Aerodynamics of bridge-stay cables in the context of rigid circular cylinder in smooth flow

Bridge stay cables are prone to dynamic excitations by wind. Depending on the orientation and mechanical properties of cable, wind speed, and other environmental factors, unstable cable response of different features could occur. The current work focuses on exploring the possible excitation mechanisms associated with two different types of wind-induced unstable responses observed on a rigid circular cylinder model in a series of wind tunnel tests. Characteristics of critical flow past a circular cylinder model in cross-flow were first studied to provide additional insight into the impact of critical Reynolds number regime. Then, the limited-amplitude and divergent type responses of a wind tunnel cable model were investigated. Unsteady surface pressure data were utilized to determine the separation angle, aerodynamic damping ratio, spatial correlation, and power spectra of lift and drag forces. It has been found that the divergent type response was not only accompanied with negative aerodynamic damping ratio, but also it occurred when the spatial flow was highly correlated along the cylinder. In addition, a breakdown range was detected for cable-wind relative angle around 60° within which flow characteristics could be significantly altered. This would lead to suppression of regular Karman vortex shedding in the subcritical Reynolds number range which is known to be the reason for the limited-amplitude response

The synergistic effect of operational research and big data analytics in greening container terminal operations: a review and future directions

Container Terminals (CTs) are continuously presented with highly interrelated, complex, and uncertain planning tasks. The ever-increasing intensity of operations at CTs in recent years has also resulted in increasing environmental concerns, and they are experiencing an unprecedented pressure to lower their emissions. Operational Research (OR), as a key player in the optimisation of the complex decision problems that arise from the quay and land side operations at CTs, has been therefore presented with new challenges and opportunities to incorporate environmental considerations into decision making and better utilise the ‘big data’ that is continuously generated from the never-stopping operations at CTs. The state-of-the-art literature on OR's incorporation of environmental considerations and its interplay with Big Data Analytics (BDA) is, however, still very much underdeveloped, fragmented, and divergent, and a guiding framework is completely missing. This paper presents a review of the most relevant developments in the field and sheds light on promising research opportunities for the better exploitation of the synergistic effect of the two disciplines in addressing CT operational problems, while incorporating uncertainty and environmental concerns efficiently. The paper finds that while OR has thus far contributed to improving the environmental performance of CTs (rather implicitly), this can be much further stepped up with more explicit incorporation of environmental considerations and better exploitation of BDA predictive modelling capabilities. New interdisciplinary research at the intersection of conventional CT optimisation problems, energy management and sizing, and net-zero technology and energy vectors adoption is also presented as a prominent line of future research

Hot Potatoes: The Merits and Demerits

The present study was firstly meant to review and study the main functions and applications of the Hot Potatoes program and further to identify its main features in terms of the development of various types of language tests and exercises. Secondly the study identified a number of deficiencies both in connection with the applications and the modality of the exercises it produces. The analysis revealed that although the program offers facility in creating different types of exercises together with teacher’s feedback that can be posted online for the ease of access, it is limited in some important areas such as providing interactive activities and synchronous feedback for the learners. Moreover, it was found that the efficiency and usefulness of this program to a great extent depends on the creativity and skills of the teacher who uses the program to create tests. Similarly, the language contents that the teacher uses can have a great influence on the effectiveness of the exercises developed by Hot Potatoes. Therefore, the program by itself gives no advantage in helping learners with their language learning practice and exposure, but only acts as a learning tool

Aerodynamic characteristics of generic ice shells

Abstract Freezing rain and wet snow can cause ice to accumulate on the surface of bridge cables. Subsequently, a rise in temperature and wind can cause ice to shed from the surface of cables. Several instances of ice and wet snow shedding from bridge cables have been observed in Canada. Environmental predictive models have been proposed to predict the ice shedding behaviour and its trajectory from bridge cables. The current study aims at measuring the aerodynamic force and moment coefficients of generic ice fragments detached from a bridge cable as a priori for a subsequent ice trajectory model. Nine representative generic, ice shells were selected to represent different aspect ratios, curvatures, ice thicknesses, and external ice surface conditions. Aerodynamic forces and moments were measured for each of the ice shell models in turbulent flow for a wide range of orientations. The use of a curved shape as opposed to a flat plate resulted in a significant difference in the aerodynamic coefficients. It was found that the aspect ratio was the most important geometric factor in determining the aerodynamic forces and moments on the curved models. The findings of this study will be implemented in future ice trajectory models

