Bulletin of the American Physical Society
72nd Annual Meeting of the APS Division of Fluid Dynamics
Volume 64, Number 13
Saturday–Tuesday, November 23–26, 2019; Seattle, Washington
Session P08: Non-Newtonian Flows: General Flows II |
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Chair: Paul Salipante, NIST Room: 212 |
Monday, November 25, 2019 5:16PM - 5:29PM |
P08.00001: Entrance effects and high shear rate rheology of shear banding wormlike micelle fluids in microcapillary flow Paul Salipante, Vishnu Dharmaraj, Steven Hudson The viscosity of a shear-banding wormlike micelle solution at high shear rates is investigated using capillary rheology and particle streak velocimetry. Measurements of the flow profile and pressure gradient show an extended entrance region, which exceeds a length to diameter ratio of 100, to reach a fully developed flow. We characterized this entrance region for capillaries with different cross-sections and use the results to select a downstream portion of the capillary where viscosity measurements can be made on fully developed flow. Measurements from this portion of the channel show a shear-thinning power-law behavior for all channel geometries from shear rates of 1,000 1/s to 120,000 1/s. Varying the surfactant concentration shows two distinct power-law behaviors that depend on both shear rate and concentration and are an indication of change in micelle length. [Preview Abstract] |
Monday, November 25, 2019 5:29PM - 5:42PM |
P08.00002: Gels formed by worm-like micelles : Yielding and fluidization characteristics Ronak Gupta, Rodrigo Mitishita, Gwynn Elfring, Ian Frigaard A rarely studied system of long chain surfactant molecules has been shown to display 'gel-like' rheology at room temperature despite the absence of cross-linking.\footnote{Kumar, Rakesh, et al. "Wormlike micelles of a C22-tailed zwitterionic betaine surfactant: from viscoelastic solutions to elastic gels." Langmuir 23.26 (2007): 12849-12856.} Using a similar model system, we investigate the yielding characteristics of micellar gels using creep and amplitude sweeps and elucidate dependencies on temperature and surfactant concentration. Further, we study the phenomenon of shear driven fluidization to better quantify the solid-liquid and yielding transitions in worm-like micellar gels. [Preview Abstract] |
Monday, November 25, 2019 5:42PM - 5:55PM |
P08.00003: Linear and non-linear rheological study of long-chained surfactant solutions for gravel packing operations Rodrigo Mitishita, Ronak Gupta, Gwynn Elfring, Ian Frigaard Long chained zwitterionic surfactants are extensively used in the oil industry, such as fracturing and gravel packing operations. Specifically in the context of gravel packing, the surfactant solutions need high viscosities over a wide range of shear rates and temperatures to successfully carry the gravel particles. The surfactant fluids are also drag-reducing due to their viscoelasticity, which aids in the transport over long distances at high pumping rates. In this study, we characterize a commercial surfactant for gravel packing by carrying out linear and non-linear rheology experiments. We show that the surfactant+water system exhibits a gel-sol transition with temperature. The results also quantify how the relaxation time of the solution and elastic modulus of the gel state depend on surfactant concentration and temperature. Finally, we discuss implications of rheology on gravel packing and turbulent drag reduction. [Preview Abstract] |
Monday, November 25, 2019 5:55PM - 6:08PM |
P08.00004: Experimental method to measure liquid extensional properties during atomization. Marie-Charlotte Renoult, Christophe Tirel, Christophe Dumouchel An experimental method has been developed to measure the extensional properties of a viscoelastic polymer solution experiencing atomization. It is based on the statistical and 3D multi-scale analysis of the capillary thinning of liquid ligaments controlled either by elasticity or viscosity. The method principle will be first presented and validated using an ensemble of emulated ligaments. Then, the method procedure will be described from a free jet imaging setup to the extraction of the liquid extensional properties, i.e. the relaxation time and the terminal elongational viscosity. This procedure will be applied to a series of experiments conducted with several viscoelastic solutions, flow rates and quasi-cylindrical nozzles. Finally, the influence of the polymer concentration, of the jet velocity and of the nozzle dimensions on viscoelastic properties will be discussed. [Preview Abstract] |
Monday, November 25, 2019 6:08PM - 6:21PM |
P08.00005: Taylor-Couette flow of shear-thinning and viscoelastic polymer solutions Neil Cagney, Tom Lacassagne, Stavroula Balabani We study Taylor-Couette (TC) flow of a glycerol-water mixture containing xanthan gum (0 to 2000 ppm concentration). Both shear-thinning and viscoelasticity are induced, to assess the effect of the changes in rheology on various flow instabilities. The Reynolds number is slowly increased, and the flow is monitored continuously using flow visualisation [Cagney and Balanbani, Phys. Fluids, 2019]. Shear-thinning is found to suppress many phenomena observed in previous studies of viscoelastic TC flow (e.g. diwhirls, disordered oscillations [Groisman and Steinberg, Phys. Rev, 1997]). The addition of polymers reduces the critical Reynolds number for the formation of Taylor vortices, but delays the onset of wavy flow. In the viscoelastic regime, the flow becomes unsteady soon after the formation of Taylor vortices, waviness changing with Reynolds number. Vortices are found to merge as Reynolds number increases, with the number of mergers increasing with polymer concentration. These changes in wavelength are hysteretic and occur in both steady and wavy regimes. Vortices in moderate and dense polymer solutions undergo a gradual drift in both their size and position, which appears to be closely linked to the splitting and merger of vortices. [Preview Abstract] |
