Onset of turbulence in a regular porous medium : An experimental study

Peer reviewedPublisher PD

On the role of infiltration and exfiltration in swash zone boundary layer dynamics

Funded by Mexican National Council of Science and Technology (CoNACyT) . Grant Number: 490080 Fulbright-Garcia Robles grant Instituto de Ingeniería UNAM International Collaborative Research project University of Delaware DGAPA UNAM National Science Foundation . Grant Numbers: OCE-0845004 , OCE-1332703 University of Delaware UK Engineering and Physical Sciences Research Council ‘Flood MEMORY: Multi-Event Modelling Of Risk & recoverY’ . Grant Number: EP EP/K013513/1Peer reviewedPublisher PD

Three-dimensional in situ observations of compressive damage mechanisms in syntactic foam using X-ray microcomputed tomography

Royal Society Grant number RG140680 Lloyd's Register Foundation (GB) Oil and Gas Academy of Scotland Open access via Springer Compact AgreementPeer reviewedPublisher PD

Experimental study of bore-driven swash hydrodynamics on impermeable rough slopes

Copyright 2012 Elsevier B.V., All rights reserved.Peer reviewedPublisher PD

Bed-load effects on hydrodynamics of rough-bed open-channel flows

Peer reviewedPublisher PD

The structure of gravel-bed flow with intermediate submergence: a laboratory study

The paper reports an experimental study of the flow structure over an immobile gravel bed in open channel at intermediate submergence, with particular focus on the near-bed region. The experiments consisted of velocity measurements using three-component (stereoscopic) Particle Image Velocimetry (PIV) in near-bed horizontal plane and two-component PIV in three vertical planes that covered three distinctly different hydraulic scenarios where the ratio of flow depth to roughness height (i.e., relative submergence) changes from 7.5 to 10.8. Detailed velocity measurements were supplemented with fine-scale bed elevation data obtained with a laser scanner. The data revealed longitudinal low-momentum and high-momentum "strips'' in the time-averaged velocity field, likely induced by secondary currents. This depth-scale pattern was superimposed with particle-scale patches of flow heterogeneity induced by gravel particle protrusions. A similar picture emerged when considering second-order velocity moments. The interaction between the flow field and gravel-bed protrusions is assessed using cross correlations of velocity components and bed elevations in a horizontal plane just above gravel particle crests. The cross correlations suggest that upward and downward fluid motions are mainly associated with upstream-facing and lee sides of particles, respectively. Results also show that the relative submergence affects the turbulence intensity profiles for vertical velocity over the whole flow depth, while only a weak effect, limited to the near-bed region, is noticed for streamwise velocity component. The approximation of mean velocity profiles with a logarithmic formula reveals that log-profile parameters depend on relative submergence, highlighting inapplicability of a conventional "universal'' logarithmic law for gravel-bed flows with intermediate submergence

Subsurface processes generated by bore-driven swash on coarse-grained beaches

Peer reviewedPublisher PD

Surface and subsurface contributions to the build-up of forces on bed particles

In nature and in many industrial applications, the boundary of a channel flow is made of solid particles which form a porous wall, so that there is a mutual influence between the free flow and the subsurface flow developing inside the pores. While the influence of the porous wall on the free flow has been well studied, less well characterized is the subsurface flow, due to the practical difficulties in gathering information in the small spaces given by the pores. It is also not clear whether the subsurface flow can host turbulent events able to contribute significantly to the build-up of forces on the particles, potentially leading to their dislodgement. Through large eddy simulations, we investigate the interface between a free flow and a bed composed of spherical particles in a cubic arrangement. The communication between surface and subsurface flow is in this case enhanced, with relatively strong turbulent events happening also inside the pores. After comparing the simulation results with a previous experimental work from a similar setting, the forces experienced by the boundary particles are analysed. While it remains true that the lift forces are largely dependent on the structure of the free flow, turbulence inside the pores can also give a significant contribution. Pressure inside the pores is weakly correlated to the pressure in the free flow, and strong peaks above and below a particle can happen independently. Ignoring the porous layer below the particle from the computations leads then in this case to an underestimation of the lift forces

Dimensionamento das armaduras de compressão em chapas de concreto armado

This paper presents a method to design membrane elements of concrete with orthogonal mesh of reinforcement which are subject to compressive stress. Design methods, in general, define how to quantify the reinforcement necessary to support the tension stress and verify if the compression in concrete is within the strength limit. In case the compression in membrane is excessive, it is possible to use reinforcements subject to compression. However, there is not much information in the literature about how to design reinforcement for these cases. For that, this paper presents a procedure which uses the model based on Baumann's [1] criteria. The strength limits used herein are those recommended by CEB [3], however, a model is proposed in which this limit varies according to the tensile strain which occur perpendicular to compression. This resistance model is based on concepts proposed by Vecchio e Collins [2]