Now showing 1 - 5 of 5
  • Publication
    Liquid Wicking in Hierarchical Microstructures
    (European Study Group with Industry, 2018-06-29) ; ;
    The aim of this work is to model the flow of liquid as it spreads through a structured cavity (‘wicking’), as described schematically in Figure 1. The problem was posed by Analog Devices in the context of the 118th European Study Group with Industry, which was held in UCD in July 2018. The aim of the modelling exercise is to find the optimum structure morphology/size/porosity/materials for wicking/routing of liquid inside a cavity under various temperature and environment conditions? Wicking of surfaces has many applications in the fields of biology, sensing and integrated chip cooling. As such, the existing literature on the subject is extensive. Therefore, the first objective of this report is to carry out a detailed literature review (Section 2), wherein we outline how the answers to many of the questions posed by Analog Devices can be answered by methods from the existing literature. Further refinements of this approach could be carried out, if any of the questions are not answered in this report. In this existing literature, the fluid that permeates the substrate is assumed to come from an infinite reservoir. Therefore, in section 3 we examine how including the finite volume of the liquid drop that permeates into the substrate affects the spreading dynamics. Additionally, we have also examined lubrication theory as a way of providing a very detailed and mathematically consistent description of wetting on rough surfaces, which we describe below in Section 4. Finally, our conclusions are presented in Section 5.
  • Publication
    Incorporating Wave Spectrum Information in Real-time Free-surface Elevation Forecasting: Real-sea Experiments
    Real-time prediction of free-surface elevation is necessary for a variety of applications. Assuming a Gaussian wave field, the wave spectrum can be used to calculate the statistically optimal predictor, for a given prediction configuration (i.e. for a given combination of measurement instants and spatial locations, relative to the instants and locations where and when the wave is predicted). More specifically, the optimal predictor is linear, and its coefficients need only be updated as the wave condition evolves. This spectrum-based prediction (SBP) approach encompasses, in a unified theoretical framework, both “time-series” and “spatially-distributed” prediction configurations. In this paper, the validity of the SBP theoretical framework is tested against real-sea wave data, which originate from a measurement campaign using an Acoustic Doppler Current Profiler (ADCP), and consist of free-surface elevation time series, at the corners and centre of a 25m-by-25m square. The directional wave spectra, corresponding to the sea states where the time series are provided, have also been calculated. The empirical SBP accuracy, obtained by applying the SBP in the real-sea time series, is assessed in various sea conditions and prediction configurations, and compared with the theoretical SBP accuracy, evaluated based on the wave spectra. Although the ADCP measurement layout is clearly not ideal for the purpose of wave forecasting, empirical results are physically and statistically consistent, and show good agreement with theoretical results, thus supporting the relevance of the SBP framework.
      432Scopus© Citations 6
  • Publication
    Liquid interactions with porous media and the fate of toxic materials
    Toxic liquid chemicals released into the environment may pose an immediate risk to human health through contact or related vapour hazards. However, they can also interact with surfaces and remain in situ, potentially presenting a subsequent hazard. To improve understanding of the fate of these materials in different environments, the study group investigated interactions between liquid droplets and porous media across a range of different time scales.
  • Publication
    Bananas - defects in the jet stripping process
    (European Study Group with Industry, 2016-08-31) ; ; ; ;
    The problem of coating steel by passing it through a bath of molten alloy is considered. The thickness of the coating is determined by the operating conditions of the process, including the speed of travel, temperature of the sheeting and the air pressure and shear from the air knives that operate to strip off excess liquid alloy. During the process, on wider sheets and those with thicker coatings, there sometimes appear defects - known as bananas. These appear at the edges and curve upwards. These regions are almost completely devoid of any coating and hence are not suitable for sale. The group revisited previous work before considering several processes that may be relevant to the problem. These included a two-dimensional model allowing variation in air pressure across the sheet, a study of the backflow generated by the air knives and the Marangoni (surface tension) effect near the edge of the sheet.
  • Publication
    Segmentation and Scene Content in Moving Images
    The problem of scene content in moving images was brought by Aralia. The goal in this study group was to consider two problems. The first was image segmentation and the second is the context of the scene. These problems were explored in different areas, namely the Bayesian approach to image segmentation, shadow detection, shape recognition and background separation.