  
pp. 341-346 ◽  
Author(s):  
Ze Wang ◽  
Shan-qun Chen
Keyword(s):  
Pipe Flow ◽  
Vortex Breakdown ◽  
Constant Diameter ◽  
Diameter Pipe

scholarly journals Numerical and experimental investigation of leaks in viscoelastic pressurized pipe flow

2013 ◽  
Vol 6 (1) ◽  
pp. 11-16 ◽  
Author(s):  
S. Meniconi ◽  
B. Brunone ◽  
M. Ferrante ◽  
C. Massari
Keyword(s):  
Experimental Investigation ◽  
Cross Section ◽  
Pipe Flow ◽  
Laboratory Experiments ◽  
Numerical Models ◽  
External Flow ◽  
Constant Diameter ◽  
Diameter Pipe ◽  
In Series ◽  
The University

Abstract. This paper extends the analysis concerning the importance in numerical models of unsteady friction and viscoelasticity to transients in plastic pipes with an external flow due to a leak. In fact recently such a benchmarking analysis has been executed for the cases of a constant diameter pipe (Duan et al., 2010), a pipe with a partially closed in-line valve (Meniconi et al., 2012a), and a pipe with cross-section changes in series (Meniconi et al., 2012b). Tests are based on laboratory experiments carried out at the Water Engineering Laboratory (WEL) of the University of Perugia, Italy, and the use of different numerical models. The results show that it is crucial to take into account the viscoelasticity to simulate the main characteristics of the examined transients.

scholarly journals Transient Behavior of Vortical Flow through a Constant Diameter Pipe

2001 ◽  
Vol 13 (9) ◽  
pp. S8-S8 ◽  
Author(s):  
T. W. Mattner ◽  
M. S. Chong ◽  
P. N. Joubert
Keyword(s):  
Transient Behavior ◽  
Vortical Flow ◽  
Constant Diameter ◽  
Diameter Pipe ◽  
Flow Through

Drag Reduction by Culture Solutions of Dry Malted Rice

2009 ◽  
Author(s):  
Keizo Watanabe ◽  
Satoshi Ogata
Keyword(s):  
Drag Reduction ◽  
Pipe Flow ◽  
Reynolds Numbers ◽  
Type B ◽  
Turbulent Drag Reduction ◽  
Turbulent Drag ◽  
Diameter Pipe ◽  
Maximum Drag Reduction ◽  
Inner Diameter ◽  
Biopolymer Solutions

Turbulent drag reduction by culture solutions of dry malted rice was investigated in a 2.00mm-inner-diameter pipe flow of length 50 diameters at Reynolds numbers from 500 to 8000. The drag reducing abilities of the solutions were tested by comparing drag reduction effectiveness at different concentrations and culture times in water. Comparisons between polysaccharide biopolymer solutions and culture solutions of dry malted rice revealed that the test solutions exhibited Type B drag reduction, which were roughly parallel to, but displaced upwards from, the Newtonian Prandtl-Ka´rma´n law. The maximum drag reduction ration was about 30% at a Reynolds number of 8,000. It is shown also that the onset point of drag reduction phenomena was Ref = 200.

The Preston tube as a means of measuring skin friction

1962 ◽  
Vol 14 (1) ◽  
pp. 1-17 ◽  
Author(s):  
M. R. Head ◽  
I. Rechenberg
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Skin Friction ◽  
Pipe Flow ◽  
Large Diameter ◽  
Turbulent Pipe Flow ◽  
Pitot Tube ◽  
Diameter Pipe ◽  
Flow Similarity ◽  
Considerable Doubt

Preston's method of measuring skin friction, which makes use of a Pitot tube resting on the surface, depends upon the assumption of a region of flow similarity, adjacent to the wall, common to fully developed turbulent pipe flow and the turbulent boundary layer. Experiments performed elsewhere have cast considerable doubt on the validity of this assumption, and the present investigation was undertaken to establish whether or not it is justified.Experiments were carried out in a short length of large-diameter pipe which could either form part of a very much longer pipe, giving fully developed turbulent pipe flow, or could be preceded by a conventional contraction and screens, giving a developing turbulent boundary layer.Final results showed that for a given skin friction the Pitot tube reading was the same for both boundary layer and pipe flows, thus vindicating Preston's method and confirming the existence of a universal region of wall similarity. Initial experimental difficulties were found to be due to unexpectedly large circumferential variations in skin friction in the growing boundary layer.

scholarly journals Parametric study of cone angle influence on bubble vortex breakdown onset in laminar conical flow at various swirl numbers

2021 ◽  
Vol 2119 (1) ◽  
pp. 012019
Author(s):  
S G Skripkin
Keyword(s):  
Pipe Flow ◽  
Vortex Breakdown ◽  
Cone Angle ◽  
Working Fluid ◽  
Opening Angle ◽  
Nonlinear Relationship ◽  
Conical Flow ◽  
Swirl Number ◽  
Flow Swirl ◽  
Two Parameters

