Mechanical Engineering - Research Publications
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ItemNo Preview AvailableFrom supply chain risk to system-wide disruptions: research opportunities in forecasting, risk management and product design(EMERALD GROUP PUBLISHING LTD, 2023-02-28)Purpose Supply chains must rebuild for resilience to respond to challenges posed by systemwide disruptions. Unlike past disruptions that were narrow in impact and short-term in duration, the Covid pandemic presented a systemic disruption and revealed shortcomings in responses. This study outlines an approach to rebuilding supply chains for resilience, integrating innovation in areas critical to supply chain management. Design/methodology/approach The study is based on extensive debates among the authors and their peers. The authors focus on three areas deemed fundamental to supply chain resilience: (1) forecasting, the starting point of supply chain planning, (2) the practices of supply chain risk management and (3) product design, the starting point of supply chain design. The authors’ debated and pooled their viewpoints to outline key changes to these areas in response to systemwide disruptions, supported by a narrative literature review of the evolving research, to identify research opportunities. Findings All three areas have evolved in response to the changed perspective on supply chain risk instigated by the pandemic and resulting in systemwide disruptions. Forecasting, or prediction generally, is evolving from statistical and time-series methods to human-augmented forecasting supplemented with visual analytics. Risk management has transitioned from enterprise to supply chain risk management to tackling systemic risk. Finally, product design principles have evolved from design-for-manufacturability to design-for-adaptability. All three approaches must work together. Originality/value The authors outline the evolution in research directions for forecasting, risk management and product design and present innovative research opportunities for building supply chain resilience against systemwide disruptions.
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ItemNo Preview AvailableAutomatic Facial Expression Analysis as a Measure of User-Designer Empathy(ASME, 2023-03-01)Abstract In human-centered product design and development, understanding the users is essential. Empathizing with the user can help designers gain deeper insights into the user experience and their needs. However, a few studies have captured empathy real time during user interactions. Accordingly, the degree to which empathy occurs and enhances user understanding remains unclear. To narrow this gap, a study was performed exploring the use of video-based facial expression analysis during user interviews, as a means to capture empathy related to understanding vehicle driving experiences under challenging conditions. Mimicry and synchrony have been shown to be predictors of empathy in cognitive psychology. In this study, we adapted this method to study 46 user-designer interviews. The results show that the user and designer exhibited mimicry in their facial expressions, which thereby indicated that affective empathy can be captured via simple video facial recognition. However, we found that the user's facial expressions might not represent their actual emotional tone, which can mislead the designer, and they achieve false empathy. Further, we did not find a link between the observed mimicry of facial expressions and the understanding of mental contents, which indicated that the affective and some cognitive parts of user empathy may not be directly connected. Further studies are needed to understand how facial expression analysis can further be used to study and advance empathic design.
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ItemNo Preview AvailableDefining an equivalent homogeneous roughness length for turbulent boundary layers developing over patchy or heterogeneous surfaces(Elsevier BV, 2023-03-01)A new approach based on the power mean is suggested for defining an equivalent homogeneous roughness length kehr which takes into account patchiness or heterogeneous distribution of roughness on ship hulls and can be readily incorporated into existing full-scale drag prediction methods. In the limit where patch sizes are much greater than the boundary layer thickness, it is readily shown that the relationship between drag coefficient and roughness length is non-linear, highlighting an obvious source of error with current approaches that attempt to define an equivalent homogeneous roughness through an area-weighed arithmetic mean. The degree of error is dependent on the roughness distribution, but is estimated to exceed 16% for highly skewed beta heterogeneous distributions. For fully-rough models, the power-mean approach returns errors of <1% for the distributions tested here. The efficacy of the power-mean approach is also evaluated in the transitional regime and with different transitional roughness models (Nikuradse and Colebrook) and retains accuracy for most realistic operating scenarios.
