Surface tension

About: Surface tension is a research topic. Over the lifetime, 25410 publications have been published within this topic receiving 695471 citations.

Water drops on surfaces

Abstract: We present a physically-based method to enforce contact angles at the intersection of fluid free surfaces and solid objects, allowing us to simulate a variety of small-scale fluid phenomena including water drops on surfaces. The heart of this technique is a virtual surface method, which modifies the level set distance field representing the fluid surface in order to maintain an appropriate contact angle. The surface tension that is calculated on the contact line between the solid surface and liquid surface can then capture all interfacial tensions, including liquid-solid, liquid-air and solid-air tensions. We use a simple dynamic contact angle model to select contact angles according to the solid material property, water history, and the fluid front's motion. Our algorithm robustly and accurately treats various drop shape deformations, and handles both flat and curved solid surfaces. Our results show that our algorithm is capable of realistically simulating several small-scale liquid phenomena such as beading and flattened drops, stretched and separating drops, suspended drops on curved surfaces, and capillary action.

Surface Tension and Surface Potential of Na n-Dodecyl Sulfate at the Air−Solution Interface: Model and Experiment

Abstract: Surface potential vs concentration isotherms of Na n-dodecyl sulfate (SDDS) adsorbed at the air−solution interface, measured using the vibrating plate method at various concentrations of added salt, exhibit a pronounced minimum. The results of surface tension measurements indicate that the minimum occurs within the concentration range that corresponds to the transition from the Henry regime of adsorption for low surface coverages to the one typical for adsorption of amphiphiles at high surface coverages. We proposed a simple model of adsorption of ionic surfactants at air−fluid interfaces based on the assumption that surfactant headgroups and counterions can adsorb in the Stern layer at the same Helmholtz plane. The electric potential in the electric double layer was calculated according to the Gouy−Chapman model for the diffuse part of the double layer and a modified Stern model for the inner layer with corrections for the discrete charge effects. The total potential drop across the interface was assumed...

Investigation of Mixing in Binary Surfactant Solutions by Surface Tension and Neutron Reflection: Anionic/Nonionic and Zwitterionic/Nonionic Mixtures

Abstract: Surface tension and neutron reflection measurements have been used to study the surface composition of aqueous solutions of mixtures of sodium dodecyl sulfate (SDS) and n-dodecyl-β-d-maltoside (C12maltoside) and C12maltoside and n-dodecyl-N,N‘-dimethylamino betaine (C12betaine). From measurements of surface tension and mixed critical micelle concentrations (cmc) the pseudo-phase separation model has been used to calculate values of the interaction parameters in the micelle, βM, and at the surface, βσ. SDS/C12maltoside mixtures behave nonideally and both βM are negative, indicating attractive interactions between the two surfactants, but the C12maltoside/C12betaine mixtures are closer to being ideal. Direct measurements of the surface excess using neutron reflection on isotopic mixtures of the surfactants are shown to be consistent with the surface tension measurements using the integrated form of the Gibbs equation. These direct values of the surface excess were found to agree with predictions from the pa...

Numerical simulation of behavior of gas bubbles using a 3‐D front‐tracking method

Abstract: In this paper a three-dimensional (3-D) front-tracking (FT) model is presented featuring a new method to evaluate the surface force model that circumvents the explicit computation of the interface curvature. This method is based on a direct calculation of the net tensile forces acting on a differential element of the interface. Our model can handle a large density and viscosity ratio and a large value of the surface tension coefficient characteristic for gas-liquid systems. First, the results of a number of test cases are presented to assess the correctness of the implementation of the interface advection and remeshing algorithms and the surface tension model. Subsequently, the computed terminal Reynolds numbers and shapes of isolated gas bubbles rising in quiescent liquids are compared with data taken from the bubble diagram of Grace. In addition drag coefficients for rising air bubbles in water were successfully computed, a system that has proven difficult to simulate by other methods, and showed good agreement with existing correlations. Finally, a number of sample calculations involving multiple bubbles are reported to demonstrate the capabilities of our three-dimensional FT model.