Experimental correlation for pipe flow drag reduction using relaxation time of linear flexible polymers in a dilute solution

2019 ◽  
Vol 98 (3) ◽  
pp. 792-803 ◽  
Author(s):  
Xin Zhang ◽  
Xili Duan ◽  
Yuri Muzychka ◽  
Zongming Wang
Keyword(s):  
Relaxation Time ◽  
Drag Reduction ◽  
Pipe Flow ◽  
Dilute Solution ◽  
Flexible Polymers ◽  
Experimental Correlation ◽  
Flow Drag

Predicting Drag Reduction in Turbulent Pipe Flow With Relaxation Time of Polymer Additives

2018 ◽  
Author(s):  
Xin Zhang ◽  
Xili Duan ◽  
Yuri Muzychka ◽  
Zongming Wang
Keyword(s):  
Experimental Data ◽  
Relaxation Time ◽  
Drag Reduction ◽  
Pipe Flow ◽  
Polymer Concentration ◽  
Weissenberg Number ◽  
Turbulent Pipe Flow ◽  
Dimensionless Number ◽  
Polymer Additives ◽  
Dilute Solution

This paper presents an experimental study on drag reduction induced by PEO (Polyethylene oxide) in a fully turbulent pipe flow. The objective of this work is to develop a correlation to predict drag reduction using the relaxation time of the polymer additives under dilute solution conditions, i.e., the polymer concentration is less than the overlap concertation. This paper discusses the meaning of relaxation time of polymers, and why the Weissenberg number, a dimensionless number that is related to the relaxation time and shear rate, is independent on the concentration in the dilute solution. Experimental data of drag reduction in a pipe flow are obtained from measurements using a flow loop. A correlation to predict drag reduction with the Weissenberg number and polymer concentration is established and a good agreement is shown between the predicted values and experimental data. The new correlation using the Weissenberg number and polymer concentration is shown to cost less to develop than one using the Reynolds number, in which larger pipes or higher flow rates are required.

Analytical Upper Limit of Drag Reduction With Polymer Additives in Turbulent Pipe Flow

2018 ◽  
Vol 140 (5) ◽  
Author(s):  
Xin Zhang ◽  
Xili Duan ◽  
Yuri Muzychka
Keyword(s):  
Mathematical Model ◽  
Drag Reduction ◽  
Pipe Flow ◽  
Critical Concentration ◽  
Turbulent Pipe Flow ◽  
Chemical Additives ◽  
Upper Limit ◽  
Maximum Drag Reduction ◽  
Flow Drag ◽  
Nonlinear Elastic

Flow drag reduction induced by chemical additives, more commonly called drag-reducing agents (DRAs), has been studied for many years, but few studies can manifest the mechanism of this phenomenon. In this paper, a new mathematical model is proposed to predict the upper limit of drag reduction with polymer DRAs in a turbulent pipe flow. The model is based on the classic finitely extensible nonlinear elastic-Peterlin (FENE-P) theory, with the assumption that all vortex structures disappear in the turbulent flow, i.e., complete laminarization is achieved. With this model, the maximum drag reduction by a DRA at a given concentration can be predicted directly with several parameters, i.e., bulk velocity of the fluid, pipe size, and relaxation time of the DRA. Besides, this model indicates that both viscosity and elasticity contribute to the drag reduction: before a critical concentration, both viscosity and elasticity affect the drag reduction positively; after this critical concentration, elasticity still works as before but viscosity affects drag reduction negatively. This study also proposes a correlation format between drag reduction measured in a rheometer and that estimated in a pipeline. This provides a convenient way of pipeline drag reduction estimation with viscosity and modulus of the fluids that can be easily measured in a rheometer.

scholarly journals A note to further explain the mechanism of turbulent flow drag reduction by polymer from chemistry view

2021 ◽  
Author(s):  
Xin Zhang ◽  
Xiaodong Dai ◽  
Jishi Zhao ◽  
Dengwei Jing ◽  
Fei Liu ◽  
...  
Keyword(s):  
Fourier Series ◽  
Turbulent Flow ◽  
Drag Reduction ◽  
Phase Angle ◽  
Linear Polymers ◽  
Flexible Polymers ◽  
Viscoelastic Theory ◽  
Maximum Drag Reduction ◽  
Flow Drag ◽  
Drag Reducing Polymer

