Production and Dissipation of Energy in the Turbulent Flow of a Particle-Fluid Mixture, With Some Results on Drag Reduction

1976 ◽  
Vol 43 (4) ◽  
pp. 543-547 ◽  
Author(s):  
D. A. Drew
Keyword(s):  
Energy Balance ◽  
Turbulent Flow ◽  
Drag Reduction ◽  
Large Reynolds Number ◽  
Motion Model ◽  
Mean Flow ◽  
Two Phase ◽  
Dissipation Energy ◽  
Fluid Mixture ◽  
Dissipation Of Energy

The production and dissipation of energy in a two-phase model for particle-fluid turbulent flow is considered. For plane parallel mean flow use of several scaling arguments yields a balance between production and drag dissipation for the particles, and between production and viscous dissipation for the fluid. A simple particle motion model is used to obtain estimates of the drag dissipation. Energy balance considerations are made for situations where drag reduction by the addition of particles is observed. Significant drag reduction is found to occur for sufficiently large Reynolds number. Discussion of the extra effectiveness of polymers for drag reduction is given within the framework of energy balance.

Wavelet Analysis on Eddy Structure in Micro Bubble Two Phase Flow Using PIV

2004 ◽  
Author(s):  
Ling Zhen ◽  
Claudia del Carmen Gutierrez-Torres
Keyword(s):  
Boundary Layer ◽  
Turbulent Flow ◽  
Drag Reduction ◽  
Large Scale ◽  
Operating Conditions ◽  
Small Scale ◽  
Turbulent Structures ◽  
Two Phase ◽  
Multi Scale ◽  
Eddy Structures

The question of “where and how the turbulent drag arises” is one of the most fundamental problems unsolved in fluid mechanics. However, the physical mechanism responsible for the friction drag reduction is still not well understood. Over decades, it is found that the turbulence production and self-containment in a boundary layer are organized phenomena and not random processes as the turbulence looks like. The further study in the boundary layer should be able to help us know more about the mechanisms of drag reduction. The wavelet-based vector multi-resolution technique was proposed and applied to the two dimensional PIV velocities for identifying the multi-scale turbulent structures. The intermediate and small scale vortices embedded within the large-scale vortices were separated and visualized. By analyzing the fluctuating velocities at different scales, coherent eddy structures were obtained and this help us obtain the important information on the multi-scale flow structures in the turbulent flow. By comparing the eddy structures in different operating conditions, the mechanism to explain the drag reduction caused by micro bubbles in turbulent flow was proposed.

An Experimental Investigation of Turbulent Drag Reduction in Concentric Annulus Using Particle Image Velocimetry Technique

2013 ◽  
Author(s):  
Fabio Ernesto Rodriguez Corredor ◽  
Majid Bizhani ◽  
Ergun Kuru
Keyword(s):  
Particle Image Velocimetry ◽  
Turbulent Flow ◽  
Drag Reduction ◽  
Particle Image ◽  
Reynolds Shear Stress ◽  
Polymer Concentration ◽  
Mean Flow ◽  
Flow Loop ◽  
Mean Velocity ◽  
Image Velocimetry

Polymer drag reduction is investigated using the Particle Image Velocimetry (PIV) technique in fully developed turbulent flow through a horizontal flow loop with concentric annular geometry (inner to outer pipe radius ratio = 0.4). The polymer used was a commercially available partially hydrolyzed polyacrylamide (PHPA). The polymer concentration was varied from 0.07 to 0.12% V/V. The drag reduction is enhanced by increasing polymer concentration until the concentration reaches an optimum value. After that, the drag reduction is decreased with the increasing polymer concentration. Optimum concentration value of PHPA was found to be around 0.1% V/V. Experiments were conducted at solvent Reynolds numbers of 38700, 46700 and 56400. The percent drag reduction was found to be increasing with the increasing Reynolds number. The study was also focused on analyzing the mean flow and turbulence statistics for fully-turbulent flow using the velocity measurements acquired by PIV. Axial mean velocity profile was found to be following the universal wall law close to the wall (i.e., y+ <10), but it deviated from log law results with an increased slope in the logarithmic zone (i.e., y+ >30). In all cases of polymer application, the viscous sublayer (i.e., y+ <10) thickness was found to be higher than that of the water flow. Reynolds shear stress in the core flow region was found to be decreasing with the increase in polymer concentration.

