Surfactant Solution Flow Research Articles

Flow Property and Micellar Structures in Capillary Flows of Surfactant Solutions

Flow property, which is expressed by the relation between wall shear stress and apparent shear rate, is examined in the flows of surfactant solutions through various capillaries. Furthermore, small angle light scattering (SALS) experiments are carried out in the flow through a slit cell. In the present experiments, aqueous solutions of Cetyltrimethylammonium bromide (CTAB) and Sodium Salicylate (NaSal) are used. The flow curve has a break point and its slope below the bending point significantly depends on the ratio of salt concentration CS to surfactant concentration C D. From the experiments on the effect of capillary diameter, it is found that eqimolar solution for CD= 0.03M exhibits a remarkable diameter dependence below the break point while the solution for CD= 0.03M and CS /CD = 7.7 exhibits a diameter dependence only in a narrow region at intermediate shear rates. In the SALS experiments the butterfly pattern is observed for CS / CD=1 and the four-fold symmetry pattern for CS /CD = 7.7. The characteristic scattering pattern is destroyed just after the startup of the flow at high shear rates where the flow curves overlaps regardless of salt concentration and length and diameter of capillary. This fact suggests that micellar network structures are broken at the high shear rates.

237 円管の助走区間における界面活性剤水溶液の流れ(G05-3 剥離制御・抵抗低減,G05 流体工学)

Developing pipe flow of surfactant solutions is investigated experimentally at surfactant concentrations below 100ppm. The rheological behavior of the surfactant solution is clarified based on measurements of the relationship between shear stress and shear rate, and the velocity distribution is investigated based on laser Doppler velocimetry measurements. The results indicate that a maximum drag reduction effect of 70% can be achieved by the addition of surfactant to water, and close to laminar flow can be achieved under drag-suppressed conditions. The velocity distribution under drag-suppressed flow is shown to approach that given by Virk's equation.

Experimental investigation of turbulent boundary layer flow with surfactant additives using PIV and PDA

Drag reduction of turbulent water flow with surfactant (CTAC) additives was experimentally investigated. By using PIV and PDA measurements, the spatial velocity distribution of surfactant solution flow was clarified in a two-dimensional water channel. With an increasing Reynolds number, it was found that drag reduction of surfactant solution flow is enhanced within the region of drag reduction. However, in the region of post drag reduction, the drag-reducing coefficient approaches one without surfactant when Reynolds number is increased. In the near-wall region, velocity profiles of the drag-reducing fluid are similar to, but not the same as, the laminar profiles of the Newtonian fluid. When compared to the case of water flow without surfactant, the velocity contour lines of the drag-reducing fluid run approximately parallel to the wall. © 2005 Wiley Periodicals, Inc. Heat Trans Asian Res, 34(2): 99–107, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20047

Instability of surfactant solution flow in a Taylor cell

The hydrodynamic instability of surfactant solutions between two coaxial cylinders was investigated by using a laser-induced-fluorescence flow visualization technique to clarify the effect of drag-reducing additives on vortex formation in Taylor-Couette flow. The test fluids were Ethoquad O/12 surfactant solutions, which have a gel-like structure called "shear-induced structure" (SIS). Photographs of the formation of Gortler vortices were taken and compared with these of tap water. In the Taylor number range of 1.2 × 10$^5$ l T$_a$ l 7.1×10$^5$, tap water and 10 ppm surfactant solution flows consisted of Taylor vortices and much smaller Gortler vortices at the rotating inner wall. However, for 50 and 100 ppm surfactant solutions, Taylor vortices were not apparent and Gortler vortices were collapsed. Measurements of the wavelength of Gortler vortices lead to the conclusion that surfactant solutions have a stabilizing effect on Gortler instabilities. This effect depends on surfactant concentration and becomes considerable with increasing acceleration of the inner cylinder.