Monday, November 25, 2019 6:21PM - 6:34PM |
P08.00006: Co- and Counter-rotating Taylor-Couette Flows with Polyelectrolyte Solutions Vishal Panwar, Athena Metaxas, Cari Dutcher Taylor-Couette flow, which is flow between two concentric, rotating cylinders, is ideal for studying flow behavior of complex solutions due to the wide variation of hydrodynamic flow states available. The addition of non-Newtonian polymer solutions increases the solution's elasticity, which in turn can modify flow states that are typically dominated by inertial forces. In this study, a cationic polyacrylamide was used to modify the elasticity of the solution, and with varying concentrations of NaCl to alter the ionic strength of the solution. The coil conformation and relaxation times of charged polymers changes depending on the ionic strength, from a more rigid conformation at low ionic strengths to a more flexible conformation at high ionic strengths, resulting in different non-Newtonian responses to shear. The effect of polymer conformation as a result of varying solution ionic strength on TC flows with co- and counter-rotation of the cylinders will be discussed. In general, increasing ionic strength decreases elasticity, resulting in a shift towards a more Newtonian-like flow behavior. As the polymer conformation becomes more flexible, an overall trend of delayed transitions of flow states was observed. [Preview Abstract] |
Monday, November 25, 2019 6:34PM - 6:47PM |
P08.00007: Viscosity measurement method of non-Newtonian fluids in pressure-driven flows based on energy dissipation rate. Wook Ryol Hwang, Hye Kyeong Jang, Sun Ok Hong, Sang Bok Lee, Ju Min Kim A novel viscosity measurement method is presented, which is established on the balance of the energy dissipation rate such that the external power is dissipated within the system as viscous dissipation in a laminar. The effective viscosity can be expressed algebraically in terms of the pressure drop and flow rate and the corresponding effective shear rate is readily determined by flow rate; the relationship between effective viscosity and effective shear rate is found identical to the true material viscosity behavior. The two flow numbers, which depend on flow geometry only and are almost independent of fluid rheology, are involved: the coefficient of energy dissipation rate that associates the total energy dissipation rate to the Reynolds number; and the coefficient of effective shear rate, which relates flow rate to effective shear rate. Three different flows with complicated geometries were tested: numerical validations for axisymmetric expansion-contraction flows and flows in a Kenics mixer, and experimental validation for flows in a complex microfluidic array with Xanthan gum solutions. [Preview Abstract] |
Monday, November 25, 2019 6:47PM - 7:00PM |
P08.00008: Impacts of geometric parameters on bulge structure appearance in a cavity swept by a visco-elastic fluid Hiroshi Suzuki, Masaki Kawata, Ruri Hidema We previously reported a bulge like flow structure is formed in a cavity swept by a visco-elastic fluid. In this study, effects of geometric parameters of the cavity on the bulge structure appearance have been investigated by flow visualization. As visco-elastic fluids, cationic surfactant aqueous solutions were treated with counter-ion suppliers of sodium salicylate. The molar ratios of sodium salicylate to cationic surfactants, oleylbishydroxyethylmethyammonium chloride, were changed from 1.5 to 10. The geometric parameters were also changed. The cavity depth, the wide flow path and the cavity length raged from 5 to 30 mm, from 25 to 40 mm and from 50 to 100 mm, respectively. From the results, three kinds of flow regimes were observed; 1. simple separation and reattachment occurrence, 2. bulge structure appearance and 3. recirculation region covering the cavity. In the cases when the molar ratio is high, bulge structure was not found to appear. When the aspect ratio of the narrow flow path was high, the flow also transited directly from 1 to 3 of the above flow regime. This flow regime was concluded to relate to the Deborah number of fluids. [Preview Abstract] |
Monday, November 25, 2019 7:00PM - 7:13PM |
P08.00009: Assessing the Mixing Effectiveness of Dual-Impeller Systems in the Agitation of Viscoplastic Fluids Andrew Russell, Lyes Kahouadji, Seungwon Shin, Jalel Chergui, Damir Juric, Richard Craster, Paul Luckham, Christos Markides, Omar Matar Carbopol 980 (C980) solutions are agitated with impeller systems comprising either a two 6-bladed Rushton turbine (RT) impellers, two 4-bladed 45° pitched blade turbine (PBT) impellers, or a combination of both impeller types. The effects of impeller rotational speed, $N$, impeller separations, $G$, and the impeller combinations on the flow were investigated. Phenomena including mixing, cavern-cavern segregation and flow compartmentalisation are explained with respect to the velocity field and streamlines that result from agitation by the various impeller combinations. The quality of mixing is compared for each impeller geometrical setup, with the best mixing, in terms of achieving a state of homogeneity throughout the entire vessel at the lowest $N$, modified power-law Reynolds numbers ($Re_{\rm m}$), yield stress Reynolds numbers ($Re_{\rm y}$) and mixing times, being the PBT(upper)-RT(lower) impeller setup with $G = 0.05$ m. These numerical results, validated against flow visualisation experiments, are important in the context of achieving flow homogeneity in fluids with complex rheological properties in stirred vessel systems, and can be used to show that these flows are sensitive to impeller geometrical setup and other important operating conditions. [Preview Abstract] |
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