Bulletin of the American Physical Society
66th Annual Meeting of the APS Division of Fluid Dynamics
Volume 58, Number 18
Sunday–Tuesday, November 24–26, 2013; Pittsburgh, Pennsylvania
Session E32: Surface Tension Effects III: General Interfacial Phenomena |
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Chair: Sushanta Mitra, University of Alberta Room: 403 |
Sunday, November 24, 2013 4:45PM - 4:58PM |
E32.00001: Low Interfacial Tension Measurement with Synthetic Schlieren Imaging Avanish Mishra, Varun Kulkarni, Jian-Wei Khor, Steve Wereley Interfacial tension in liquid-liquid systems can be deduced by measuring shape of the static meniscus profile near a vertical solid wall. When interfacial tension is low (less than 1 mN/m), meniscus becomes too small in size to be properly measured by side view imaging. In this work, instead of relying on the side view imaging, we use the Free Surface Synthetic Schlieren (FS-SS) method for the measurement of surface gradient of the meniscus from top view images. The interfacial tension is estimated by fitting the measured surface gradient profile with the theoretical results. Since this method utilizes distortion in a background pattern for estimating the surface gradient, it allows us to measure very low values of the interfacial tension. [Preview Abstract] |
Sunday, November 24, 2013 4:58PM - 5:11PM |
E32.00002: Inertial Rise in Short Capillaries Orest Shardt, Prashant Waghmare, Sushanta Mitra, Jos Derksen We investigate the primarily inertial rise of liquid in vertical glass capillaries that are shorter than the equilibrium rise height (Jurin height). We focus on the behavior of the liquid upon reaching the top of the capillary and use high-speed imaging to observe the motion of the liquid-air interface with high spatial and temporal resolution. We examine the dependence of the interface behavior on the meniscus speed and capillary height and describe a new phenomenon. Upon reaching the upper edge of a sufficiently short capillary, the meniscus inverts, rises upward, and bulges out radially. The bulging liquid then wets the external surface of the capillary and slides down. The meniscus inside the capillary retracts, falling below the upper edge, and then oscillates vertically with decaying amplitude, inverting several times before reaching a steady shape. A theoretical analysis is used to interpret the conditions required for this phenomenon to occur. A key assumption in the analysis is that the transient flow is inertial and therefore the capillary driving force is balanced by the weight and inertia of the rising liquid column while viscous forces are comparatively small. The analysis points to the possibility of obtaining previously-unseen behavior under reduced gravity. [Preview Abstract] |
Sunday, November 24, 2013 5:11PM - 5:24PM |
E32.00003: Controlled Coating of Self-Assembled Sphere Clusters by Gravitational Forcing Steven G. Jones, Abhinav Ahuja, Vivian Truong, Scott S.H. Tsai The motion of a spherical particle moving through a liquid-liquid interface due to gravitational force is one of the classical problems of fluid dynamics. In some situations, a single particle has insufficient gravitational energy to break through the interface, but a cluster of multiple particles overcomes the interfacial tension energy barrier to pass through. Here we show with experiments that particles self-assemble into clusters upon settling at an oil-water interface. When a cluster is sufficiently large, the cluster will pass through the interface and becomes conformally coated. We find that the number of particles inside one cluster is proportional to a power-law of the Bond number, which describes the ratio between gravitational and surface tension energies. We demonstrate that the size of the coated particle cluster can be tuned by altering the radius of the particles and changing the interfacial tension. [Preview Abstract] |
Sunday, November 24, 2013 5:24PM - 5:37PM |
E32.00004: Electric field driven bubble motion in microgravity Boris Khusid, Dana Qasem, Ezinwa Elele, John Tang, Yueyang Shen The lack of the gravity-driven gas-liquid phase separation in microgravity has severely compromised a wide range of space technologies. The proposed electro-hydrodynamic (EHD) control of the bubble motion in microgravity employs an electric force generated by an alternating current (AC) field applied directly to a fluid via capacitive coupling to external electrodes. Contrary to the currently available direct current (DC) field-based microgravity techniques, the EHD method employs flow- and field-induced forces to drive bubbles and suppresses electro-chemical reactions at the fluid/electrode interface. The overall goal of the parabolic flight tests planned in July-Aug 2013 is the validation of the EHD method for the control and manipulation of bubbles in microgravity. We will present test results at the meeting. [Preview Abstract] |
Sunday, November 24, 2013 5:37PM - 5:50PM |
E32.00005: Effects of particle self-assembly and structural disjoining pressure on wetting kinetics of nanofluid droplet Gui Lu, Han Hu, Yuanyuan Duan, Ying Sun The wettability of nanofluids, fluids containing suspensions of nanometer-sized particles, is of particular interest to microfluidic systems. Previous studies showed that the self-assembly of nanoparticles in the vicinity of the contact line gives rise to a structural disjoining pressure, which greatly affects the wettability of nanofluid droplets of micron size or larger. In this study, dynamic wetting of water nano-droplets containing non-surfactant gold nanoparticles on a gold substrate was studied via molecular dynamics simulations to examine the effects nanoparticle self-assembly. To mimic the effect of structural disjoining pressure, the excess disjoining pressure was calculated for a pure water film on a gold substrate with a smooth surface on one end and ordered nano-pillar structures on the other. The results show that the addition of non-surfactant nanoparticles hinders the nano-second droplet wetting process, attributed to the increases in both surface tension of the nanofluid and friction between nanofluid and substrate. The spreading enhancement of nanofluids due to the presence of structural disjoining pressure as a result of nanoparticle ordering is not the case for this nano-droplet spreading system. [Preview Abstract] |
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