Characterization of Turbulent Flow in a Flume with Surfactant

Summary The drag reducing effect of a surfactant additive from the alkylpolyglycosides family was investigated experimentally. In thepresent study, PIV measurements were done to investigate theturbulent flow in the streamwise-spanwise plane of a flume aty 1 580, in the buffer zone, where about 80% of the energy pro- Fig. 4 PDF’s of the u rms8 O U q for water —circles– and surfactant—squares–. u rms8 —x,z– ˜ −—u—x,z– A −u—x,z–‰– 2 ‰and the PDF is rep-resenting the spatial distribution of the rms values, normalizedby the flow-rate velocity U q .Fig. 5 Two-point—auto–correlation function R uu of the stream-wise velocity along the streamwise x and spanwise z coordi-nates, for water —circles and plus symbols– and for surfactant—square and triangular markers–, respectively.Table 1 Statistical properties of the Reynolds stress A −u 8 w 8 ‰ O U q2 .Statistics Maximum Minimum Average Std. dev. SkewnessWater 0.05 20.035 0.35310 23 0.0045 0.93Surfactant 0.03 20.035 0.35310 24 0.0032 0.003Table 2 Statistical properties of the turbulent energy production term

Electrokinetic aspects of turbulent drag reduction in surfactant solutions

Electrokinetic mechanism of drag reduction of turbulent flow of surfactant solutions is proposed. The surfactant micelles with surface charge attract ions of the solvent or counterions, forming an electric double layer. The ions in the layer are “frozen” in a strongly bonded structure, which reduces the local flow around micelle. The local flow is the strain of small turbulent scale fluctuation. Numerical example indicates that electrokinetic mechanism supplies a reasonable explanation of the drag reduction in surfactant solutions. The proposed model is only the preliminary one, which points on the electrokinetics as an additional mechanism which contributes to the hydrodynamics of surfactant solutions.

Straining flow of a micellar surfactant solution

We present a mathematical model describing the distribution of monomer and micellar surfactant in a steady straining flow beneath a fixed free surface. The model includes adsorption of monomer surfactant at the surface and a single-step reaction whereby monomer molecules combine to form each micelle. The equations are analysed asymptotically and numerically and the results are compared with experiments. Previous studies of such systems have often assumed equilibrium between the monomer and micellar phases, i.e. that the reaction rate is effectively infinite. Our analysis shows that such an approach inevitably fails under certain physical conditions and also cannot accurately match some experimental results. Our theory provides an improved fit with experiments and allows the reaction rates to be estimated.

Investigation on the characteristics of turbulence transport for momentum and heat in a drag-reducing surfactant solution flow

Simultaneous measurements of the velocity (u and ν in the streamwise and wall-normal directions, respectively) and temperature fluctuations (θ) in the thermal boundary layer were carried out for a heated drag-reducing surfactant solution flow in a two-dimensional channel by means of a two-component laser Doppler velocimetry and a fine-wire thermocouple probe. The drag-reducing fluid tested was a dilute aqueous solution of a cationic surfactant, cetyltrimethylammonium chloride (CTAC), with 30 ppm concentration. Measurements were performed for CTAC solution flows at an inlet temperature of 31 °C and at three Reynolds numbers of 3.5×104, 2.5×104, and 1.5×104, respectively, and for water flow at the Reynolds number of 2.5×104. Drag reduction (DR) and heat transfer reduction (HTR) for the three CTAC solution flows were DR(HTR)=33.0(20.2), 70.0(77.3), and 65.1(77.0) percentage, respectively. At a high HTR level, a large temperature gradient appeared when y+<50 in the measured range (the superscript “+” denotes normalization with inner variables). Temperature fluctuation intensity, θ′+, and the streamwise turbulent heat flux, u+θ+¯, were enhanced in the layer with large temperature gradient for the drag-reducing flow, whereas the wall-normal turbulent heat flux, −ν+θ+¯, was depressed throughout the measured range. The depression of −ν+θ+¯ was due to a cause similar to that of the depression of the Reynolds shear stress −u+ν+¯, i.e., in addition to the decrease of ν′+, decorrelation between the two variables occurred. The decrease of −ν+θ+¯ resulted in HTR, which was similar to that of the decrease of −u+ν+¯ resulted in DR for the drag-reducing flow by additives. The turbulence production terms, −u+ν+¯(∂U+/∂y+) and −ν+θ+¯(∂Θ+/∂y+) where U and Θ are mean velocity and temperature, were reduced in the drag-reducing CTAC solution flows. The estimated power spectra of temperature fluctuations implied that the drag-reducing surfactant additive depressed the turbulence at high frequencies or at small scales, whereas it increased the turbulent energy at low frequencies or at large scales. The profiles of the eddy diffusivities for momentum and heat in the CTAC solution flows were both decreased. The turbulent Prandtl number deviated from that of the water flow near the heated wall with a value close to the molecular Prandtl number of the solvent.

