The Experts below are selected from a list of 7008 Experts worldwide ranked by ideXlab platform
Bharat Bhushan - One of the best experts on this subject based on the ideXlab platform.
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Movement of air bubbles under various liquids using bioinspired conical surfaces
Journal of colloid and interface science, 2020Co-Authors: Dev Gurera, Bharat BhushanAbstract:Gas bubbles are of interest in various applications. The study of their movement is of importance. Gas bubbles are typically formed under liquids. Movement of liquid droplets on bioinspired conical surfaces is known to be facilitated by the Laplace Pressure gradient. These conical surfaces, with various wettabilities and shapes, can also be used to move gas bubbles. In this study, effect of various liquids on movement of air bubble under liquid was studied. It was found that liquids with high surface tension and high density are more efficient in moving air bubbles. High surface tension and higher density increases the Laplace Pressure gradient force and the buoyancy force, respectively, which drive under liquid air bubbles.
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Designing bioinspired conical surfaces for water collection from condensation.
Journal of colloid and interface science, 2019Co-Authors: Dev Gurera, Bharat BhushanAbstract:In arid deserts, water supply is supplemented by water from fog and condensation. Once the droplets are collected, they are transported to a location where they are consumed or stored before they evaporate. Conical geometries or triangular patterns are known to create Laplace Pressure gradient inside droplets which facilitates droplet transport. Water collection by fog on conical and triangular patterns have been studied. The research on the water collection by condensation exist only on flat triangular patterns. These flat surfaces have limitations for practical purposes, such as the Laplace Pressure gradient does not act of droplets unless they touch the border. That is not the case in cones, which makes them superior for practical water collection. In this study, for the first time, water collection from condensation on cones have been studied. Cones of different tip angle, cone length, and surface area were used. Effect of inclination angle and array was also characterized. The results are compared to water collection by fog.
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Bioinspired conical design for efficient water collection from fog
Philosophical transactions. Series A Mathematical physical and engineering sciences, 2019Co-Authors: Dev Gurera, Bharat BhushanAbstract:Nature is known for using conical shapes to transport the collected water from fog for consumption or storage. The curvature gradient of the conical shape creates a Laplace Pressure gradient in the water droplets which drives them towards the region of lower curvature. Linear cones with linearly increasing radii have been studied extensively. A smaller tip angle cone transports water droplets farther because of higher Laplace Pressure gradient. Whereas a larger tip angle with a larger surface slope transports water droplets because of higher gravitational forces. In this study, for the first time, a nonlinear cone with a concave profile has been designed with small tip angle and nonlinearly increasing radius to maximize water collection. This article is part of the theme issue 'Bioinspired materials and surfaces for green science and technology (part 2)'.
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Bioinspired triangular patterns for water collection from fog.
Philosophical transactions. Series A Mathematical physical and engineering sciences, 2019Co-Authors: Dong Song, Bharat BhushanAbstract:Cacti use spines with conical geometry to transport water to its base. A conical shape with curvature gradient generates a Laplace Pressure gradient along the droplet, which is responsible for droplet motion. In this study, the triangular shape was used which also generates a Laplace Pressure gradient along the droplet. A bioinspired surface, composed of a hydrophilic triangular pattern surrounded by a rim of superhydrophobic region, was used to transport water collected from the fog on the hydrophilic pattern. The growing droplets start to coalesce into bigger ones. Eventually, they are big enough to touch the superhydrophobic borders, which trigger the transport motion. Droplet mobility and water collection measurements were made on triangular patterns with various geometries to determine the most efficient configurations. Results from this study can be used to enhance the performance of water collection systems from fog. This article is part of the theme issue 'Bioinspired materials and surfaces for green science and technology (part 2)'.
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Water droplet dynamics on bioinspired conical surfaces.
