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  • 1.
    Almgren, Martin
    et al.
    Trafikförvaltningen, SLL.
    Sylwan, Odd
    Tyréns.
    Kravställning och uppföljning av ljud- och vibrationskrav vid fordonsupphandling2013In: Transportforum 2013: Granskade artiklar / [ed] Blomqvist, Göran, Linköping: Statens väg- och transportforskningsinstitut, 2013, p. 98-107Conference paper (Refereed)
    Abstract [sv]

    Trafikförvaltningen (tidigare SL) har de senaste åren initierat och delvis genomfört tre större fordonsupphandlingar med långtgående krav på låga bullernivåer. De närliggande upphandlingarna har möjliggjort samordningsvinster, men även erfarenhetsutbyte från olika upphandlingsfaser. Erfarenheterna från upphandlingarna visar att väl underbyggda och realistiska krav betyder mycket för att uppnå goda resultat. De visar vidare att väl genomtänkta planer för löpande rapportering under projekten och påtryckningsmedel för att säkerställa kravefterlevnad också har stor betydelse. Artikeln belyser förhållanden som kan ha betydelse för kravutformning samt identifierade svårigheter och vunna erfarenheter från fordonsupphandlingar. Genomgången är tänkt att vara praktisk och lätt att tillämpa. Utformning av krav eller förslag på gränsvärden tas däremot inte upp i artikeln. Den förmedlar istället i första hand tänkesätt och användbara referenser.

  • 2.
    Bruzelius, Fredrik
    et al.
    Chalmers Tekniska Högskola.
    Uystepruyst, David
    Chalmers Tekniska Högskola.
    Jacobson, Bengt
    Chalmers Tekniska Högskola.
    Krajnovi´c, Sinisa
    Chalmers Tekniska Högskola.
    A simple real-time aerodynamic model for vehicles in overtaking situations2013In: International Journal of Vehicle Systems Modelling and Testing, ISSN 1745-6436, Vol. 8, no 3, p. 241-259Article in journal (Refereed)
    Abstract [en]

    Aerodynamic forces and moments play an important role inovertaking situations and affect the trajectory of the involved vehicles. One method of studying these effects and how the driver responds to these is via driving simulator studies. However, models that describe aerodynamic forces and moments are typically computationally complex and not suited for real time execution in driving simulators. The present work presents a simplified real time model of the moments and forces acting in an overtaking situation due to aerodynamic pressure imbalances. The model is compared with experimentally validated Navier-Stokes solutions. Despite the model’s simplicity, implemented as finite impulse response filters, it manages to capture the main features of the forces and moments. The approach used to derive the model is fairly general and might be used in similar applications where computational burden is a key issue.

  • 3.
    Forssén, Jens
    et al.
    Chalmers Tekniska Högskola.
    Hornikx, Maarten
    Eindhoven University of Technology.
    Botteldooren, Dick
    Ghent University.
    Wei, Weigang
    Ghent University.
    Van Renterghem, Timothy
    Ghent University.
    Ögren, Mikael
    Swedish National Road and Transport Research Institute, Society, environment and transport, Enviroment and traffic analysis.
    A model of sound scattering by atmospheric turbulence for use in noise mapping calculations2014In: Acta Acoustica united with Acustica, ISSN 1610-1928, E-ISSN 1861-9959, Vol. 100, no 5, p. 810-815Article in journal (Refereed)
    Abstract [en]

    Sound scattering due to atmospheric turbulence limits the noise reduction in shielded areas. An engineering model is presented, aimed to predict the scattered level for general noise mapping purposes including sound propagation between urban canyons. Energy based single scattering for homogeneous and isotropic turbulence following the Kolmogorov model is assumed as a starting point and a saturation based on the von Kármán model is used as a first-order multiple scattering approximation. For a single shielding obstacle the scattering model is used to calculate a large dataset as function of the effective height of the shielding obstacle and its distances to source and receiver. A parameterisation of the dataset is used when calculating the influence of single or double canyons, including standardised air attenuation rates as well as façade absorption and Fresnel weighting of the multiple façade reflections. Assuming a single point source, an aver aging over three receiver positions and that each ground reflection causes energy doubling, the final engineering model is formulated as a scattered level for a shielding building without canyon plus a correction term for the effect of a single or a double canyon, assuming a flat rooftop of the shielding building. Input parameters are, in addition to geometry and sound frequency, the strengths of velocity and temperature turbulence.