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ItemNo Preview AvailableTeaching and learning of industry 4.0: expectations, drivers, and barriers from a knowledge management perspective(TAYLOR & FRANCIS LTD, 2023-07-04)
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ItemNo Preview AvailableFlows past cylinders confined within ducts. Effects of the duct width(Elsevier BV, 2023-09)
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ItemDouble-Diffusive Layer and Meltwater Plume Effects on Ice Face Scalloping in Phase-Change Simulations(AMER GEOPHYSICAL UNION, 2023-09-16)Abstract Antarctic ice shelves are losing mass at increasing rates, yet the ice‐ocean interactions that cause significant ice loss are not well understood. A new approach of high‐resolution phase‐change simulations is used to model vertical ice melting into a stratified ocean. The ocean dynamics show complicated interplay between a turbulent buoyant meltwater plume and double‐diffusive layers, while the ice actively melts and changes topography. At room temperatures, the double‐diffusive layer thickness is closely linked to ice scalloping. At lower, more realistic ocean temperatures, the meltwater plume becomes prominent with a laminar‐to‐turbulent transition imprinting an indent on the melting ice. The double‐diffusive layer thickness is consistent with scaling prediction, while the real‐world application demonstrates reasonably good matching of the scaling prediction for some Antarctic regions. Our study is a key first step toward the future use of high‐resolution phase‐change fluid dynamics simulations to better understand Antarctic ice shelves in a changing climate.
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ItemEvidence that superstructures comprise self-similar coherent motions in high Reynolds number boundary layers(Cambridge University Press, 2023-08-11)We present experimental evidence that the superstructures in turbulent boundary layers comprise smaller, geometrically self-similar coherent motions. The evidence comes from identifying and analysing instantaneous superstructures from large-scale particle image velocimetry datasets acquired at high Reynolds numbers, capable of capturing streamwise elongated motions extending up to 12 times the boundary layer thickness. Given the challenge in identifying the constituent motions of the superstructures based on streamwise velocity signatures, a new approach is adopted that analyses the wall-normal velocity fluctuations within these very long motions, which reveals the constituent motions unambiguously. The conditional streamwise energy spectra of the Reynolds shear stress and the wall-normal fluctuations, corresponding exclusively to the superstructure region, are found to exhibit the well-known distance-from-the-wall scaling in the intermediate-scale range. It suggests that geometrically self-similar motions are the constituent motions of these very-large-scale structures. Investigation of the spatial organization of the wall-normal momentum-carrying eddies, within the superstructures, also lends empirical support to the concatenation hypothesis for the formation of these structures. The association between the superstructures and self-similar motions is reaffirmed on comparing the vertical coherence of the Reynolds-shear-stress-carrying motions, by computing conditionally averaged two-point correlations, which are found to match with the mean correlations. The mean vertical coherence of these motions, investigated for the log region across three decades of Reynolds numbers, exhibits a unique distance-from-the-wall scaling invariant with Reynolds number. The findings support modelling of these dynamically significant motions via data-driven coherent structure-based models.
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ItemNo Preview AvailableDirect Numerical Simulation of Riblets Applied to Gas Turbine Compressor Blades at On- and Off- Design Incidences(ASME, 2023-06-26)Any realizable increase in gas turbine efficiency has significant potential to reduce fuel burn and environmental impact. Streamwise micro-groove surfaces (‘riblets’) are well-known as a passive surface treatment to reduce drag, which may be useful in the context of increasing overall gas turbine efficiency. This paper presents the first direct numerical simulation of potentially performance-enhancing riblets on an axial flow high pressure compressor blade, where the micro-geometry of the riblets is fully resolved. The midspan section of a NACA6510 profile is considered at an engine-relevant true chord Reynolds number of 700,000 and Mach number 0.5 based on inlet conditions. Fixed triangular (or sawtooth) riblets are considered in the present numerical campaign. The current high-fidelity computational method permits the extraction of data such as the wall shear stress directly from the riblet surface. At the design incidence, the riblets tend to promote earlier transition to a turbulent flow over the suction side, yet significantly reduce the skin friction over the entire downstream chord to the trailing edge. The riblets reduce the viscous force over the blade by up to 18% at this nominal inflow incidence. Thus the current dataset permits new insight into the action of the riblets, since most studies of riblets on turbomachinery blades have been conducted experimentally where direct measurements of skin friction are not possible. The riblets are also able to reduce the skin friction over the high pressure compressor blade at off-design incidences, a promising result given axial flow compressors must cope with variable operating conditions.
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