Philosophical transactions. Series A Mathematical physical and engineering sciences, 2019Co-Authors: Charles T Schriner, Bharat BhushanAbstract:Cacti use the Laplace Pressure gradient due to conical geometry as a mechanism for collecting water from fog. Bioinspired surfaces using conical geometry can be developed for water collection from fog for human consumption. A systematic study is presented which investigates the dynamics of water droplets on a bioinspired conical surface. A series of experiments was conducted where a known volume of droplets was deposited on the cone. This was followed by an investigation into droplet dynamics where the droplets are deposited from fog and the volume is unknown. This includes a study on the macroscopic level as well as the microscopic level. The main parameters that were varied for these tests were the tip angle and the cone orientation. The droplet movement observed was compared relatively. Based on captured videos of droplet movement, distance travelled and velocities were measured. The Laplace Pressure gradient, gravity and droplet coalescence were found to be the mechanisms of droplet movement on a conical surface. The findings of this study should be of interest in designing bioinspired surfaces with high water collection. This article is part of the theme issue 'Bioinspired materials and surfaces for green science and technology (part 2)'.
Laetitia Martinie - One of the best experts on this subject based on the ideXlab platform.
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Apparent elongational yield stress of soft matter
Journal of Rheology, 2013Co-Authors: Laetitia Martinie, Hans Buggisch, Norbert WillenbacherAbstract:Apparent elongational yield stresses of soft matter including polymer gels, highly concentrated emulsions, and aggregated suspensions have been determined from step stretch experiments. Materials display apparent shear yield stresses in the range 1–100 Pa and large but finite shear relaxation times tR. For all investigated fluids, the Laplace Pressure within the stretched filaments is essentially constant during an initial period of time after the step strain. Then, it increases rapidly and finally the filaments break. Filament lifetime tf strongly increases with decreasing stretching ratio e. The apparent elongational yield stress is identified as the initial value of the Laplace Pressure obtained at a critical stretching ratio ec corresponding to a Deborah number De = tR /tf = 1. For all fluids, the ratio of this elongational yield stress to shear yield stress is √3 in agreement with the von Mises plasticity criterion, irrespective of the physical nature of structural breakdown. Elongational experiments performed at different e or tf covering Deborah numbers between 0.1 and 100 reveal a universal relationship between the initial plateau value of the Laplace Pressure normalized to the shear yield stress and De. This stress ratio varies between 0.5 and 5, and equals √3 only for De ≈ 1.
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Apparent elongational yield stress of soft matter
Journal of Rheology, 2013Co-Authors: Laetitia Martinie, Buggisch, Hans, Willenbacher NorbertAbstract:Apparent elongational yield stresses of soft matter including polymer gels, highly concentrated emulsions, and aggregated suspensions have been determined from step stretch experiments. Materials display apparent shear yield stresses in the range 1–100 Pa and large but finite shear relaxation times tR. For all investigated fluids, the Laplace Pressure within the stretched filaments is essentially constant during an initial period of time after the step strain. Then, it increases rapidly and finally the filaments break. Filament lifetime tf strongly increases with decreasing stretching ratio ε. The apparent elongational yield stress is identified as the initial value of the Laplace Pressure obtained at a critical stretching ratio εc corresponding to a Deborah number De = tR /tf = 1. For all fluids, the ratio of this elongational yield stress to shear yield stress is √3 in agreement with the von Mises plasticity criterion, irrespective of the physical nature of structural breakdown. Elongational experiments performed at different ε or tf covering Deborah numbers between 0.1 and 100 reveal a universal relationship between the initial plateau value of the Laplace Pressure normalized to the shear yield stress and De. This stress ratio varies between 0.5 and 5, and equals √3 only for De ≈ 1.
B. M. Marino - One of the best experts on this subject based on the ideXlab platform.
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Laplace Pressure driven drop spreading
Physics of Fluids, 1994Co-Authors: Javier A. Diez, Roberto Gratton, L. P. Thomas, B. M. MarinoAbstract:This work concerns the spreading of viscous droplets on a smooth rigid horizontal surface, under the condition of complete wetting (spreading parameter S≳0) with the Laplace Pressure as the dominant force. Owing to the self‐similar character foreseeable for this flow, a self‐similar solution is built up by numerical integration from the center of symmetry to the front position to be determined, defined as the point where the free‐surface slope becomes zero. Mass and energy conservation are invoked as the only further conditions to determine the flow. The resulting fluid thickness at the front is a small but finite (≊10−7) fraction of the height at the center. By comparison with experimental results the regime is determined in which the spreading can be described by this solution with good accuracy. Moreover, even within this regime, small but systematic deviations from the predictions of the theory were observed, showing the need to add terms modifying the Laplace Pressure force.
