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Salati L., Schito P., Cheli F., “Heavy truck drag reduction devices installed on the trailer: front and rear appendages”, Aerovehicles 1, Bordeaux (France), June 2014
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Heavy Truck Drag Reduction Obtained from Devices Installed on the Trailer
Get PDFThe flow-field around a “common” European heavy truck, equipped with several different trailer devices, is investigated using steady and unsteady simulations.
This work demonstrates how with simple devices added on the trailer it is possible to strongly decrease the aerodynamic drag over 10%, with an increase of overall dimensions below 1% without any change to the load capacity of the trailer.
Several devices, installed on the trailer, are tested on a target vehicle and the shape of the “airbag”, the “fin”, the “boat tail” and the “front-rear trailer device” has been optimized to achieve the maximum in drag reduction in front wind. The performance of the optimized devices are tested also in cross wind conditions with the yaw angle varying from 0° to 30°.
The truck equipped with the front-rear trailer device is also investigated using time variant simulation with yaw angle of 0°, 5°, 10°.
Detached eddy simulation (DES) with one equation Spalart-Allmaras as turbulence model is used to perform the analysis of the unsteady flow; the two equation k-ω SST turbulence model is selected for the steady-state RANS simulations. The unsteady simulations are performed using computational meshes on the order of 40 million of elements while RANS simulation are done with mesh of 10 million of elements
A force-distribution approach to simulate the aerodynamic loads acting on a vehicle passing by a bridge tower: comparison with CFD simulations
No full textRollover of high-sided vehicles represents a serious concern for running safety, especially when they run on exposed sites such as viaducts and bridges. In particular, the present paper investigates the interaction between a tractor semitrailer combination and the wake of a tower bridge in cross wind conditions. The proposed methodology is based on a multi-body ve-hicle model coupled with a force distribution approach to calculate the aerodynamic forces acting on the vehicle during the tower wake crossing, which relies on static vehicle CFD simula-tions/wind tunnel tests. To asses reliability of the developed methodology, obtained results are compared with moving vehicle CFD simulations (based on a moving mesh approach). Numerical results state that the developed model may represent a valuable tool for investigating wind-shield-ing solutions at the design stage of bridges. The developed model in fact provides results in good agreement with moving vehicle CFD data, but allows to significantly reduce computation effort and the coupling with a driver model
Comparison of different approaches for analysing cross-wind effects on high sided vehicles passing by a bridge tower
No full textOne of the risks connected to running safety of heavy vehicles is associated to rollover due to the high cross winds which may occur in exposed sites such as embankments, bridges, etc. Specifically, the present paper compares two methodologies for investigating the interaction between a tractor semitrailer combination and the wake of a tower bridge in cross wind conditions. The first methodology employs moving vehicle CFD simulations to evaluate the aerodynamic loads acting on the vehicle. In particular, motion of the vehicle is introduced into the CFD model using a moving mesh approach. The second methodology is instead base on a multi-body vehicle model coupled with a force distribution approach to calculate the aerodynamic forces acting on the vehicle during the tower wake crossing, which relies on static vehicle CFD simulations/wind tunnel tests. In the paper, the results of the two methodologies are presented and compared, illustrating relative advantages and drawbacks
Aerodynamic Study on a Heavy Truck Passing by a Bridge Pylon under Crosswinds Using CFD
No full textHigh-sided vehicles experience sudden changes in aerodynamic forces when passing through the wake of towers of bridges under crosswind. This may lead, in the worst case, to vehicle rollover or undesired lane changes, thus representing a critical concern for running safety. Computational fluid dynamics (CFD) is used to simulate and investigate the aerodynamic forces acting on a heavy goods vehicle (HGV) during the overtaking maneuver of a bridge tower when the vehicle is passing through the wake of the pylon generated by lateral wind. Dynamic mesh techniques are adopted to simulate the relative velocity between the vehicle and the infrastructure. Such an approach can be used to design lateral shields to be installed on existing infrastructure, reducing the risk of a wind-induced accident involving overturning of the HGV. The validation of the moving mesh strategies is performed comparing numerical and wind tunnel test results in terms of aerodynamic forces and moments acting on a stationary vehicle for different exposure angles
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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