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A platform for research: civil engineering, architecture and urbanism
CFD analysis of transpirational cooling by vegetation: Case study for specific meteorological conditions during a heat wave in Arnhem, Netherlands
https://orcid.org/0000-0002-8737-4632
Abstract The transpirational cooling of vegetation as a measure to mitigate outdoor air temperatures was investigated for a street canyon in the city center of Arnhem, the Netherlands for the meteorological conditions of an afternoon hour on a hot summer day during a heat wave with wind of speed 5.1 m s−1 at 10 m above ground and direction along the canyon. Computational Fluid Dynamics (CFD) simulations with locally applied vegetation in the street, i.e. avenue-trees, facade greening, roof greening and all three combined, were performed. The 3D steady-state Reynolds-averaged Navier–Stokes (RANS) equations were closed by the realizable k-ε turbulence model extended with source and sink terms to represent the effects of vegetation on air flow. By specifying a cooling power term in the energy equation, the transpirational cooling by vegetation was accounted for. The strongest cooling by a single vegetative measure was obtained with the avenue-trees with mean and maximum temperature reductions at pedestrian level of 0.43 °C and 1.6 °C, respectively. Facade greening resulted in rather small changes with mean and maximum reductions of 0.04 °C and 0.3 °C, respectively. For roof greening no noticeable reductions inside the canyon were found. In the case of a combination of all vegetative measures, cooling in terms of spatial distribution and intensity overall resembled a linear superposition of those of the vegetative measures solely applied with 0.52 °C mean and 2.0 °C maximum temperature reduction. Overall, the cooling was restricted to the vicinity of the vegetative measures, i.e. up to a distance of a few meters.
Graphical abstract Display Omitted
Highlights Transpirational cooling by vegetative measures in an urban street canyon was studied. Avenue-trees were the most effective measure for reducing air temperatures. Cooling by facade greening was noticeable but less strong than by avenue-trees. Roof greening did not result in noticeable air temperature reductions in the canyon. Cooling effects were restricted to the vicinity (≤10 m) of the vegetative measures.
CFD analysis of transpirational cooling by vegetation: Case study for specific meteorological conditions during a heat wave in Arnhem, Netherlands
https://orcid.org/0000-0002-8737-4632
Abstract The transpirational cooling of vegetation as a measure to mitigate outdoor air temperatures was investigated for a street canyon in the city center of Arnhem, the Netherlands for the meteorological conditions of an afternoon hour on a hot summer day during a heat wave with wind of speed 5.1 m s−1 at 10 m above ground and direction along the canyon. Computational Fluid Dynamics (CFD) simulations with locally applied vegetation in the street, i.e. avenue-trees, facade greening, roof greening and all three combined, were performed. The 3D steady-state Reynolds-averaged Navier–Stokes (RANS) equations were closed by the realizable k-ε turbulence model extended with source and sink terms to represent the effects of vegetation on air flow. By specifying a cooling power term in the energy equation, the transpirational cooling by vegetation was accounted for. The strongest cooling by a single vegetative measure was obtained with the avenue-trees with mean and maximum temperature reductions at pedestrian level of 0.43 °C and 1.6 °C, respectively. Facade greening resulted in rather small changes with mean and maximum reductions of 0.04 °C and 0.3 °C, respectively. For roof greening no noticeable reductions inside the canyon were found. In the case of a combination of all vegetative measures, cooling in terms of spatial distribution and intensity overall resembled a linear superposition of those of the vegetative measures solely applied with 0.52 °C mean and 2.0 °C maximum temperature reduction. Overall, the cooling was restricted to the vicinity of the vegetative measures, i.e. up to a distance of a few meters.
Graphical abstract Display Omitted
Highlights Transpirational cooling by vegetative measures in an urban street canyon was studied. Avenue-trees were the most effective measure for reducing air temperatures. Cooling by facade greening was noticeable but less strong than by avenue-trees. Roof greening did not result in noticeable air temperature reductions in the canyon. Cooling effects were restricted to the vicinity (≤10 m) of the vegetative measures.
CFD analysis of transpirational cooling by vegetation: Case study for specific meteorological conditions during a heat wave in Arnhem, Netherlands
https://orcid.org/0000-0002-8737-4632
Abstract The transpirational cooling of vegetation as a measure to mitigate outdoor air temperatures was investigated for a street canyon in the city center of Arnhem, the Netherlands for the meteorological conditions of an afternoon hour on a hot summer day during a heat wave with wind of speed 5.1 m s−1 at 10 m above ground and direction along the canyon. Computational Fluid Dynamics (CFD) simulations with locally applied vegetation in the street, i.e. avenue-trees, facade greening, roof greening and all three combined, were performed. The 3D steady-state Reynolds-averaged Navier–Stokes (RANS) equations were closed by the realizable k-ε turbulence model extended with source and sink terms to represent the effects of vegetation on air flow. By specifying a cooling power term in the energy equation, the transpirational cooling by vegetation was accounted for. The strongest cooling by a single vegetative measure was obtained with the avenue-trees with mean and maximum temperature reductions at pedestrian level of 0.43 °C and 1.6 °C, respectively. Facade greening resulted in rather small changes with mean and maximum reductions of 0.04 °C and 0.3 °C, respectively. For roof greening no noticeable reductions inside the canyon were found. In the case of a combination of all vegetative measures, cooling in terms of spatial distribution and intensity overall resembled a linear superposition of those of the vegetative measures solely applied with 0.52 °C mean and 2.0 °C maximum temperature reduction. Overall, the cooling was restricted to the vicinity of the vegetative measures, i.e. up to a distance of a few meters.
Graphical abstract Display Omitted
Highlights Transpirational cooling by vegetative measures in an urban street canyon was studied. Avenue-trees were the most effective measure for reducing air temperatures. Cooling by facade greening was noticeable but less strong than by avenue-trees. Roof greening did not result in noticeable air temperature reductions in the canyon. Cooling effects were restricted to the vicinity (≤10 m) of the vegetative measures.
CFD analysis of transpirational cooling by vegetation: Case study for specific meteorological conditions during a heat wave in Arnhem, Netherlands
Gromke, Christof (author) / Blocken, Bert (author) / Janssen, Wendy (author) / Merema, Bart (author) / van Hooff, Twan (author) / Timmermans, Harry (author)
Building and Environment ; 83 ; 11-26
2014-04-25
16 pages
Article (Journal)
Electronic Resource
English
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