scholarly journals Perspective on the Response of Turbulent Pipe Flows to Strong Perturbations

Fluids ◽  
2021 ◽  
Vol 6 (6) ◽  
pp. 208
Author(s):  
Liuyang Ding ◽  
Tyler Van Buren ◽  
Ian E. Gunady ◽  
Alexander J. Smits
Keyword(s):  
Pipe Flow ◽  
Abrupt Change ◽  
Pipe Wall ◽  
Surface Condition ◽  
Initial Response ◽  
Body Of Revolution ◽  
Future Directions ◽  
Pipe Flows ◽  
Roughness Elements ◽  
Pipe Geometry

Pipe flow responds to strong perturbations in ways that are fundamentally different from the response exhibited by boundary layers undergoing a similar perturbation, primarily because of the confinement offered by the pipe wall, and the need to satisfy continuity. We review such differences by examining previous literature, with a particular focus on the response of pipe flow to three different kinds of disturbances: the abrupt change in surface condition from rough to smooth, the obstruction due to presence of a single square bar roughness elements of different sizes, and the flow downstream of a streamlined body-of-revolution placed on the centerline of the pipe. In each case, the initial response is strongly influenced by the pipe geometry, but far downstream all three flows display a common feature, which is the very slow, second-order recovery that can be explained using a model based on the Reynolds stress equations. Some future directions for research are also given.

Laminar Forced Convection Over Rotating Bodies

1974 ◽  
Vol 96 (4) ◽  
pp. 463-466 ◽  
Author(s):  
B. T. Chao ◽  
R. Greif
Keyword(s):  
Mass Transfer ◽  
Forced Convection ◽  
Schmidt Number ◽  
Surface Condition ◽  
Computational Procedure ◽  
Body Of Revolution ◽  
Nonuniform Surface ◽  
Rotating Body ◽  
Laminar Forced Convection ◽  
Rotating Bodies

A simple computational procedure is described for ascertaining the heat or mass transfer in laminar forced convection over a rotating body of revolution. The analysis is applicable to nonuniform surface condition and for fluids having a large or a moderate value of the Prandtl (Schmidt) number. Examples are given to illustrate the usefulness of the analysis as well as to expose its limitation.

Mean Flow Downstream of Two-Dimensional Roughness Elements

1989 ◽  
Vol 111 (2) ◽  
pp. 149-153 ◽  
Author(s):  
E. Logan ◽  
P. Phataraphruk
Keyword(s):  
Reynolds Number ◽  
Cross Section ◽  
Pipe Flow ◽  
Rectangular Cross Section ◽  
Roughness Element ◽  
Two Dimensional ◽  
Hot Wire ◽  
Mean Flow ◽  
Roughness Elements ◽  
Three Stages

The response of a fully developed pipe flow to wall mounted roughness elements of rectangular cross section was investigated experimentally using a probe with a single hot-wire. Four heights of rectangular, ring-type elements were installed rigidly in a 63.5-mm diameter, smooth-walled, circular pipe in which air was flowing at a Reynolds number of 50,000. After passing over the roughness element, the flow recovery occurred in three stages. The three flow regions are delineated, and the velocity profiles for each are correlated.

scholarly journals Boundary Layer Control by Means of Strong Injection

1984 ◽  
Vol 51 (1) ◽  
pp. 27-34 ◽  
Author(s):  
R.-J. Yang ◽  
M. Holt
Keyword(s):  
Pipe Flow ◽  
Pipe Wall ◽  
Flow System ◽  
Wall Jet ◽  
Direction Parallel ◽  
Coal Gas ◽  
Coal Gasifier ◽  
Gas Products ◽  
Strong Injection ◽  
Layer Control

The gas mixture produced by coal gasifier contains components that have serious corrosive effects on the walls of the pipe flow system. To reduce these, a non-corrosive gas is injected into the stream of the coal gas products, in a direction parallel to the pipe wall. The interaction between the injected stream and the original pipe flow is investigated analytically and is an example of the so-called Wall Jet Problem.

Laminar-To-Turbulent Transition on a Body of Revolution With an Extended Favorable Pressure Gradient Forebody

1984 ◽  
Vol 106 (2) ◽  
pp. 202-210 ◽  
Author(s):  
R. J. Hansen ◽  
J. G. Hoyt
Keyword(s):  
Boundary Layer ◽  
Pressure Gradient ◽  
The Body ◽  
Boundary Layer Transition ◽  
Single Element ◽  
Body Of Revolution ◽  
Laminar To Turbulent Transition ◽  
Turbulent Transition ◽  
Roughness Elements ◽  
Favorable Pressure Gradient

An experimental study of the laminar-to-turbulent transition and resulting hydrodynamic forces on a body of revolution with a long, favorable pressure gradient forebody (i.e., where pressure is dropping and the flow accelerating) is reported. Over a substantial range of body velocity and angle of attack the favorable pressure gradient is shown to postpone transition to the point of laminar separation, and this extended laminar region results in a much lower hydrodynamic drag than is characteristic of an all-turbulent body. The intermittency of the boundary layer and the propagation characteristics of turbulent spots in the extended favorable pressure gradient region are quantified by hot film probes mounted flush with the body surface. The sensitivity of the boundary layer transition to three-dimensional surface roughness elements located in tandem (along a streamline) is also quantified. A number of such elements in tandem causes transition at a lower Reynolds number than would a single element of the same size, this effect becoming more pronounced with increasing number of roughness elements and decreasing space between them.

