Turbulent drag reduction of boundary layer flow with non-ionic surfactant injection

Abstract

We experimentally investigated streamwise variations of turbulent dynamics in drag-reducing turbulent boundary layer flows following the injection of non-ionic surfactant solutions, which mainly consisted of oleyldimethylamine oxide. We focus on the comparison of turbulence statistics between injected (i.e. heterogeneous) and premixed (i.e. homogeneous) surfactant solutions, in which the maximum drag reduction ratio of 50 % is the same at the most downstream position for both cases. The wall-normal profiles of turbulence statistics, such as streamwise and wall-normal turbulence intensities, seem to be noticeably different between heterogeneous and homogeneous surfactant solutions. However, streamwise variations in these maxima and the wall-normal locations are essentially similar to one another, except for the maximum of streamwise turbulence intensity, which is not arranged by the amount of drag reduction and is also dependent on the normalization due to outer and inner variables. Such complex behaviour of streamwise turbulence intensity would be caused by the formation of near-wall layered structures that are parallel to the wall. For both heterogeneous and homogeneous surfactant solutions, the streamwise variation in the drag reduction ratio corresponds well to those of the mean velocity in wall units and the wall-normal locations of maxima of streamwise and wall-normal turbulence intensities with both outer and inner scaling. Unlike the Reynolds shear stress, the correlation coefficient of the streamwise and wall-normal turbulent fluctuations is correlated well with the drag reduction ratio. We present plausible pictures of the development of turbulence structures such as hairpin vortices and low-speed streaks for the drag-reducing turbulent boundary layer in heterogeneous and homogeneous surfactant solutions, which are comprehensively derived from the present set of experimental measurements such as flow visualization, planar laser-induced fluorescence, two-component laser-Doppler velocimetry and particle image velocimetry on the streamwise and wall-normal plane and the streamwise and spanwise plane.

Polymer drag reduction in surfactant-contaminated turbulent bubbly channel flows

“…It is known that addition of small amount of surfactant can alter the behavior of bubbly flows completely [1]. The long-chain surfactant molecules do not only modify the interfacial properties (e.g., reduce the surface tension) but they also make the host fluid viscoelastic [2]. Moreover, long-chain polymers are often added to turbulent liquid flows for the purpose of drag reduction (DR) known as Toms effect [3,4].…”

Drag Reduction Study of Xathan Gum with Polydiallyldimethylammonium Chloride (PDDAC) Solutions in Turbulent Flow

“…Some of these polymers were used successfully as drag reducers in many commercial applications such as crude oil pipeline flow , firefighting, waterborne shipping , water supply and irrigation systems and cooling and heating circulation systems [2][3][4]. Other possible applications include the improvement of blood flow for treating circulatory diseases [5][6]. Several types of water -soluble polymers are classified as an effective DRA's in a turbulent water flow media such as (PEO), poly (acrylic acid) (PAA) poly (acryl amide), and poly (ethylene oxide) [3,4], but their drag reduction effectiveness was reclassified depending on their mechanical degradation resistance [5].…”

“…On another words, The use of these polymeric Drag Reducing Agents (DRA's) was accompanied with many drawbacks such as the resistance of these long-chained polymers to high shear forces when it interacts with turbulent structures inside the pipelines (eddies) or when it passes through the main high precession pumps .Such high shear force will cause breaking-up the polymer molecules which will lead to lose its drag reduction capabilities. Several solutions suggested by several authors for the polymer shear degradation resistance problem, most of the efforts focuses on changing, modifying and reconstructing the polymer itself in order to give it more firm and shear-resistive structure that can last longer when injected in the pipelines [6,7]. Energy saving in form of pumping power as an important concept to be noted in frictional losses reduction, this is as a result of the high volume of fluid to be transported viz a viz cost of transmission, this becomes a crucial issue in the transmission of fluids from one point to another.…”

A Volumetric Approach to Wake Reduction: Design, Optimization, and Experimental Verification

“…Existing work in hydrodynamic flow control via structures includes tangential surface motion control on a cylinder [1] and active and passive structures in sea creatures [2]. Chemistry and fluid heterogeneity offer another avenue into drag reduction, such as studies considering hydrophobic surfaces [3], surfactant injection [4], bubble injection [5], and supercavitation [6]. Attention to the wake in hydrodynamics was given mostly to the extent that it is useful to control the drag coefficient.…”