1,721,099 research outputs found
Unsteady Reynolds averaged Navier-Stokes simulation of the post-critical flow around a closely spaced group of silos
No full textDuring a storm in October 2002, wind induced ovalling oscillations were observed on several empty silos of a closely spaced group of 8 by 5 silos in the port of Antwerp (Belgium). Present day standards describe only basic wind load cases, unable to explain this ovalling phenomenon. In order to improve the design of engineering structures with cylinders placed in groups, a thorough understanding of the fluid flow around such groups is required. 2D unsteady Reynolds averaged Navier-Stokes (URANS) equations using Menter's shear stress transport turbulence model were performed, considering the wind flow around the rectangular group for a range of angles of incidence (0° < a < 90°). The 2D highly turbulent post-critical flow (Re = 1.24 × 107) around a single cylinder was computed to elucidate the influence of the applied turbulence model and to validate the spatial and temporal discretization. Similarities of the flow regime around and within the present silo group and the flow around rectangular cylinders and the flow within tube arrays (e.g. heat exchangers) respectively are discussed to qualitatively assess the results of the simulations. Static and dynamic pressure loadings on separate silos of the group are studied to explain the existence and location of wind induced vibrations in closely spaced silo groups. It is found that ovalling oscillations in the third and fourth ovalling eigenmodes can be excited by dynamic pressure fluctuations at the lee side of the group, corresponding with the visually observed vibrations in 2002.status: Publishe
Soil vibration and auralisation software tools for application in railways
No full textThe main objective of the SILVARSTAR Shift2Rail project is to develop validated software tools in the field of ground vibrationand auralisation. The first project work stream focuses on the prediction of ground vibration through the development of a hybridapproach, combining numerical prediction with experimental results. The general framework adopted expresses the vibration levelin a building as the product of terms describing the source, the propagation through the soil and the receiver. In the second workstream, auralisation and Virtual Reality (VR) software tools are developed based on physical models to synthesise railway noise inhigh quality. The novel auralisation and VR tools enable perception-based evaluation of noise mitigation technologies and aneffective demonstration of different noise scenarios, including noise mitigation measures and vehicle design variants
On the variational modeling of non-associative plasticity
No full textsponsorship: R. Alessi acknowledges the Italian Ministry of Education, University and Research (MIUR) under the PRIN 2017 20177TTP3S grant. (Italian Ministry of Education, University and Research (MIUR) under the PRIN 2017|20177TTP3S)status: Publishe
Soil vibration and auralisation software tools for application in railways
No full textThe main objective of the SILVARSTAR Shift2Rail project is to develop validated software tools for application in the field of ground vibration and auralisation in the railway sector. The first project work stream focuses on the prediction of ground vibration through the development and validation of a hybrid approach, combining numerical prediction with experimental results. The general framework adopted expresses the vibration level in a building as the product of terms describing the source, the propagation through the soil and the receiver. For each term, a database of both measured and pre-computed data is provided, allowing rapid calculations to be performed. In the upcoming project phase, this ground vibration software will be integrated in an industrial noise mapping software (IMMI). This will result in a unique software platform that will allow engineers to perform noise and vibration environmental impact studies within the same software environment, on a large scale. In the second work stream, auralisation and Virtual Reality (VR) software tools are developed based on physical models to synthesise railway noise in high quality. The novel auralisation and VR tools enable perception-based evaluation of noise mitigation technologies and an effective demonstration of different noise scenarios, including noise mitigation measures and vehicle design variants. This will support decision-making and facilitate communication with stakeholders through VR prior to project delivery. The new software tools will be made available to the industry at the end of 2022
Demonstration and validation of a hybrid vibration prediction tool for railway induced vibration
No full textAlthough rail is a sustainable and climate-friendly mode of transport, noise and vibration remain particular environmental concerns. Within SILVARSTAR, a two-year collaborative project funded under the Shift2Rail Joint Undertaking in Horizon 2020, the aim is to develop validated software tools to assess the noise and vibration environmental impact of new railway lines or the extension of existing lines. One of two major objectives is the development of a hybrid vibration prediction tool for railway induced vibration incorporating widely accepted solution methods and standards. In order to keep the computational effort low, the soil impedance and track-soil transfer functions are pre-computed for a large number of cases and stored in a numerical database. Additionally, the vibration velocity level is predicted using a low speed approximation, which disregards the Doppler effect. Incoherent axle loads are also assumed. This paper demonstrates the use of the vibration prediction tool for tracks at grade and in tunnels; results are validated with state-of-the-art numerical models
Nonlinear Modelling of the Response of Structures due to Ground Vibrations
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The Numerical Solution of Large Scale Dynamic Soil-structure Interaction Problems
No full textIn the analysis of the dynamic behaviour of many civil engineering structures, it is essential to account for the interaction between the structure and its environment. Despite the advance of high performance computers, the numerical solution of large scale dynamic soil-structure interaction (SSI) problems remains very challenging and in many cases beyond current computer capabilities.This dissertation addresses the development and application of fast, stable, and accurate numerical techniques for the solution of dynamic SSI problems, focusing on linear problems formulated in the frequency domain. A domain decomposition approach is employed, where finite elements for the structure(s) are coupled to boundary elements for the soil, accounting for the soil's stratification. Innovative methodologies are presented for improving the efficiency and applicability of existing three-dimensional and two-and-a-half-dimensional formulations, allowing for the solution of large scale dynamic SSI problems. The computational performance of the proposed procedures is assessed and their suitability is illustrated through numerical examples.The novel techniques are subsequently employed for the efficient solution of several challenging dynamic SSI problems related to railway induced ground vibrations. The vibration reduction efficiency of mitigation measures on the propagation path in the soil, including an open trench and a stiff wave barrier, is studied in detail, providing fundamental insight in the underlying physical mechanisms; trenches and barriers of infinite and finite length are analyzed. The wave propagation in a dense urban environment characterized by multiple closely-spaced buildings is considered as well, taking the dynamic through-soil coupling of all structures into account.status: Publishe
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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