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- Flow-3D Modelling of the Debris Effect on Maximum Scour Hole Depth at Bridge PiersPublication . Mendonça, Inês Sofia Pereira; Canilho, Hugo Daniel Leitão; Fael, Cristina Maria SenaBridge foundations are frequently inserted in riverbeds constituted by alluvial material, being, therefore, subjected to scouring processes. Such phenomenon is aggravated during flood events due to the increase of water flow or due to the increase of the debris carried by the flow that can pile up along the bridge structural elements. The debris can partially obstruct bridge spans and accumulate near bridge piers and abutments, which will have consequences in terms of reduction of flow capacity and an increment of the maximum scour depth. The dimensions, shape and its location are characteristics that must be considered when predicting the scour depth. The present study aims at analyzing the effect of the debris on the maximum clear-water scour depth at cylindrical piers inserted in uniform sand, non-ripple forming sand, fully-developed turbulent flows in wide rectangular channel, using computational fluid dynamics software, Flow-3D. For this purpose, debris with a triangular and rectangular shape, floating and on the sand bed, were tested, using the k-ε RNG turbulence model and the numerical results were compared with those obtained experimentally. It was possible to verify that the floating debris gives greater scour hole depth and the debris on sand bed behave as scour countermeasure reducing the scour hole depth. Also, rectangular shaped debris seems to cause more scour near the structures than the triangular shaped ones, which also seemed beneficial to the scour hole, by reducing it. However, the results obtained computationally are significantly lower than those obtained experimentally.
- Velocity Field Analysis of a Channel Narrowed by Spur-dikes to Maximize Power Output of In-stream TurbinesPublication . Canilho, Hugo Daniel Leitão; Fael, Cristina Maria SenaDecentralized energy is growing in importance with time. The electricity being needed even in the most remote places, far from power stations, increases the importance of small power production devices such as micro-hydro devices like turbines. In this research, the velocity field in a meandering channel is studied in its natural conditions and with the introduction of spur-dikes, structures that prevent bank erosion, a natural phenomenon observed in meandering channels, with the use of computational fluid dynamics software. With the objective of improving the power production by investigating the changes of the flume velocities with the introduction of spur-dikes, one test without any spur-dike and three tests with it were conducted. Good results were reached, with velocities increasing between 10 to 20% with the introduction of these structures. In certain cases, the increase in power production can reach up to 85% than in a normal situation without spur-dikes in the river.
- Summary of in-stream energy production devicesPublication . Canilho, Hugo Daniel Leitão; Fael, Cristina Maria SenaRenewable energy is more important as the time advances. The need to replace fossil fuels such as coal and oil is a big concern in the European union which has established goals of 20% of share of energy from renewable sources in whole European union. The importance of small energy production devices increases when we think of this goal, so energy can reach every citizen, even in a remote village which is kilometers away from the main power source. In-stream devices are optimal for remote sources, which almost always have a water source in the proximities. In-stream turbines can generate enough power to a common house and because it does not require any sort of head nor dam it is easy to mount. Its efficiency is around 40% for most recent in-stream turbines. The most recent technology in this area, the vortex induced vibration devices are still in development reaching 20-30% efficiency when a single device is working, reaching up to 40% when arrayed in some exact positions.