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.

Effects of Nanoparticles and Polymer Additives in Turbulent Pipe Flow

2010 ◽  
Author(s):  
Alparslan Oztekin ◽  
Sudhakar Neti ◽  
Ananchai Ukaew
Keyword(s):  
Heat Transfer ◽  
Drag Reduction ◽  
Pipe Flow ◽  
Turbulent Pipe Flow ◽  
Polymer Additives ◽  
Turbulent Structures ◽  
Heat Transfer Fluids ◽  
Pressure And Velocity Measurements ◽  
Nanosilica Particles ◽  
Elongated Nanoparticles

Spatial and temporal characteristics of turbulent pipe flows using nanofluids and dilute polymer solutions are examined by means of instantaneous differential pressure and velocity measurements. Spherical and elongated nanosilica particles (SiO2) are mixed into water to make nanofluid and polyacrylamide (PAC) is dissolved into water to make PAC solution. The effects of nanofluid on the drag reduction and turbulent structure are determined and compared with the effects of polymer additives on the turbulent structures and drag reduction. Suppression of turbulence near pipe wall was observed with the introduction of both spherical and elongated nanoparticles. Although experimental results show that nanofluids are not candidates for drag reduction unlike polymer additives, they do not increase pressure drop. Hence addition of nanoparticles into heat transfer fluids could have the potential for heat transfer enhancement in pipe flow without paying the penalty of increasing pumping power.

scholarly journals MATHEMATICAL MODEL TO INVESTIGATE THE DRAG REDUCTION OF KEROSENE WITH POLYMER UNDER TURBULENT FLOW

2019 ◽  
Vol 18 (4) ◽  
pp. 577-588
Author(s):  
Adil A Alwan ◽  
Ali J Mohammad
Keyword(s):  
Pressure Drop ◽  
Drag Reduction ◽  
Flow Rate ◽  
Pipe Flow ◽  
Volume Flow Rate ◽  
Polymer Concentration ◽  
Flow Region ◽  
Two Dimensions ◽  
Turbulent Pipe Flow ◽  
Effective Density

This paper present a mathematical study on drag reduction by polymer additive suchas poly isobutylene (PIB) with kerosene in turbulent pipe flow by using computational fluiddynamic commercial package program (COMSOL 4.4) solution. Theoretically thecomputational study was used to calculate the pressure drop in two dimensions geometricmodel with 6m length and 80 mm width as a diameter of the pipe, Geometric shape has beendrawing by tools of the program windows, and to simulated the flow region mathematicallythe flow region is divide into very small parts (mesh generation). The model that used in themathematical modelling method was (k-?( mathematical turbulent model to study theinternal pipe flow properties. The continuity and momentum equations and two k-? modelequations have been solved by the program to obtain the theoretical results. There variablesthat used in the theoretical study were effective density, effective viscosity, inlet velocity,and outlet pressure. The boundary condition was inlet and outlet velocity, temperature, andpressure of flow, and the velocity (u=0) at the pipe wall. The theoretical calculations showthat the velocity and drag reduction percentage increases with polymer concentration andvolume flow rate increasing where maximum DR% is 15.8% at volume flow rate 500 ??minwith polymer concentration 100 ppm, pressure drop decreases with polymer concentrationincreasing. Friction factor decreases with polymer concentration increased, also shear stressdecrease with polymer concentration increasing.

Drag reduction by polymer additives in a turbulent pipe flow: numerical and laboratory experiments

1997 ◽  
Vol 337 ◽  
pp. 193-231 ◽  
Author(s):  
J. M. J. DEN TOONDER ◽  
M. A. HULSEN ◽  
G. D. C. KUIKEN ◽  
F. T. M. NIEUWSTADT
Keyword(s):  
Numerical Simulation ◽  
Drag Reduction ◽  
Pipe Flow ◽  
Viscoelastic Model ◽  
Power Spectra ◽  
Turbulent Pipe Flow ◽  
Polymer Additives ◽  
Fourth Moment ◽  
Polymer Model ◽  
Turbulence Statistics

In order to study the roles of stress anisotropy and of elasticity in the mechanism of drag reduction by polymer additives we investigate a turbulent pipe flow of a dilute polymer solution. The investigation is carried out by means of direct numerical simulation (DNS) and laser Doppler velocimetry (LDV). In our DNS two different models are used to describe the effects of polymers on the flow. The first is a constitutive equation based on Batchelor's theory of elongated particles suspended in a Newtonian solvent which models the viscous anisotropic effects caused by the polymer orientation. The second is an extension of the first model with an elastic component, and can be interpreted as an anisotropic Maxwell model. The LDV experiments have been carried out in a recirculating pipe flow facility in which we have used a solution of water and 20 w.p.p.m. Superfloc A110. Turbulence statistics up to the fourth moment, as well as power spectra of various velocity components, have been measured. The results of the drag-reduced flow are first compared with those of a standard turbulent pipe flow of water at the same friction velocity at a Reynolds number of Reτ≈1035. Next the results of the numerical simulation and of the measurements are compared in order to elucidate the role of polymers in the phenomenon of drag reduction. For the case of the viscous anisotropic polymer model, almost all turbulence statistics and power spectra calculated agree in a qualitative sense with the measurements. The addition of elastic effects, on the other hand, has an adverse effect on the drag reduction, i.e. the viscoelastic polymer model shows less drag reduction than the anisotropic model without elasticity. Moreover, for the case of the viscoelastic model not all turbulence statistics show the right behaviour. On the basis of these results, we propose that the viscous anisotropic stresses introduced by extended polymers play a key role in the mechanism of drag reduction by polymer additives.

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.

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