The multi-objective Steiner pollution-routing problem on congested urban road networks

This paper introduces the Steiner Pollution-Routing Problem (SPRP) as a realistic variant of the PRP that can take into account the real operating conditions of urban freight distribution. The SPRP is a multi-objective, time and load dependent, fleet size and mix PRP, with time windows, flexible departure times, and multi-trips on congested urban road networks, that aims at minimising three objective functions pertaining to (i) vehicle hiring cost, (ii) total amount of fuel consumed, and (iii) total makespan (duration) of the routes. The paper focuses on a key complication arising from emissions minimisation in a time and load dependent setting, corresponding to the identification of the full set of the eligible road-paths between consecutive truck visits a priori, and to tackle the issue proposes new combinatorial results leading to the development of an exact Path Elimination Procedure (PEP). A PEP-based Mixed Integer Programming model is further developed for the SPRP and embedded within an efficient mathematical programming technique to generate the full set of the non-dominated points on the Pareto frontier of the SPRP. The proposed model considers truck instantaneous Acceleration/Deceleration (A/D) rates in the fuel consumption estimation, and to address the possible lack of such data at the planning stage, a new model for the construction of reliable synthetic spatiotemporal driving cycles from available macroscopic traffic speed data is introduced. Several analyses are conducted to: (i) demonstrate the added value of the proposed approach, (ii) exhibit the trade-off between the business and environmental objectives on the Pareto front of the SPRP, (iii) show the benefits of using multiple trips, and (iv) verify the reliability of the proposed model for the generation of driving cycles. A real road network based on the Chicago's arterial streets is also used for further experimentation with the proposed PEP algorithm. © 2019 Elsevier Lt

3D Object Reconstruction using Multi-View Calibrated Images

In this study, two models are proposed, one is a visual hull model and another one is a 3D object reconstruction model. The proposed visual hull model, which is based on bounding edge representation, obtains high time performance which makes it to be one of the best methods. The main contribution of the proposed visual hull model is to provide bounding surfaces over the bounding edges, which results a complete triangular surface mesh. Moreover, the proposed visual hull model can be computed over the camera networks distributedly. The second model is a depth map based 3D object reconstruction model which results a watertight triangular surface mesh. The proposed model produces the result with acceptable accuracy as well as high completeness, only using stereo matching and triangulation. The contribution of this model is to playing with the 3D points to find the best reliable ones and fitting a surface over them

Effect of cable surface characteristics and flow turbulence on the aerodynamic behaviour of stay cables in dry conditions

Abstract This article describes a wind-tunnel study to evaluate the aerodynamic behaviour of stay cables of a bridge with various surface geometries in dry conditions. Nine cable models were fabricated and tested. Aerodynamic forces acting on the static models were measured for different wind speeds, cable-wind angles and cable axial rotation angles, in smooth and turbulent flow. The aerodynamic forces of bare, round cable models with different roughness levels were used as a baseline to compare the aerodynamic loading of the cables with surface geometry features. A comprehensive database of existing and emerging cable geometries in a wide range of flow conditions and cable-wind angles was generated. The trends exhibited by models with geometric features are similar to results available in the open literature. The aerodynamic drag coefficient was largely affected by the presence of cable surface geometry. The model with helical strakes had the lowest drag coefficient throughout the range of Reynolds numbers that was evaluated. It was observed that turbulence had a similar effect on all models, resulting in a reduction of the drag coefficient at lower Reynolds numbers and an earlier increase in drag that is associated with the supercritical Reynolds number regime. The presence of turbulent flow resulted in higher drag coefficients at high Reynolds numbers. An important secondary finding was that models fabricated with the Selective Laser Sintering (SLS) technique have a higher surface roughness than high-density polyethylene (HDPE) stay cable sleeves but when printed, they have a similar surface roughness

Literature Review on Big Data Analytics Methods

Companies and industries are faced with a huge amount of raw data, which have information and knowledge in their hidden layer. Also, the format, size, variety, and velocity of generated data bring complexity for industries to apply them in an efficient and effective way. So, complexity in data analysis and interpretation incline organizations to deploy advanced tools and techniques to overcome the difficulties of managing raw data. Big data analytics is the advanced method that has the capability for managing data. It deploys machine learning techniques and deep learning methods to benefit from gathered data. In this research, the methods of both ML and DL have been discussed, and an ML/DL deployment model for IOT data has been proposed