Effects of non-isothermal heating on drag reduction in surfactant aqueous solution flow

In this study we investigate the control of flow characteristics and heat transfer of a drag-reducing dilute cationic surfactant solution in a channel, in order to develop a highly efficient heat exchanger. As has been reported by many authors, addition of certain polymers or surfactants reduces heat transfer in drag-reduced water flow. Therefore, other measures must be taken in order to compensate the reduction in heat transfer. Specifically, this study investigates the effects of non-isothermal heating on drag-reduced flow: experiments were conducted in order to study passive control for effecting the drag-reduction state by employing temperature-dependent physical properties and heat transfer augmentation by complex flow. In addition, velocity and temperature profiles were measured under the coexistence of turbulent and drag-reducing flow in order to clarify the effect of drag reduction. It was confirmed that the drag reduction state was changed and diminished due to the temperature rise near the wall, especially the condition in the region of 50< y +<100 greatly influence on drag reduction of pipe flow.

Drag reduction and heat transfer of surfactants flowing in a capillary tube

Pressure drop and heat transfer were measured in fully developed laminar flow in a pipe of inner diameter 1.07 mm in the range of Reynolds numbers 10⩽ Re⩽450. The study was performed for water and water–surfactant solution of 530 and 1060 ppm. It was shown that these surfactant solutions increase the pressure drop in adiabatic and diabatic flows. The dependence of friction coefficients as a function of solvent Reynolds number was used to predict the ability of certain surfactant solutions to increase drag in laminar flows. The experimental values of the Nusselt number depend significantly on the thermal conduction through the tube wall. They become lower than theoretically predicted for tubes heated with constant heat flux on the wall. The heat transfer coefficients with surfactant solutions were higher than that in water flow at the same bulk velocity. The results showed that the Peclet number is an additional parameter needed for a description of the averaged Nusselt number in laminar pipe flow of water and surfactant solution.

Drag reduction and heat transfer of surfactants flowing in a capillary tube

Pressure drop and heat transfer were measured in fully developed laminar flow in a pipe of inner diameter 1.07 mm in the range of Reynolds numbers 10⩽ Re ⩽450. The study was performed for water and water–surfactant solution of 530 and 1060 ppm. It was shown that these surfactant solutions increase the pressure drop in adiabatic and diabatic flows. The dependence of friction coefficients as a function of solvent Reynolds number was used to predict the ability of certain surfactant solutions to increase drag in laminar flows. The experimental values of the Nusselt number depend significantly on the thermal conduction through the tube wall. They become lower than theoretically predicted for tubes heated with constant heat flux on the wall. The heat transfer coefficients with surfactant solutions were higher than that in water flow at the same bulk velocity. The results showed that the Peclet number is an additional parameter needed for a description of the averaged Nusselt number in laminar pipe flow of water and surfactant solution.

Development characteristics of drag-reducing surfactant solution flow in a duct

Development characteristics of dilute cationic surfactant solution flow have been studied through the measurements of the time characteristics of surfactant solution by birefringence experiments and of the streamwise mean velocity profiles of surfactant solution duct flow by a laser Doppler velocimetry system. For both experiments, the concentration of cationic surfactant (oleylbishydroxymethylethylammonium chloride: Ethoquad O/12) was kept constant at 1000 ppm and the molar ratio of the counter ion of sodium salicylate to the surfactants was at 1.5. From the birefringence experiments, dilute surfactant solution shows very long retardation time corresponding to micellar shear induced structure formation. This causes very slow flow development of surfactant solution in a duct. Even at the end of the test section with the distance of 112 times of hydraulic diameter form the inlet, the flow is not fully developed but still has the developing boundary layer characteristics on the duct wall. From the time characteristics and the boundary layer development, it is concluded that the entry length of 1000 to 2000 times hydraulic diameter is required for fully developed surfactant solution flow.

界面活性剤水溶液流れにおける空気混入の影響(オーガナイズドセッション8 伝熱促進)

This paper presents an experimental investigation on flow and heat transfer characteristics of surfactant solution - air two-phase flow. The test tube is 5.0mm in inner diameter, and consists of the flow developing and heating sections, which are 2000mm and 900mm in length, respectively. Two-phase flow was produced by injecting air into the in-tube flow of surfactant solution (TTAB+NaSa, the concentration is 500 and 1000 ppm). Friction factors and heat transfer coefficients were measured in the heating section (900mm in length). Heat transfer enhancement by injecting air was larger for surfactant solution flow than that for water flow. This indicates that air injection has the effects of not only mixing flow, but also breaking micelle structure for surfactant solution flow.