Direct numerical simulation of turbulent flow over a modeled riblet covered surface

1995 ◽  
Vol 302 ◽  
pp. 333-376 ◽  
Author(s):  
D. Goldstein ◽  
R. Handler ◽  
L. Sirovich
Keyword(s):  
Turbulent Flow ◽  
Drag Reduction ◽  
Flow Velocity ◽  
Body Force ◽  
Complex Geometry ◽  
Cross Flow ◽  
Immersed Boundary ◽  
Computational Domain ◽  
Mean Flow ◽  
Velocity Fluctuations

An immersed boundary technique is used to model a riblet covered surface on one wall of a channel bounding fully developed turbulent flow. The conjecture that the beneficial drag reduction effect of riblets is a result of the damping of cross-flow velocity fluctuations is then examined. This possibility has been discussed by others but is unverified. The damping effect is explicitly modelled by applying a cross-flow damping force field in elongated streamwise zones with a height and spacing corresponding to the riblet crests. The same trends are observed in the turbulence profiles above both riblet and damped surfaces, thus supporting cross-flow damping as a beneficial mechanism. It is found in the examples presented that the effect of the riblets on the mean flow field quantities (mean velocity profile, velocity fluctuations, Reynolds shear stress, and low–speed sreak spacing) is small. The riblests cause a relatively small drag reduction of about 4%, a figure that is in rough agreement with experiments and other computations. The simulations also suggest a mechanism for the observed displacement of the turbulence quantities away from the wall.The immersed boundary technique used to model the riblets consists of creating an externally imposed spatially localized body force which opposes the flow velocity and creates a riblet-like surface. For unstead viscous flow the calculation of the force is done with a feedback scheme in which the velocity is used to iteratively determine the desired value. In particular, the surface body force is determined by the relation f(xs, t) = α ∫ t0U(xs,t′)dt′ + βU(xs, t) for surface points xs, velocity U time t and negative constants α and β. All simulations are done with a spectral code in a single computational domain without any mapping of the mesh. The combination of the immersed boundary and spectral techniques can potentially be used to solve other problems having complex geometry and flow physics.

scholarly journals Slip Effects on Peristaltic Transport of a Particle-Fluid Suspension in a Planar Channel

2015 ◽  
Vol 2015 ◽  
pp. 1-14 ◽  
Author(s):  
Mohammed H. Kamel ◽  
Islam M. Eldesoky ◽  
Bilal M. Maher ◽  
Ramzy M. Abumandour
Keyword(s):  
Amplitude Ratio ◽  
Muscular Contraction ◽  
Slip Condition ◽  
Spherical Particles ◽  
Free Fluid ◽  
Mean Flow ◽  
Two Phase ◽  
Flow Process ◽  
Fluid Mixture ◽  
Slip Conditions

Peristaltic pumping induced by a sinusoidal traveling wave in the walls of a two-dimensional channel filled with a viscous incompressible fluid mixed with rigid spherical particles is investigated theoretically taking the slip effect on the wall into account. A perturbation solution is obtained which satisfies the momentum equations for the case in which amplitude ratio (wave amplitude/channel half width) is small. The analysis has been carried out by duly accounting for the nonlinear convective acceleration terms and the slip condition for the fluid part on the wavy wall. The governing equations are developed up to the second order of the amplitude ratio. The zeroth-order terms yield the Poiseuille flow and the first-order terms give the Orr-Sommerfeld equation. The results show that the slip conditions have significant effect within certain range of concentration. The phenomenon of reflux (the mean flow reversal) is discussed under slip conditions. It is found that the critical reflux pressure is lower for the particle-fluid suspension than for the particle-free fluid and is affected by slip condition. A motivation of the present analysis has been the hope that such theory of two-phase flow process under slip condition is very useful in understanding the role of peristaltic muscular contraction in transporting biofluid behaving like a particle-fluid mixture. Also the theory is important to the engineering applications of pumping solid-fluid mixture by peristalsis.

