Bulletin of the American Physical Society
73rd Annual Meeting of the APS Division of Fluid Dynamics
Volume 65, Number 13
Sunday–Tuesday, November 22–24, 2020; Virtual, CT (Chicago time)
Session K10: Non-Newtonian Flows: General (8:45am - 9:30am CST)Interactive On Demand
|
Hide Abstracts |
|
K10.00001: Effects of shear and extensional rheology on liquid transfer between two flat surfaces Satish Kumar, Jyun-Ting Wu, Marcio Carvalho Liquid bridges with moving contact lines play a central role in several industrial applications and natural phenomena. In printing processes, liquid bridges undergo significant extension so that liquid can be transferred from one surface to another. In addition, shear deformation arises as the contact lines move along the surfaces. Although the liquids involved often exhibit non-Newtonian rheology, the influence of rheology on liquid transfer is not well understood. To address this issue, flow visualization experiments complemented with numerical simulations are used to determine the role of shear and extensional rheology in liquid transfer between two vertically separating flat surfaces. Shear thinning is found to enhance liquid transfer to the more-wettable surface compared to the Newtonian case at the same capillary number. This enhancement increases with stronger shear-thinning effects and allows nearly complete transfer with a sufficiently large surface-wettability difference and capillary number. The underlying mechanism involves reduced viscosities near the contact line on the less-wettable surface, which allow that contact line to slip more. Extensional rheology extends the breakup time, but has little effect on contact-line motion and the amount of liquid transferred. [Preview Abstract] |
|
K10.00002: Recovery of viscoelastic turbulent pipeflow past square bar roughness Shubham Goswami, Arman Hemmati High molecular weight polymers are typically used in turbulent flows to reduce stresses and damp out turbulence (Ptasinski \textit{et. al.}, 2001). This is particularly important in crude oil and sewage pipelines, in which the non-Newtonian viscoelastic characteristics lead to drag reduction (Burger \textit{et. al.}, 1982 and sellin, 1978). In this study, the response and recovery of viscoelastic flow past square bar roughness are examined for Newtonian (base-flow) and viscoelastic fluids using Direct Numerical Simulations and FENE-P model, at Re$=$5000$^{\mathrm{\thinspace }}$--10000. The roughness elements have a height of h/D $=$ 0.05 and 0.1, where D is the pipe diameter. Preliminary results show a reduction in the reattachment length, as well as a significant drop in near-wall stresses with the addition of polymers. The recovery by viscoelastic fluid is significantly faster compared to the base flow. Moreover, the flow unsteadiness is greatly impacted by the viscoelastic damping of flow instabilities past the roughness element. We aim to expand this study by properly identifying the behaviour of viscoelastic fluid flow and influence of elasto-inertial turbulence on the wake dynamics of pipeflows. [Preview Abstract] |
|
K10.00003: Viscous filament coiling: viscoelastic effects Yunxing Su, Bernardo Palacios, Roberto Zenit A viscous filament falling from a certain height onto itself on a horizontal surface can form coils. This phenomenon has been extensively studied for the case of Newtonian fluids (Ribe 2004, Maleki et al. 2004). Although viscoelastic liquid properties are prominent in many biological and industrial flows, their effects on filament coiling have not yet been studied in depth. Here, we present experimental measurements of the coiling performance considering Boger (viscoelastic with constant viscosities) and Newtonian fluids. To ensure a fair comparison, a series of glucose-based fluids were prepared such that the shear viscosity for both Boger and Newtonian fluids were closely matched. Compared to Newtonian fluids, the onset of Boger fluid coiling is delayed and the coiling frequency was smaller under the same experimental conditions. We hypothesize that these differences are due to the prevalence of high extensional viscosity values in viscoelastic Boger fluids, in accordance with previous rheological measurements. Moreover, we show that the coiling frequency curves of different Newtonian fluids can be collapsed using a pendulum frequency and gravitational length scaling. This frequency and length scales can also be used to collapse the viscoelastic coiling data by considering the extensional viscosity instead of shear viscosity. This corrected scaling confirms the prevalence of extensional viscosity effects on filament coiling of Boger fluids. Data of the filament radius and coiling radius are also presented in attempt to complete the understanding of coiling phenomena in viscoelastic liquids. [Preview Abstract] |
|
K10.00004: Hydrodynamic interaction between a pair of bubbles rising in a shear-thinning viscoelastic fluid Mithun Ravisankar, Yunxing Su, Roberto Zenit Bubbles ascending in non-Newtonian fluids have significantly different characteristics from their Newtonian counterparts: deformed shapes, negative wake, and clustering are a few. To improve our understanding on bubble clustering, the hydrodynamic interactions between a pair of bubbles were experimentally studied. Viscoelastic fluid with shear-dependent viscosity, prepared from water-glycerin mixtures and polyacrylamide, was used. For a single bubble in such viscoelastic fluids, there is an abrupt discontinuity in the bubble velocity beyond a critical volume. We conducted experiments for bubbles before and after the critical size. Important differences on the interaction dynamics were identified, when compared to the Newtonian fluid case: for both cases, the trailing bubble was observed to catch up with the leading one (drafting). Specifically, before the critical volume, bubbles remain close to each other after reaching each other, forming a stable chain. After the critical volume, however, the bubble pairs do not reach a steady configuration but do not drift apart either, instead, both the leading and trailing bubble stay close, alternatingly switching the leading-trailing position in time in the race to the free surface. These results are compared and contrasted with the Newtonian benchmark fluid. We discuss a possible mechanism to explain these observations. [Preview Abstract] |
|
K10.00005: Inkjet printing of viscoelastic fluids -- Effect of particle and polymer concentration on the jetting of weakly viscoelastic solutions Kashyap Rajan, Jonathan Rothstein The addition of polymeric binders and micron-sized particles to inkjet fluids can have effects that are both detrimental and advantageous to the jetting process. We will present an experimental study of how micro particle concentration and polymer properties including molecular weight, backbone rigidity and concentration effect jetting. Industrial inkjet fluids are weakly viscoelastic and challenging to characterize. Here we measured the extensional rheology using the extremely sensitive drip onto substrate capillary breakup extensional rheometry (CaBER DoS). The effect of extensional rheology on jetting were probed using a high speed imaging techniques to accurately capture the drop formation and pinch off dynamics. With increasing polymer concentration, molecular weight, backbone flexibility and particle concentration, the jet breakup dynamics transition from being dominated by inertial effects to being governed by elastic effects. This transition was quantified by measuring satellite drop size and relative velocity, droplet breakup time and breakup distance, and the persistence of the fluid threads connecting primary drops. The satellite drop velocity was found to be especially sensitive to the presence of fluid elasticity. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700