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Laplace Pressure-Driven Drop Spreading: Quasi-Self-Similar Solution
Journal of Colloid and Interface Science, 1994Co-Authors: Javier A. Diez, Roberto Gratton, L. P. Thomas, B. M. MarinoAbstract:Abstract We present a hydrodynamic calculation of the spreading of viscous droplets on a smooth rigid horizontal surface, under the condition of complete wetting (spreading parameter S > 0) with the Laplace Pressure as the dominant force. The starting point is a self-similar solution reported elsewhere which is modified by the introduction of a very simple boundary condition at the current front, namely a fixed cutoff thickness hc. As the introduction of this new parameter breaks up self-similarity, we obtain the complete solution by pasting successive self-similar solutions, each one corresponding to slightly different ratios hc /h0, where h0 is the thickness at the center of the drop. The results are in excellent agreement with our own and other authors' experimental data, showing that this heuristic model gives the right correction to the original theory.
Norbert Willenbacher - One of the best experts on this subject based on the ideXlab platform.
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Apparent elongational yield stress of soft matter
Journal of Rheology, 2013Co-Authors: Laetitia Martinie, Hans Buggisch, Norbert WillenbacherAbstract:Apparent elongational yield stresses of soft matter including polymer gels, highly concentrated emulsions, and aggregated suspensions have been determined from step stretch experiments. Materials display apparent shear yield stresses in the range 1–100 Pa and large but finite shear relaxation times tR. For all investigated fluids, the Laplace Pressure within the stretched filaments is essentially constant during an initial period of time after the step strain. Then, it increases rapidly and finally the filaments break. Filament lifetime tf strongly increases with decreasing stretching ratio e. The apparent elongational yield stress is identified as the initial value of the Laplace Pressure obtained at a critical stretching ratio ec corresponding to a Deborah number De = tR /tf = 1. For all fluids, the ratio of this elongational yield stress to shear yield stress is √3 in agreement with the von Mises plasticity criterion, irrespective of the physical nature of structural breakdown. Elongational experiments performed at different e or tf covering Deborah numbers between 0.1 and 100 reveal a universal relationship between the initial plateau value of the Laplace Pressure normalized to the shear yield stress and De. This stress ratio varies between 0.5 and 5, and equals √3 only for De ≈ 1.
Willenbacher Norbert - One of the best experts on this subject based on the ideXlab platform.
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Apparent elongational yield stress of soft matter
Journal of Rheology, 2013Co-Authors: Laetitia Martinie, Buggisch, Hans, Willenbacher NorbertAbstract:Apparent elongational yield stresses of soft matter including polymer gels, highly concentrated emulsions, and aggregated suspensions have been determined from step stretch experiments. Materials display apparent shear yield stresses in the range 1–100 Pa and large but finite shear relaxation times tR. For all investigated fluids, the Laplace Pressure within the stretched filaments is essentially constant during an initial period of time after the step strain. Then, it increases rapidly and finally the filaments break. Filament lifetime tf strongly increases with decreasing stretching ratio ε. The apparent elongational yield stress is identified as the initial value of the Laplace Pressure obtained at a critical stretching ratio εc corresponding to a Deborah number De = tR /tf = 1. For all fluids, the ratio of this elongational yield stress to shear yield stress is √3 in agreement with the von Mises plasticity criterion, irrespective of the physical nature of structural breakdown. Elongational experiments performed at different ε or tf covering Deborah numbers between 0.1 and 100 reveal a universal relationship between the initial plateau value of the Laplace Pressure normalized to the shear yield stress and De. This stress ratio varies between 0.5 and 5, and equals √3 only for De ≈ 1.