Abstract The current work studies a swirling laminar viscous pipe flow with a controllable swirl number and varying pipe divergence cone angle. Such flows are widely used in various engineering applications. When a certain level of flow swirl is reached, a phenomenon called vortex breakdown occurs, the characteristics of which depend on the intensity of swirling of the flow and the Reynolds number. However, in addition to these two parameters, an important influence is exerted by the pipe opening angle, which often does not allow generalizing the results obtained in the pipe flow with even slightly different angles. Since experimentally it is quite difficult and expensive to change the pipe angle, especially considering the water as working fluid, this issue could be solved using CFD techniques. Using the design study, 63 different combinations of S and α are considered. The effect of the pipe divergence angle on the position of the bubble vortex breakdown and its properties is demonstrated. It is shown that there is a nonlinear relationship between the position of the bubble breakdown onset and the minimum value of the axial velocity at the axis depending on the opening angle of the cone.

scholarly journals Vortical flow. Part 2. Flow past a sphere in a constant-diameter pipe

2003 ◽  
Vol 481 ◽  
pp. 1-36 ◽  
Author(s):  
T. W. MATTNER ◽  
P. N. JOUBERT ◽  
M. S. CHONG
Keyword(s):  
Vortical Flow ◽  
Flow Past ◽  
Constant Diameter ◽  
Diameter Pipe ◽  
Flow Part ◽  
Flow Past A Sphere

scholarly journals Vortical flow. Part 1. Flow through a constant-diameter pipe

2002 ◽  
Vol 463 ◽  
pp. 259-291 ◽  
Author(s):  
T. W. MATTNER ◽  
P. N. JOUBERT ◽  
M. S. CHONG
Keyword(s):  
Axial Velocity ◽  
Test Section ◽  
Velocity Profiles ◽  
Vortical Flow ◽  
Outer Flow ◽  
Spiral Vortex ◽  
Constant Diameter ◽  
Diameter Pipe ◽  
Flow Through ◽  
Streamwise Distance

This paper describes an exploration of the behaviour and properties of swirling flow through a constant-diameter pipe. The experiments reveal a complicated transition process as the swirl intensity Ω is increased at fixed pipe Reynolds number Re ≈ 4900. For Ω [les ] 1.09, the vortex was steady, laminar, axisymmetric, and developed slowly with streamwise distance. The upstream velocity profiles were similar to those commonly appearing in the literature in similar apparatus. Spiral vortex breakdown appeared in the test section for 1.09 [les ] Ω [les ] 1.31 and was associated with a localized transition from jet-like to wake-like mean axial velocity profiles. Further increase in Ω caused the breakdown to move upstream of the test section. Downstream, the core of the post-breakdown flow was unsteady and recovered toward jet-like profiles with streamwise distance. At Ω = 2.68, a global transition occurred in which the mean axial velocity profiles suddenly developed an annular axial velocity deficit. At the same time, disturbances began to appear in the outer flow. Further increase in Ω eventually led to an annulus of reversed axial flow and a completely unsteady vortex.

Nonlinear spiral waves in rotating pipe flow

1988 ◽  
Vol 190 ◽  
pp. 39-54 ◽  
Author(s):  
N. Toplosky ◽  
T. R. Akylas
Keyword(s):  
Pipe Flow ◽  
Vortex Breakdown ◽  
Reynolds Numbers ◽  
Finite Amplitude ◽  
Spiral Waves ◽  
Slow Rotation ◽  
Mean Flow ◽  
Weakly Nonlinear ◽  
Mean Pressure ◽  
Rotating Pipe Flow

A numerical investigation of finite-amplitude, non-axisymmetric disturbances, in the form of travelling spiral waves, is made in pipe flow with superimposed solid-body rotation. Rotating pipe flow is found to be supercritically unstable both in the rapid and slow-rotation regimes. Earlier weakly nonlinear calculations, suggesting subcritical instability in the slow-rotation limit, are shown to be in error. Bifurcating neutral waves are calculated for various axial and azimuthal Reynolds numbers and wavenumbers. For fixed axial mean pressure gradient, the axial mean flow induced by these waves gives rise to a significant flux defect, in certain cases as large as 40-50% of the undisturbed mass flux; the possible relevance of this finding to the phenomenon of vortex breakdown is pointed out. In non-rotating pipe flow, no neutral disturbances in the assumed form of spiral waves are found for moderate Reynolds numbers; this indicates that previous conjectures, regarding a possible connection between nonlinear spiral waves in slowly rotating pipe flow and the asymptotic neutral states of Smith & Bodonyi (1982) in non-rotating pipe flow, are not valid.

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