Drag reduction of combined effect of surfactant and microgrooves in a duct pipe flow

2021 ◽  
Author(s):  
Entian Li ◽  
Liutong Fan ◽  
Shidong Zhou ◽  
Xiaofang Lv ◽  
Pei Yao ◽  
...  
Keyword(s):  
Drag Reduction ◽  
Pipe Flow ◽  
Combined Effect

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 Degradation on Drag Reduction in Turbulent Pipe Flow of Nonionic Surfactant Aqueous Solutions

2012 ◽  
Vol 40 (2) ◽  
pp. 69-77 ◽  
Author(s):  
Shinji Tamano ◽  
Kotaro Miyagawa ◽  
Yohei Morinishi ◽  
Motoyuki Itoh ◽  
Keijiro Taga
Keyword(s):  
Aqueous Solutions ◽  
Drag Reduction ◽  
Nonionic Surfactant ◽  
Pipe Flow ◽  
Turbulent Pipe Flow

scholarly journals Stabilisation and drag reduction of pipe flows by flattening the base profile

2019 ◽  
Vol 863 ◽  
pp. 850-875 ◽  
Author(s):  
Elena Marensi ◽  
Ashley P. Willis ◽  
Rich R. Kerswell
Keyword(s):  
Drag Reduction ◽  
Nonlinear Stability ◽  
Pipe Flow ◽  
Body Force ◽  
Initial Conditions ◽  
Reynolds Numbers ◽  
Streamwise Velocity ◽  
The Body ◽  
Random Disturbance ◽  
Good Proxy

Recent experimental observations (Kühnen et al., Nat. Phys., vol. 14, 2018b, pp. 386–390) have shown that flattening a turbulent streamwise velocity profile in pipe flow destabilises the turbulence so that the flow relaminarises. We show that a similar phenomenon exists for laminar pipe flow profiles in the sense that the nonlinear stability of the laminar state is enhanced as the profile becomes more flattened. The flattening of the laminar base profile is produced by an artificial localised body force designed to mimic an obstacle used in the experiments of Kühnen et al. (Flow Turbul. Combust., vol. 100, 2018a, pp. 919–943) and the nonlinear stability measured by the size of the energy of the initial perturbations needed to trigger transition. Significant drag reduction is also observed for the turbulent flow when triggered by sufficiently large disturbances. In order to make the nonlinear stability computations more efficient, we examine how indicative the minimal seed – the disturbance of smallest energy for transition – is in measuring transition thresholds. We first show that the minimal seed is relatively robust to base profile changes and spectral filtering. We then compare the (unforced) transition behaviour of the minimal seed with several forms of randomised initial conditions in the range of Reynolds numbers $Re=2400$–$10\,000$ and find that the energy of the minimal seed after the Orr and oblique phases of its evolution is close to that of a critical localised random disturbance. In this sense, the minimal seed at the end of the oblique phase can be regarded as a good proxy for typical disturbances (here taken to be the localised random ones) and is thus used as initial condition in the simulations with the body force. The enhanced nonlinear stability and drag reduction predicted in the present study are an encouraging first step in modelling the experiments of Kühnen et al. and should motivate future developments to fully exploit the benefits of this promising direction for flow control.

Experimental study on the effect of high-molecular polymer as drag reducer on drag reduction rate of pipe flow

2019 ◽  
Vol 178 ◽  
pp. 852-856 ◽  
Author(s):  
Qing Quan ◽  
Shouxi Wang ◽  
Li Wang ◽  
Ying Shi ◽  
Jin Xie ◽  
...  
Keyword(s):  
Experimental Study ◽  
Drag Reduction ◽  
Pipe Flow ◽  
Reduction Rate

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.

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