Three-dimensional simulation of river flood flows

This thesis describes the implementation of general Computational Fluid Dynamics (CFD) techniques to laboratory and natural channels under flood flow conditions. Two commercially available codes, TELEMAC and CFX4, have been used in this work.The assessment of CFD for the calculation of flooded channel flow dynamics is carried out by simulating one laboratory test case from the Flood Channel Facility (FCF) Series B. This test case is that of a meandering two-stage channel with a depth ratio of 25% on the flood plain. Results from a computer simulation of experiment B23 are presented with a detailed quantitative comparison of the measured velocity, turbulence and bed shear stress. It supports the conclusion that CFD is able to account for the different flow mechanisms arising from the interaction between inbank and overbank flows in meandering channels. The maximum error in the prediction of the velocity is 10% and the comparisons show the calculations of bed shear stress to be reasonably accurate as well. Numerical tests indicate that the numerical solution is relatively independent of the boundary conditions, and confirm that turbulence transport is of minor importance in the experiment simulated.Numerical results from the simulation of flood flow mechanisms in natural rivers are also presented. It is hoped that these are of value to practitioners. Two 1-km reaches on the River Severn and River Ribble are modelled. They permit the investigation of two-stage channel flow dynamics at a larger scale. The numerical verification process establishes that the scale and the complex nature of the geometry are limiting factors, particularly for the numerical discretization of the domain and the calculation of the variables at the walls. It is however possible to estimate a priori part of the error such constraints generate. Away from the walls, the flow main features seem well predicted. The parallel between the velocity fields observed in river flood flows and those observed in the FCF is evident. Validation against field data suggests that the models are able to reproduce the flow mechanisms and account for bed shear stress variations correctly. Yet a significant level of uncertainty remains when the model predictions are compared against measured point data; more validation work is therefore required

Deep learning approaches to aircraft maintenance, repair and overhaul: a review

The use of sensor technology constantly gathering aircrafts' status data has promoted the rapid development of data-driven solutions in aerospace engineering. These methods assist, for instance, with determining appropriate actions for aircraft maintenance, repair and overhaul (MRO). Challenges however are found when dealing with such large amounts of data. Identifying patterns, anomalies and faults disambiguation, with acceptable levels of accuracy and reliability are examples of complex problems in this area. Experiments using deep learning techniques, however, have demonstrated its usefulness in assisting on the analysis aircraft health data. The purpose of this paper therefore is to conduct a survey on deep learning architectures and their application in aircraft MRO. Although deep learning in general is not yet largely exploited for aircraft health, from our search, we identified four main architectures employed to MRO, namely, Deep Autoencoders, Long Short-Term Memory, Convolutional Neural Networks and Deep Belief Networks. For each architecture, we review their main concepts, the types of problems to which these architectures are employed to, the type of data used and their outcomes. We also discuss how research in this area can be advanced by identifying current research gaps and outlining future research opportunities

Minimization of electro-mechanical interaction with posicast strategies for more-electric aircraft applications

This paper studies strategies to minimize the electromechanical interaction (EMI) within aircraft power systems. With the growth of electrical power on-board aircraft, the interaction between the electrical systems and the engine core will become significant. The behaviour of electrical loads (on/off, transient etc.) will have significant impacts on the engine shaft, such as producing transient vibrations, creating stability problems and reducing the efficiency etc. To avoid these problems, an advanced electrical power management system (PMS) is required. This paper introduces novel loading methods for PMS applications to minimize the interactions between electrical and mechanical systems. The strategies, referred as Single Level Multi-edge Switching Loads (SLME), Multilevel Loading (MLL), and Multi-load Single Level Multi-edge Switching Loads (MSLME) are developed based on the Posicast method. An insight look of the developed technique has been studied using the zero-pole root locus. It is demonstrated that the excited poles in the system are cancelled by the addition of zeros, and thus supressed the EMI vibrations

Minimization of electro-mechanical interaction with posicast strategies for more-electric aircraft applications

This paper studies strategies to minimize the electromechanical interaction (EMI) within aircraft power systems. With the growth of electrical power on-board aircraft, the interaction between the electrical systems and the engine core will become significant. The behaviour of electrical loads (on/off, transient etc.) will have significant impacts on the engine shaft, such as producing transient vibrations, creating stability problems and reducing the efficiency etc. To avoid these problems, an advanced electrical power management system (PMS) is required. This paper introduces novel loading methods for PMS applications to minimize the interactions between electrical and mechanical systems. The strategies, referred as Single Level Multi-edge Switching Loads (SLME), Multilevel Loading (MLL), and Multi-load Single Level Multi-edge Switching Loads (MSLME) are developed based on the Posicast method. An insight look of the developed technique has been studied using the zero-pole root locus. It is demonstrated that the excited poles in the system are cancelled by the addition of zeros, and thus supressed the EMI vibrations