  • 4.
    Hornikx, Maarten
    et al.
    Eindhoven University of Technology .
    Forssén, Jens
    Chalmers Tekniska Högskola.
    Botteldooren, Dick
    Ghent University.
    Van Renterghem, Timothy
    Ghent University.
    Wei, Weigang
    Ghent University.
    Ögren, Mikael
    Swedish National Road and Transport Research Institute, Society, environment and transport, Enviroment and traffic analysis.
    Salomons, Erik
    TNO Urban Environment and Health.
    Urban background noise mapping: The multiple-reflection correction term2014In: Acta Acoustica united with Acustica, ISSN 1610-1928, E-ISSN 1861-9959, Vol. 100, no 2, p. 293-305Article in journal (Refereed)
    Abstract [en]

    Mapping of road traffic noise in urban areas according to standardized engineering calculation methods systematically results in an underestimation of noise levels at areas shielded from direct exposure to noise, such as inner yards. In most engineering methods, road traffic lanes are represented by point sources and noise levels are computed utilizing point-to-point propagation paths. For a better prediction of noise levels in shielded urban areas, an extension of engineering methods by an attenuation term Acan has been proposed, including multiple reflections of the urban environment both in the source and in the receiver area.

    The present work has two main contributions for the ease of computing Acan. Firstly, it is shown by numerical calculations that Acan may be divided into independent source and receiver environment terms, As and Ar. Based on an equivalent free field analogy, the distance dependence of these terms may moreover be expressed analytically. Secondly, an analytical expression is proposed to compute As and Ar for 3D configurations from using 2D configurations only. The expression includes dependence of the street width-to-height ratio, the difference in building heights and the percentage of facade openings in the horizontal plane. For the expression to be valid, the source should be separated from the receiver environment by at least four times the street width.

  • 5.
    Wei, Weigang
    et al.
    Ghent University.
    Botteldooren, Dick
    Ghent University.
    Renterghem, Timothy Van
    Ghent University.
    Hornikx, Maarten C J
    Chalmers Tekniska Högskola.
    Forssén, Jens
    Chalmers Tekniska Högskola.
    Salomons, Erik M
    TNO Urban Environment and Health.
    Ögren, Mikael
    Swedish National Road and Transport Research Institute, Society, environment and transport, Enviroment and traffic analysis.
    Erratum: Urban background noise mapping: The general model (Acta Acustica united with Acustica (2014) 100 (1098-1111) DOI:10.3813/AAA.918789)2015In: Acta Acoustica united with Acustica, ISSN 1610-1928, E-ISSN 1861-9959, Vol. 101, no 1Article in journal (Refereed)
  • 6.
    Wei, Weigang
    et al.
    Ghent University.
    Botteldooren, Dick
    Ghent University.
    Renterghem, Timothy Van
    Ghent University.
    Hornikx, Maarten C J
    Chalmers Tekniska Högskola.
    Forssén, Jens
    Chalmers Tekniska Högskola.
    Salomons, Erik M
    TNO Urban Environment and Health.
    Ögren, Mikael
    Swedish National Road and Transport Research Institute, Society, environment and transport, Enviroment and traffic analysis.
    Urban background noise mapping: The general model2014In: Acta Acoustica united with Acustica, ISSN 1610-1928, E-ISSN 1861-9959, Vol. 100, no 6, p. 1098-1111Article in journal (Refereed)
    Abstract [en]

    Surveys show that inhabitants of dwellings exposed to high noise levels benefit from having access to a quiet side. However, current practice in noise prediction often underestimates the noise levels at a shielded façade. Multiple reflections between façades in street canyons and inner yards are commonly neglected and façades are approximated as perfectly flat surfaces yielding only specular reflection. In addition, sources at distances much larger than normally taken into account in noise maps might still contribute significantly. Since one of the main reasons for this is computational burden, an efficient engineering model for the diffraction of the sound over the roof tops is proposed, which considers multiple reflections, variation in building height, canyon width, façade roughness and different roof shapes. The model is fitted on an extensive set of full-wave numerical calculations of canyon-to-canyon sound propagation with configurations matching the distribution of streets and building geometries in a typical historically grown European city. This model allows calculating the background noise in the shielded areas of a city, which could then efficiently be used to improve existing noise mapping calculations. The model was validated by comparison to long-term measurements at 9 building façades whereof 3 were at inner yards in the city of Ghent, Belgium. At shielded façades, a strong improvement in prediction accuracy is obtained.

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