Identification of Transition to Turbulence in a Highly Accelerated Start-Up Pipe Flow

2005 ◽  
Vol 128 (4) ◽  
pp. 680-686 ◽  
Author(s):  
T. Koppel ◽  
L. Ainola
Keyword(s):  
Pipe Flow ◽  
Laplace Transformation ◽  
Transformation Method ◽  
Transition To Turbulence ◽  
Unsteady Boundary Layer ◽  
Physical Explanation ◽  
Pipe Flows ◽  
Flow Parameters ◽  
Start Up ◽  
Laplace Transformation Method

The transition from a laminar to a turbulent flow in highly accelerated start-up pipe flows is described. In these flows, turbulence springs up simultaneously over the entire length of the pipe near the wall. The unsteady boundary layer in the pipe was analyzed theoretically with the Laplace transformation method and the asymptotic method for small values of time. From the experimental results available, relationships between the flow parameters and the transition time were derived. These relationships are characterized by the analytical forms. A physical explanation for the regularities in the turbulence spring-up time is proposed.

scholarly journals Laminar-to-turbulent transition of pipe flows through puffs and slugs

2008 ◽  
Vol 614 ◽  
pp. 425-446 ◽  
Author(s):  
MINA NISHI ◽  
BÜLENT ÜNSAL ◽  
FRANZ DURST ◽  
GAUTAM BISWAS
Keyword(s):  
Reynolds Number ◽  
Pipe Flow ◽  
Axial Direction ◽  
Reynolds Numbers ◽  
Turbulent Pipe Flow ◽  
Test Facility ◽  
Pipe Flows ◽  
Laminar To Turbulent Transition ◽  
Turbulent Transition ◽  
Slug Flows

Laminar-to-turbulent transition of pipe flows occurs, for sufficiently high Reynolds numbers, in the form of slugs. These are initiated by disturbances in the entrance region of a pipe flow, and grow in length in the axial direction as they move downstream. Sequences of slugs merge at some distance from the pipe inlet to finally form the state of fully developed turbulent pipe flow. This formation process is generally known, but the randomness in time of naturally occurring slug formation does not permit detailed study of slug flows. For this reason, a special test facility was developed and built for detailed investigation of deterministically generated slugs in pipe flows. It is also employed to generate the puff flows at lower Reynolds numbers. The results reveal a high degree of reproducibility with which the triggering device is able to produce puffs. With increasing Reynolds number, ‘puff splitting’ is observed and the split puffs develop into slugs. Thereafter, the laminar-to-turbulent transition occurs in the same way as found for slug flows. The ring-type obstacle height, h, required to trigger fully developed laminar flows to form first slugs or puffs is determined to show its dependence on the Reynolds number, Re = DU/ν (where D is the pipe diameter, U is the mean velocity in the axial direction and ν is the kinematic viscosity of the fluid). When correctly normalized, h+ turns out to be independent of Reτ (where h+ = hUτ/ν, Reτ = DUτ/ν and $U_{\tau}\,{=}\,\sqrt{\tau_{w}/ \rho}$; τw is the wall shear stress and ρ is the density of the fluid).

scholarly journals Impact of Main Pipe Flow Velocity on Leakage and Intrusion Flow: An Experimental Study

Water ◽  
2019 ◽  
Vol 11 (1) ◽  
pp. 118 ◽  
Author(s):  
Yu Shao ◽  
Tian Yao ◽  
Jinzhe Gong ◽  
Jinjie Liu ◽  
Tuqiao Zhang ◽  
...  
Keyword(s):  
Flow Velocity ◽  
Pipe Flow ◽  
Pressure Difference ◽  
Discharge Coefficient ◽  
Pipe Wall ◽  
Technical Note ◽  
Opposite Pattern ◽  
Main Pipe ◽  
Pressurized Pipelines ◽  
The Impact

The classic orifice equation is commonly used to calculate the leakage and intrusion rate for pressurized pipelines with cracks on the pipe wall. The conventional orifice equation does not consider the effect of the flow velocity in the main pipe, and there is a lack of studies on this matter. For this technical note, the influence of the main pipe flow velocity on the outflow and inflow through a crack on the pipe wall was studied in the laboratory. The experimental results show that the impact of the main pipe flow velocity can be significant. When the pressure difference across the orifice was constant, with the increase of the main pipe flow velocity, the outflow velocity increased, but the contraction area of the jet and the outflow discharge coefficient decreased. By comparing orifices with different shapes, it was found that the discharge from the circumferential crack was most sensitive to the main pipe flow velocity. In addition, the main pipe flow promoted the orifice inflow. When the pressure difference across the orifice was constant, with the increase of the main pipe flow velocity, the inflow discharge coefficient increased, which is the opposite pattern to that of the orifice outflow.

Receptivity of pipe Poiseuille flow

1996 ◽  
Vol 315 ◽  
pp. 119-137 ◽  
Author(s):  
Anatoli Tumin
Keyword(s):  
Collocation Method ◽  
Poiseuille Flow ◽  
Chebyshev Polynomials ◽  
Pipe Flow ◽  
Pipe Wall ◽  
Numerical Procedure ◽  
Amplitude Distribution ◽  
Narrow Gap ◽  
Method Of Solution ◽  
Similar Character

The receptivity problem is considered for pipe flow with periodic blow–suction through a narrow gap in the pipe wall. Axisymmetric and non-axisymmetric modes (1, 2, and 3) are analysed. The method of solution is based on global eigenvalue analysis for spatially growing disturbances in circular pipe Poiseuille flow. The numerical procedure is formulated in terms of the collocation method with the Chebyshev polynomials application. The receptivity problem is solved with an expansion of the solution in a biorthogonal eigenfunction system, and it was found that there is an excitation of many eigenmodes, which should be taken into account. The result explains the non-similar character of the amplitude distribution in the downstream direction that was observed in experiments.

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