Turbulent Flow of Drag Reducing Fluids Between Concentric Rotating Cylinders

1972 ◽  
Vol 1 (1) ◽  
pp. 25-30 ◽  
Author(s):  
E. Bilgen ◽  
R. Boulos
Keyword(s):  
Reynolds Number ◽  
Turbulent Flow ◽  
Drag Reduction ◽  
Polyethylene Oxide ◽  
Guar Gum ◽  
Rotating Cylinder ◽  
Large Reynolds Number ◽  
Reduction Mechanism ◽  
Dilute Solutions ◽  
Concentric Cylinders

The turbulent flow of drag reducing fluids between concentric cylinders, the inner cylinder rotating and the outer one at rest, has been studied experimentally. The drag reducing fluids were dilute solutions of polyethylene oxide, polyacrylamide and guar gum. The torques exerted by the inner rotating cylinder have been measured for various gap widths and over a relatively large Reynolds number. The results have been reduced in dimensionless parameters and correlated. The velocity profiles between the cylinders have also been measured and the drag reduction mechanism has been discussed briefly.

Peristaltic Transport of a Particle-Fluid Suspension

1989 ◽  
Vol 111 (2) ◽  
pp. 157-165 ◽  
Author(s):  
L. M. Srivastava ◽  
V. P. Srivastava
Keyword(s):  
Particle Concentration ◽  
Amplitude Ratio ◽  
Flow Reversal ◽  
Spherical Particles ◽  
Free Fluid ◽  
Mean Flow ◽  
Two Phase ◽  
Flow Process ◽  
Fluid Mixture ◽  
The Mean

Peristaltic pumping by a sinusoidal traveling wave in the walls of a two-dimensional channel filled with a viscous incompressible fluid in which are distributed identical rigid spherical particles, is investigated theoretically. A perturbation solution is obtained which satisfies the momentum equations for the case in which amplitude ratio (wave amplitude/channel half width) is small. The results show that the fluid phase mean axial velocity decreases with increase in the particle concentration. The phenomenon of reflux (the mean flow reversal) is discussed. A reversal of velocity in the neighborhood of the centerline occurs when the pressure gradient is greater than that of the critical reflux condition. It is found that the critical reflux pressure is lower for the particle-fluid suspension than for the particle-free fluid. It is further observed that the mean flow reversal is strongly dependent on the particle concentration and the presence of particles in the fluid favors the reversal flow. A motivation of the present analysis has been the hope that such a theory of two-phase flow process is very useful in understanding the role of peristaltic muscular contraction in transporting bio-fluid behaving like a particle-fluid mixture. Also the theory is important to the engineering applications of pumping solid-fluid mixtures by peristalsis.

scholarly journals Epidermal biopolysaccharides from plant seeds enable biodegradable turbulent drag reduction

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Anoop Rajappan ◽  
Gareth H. McKinley
Keyword(s):  
Turbulent Flow ◽  
Drag Reduction ◽  
Large Scale ◽  
Molar Mass ◽  
Raw Material ◽  
Large Reynolds Number ◽  
Frictional Drag ◽  
High Molar Mass ◽  
Plant Seeds ◽  
Cost Constraints

AbstractThe high cost of synthetic polymers has been a key impediment limiting the widespread adoption of polymer drag reduction techniques in large-scale engineering applications, such as marine drag reduction. To address consumable cost constraints, we investigate the use of high molar mass biopolysaccharides, present in the mucilaginous epidermis of plant seeds, as inexpensive drag reducers in large Reynolds number turbulent flows. Specifically, we study the aqueous mucilage extracted from flax seeds (Linum usitatissimum) and compare its drag reduction efficacy to that of poly(ethylene oxide) or PEO, a common synthetic polymer widely used as a drag reducing agent in aqueous flows. Macromolecular and rheological characterisation confirm the presence of high molar mass (≥2 MDa) polysaccharides in the extracted mucilage, with an acidic fraction comprising negatively charged chains. Frictional drag measurements, performed inside a bespoke Taylor-Couette apparatus, show that the as-extracted mucilage has comparable drag reduction performance under turbulent flow conditions as aqueous PEO solutions, while concurrently offering advantages in terms of raw material cost, availability, and bio-compatibility. Our results indicate that plant-sourced mucilage can potentially serve as a cost-effective and eco-friendly substitute for synthetic drag reducing polymers in large scale turbulent flow applications.

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