界面活性剤水溶液流れの伝熱促進(熱輸送・伝熱促進,熱工学部門一般講演)

界面活性剤水溶液流れの伝熱促進(熱輸送・伝熱促進,熱工学部門一般講演)

界面活性剤水溶液の回転円板による容器内流れ(S23-1 複雑流体の流れとその応用(1),S23 複雑流体の流れとその応用)

This paper deals with a flow of an aqueous surfactant solution due to a rotating disc in a cylindrical casing with aspect ratio H/R=2, where H and R is the height of the cylindrical casing and the radius of the rotating disc, respectively. The aqueous surfactant solution (C_<14>TASal), whose concentration is 0.4, 0.8 and 1.2%, is consisted of n-tetradecyltrimethylammonium bromide (C_<14>TABr) and sodium salicylate (NaSal). The swirling flow was investigated using a flow visualization technique and a two-component laser Doppler velocimetry (LDV) system. It was found that the projection was moving up and down at a constant frequency near the rotating disc, as not seen in polymer solutions.

正方形断面曲がり管内における界面活性剤水溶液の二次流れに関する研究(S23-2 複雑流体の流れとその応用(2),S23 複雑流体の流れとその応用)

正方形断面曲がり管内における界面活性剤水溶液の二次流れに関する研究(S23-2 複雑流体の流れとその応用(2),S23 複雑流体の流れとその応用)

Simultaneous measurements of velocity and temperature fluctuations in thermal boundary layer in a drag-reducing surfactant solution flow

The mechanism of turbulent heat transfer in the thermal boundary layer developing in the channel flow of a drag-reducing surfactant solution was studied experimentally. A two-component laser Doppler velocimetry and a fine-wire thermocouple probe were used to measure the velocity and temperature fluctuations simultaneously. Two layers of thermal field were found: a high heat resistance layer with a high temperature gradient, and a layer with a small or even zero temperature gradient. The peak value of \( \overline{{u^{ + } \theta ^{ + } }} \) was larger for the flow with the drag-reducing additives than for the Newtonian flow, and the peak location was away from the wall. The profile of \( - \overline{{v^{ + } \theta ^{ + } }} \) was depressed in a similar manner to the depression of the profile of \( - \overline{{u^{ + } v^{ + } }} \) in the flow of the surfactant solution, i.e., decorrelation between v and θ compared with decorrelation between u and v. The depression of the Reynolds shear stress resulted in drag reduction; similarly, it was conjectured that the heat transfer reduction is due to the decrease in the turbulent heat flux in the wall-normal direction for a flow with drag-reducing surfactant additives.

A study on viscoelastic fluid flow in a square-section 90-degrees bend

It is well known that the drag-reducing effect is obtained in a surfactant solution flow in a straight pipe. We investigate about a viscoelastic fluid flow such as a surfactant solution flow in a square-section 90° bend. In the experimental study, drag-reducing effect and velocity field in a surfactant solution flow are investigated by measurements of wall pressure loss and LDV measurements. For the numerical method, LES with FENE-P model is used in the viscoelastic fluid flow in the bend. The flow characteristics of viscoelastic fluid are discussed compared with that of a Newtonian fluid.

Stick-slip transition at the nanometer scale.

We report the first observation of a stick-slip transition of surfactant solution flow through nanopores. From the experimental data, we were able to determine both the slip length and the critical wall shear stress from which slip occurs. Whereas the latter is found to increase linearly with the concentration, the former remains constant and approximately equal to 20 nm over the studied range of concentrations. We model slip to occur in the surfactant bilayer adsorbed at the nanopore wall. The stick-slip transition is then related to a reorganization of the surfactant bilayer from an entangled structure into independent layers flowing past one another, as evidenced by independent surface plasmon resonance experiments. We conclude from our analysis that surfactant solutions are always slipping in larger tubes. However, the larger the tube diameter, the smaller the relative slip contribution to the total flow.

The Effect of a Cationic Surfactant on Turbulent Flow Patterns

The thermal pattern on a heated wall was studied for the flow of water and drag-reducing surfactant solutions in a channel. The wall of the channel was made of a thin foil, which was heated by direct current. The temperature of the foil, which reflects the local flow velocities, was measured by an infrared technique with high spatial and temperature resolution. The microstructure of the surfactant solution was studied by direct imaging cryogenic temperature transmission electron microscopy (Cryo-TEM). The most prevalent structures observed are thread-like micelles, which have been suggested to cause the modification of the thermal patterns.