1,721,002 research outputs found
Simulated flow around a rectangular 5:1 cylinder: Spanwise discretisation effects and emerging flow features
No full textIn the present contribution, a systematic parametrical study on the spanwise length of the computational domain and on the spanwise grid density is proposed in the framework of the Benchmark on the Aerodynamics of a Rectangular 5:1 Cylinder (BARC). The study aims at evaluating the effects of these computational features on the simulated flow field in terms of bulk parameters, spanwise-averaged distributions, correlation coefficient and correlation length. The effectiveness of the adopted computational approach to provide the correlation measures is discussed. In particular, dense spanwise grids seem to be a key element to simulate some emerging and unexpected features of the cylinder aerodynamic behaviour, such as the asymmetry of the time-averaged flow fiel
Life-Cycle Performance and Cost Analysis of Sand Mitigation Measures: Toward a Hybrid Experimental-Computational Approach
Get PDFWindblown sand action affects civil structures and infrastructures in sandy environments, such as deserts and coasts. The wind interacts with human built structures of any kind leading to harmful effects, endangering their serviceability and users' safety. To counter it, a number of sand mitigation measures (SMM) have been proposed, primarily through the trial-and-error empirical approach. As such, innovative approaches to properly quantify windblown sand action and to design SMM are needed in the current state-of-art and practice. In this study, the authors propose a novel hybrid approach to derive the life-cycle performance of SMM based on the combination of reliable wind-sand tunnel tests and innovative wind-sand computational simulations. Wind-sand tunnel tests are carried out to characterize the incoming sand flux in open field conditions. In a hybrid approach perspective, wind-sand tunnel measurements allow to properly tuned cheaper wind-sand computational simulations of the full-scale SMM performance. A probabilistic approach for determining windblown sand action and frequencies of sand removal maintenance is applied to a case study on a desert railway. Finally, a life-cycle cost analysis is carried out to assess extra-costs and savings derived from the implementation of the SMM. The proposed approach paves the way toward a comprehensive hybrid approach to the performance assessment of SMM
Effect of the spanwise features of the computational domain on the simulated flow around a rectangular 5:1 cylinder
No full textAnalysis of the separated flow around a 5:1 rectangular cylinder through computational simulation
No full textThe aim of this paper is to provide a contribution to the analysis of the 3D, high Reynolds number, turbulent, separated and reattached flow around a fixed sharp-edged rectangular cylinder with a chord-to-depth ratio equal to 5. The present computational study is developed in the frame of the Benchmark on the Aerodynamics of a Rectangular Cylinder (BARC). First, the adopted flow modelling and computational approach are described. Second, some of the 2D mechanisms that are responsible for the variation of the fluctuating pressure on the side surface are scrutinised: the computational approach post-processing facilities are employed to point out the flow structures which mainly affect the vortex formation and shedding past the separation point and to look for significant relationships between them and the pressure field on the cylinder side surfac
Determination of flutter derivatives for streamlined bodies by means of computational wind engineering
No full textThis paper proposes a method to determine the utter derivatives of 2-dimensional streamlined cylinders by means of a modied indicial approach adapted to a Navier-Stokes solver using an Arbitrary Lagrangian Eulerian formulation. The method relies on heave or pitch motion imposed to the section according to smoothed ramp time histories and on the computational evaluation of the transient forces arising on the obstacle. Hence, the indicial transfer function mapping the plate motion and the induced force in frequency domain is obtained. An application to a at plate of nite thickness and length is proposed. The steady viscous flow simulated around the motionless plate is compared with the well-known Blasius solution. The computed flutter derivatives are compared with the ones obtained from the Theodorsen function in the frame of the thin airfoil theory
3D flow around a rectangular cylinder: a computational study
No full textThe aim of this paper is to provide a contribution to the study of the 3D, high Reynolds number, turbulent, separated and reattached flow around a fixed rectangular cylinder with a chord-to-depth ratio of 5. In spite of the simple geometry, it is believed that the problem could be of interest not only for fundamental research purposes, but also to provide useful information on the aerodynamics of a wide range of bluff bodies of interest in Civil Engineering (e.g. long span bridge decks, high-rise buildings, and so on) and in other Engineering applications. First, the obtained main aerodynamic integral parameters are compared with those proposed in literature. Second, the 3D features of the flow are investigated by means of both Proper Orthogonal Decomposition and coherence function of the side-surface fluctuating pressure field. Once the main 2D nature of the flow has been pointed out, some of the 2D mechanisms that are responsible for the variation of the fluctuating aerodynamic forces are scrutinised: the computational approach post-processing facilities are employed to look for significant relationships between the flow structures, pressure field and aerodynamic force
A multi-scale gap-bridging CWE approach to windblown sand action on critical infrastructures: Modelling framework and case study on a high-speed railway line
Get PDFWindblown sand action on critical infrastructures, such as high-speed railway lines, can completely inhibit their operation detrimentally affecting their safety and capacity. Several key components of the infrastructure are affected, among them the rolling stock material and infrastructure equipment. Computational Wind Engineering (CWE) is becoming more and more adopted during the different design stages to assess the impact of windblown sand. However, CWE-based analysis and design remain challenging because of the different scales involved in windblown sand transport starting from the full alignment scale (macro-scale), to the railway body (meso-scale), to the rolling stock (micro-scale). An innovative multi-scale modelling approach is proposed to bridge the gap between macro and micro scales involved in windblown sand processes, allowing to assess windblown sand action on key components. An exploratory case study addressing rolling stock operation in sandy environment along an high-speed railway line is analysed and discussed. This demonstrates the soundness of the approach in identifying most endangered railway segments, railway body sedimentation-prone areas and rolling stock components, and in quantifying windblown sand action at different scales. The proposed approach is well suited also to support the conceptual design of Sand Mitigation Measures
3D flow around a rectangular cylinder: a computational study
No full textThe aim of this paper is to provide a contribution to the analysis of the 3D, high Reynolds number, turbulent, separated and reattached flow around a fixed sharp-edged rectangular cylinder with a chord-to-depth ratio equal to 5. The work is developed in the perspective of the Benchmark on the Aerodynamics of a Rectangular Cylinder (BARC), in terms of an exploratory computational study. First, the adopted flow modelling and computational approach are shortly described. Second, the obtained main aerodynamic integral parameters are compared with other results proposed in literature. Hence, the 3D flow features around the nominally 2D cylinder are investigated by means of both Proper Orthogonal Decomposition and coherence function of the side-surface fluctuating pressure field. Once the main 2D nature of the flow has been pointed out, some of the 2D mechanisms that are responsible for the variation of the fluctuating aerodynamic forces are scrutinised: the computational approach post-processing facilities are employed to look for significant relationships between the flow structures, the pressure field and the aerodynamic force components
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