dorsal/arxiv
View SchemaTwo-dimensional flow of foam around a circular obstacle: local measurements of elasticity, plasticity and flow
| Authors | Benjamin Dollet, Francois Graner |
|---|---|
| Categories | |
| ArXiv ID | physics/0606170 |
| URL | https://arxiv.org/abs/physics/0606170 |
| DOI | 10.1017/S0022112007006830 |
Abstract
We investigate the two-dimensional flow of a liquid foam around circular obstacles by measuring all the local fields necessary to describe this flow: velocity, pressure, bubble deformations and rearrangements. We show how our experimental setup, a quasi-2D "liquid pool" system, is adapted to the determination of these fields: the velocity and bubble deformations are easy to measure from 2D movies, and the pressure can be measured by exploiting a specific feature of this system, a 2D effective compressibility. To describe accurately bubble rearrangements, we propose a new, tensorial descriptor. All these quantities are evaluated via an averaging procedure that we justify showing that the fluctuations of the fields are essentially random. The flow is extensively studied in a reference experimental case; the velocity presents an overshoot in the wake of the obstacle, the pressure is maximum at the leading side and minimal at the trailing side. The study of the elastic deformations and of the velocity gradients shows that the transition between plug flow and yielded regions is smooth. Our tensorial description of T1s highlight their correlation both with the bubble deformations and the velocity gradients. A salient feature of the flow, notably on the velocity and T1 repartition, is a marked asymmetry upstream/downstream, signature of the elastic behaviour of the foam. We show that the results do not change qualitatively when various control parameters vary, identifying a robust quasistatic regime. These results are discussed in the frame of the actual foam rheology literature, and we argue that they constitute a severe test for existing rheological models, since they capture both the elastic, plastic and fluid behaviour of the foam.
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"abstract": "We investigate the two-dimensional flow of a liquid foam around circular\nobstacles by measuring all the local fields necessary to describe this flow:\nvelocity, pressure, bubble deformations and rearrangements. We show how our\nexperimental setup, a quasi-2D \"liquid pool\" system, is adapted to the\ndetermination of these fields: the velocity and bubble deformations are easy to\nmeasure from 2D movies, and the pressure can be measured by exploiting a\nspecific feature of this system, a 2D effective compressibility. To describe\naccurately bubble rearrangements, we propose a new, tensorial descriptor. All\nthese quantities are evaluated via an averaging procedure that we justify\nshowing that the fluctuations of the fields are essentially random. The flow is\nextensively studied in a reference experimental case; the velocity presents an\novershoot in the wake of the obstacle, the pressure is maximum at the leading\nside and minimal at the trailing side. The study of the elastic deformations\nand of the velocity gradients shows that the transition between plug flow and\nyielded regions is smooth. Our tensorial description of T1s highlight their\ncorrelation both with the bubble deformations and the velocity gradients. A\nsalient feature of the flow, notably on the velocity and T1 repartition, is a\nmarked asymmetry upstream/downstream, signature of the elastic behaviour of the\nfoam. We show that the results do not change qualitatively when various control\nparameters vary, identifying a robust quasistatic regime. These results are\ndiscussed in the frame of the actual foam rheology literature, and we argue\nthat they constitute a severe test for existing rheological models, since they\ncapture both the elastic, plastic and fluid behaviour of the foam.",
"arxiv_id": "physics/0606170",
"authors": [
"Benjamin Dollet",
"Francois Graner"
],
"categories": [
"physics.flu-dyn"
],
"doi": "10.1017/S0022112007006830",
"title": "Two-dimensional flow of foam around a circular obstacle: local measurements of elasticity, plasticity and flow",
"url": "https://arxiv.org/abs/physics/0606170"
},
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