We present an experimental study of gravity currents in a cylindrical geometry, in the presence of vegetation. Forty tests were performed with a brine advancing in a fresh water ambient fluid, in lock release, and with a constant and time-varying flow rate. The tank is a circular sector of angle $30^circ$ with radius equal to 180 cm. Two different densities of the vegetation were simulated by vertical plastic rods with diameter $D=1.6; extrm{cm}$. We marked the height of the current as a function of radius and time and the position of the front as a function of time. The results indicate a self-similar structure, with lateral profiles that after an initial adjustment collapse to a single curve in scaled variables. The propagation of the front is well described by a power law function of time. The existence of self-similarity on an experimental basis corroborates a simple theoretical model with the following assumptions: (i) the dominant balance is between buoyancy and drag, parameterized by a power law of the current velocity $sim |u|^{lambda-1}u$; (ii) the current advances in shallow-water conditions; (iii) ambient-fluid dynamics is negligible. In order to evaluate the value of ${lambda}$ (the only tuning parameter of the theoretical model), we performed two additional series of measurements. We found that $lambda$ increased from 1 to 2 while the Reynolds number increased from 100 to approximately $6cdot10^3$, the drag coefficient and the transition from $lambda=1$ to $lambda=2$ are quantitatively affected by $D$, but the structure of the model is not.

Experimental study on radial gravity currents flowing in a vegetated channel / Petrolo, Diana; Ungarish, Marius; Chiapponi, Luca; Longo, Sandro Giovanni. - In: JOURNAL OF FLUID MECHANICS. - ISSN 1469-7645. - 933:(2022), pp. A46.1-A46.38. [10.1017/jfm.2021.1059]

Experimental study on radial gravity currents flowing in a vegetated channel

Diana Petrolo;Marius Ungarish;Luca Chiapponi;Sandro Longo
2022

Abstract

We present an experimental study of gravity currents in a cylindrical geometry, in the presence of vegetation. Forty tests were performed with a brine advancing in a fresh water ambient fluid, in lock release, and with a constant and time-varying flow rate. The tank is a circular sector of angle $30^circ$ with radius equal to 180 cm. Two different densities of the vegetation were simulated by vertical plastic rods with diameter $D=1.6; extrm{cm}$. We marked the height of the current as a function of radius and time and the position of the front as a function of time. The results indicate a self-similar structure, with lateral profiles that after an initial adjustment collapse to a single curve in scaled variables. The propagation of the front is well described by a power law function of time. The existence of self-similarity on an experimental basis corroborates a simple theoretical model with the following assumptions: (i) the dominant balance is between buoyancy and drag, parameterized by a power law of the current velocity $sim |u|^{lambda-1}u$; (ii) the current advances in shallow-water conditions; (iii) ambient-fluid dynamics is negligible. In order to evaluate the value of ${lambda}$ (the only tuning parameter of the theoretical model), we performed two additional series of measurements. We found that $lambda$ increased from 1 to 2 while the Reynolds number increased from 100 to approximately $6cdot10^3$, the drag coefficient and the transition from $lambda=1$ to $lambda=2$ are quantitatively affected by $D$, but the structure of the model is not.
Experimental study on radial gravity currents flowing in a vegetated channel / Petrolo, Diana; Ungarish, Marius; Chiapponi, Luca; Longo, Sandro Giovanni. - In: JOURNAL OF FLUID MECHANICS. - ISSN 1469-7645. - 933:(2022), pp. A46.1-A46.38. [10.1017/jfm.2021.1059]
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11381/2906330
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