Turbulent flow drag reduction

Patterson RW, Abernathy FH (1970) Turbulent flow drag reduction and degradation with dilute polymer solutions Fluid Mech 43 689... 

Patterson, R.W. Abernathy, F.H. Turbulent Flow Drag Reduction and Degradation with Dilute Polymer Solutions. 

Berner C, Scrivener O (1980) Drag reduction and structure of turbulence in dilute polymer solutions Prog. Astronaut. Aeronaut., Vol 72 Viscous flow drag reduction (AIAA), 290... 

In turbulent internal flows, drag reduction, often expressed as a percentage, is calculated as follows ... 

Experiments are reported in which.a concentrated polymer solution is injected into the centre of a turbulent pipe flow. Drag reduction is obtained even if the polymer forms a liquid thread which is conveyed in the core region of the flow, i.e. no significant part of the injected polymer is present in the near-wall region. This type of drag reduction differs from that found in homogeneous solutions and seems to be due to an interaction between the polymer thread and the large-scale structure. 

Berner C. and 0.Scrivener Drag Reduction and Structure of Turbulence in Dilute Polymer Solution. Proc. Astronautics and Aeronautics, 72, Viscous flow drag reduction (AIAA) p.p. 290-299. 1980. 

Choi, U. S. and Kasza, K. E., Long-term degradation of dilute polyacrylamide solutions in turbulent pipe flow, Drag Reduction in Fluid flows Techniques for Friction Control, Proc. Fourth Int. Conf on Drag Reduction (R. H. J. Sellin and R. T. Moses eds.), Ellis Horwood, Chichester, 1989, p. 163. 

Recent developments in turbulence management Proceedings of the 5th drag reduction in engineering flows meeting, Choi K.S, Kluwer, 1991, 139.50 Structure of turbulence and drag reduction lUTAM Symposium, Gyr A,... 

The effect of polymer additives on turbulent flow is at the origin of the important phenomenon of drag reduction and has found other industrial applications such as oil recovery and antimisting action. Drag reduction in dilute polymer solutions... 

Chain degradation in turbulent flow has been frequently reported in conjunction with drag reduction and in simple shear flow at high Reynolds numbers [187], Using poly(decyl methacrylate) under conditions of turbulent flow in a capillary tube, Muller and Klein observed that the hydrodynamic volume, [r ] M, is the determining factor for the degradation rate in various solvents and at various polymer concentrations [188], The initial MWD of the polymers used in their experiments are, however, too broad (Mw/Iiln = 5 ) to allow for a precise... 

A. Gyr and H.-W. Bewersdorff, Drag reduction of turbulent flows by additives, Kluwer Academic Publishers, Dordrecht (1995). 

A review on drag-reducing polymers is given in the literature [1359]. It has been suggested that drag reduction occurs by the interactions between elastic macromolecules and turbulent-flow macrostructures. In turbulent pipe flow, the region near the wall, composed of a viscous sublayer and a buffer layer, plays a major role in drag reduction. 

Experiments have been conducted to investigate the effect of a soapy industrial cleaner on reducing the skin friction of a Jordanian crude oil flowing turbulently in pilot-scale pipes of different sizes. Experiments showed that a concentration of only 2 ppm of the chemical additive injected into the crude oil line caused an appreciable amount of drag reduction [1165]. The effects of additive concentration and pipe diameter on drag reduction have been investigated. 

The model for turbulent drag reduction developed by Darby and Chang (1984) and later modified by Darby and Pivsa-Art (1991) shows that for smooth tubes the friction factor versus Reynolds number relationship for Newtonian fluids (e.g., the Colebrook or Churchill equation) may also be used for drag-reducing flows, provided (1) the Reynolds number is defined with respect to the properties (e.g., viscosity) of the Newtonian solvent and (3) the Fanning friction factor is modified as follows ... 

A drastic reduction of drag in the turbulent flow of solutions in comparison to the pure solvent can be observed, even when only minute amounts of suitable additives are added. This report shows that a wide range of technical and biochemical applications exists but that these applications have so far only been realized in a few exceptional cases. The reason for this must surely lie in the fact that a precise explanation for the effectiveness of drag reducing agents is neither possible from mathematical theories nor from molecular modelling. 

Drag reduction decreases with flow time — which is in most application undesirable — and is obviously caused by a degradation of the polymer chain. Degradation of polymeric additives in turbulent flow cannot be easily understood on the basis of present knowledge, i.e., predictions towards the onset of chain scission cannot yet be made. These difficulties can be attributed, on the one hand, to the complex fluid structure and, on the other hand, to the fact that both shear and tensile stresses act simultaneously in turbulent flows. 

In the area of hydrodynamics the term drag reduction has become a familiar name for characterizing the reduction of friction in turbulent flow through pipes. This is not caused by an improvement in the wall properties as this would only lead to a decrease in friction of a few percent. It is possible, however, to reduce the degree of friction in turbulent flow by a considerable extent, if small amounts of a suitable additive in a concentration range of only a few parts per million by weight are used a reduction in friction of 80 percent can be reached. A tremendous change in the flow field will result, while turbulent flow still remains. 

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