Frictional Effects in Unsteady Turbulent Pipe Flows

1997 ◽  
Vol 50 (11S) ◽  
pp. S241-S244 ◽  
Author(s):  
E. B. Wylie
Keyword(s):  
Reynolds Number ◽  
Turbulent Flow ◽  
Method Of Characteristics ◽  
Pipe Flows ◽  
The Method Of Characteristics ◽  
Viscous Losses ◽  
Oscillatory Response ◽  
Transient Events ◽  
Frictional Effects

In the simulation of rapid transient events in fluid-filled pipelines, the method of characteristics is recognized to provide reliable results during the first pressure excursion. However, if a long term oscillatory response of a rapid event is needed, traditional methods of evaluating viscous losses are inadequate in low Reynolds number turbulent flow events. This paper looks at a method to implement frequency-dependent viscous losses in the method of characteristics for turbulent flow and provides comparisons with experimental records.

scholarly journals Rapid Filling Analysis of Pipelines with Undulating Profiles by the Method of Characteristics

2011 ◽  
Vol 2011 ◽  
pp. 1-16 ◽  
Author(s):  
A. Malekpour ◽  
B. W. Karney
Keyword(s):  
Experimental Data ◽  
Method Of Characteristics ◽  
Computational Grid ◽  
Filling Process ◽  
Pipe System ◽  
The Method Of Characteristics ◽  
Proposed Model ◽  
Water Conveyance ◽  
Filling Analysis ◽  
Transient Events

On the premise of water hammer theory, a numerical model is proposed for simulating the filling process in an initially empty water conveyance pipeline with an undulating profile. Assuming that the pipeline remains full and ignoring air and water interactions in the already filled pipeline, the ongoing filling is simulated using the method of characteristics on an adaptive computational grid. The performance of the model is verified using previously published experimental and rigid column data. The model nicely replicates published experimental data. The model shows that the movement of the filling front into the system can be assumed as a rigid column as long as the flow away from the filling front is undisturbed elsewhere. Furthermore, applying the model to a hypothetical pipe system with an inline-partially open valve shows that the proposed model is robust enough to capture the transient events initiated within the moving column, a vital capability that the existing rigid water column models lack.

scholarly journals Small-scale universality in the spectral structure of transitional pipe flows

2020 ◽  
Vol 6 (4) ◽  
pp. eaaw6256
Author(s):  
Rory T. Cerbus ◽  
Chien-chia Liu ◽  
Gustavo Gioia ◽  
Pinaki Chakraborty
Keyword(s):  
Reynolds Number ◽  
Turbulent Flow ◽  
Turbulent Flows ◽  
Turbulence Theory ◽  
Small Scale ◽  
Spectral Structure ◽  
Pipe Flows ◽  
Wide Range ◽  
Small Scales

Turbulent flows are not only everywhere, but every turbulent flow is the same at small scales. The extraordinary simplification engendered by this “small-scale universality” is a hallmark of turbulence theory. However, on the basis of the restrictive assumptions invoked by A. N. Kolmogorov to demonstrate this universality, it is widely thought that only idealized turbulent flows conform to this framework. Using experiments and simulations that span a wide range of Reynolds number, we show that small-scale universality governs the spectral structure of a class of flows with no apparent ties to the idealized flows: transitional pipe flows. Our results not only extend the universality of Kolmogorov’s framework beyond expectation but also establish an unexpected link between transitional pipe flows and Kolmogorovian turbulence.

scholarly journals Numerical modelling of unsteady turbulent flow in tubes, including the effects of roughness and large changes in Reynolds number

2011 ◽  
Vol 225 (8) ◽  
pp. 1874-1885 ◽  
Author(s):  
D N Johnston
Keyword(s):  
Reynolds Number ◽  
Pipe Flow ◽  
Effective Viscosity ◽  
Method Of Characteristics ◽  
Turbulence Energy ◽  
Turbulent Friction ◽  
Pipe Flows ◽  
Lumped Parameter ◽  
Lumped Parameter Models ◽  
Long Time

A method has been developed for predicting unsteady turbulent friction in smooth, transitional, and rough pipe flows. For transitional and rough pipe flows the effective viscosity at the wall is varied depending on Reynolds number and roughness. An approximation has been made for the transition region using a cubic spline for the friction factor between the smooth and rough regions. This turbulence model can be implemented readily in several types of numerical model for pipe flow, including simple lumped parameter models, finite difference/finite element methods, and the method of characteristics. An approximate method for representing changes in turbulence energy is discussed. Using this, the method is suitable for small and large changes in flow, and for short and long time scales, but further validation is needed.

Numerical and Experimental Analysis of Turbulent Flow in Corrugated Pipes

2010 ◽  
Vol 132 (7) ◽  
Author(s):  
Henrique Stel ◽  
Rigoberto E. M. Morales ◽  
Admilson T. Franco ◽  
Silvio L. M. Junqueira ◽  
Raul H. Erthal ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Pressure Drop ◽  
Turbulent Flow ◽  
Friction Factor ◽  
Turbulence Models ◽  
Reynolds Numbers ◽  
Velocity Magnitude ◽  
Geometric Configurations ◽  
Corrugated Surfaces ◽  
Friction Factors

This article describes a numerical and experimental investigation of turbulent flow in pipes with periodic “d-type” corrugations. Four geometric configurations of d-type corrugated surfaces with different groove heights and lengths are evaluated, and calculations for Reynolds numbers ranging from 5000 to 100,000 are performed. The numerical analysis is carried out using computational fluid dynamics, and two turbulence models are considered: the two-equation, low-Reynolds-number Chen–Kim k-ε turbulence model, for which several flow properties such as friction factor, Reynolds stress, and turbulence kinetic energy are computed, and the algebraic LVEL model, used only to compute the friction factors and a velocity magnitude profile for comparison. An experimental loop is designed to perform pressure-drop measurements of turbulent water flow in corrugated pipes for the different geometric configurations. Pressure-drop values are correlated with the friction factor to validate the numerical results. These show that, in general, the magnitudes of all the flow quantities analyzed increase near the corrugated wall and that this increase tends to be more significant for higher Reynolds numbers as well as for larger grooves. According to previous studies, these results may be related to enhanced momentum transfer between the groove and core flow as the Reynolds number and groove length increase. Numerical friction factors for both the Chen–Kim k-ε and LVEL turbulence models show good agreement with the experimental measurements.

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