Search results for "Fluid dynamics"

2020

Abstract. Fluid flow on different scales is of interest for several Earth science disciplines like petrophysics, hydrogeology and volcanology. To parameterize fluid flow in large-scale numerical simulations (e.g. groundwater and volcanic systems), flow properties on the microscale need to be considered. For this purpose experimental and numerical investigations of flow through porous media over a wide range of porosities are necessary. In the present study we sinter glass bead media with various porosities and measure the permeability experimentally. The microstructure, namely effective porosity and effective specific surface, is investigated using image processing. We determine flow proper…

Combined numerical and experimental study of microstructure and permeability in porous granular media

2020

<div> <div> <div> <p>Fluid flow on different scales is of interest for several Earth science disciplines like petrophysics, hydrogeology and volcanology. To parameterize fluid flow in large-scale numerical simulations (e.g. groundwater and volcanic systems), flow properties on the microscale need to be considered. For this purpose experimental and numerical investigations of flow through porous media over a wide range of porosities are necessary. In the present study we sinter glass bead media with various porosities, representing shallow depth crustal sediments. The microstructure, namely effective porosity …

Wind- and tide-induced currents in the Stagnone Lagoon (Sicily)

2011

The hydrodynamic circulation is analyzed in the coastal lagoon of Stagnone di Marsala, a natural reserve located in the north-western part of Sicily, using both experimental measurements and numerical simulations. Field measurements of velocities and water levels, carried out using an ultrasound sensor (3D), are used to validate the numerical model. A 3D finite-volume model is used to solve the Reynolds-averaged momentum and mass balance differential equations on a curvilinear structured grid, employing the k– $${\varepsilon}$$ turbulence model for the Reynolds stresses. The numerical analysis allows to identify the relative contribution of the forces affecting the hydrodynamic circulation …

A laboratory and theoretical study on the uptake of sulfur dioxide gas by small water drops containing hydrogen peroxide under laminar and turbulent …

2000

Abstract Laboratory experiments are described where the uptake of SO2 gas by water drops containing H2O2 is investigated where the taken up S(IV) is quickly converted to S(VI). During the gas uptake the drops were freely suspended at their terminal velocity by means of the Mainz vertical wind tunnel. Two series of experiments were carried out, one with a laminar air flow in the wind tunnel, one with a turbulent air flow in the wind tunnel. Afterwards, the experimental results were compared against model computations using the so-called fully mixed convective diffusion model. The experimental results for laminar flow conditions showed that the fully mixed convective diffusion model for the u…

Bench-scale investigation of inclined dense jets

2005

In this work experimental data on the geometry of dense inclined jets issuing in a lab-scale glass rectangular tank are presented. The surrounding fluid was always tap water at room temperature while the dense jets were water solutions of NaCl. Four parameters were changed in the experiments, namely nozzle diameter and inclination, and jet density and flow rate. Jet trajectories were revealed by a colored tracer. Images of the jet were recorded by a digital camera and then further digitally processed, eventually resulting in a time-averaged tracer intensity field. All the jet geometrical parameters, once normalized, were found to be very well correlated to the densimetric Froude number. Mod…

Experimental investigation on dispersion mechanisms in rigid and flexible vegetated beds

2018

Vegetation in channels strongly affects flow structure and turbulence, with consequences on the hydrological storage of nutrients and chemical tracers, the shelter of stream biota as well as the trapping or transport of sediments. At the same time, all these phenomena are inevitably subjected to alteration of hydrological conditions in fluvial systems due to climate change. The present study intends to provide a thorough investigation into the processes of transport and dispersion induced by flow turbulence within the vegetation structure. Specifically, velocity measurements in vegetated channels were intensively conducted and analyzed in the case of both flexible submerged and rigid emerge…

Flow Velocity Measurements in Vegetated Channels

2002

Understanding of the hydraulics of flow over vegetation is very important to support the management of fluvial processes. In this paper the flow over flexible bottom vegetation is experimentally studied. A two-dimensional-acoustic doppler velocimeter is used to measure the local flow velocities for different vegetation concentrations, discharges, and flume slopes. The influence of vegetation concentration and the depth/vegetation height ratio on the measured velocity profiles is analyzed. All measured velocity distributions are S-shaped and exhibit a three-zone profile. The relationship between the velocity distribution and the turbulence intensity distribution is also analyzed. The charact…

New stage-discharge relationships for radial gates

2013

Calibration of gates under free and submerged flow regimes is a classical hydraulic problem. In this paper dimensional analysis was applied to investigate both free and submerged flow conditions through a radial gate. The original Ferro’s method for submerged flow regime was modified by introducing the maximum allowable tail water depth permitting free flow. Based on Buckingham theorem and applying the Incomplete Self Similarity (ISS) concept different forms of the dimensional equations were proposed. According to the current available experimental data the most accurate dimensionless formula was proposed. The proposed dimensional equation not only is more accurate than the original Ferro’s…

Testing the Outflow Process over a Triangular Labyrinth Weir

2017

In this paper, the dimensionless stage-discharge relation for a sharp-crested triangular labyrinth weir, determined in a previous study, is initially tested by some experimental runs carried out in a laboratory flume. According to this relationship, the flow magnification is affected by the length-magnification ratio and the head to one cycle width ratio. The measurements allowed to test the applicability of this dimensionless relation for different values of both the angle of the sidewall to the main flow direction and the weir height. Finally, the proposed dimensionless equation was also tested by using experimental measurements carried out for broad-crested triangular labyrinth weir.

Vegetation effects on cross-sectional flow in a large amplitude meandering bend

2017

ABSTRACTCross-stream circulation, which develops in meandering bends, exerts an important role in velocity redistribution. This paper investigates how the presence of vegetation could affect the evolution pattern of cross-stream flow along a high-curvature meandering bend. The analysis is conducted with the aid of data collected in a meandering laboratory flume over non-vegetated and vegetated beds. The experiments reveal that, once the vegetation is introduced, the flow pattern determined by the channel’s curvature is interrupted. In the presence of vegetation, the central-region circulation cell seems to be divided into thin circulation cells developing at the top of the vegetated layer a…