The chapter summarises the results of the TRAPOS working group “Traffic Produced Turbulence” (TPT). The main goals of these working group have been i) to summarise the TPT results that had already been achieved by the different teams, ii) to exchange the views and knowledge regarding TPT effects iii) to find a consensus concerning the relevance of traffic produced turbulence for dispersion modelling, iv) to improve TPT scaling concepts v) to verify TPT parameterisations for numerical dispersion models and vi) to present concepts for an incorporation of TPT effects in regulatory dispersion models. The studies performed within the TRAPOS TPT working group have shown that TPT is an important aspect for dispersion of traffic emissions. Neglecting TPT parameterisations in dispersion models causes significant over-predictions of pollutant concentrations in urban street canyons that range up to a factor of 4 to 5. Empirical formulas like the so-called VDI method lead to improvements, but operationally significant differences between model calculations and measured concentration values still occur for above-roof wind speeds smaller than approximately 4-5 m/s. Based on the findings of the TRAPOS TPT working group the following recommendations are made for practical applications of dispersion models: The TPT parameterisation implemented in the OSPM model works satisfactorily and dispersion models similar to OSPM should include the OSPM TPT concept. The traditional velocity scaling of concentrations and the empirical VDI method have deficiencies and must be reconsidered. The approach presented in Kastner-Klein et al. (2001) and Ketzel et al. (2001) that is based on a velocity scale which is defined as composition of velocity variances due to the external flow and due to traffic motions is an improvement and can be recommended. In CFD models TPT parameterisations must be implemented and the developed concepts are an improvement compared to model calculations without TPT parameterisations. However, for recommendations of particular modifications in the system of equations further verification studies are necessary.
The Modelling of Traffic Produced Turbulence
DI SABATINO, SILVANA;
2004
Abstract
The chapter summarises the results of the TRAPOS working group “Traffic Produced Turbulence” (TPT). The main goals of these working group have been i) to summarise the TPT results that had already been achieved by the different teams, ii) to exchange the views and knowledge regarding TPT effects iii) to find a consensus concerning the relevance of traffic produced turbulence for dispersion modelling, iv) to improve TPT scaling concepts v) to verify TPT parameterisations for numerical dispersion models and vi) to present concepts for an incorporation of TPT effects in regulatory dispersion models. The studies performed within the TRAPOS TPT working group have shown that TPT is an important aspect for dispersion of traffic emissions. Neglecting TPT parameterisations in dispersion models causes significant over-predictions of pollutant concentrations in urban street canyons that range up to a factor of 4 to 5. Empirical formulas like the so-called VDI method lead to improvements, but operationally significant differences between model calculations and measured concentration values still occur for above-roof wind speeds smaller than approximately 4-5 m/s. Based on the findings of the TRAPOS TPT working group the following recommendations are made for practical applications of dispersion models: The TPT parameterisation implemented in the OSPM model works satisfactorily and dispersion models similar to OSPM should include the OSPM TPT concept. The traditional velocity scaling of concentrations and the empirical VDI method have deficiencies and must be reconsidered. The approach presented in Kastner-Klein et al. (2001) and Ketzel et al. (2001) that is based on a velocity scale which is defined as composition of velocity variances due to the external flow and due to traffic motions is an improvement and can be recommended. In CFD models TPT parameterisations must be implemented and the developed concepts are an improvement compared to model calculations without TPT parameterisations. However, for recommendations of particular modifications in the system of equations further verification studies are necessary.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