In our previous work regarding the mechanism of drag reduction and degradation by flexible linear polymers, we proposed a correlation based on the Fourier series to predict the drag reduction and its degradation, where a phase angle was involved, but the physical meaning for the correlation especially of the employed phase angle was not clear, which is however important for reasonable explanation of the drag reduction mechanism over flexible linear polymers. This letter aims to clarify this issue. We use several steps of deduction from the viscoelastic theory, and conclude that the Fourier series employed to predict the drag reduction and its degradation is due to viscoelastic property of drag-reducing polymer solution, and the phase angle represents the hysteresis of polymer in turbulent flow. Besides, our new view of drag reduction by flexible polymers can also explain why a maximum drag reduction in rotational flow appears before degradation happens.

Pipe flow drag reduction effects from carbon nanotube additives

Carbon ◽  
2014 ◽  
Vol 77 ◽  
pp. 1183-1186 ◽  
Author(s):  
Adam Steele ◽  
Ilker S. Bayer ◽  
Eric Loth
Keyword(s):  
Carbon Nanotube ◽  
Drag Reduction ◽  
Pipe Flow ◽  
Flow Drag

Modelling the new stress for improved drag reduction predictions of viscoelastic pipe flow

2004 ◽  
Vol 121 (2-3) ◽  
pp. 127-141 ◽  
Author(s):  
D.O.A. Cruz ◽  
F.T. Pinho ◽  
P.R. Resende
Keyword(s):  
Drag Reduction ◽  
Pipe Flow

scholarly journals Dynamics of viscoelastic pipe flow at low Reynolds numbers in the maximum drag reduction limit

2019 ◽  
Vol 874 ◽  
pp. 699-719 ◽  
Author(s):  
Jose M. Lopez ◽  
George H. Choueiri ◽  
Björn Hof
Keyword(s):  
Drag Reduction ◽  
Turbulent Flows ◽  
Pipe Flow ◽  
Domain Size ◽  
Reynolds Numbers ◽  
Weissenberg Number ◽  
Pipe Length ◽  
Low Reynolds Numbers ◽  
Maximum Drag Reduction ◽  
Low Reynolds

Polymer additives can substantially reduce the drag of turbulent flows and the upper limit, the so-called state of ‘maximum drag reduction’ (MDR), is to a good approximation independent of the type of polymer and solvent used. Until recently, the consensus was that, in this limit, flows are in a marginal state where only a minimal level of turbulence activity persists. Observations in direct numerical simulations at low Reynolds numbers ($Re$) using minimal sized channels appeared to support this view and reported long ‘hibernation’ periods where turbulence is marginalized. In simulations of pipe flow at $Re$ near transition we find that, indeed, with increasing Weissenberg number ($Wi$), turbulence expresses long periods of hibernation if the domain size is small. However, with increasing pipe length, the temporal hibernation continuously alters to spatio-temporal intermittency and here the flow consists of turbulent puffs surrounded by laminar flow. Moreover, upon an increase in $Wi$, the flow fully relaminarizes, in agreement with recent experiments. At even larger $Wi$, a different instability is encountered causing a drag increase towards MDR. Our findings hence link earlier minimal flow unit simulations with recent experiments and confirm that the addition of polymers initially suppresses Newtonian turbulence and leads to a reverse transition. The MDR state on the other hand results at these low$Re$ from a separate instability and the underlying dynamics corresponds to the recently proposed state of elasto-inertial turbulence.

scholarly journals Effects of Side Walls on Pipe Inlet Flow (Drag Reduction by Separated Flow Control Using Ring Shaped Small Obstacle)

2009 ◽  
Vol 4 (2) ◽  
pp. 468-478 ◽  
Author(s):  
Toshitake ANDO ◽  
Toshihiko SHAKOUCHI ◽  
Hiroyuki YAMAMOTO ◽  
Koichi TSUJIMOTO
Keyword(s):  
Drag Reduction ◽  
Flow Control ◽  
Separated Flow ◽  
Inlet Flow ◽  
Side Walls ◽  
Flow Drag ◽  
Small Obstacle ◽  
Pipe Inlet
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