FYFD

Tag: urban environment

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    Predicting Contamination in Urban Environs

    The canyons of a city’s streets form a complex flow environment. To better understand the risks of a spreading contaminant, researchers simulated a release in lower Manhattan’s urban jungle. The released particles spread due to the dominant wind pattern of the area. Initially, the particles follow the street pattern and stay at a low elevation. But updrafts on the downwind side of skyscrapers lift the particles higher, spreading them to lower concentrations at more elevations.

    Public officials study simulations like these to understand what response is needed to protect people in the event of an accidental or intentional release of harmful materials. (Image and video credit: W. Oaks and A. Khosronejad)

  • Windy Urban Corridors (*)

    Windy Urban Corridors (*)

    For pedestrians, windy conditions can be uncomfortable or even downright dangerous. And while you might expect the buildings of an urban environment to protect people from the wind, that’s not always the case. The image above shows a simulation of ground-level wind conditions in Venice on a breezy day. While many areas, shown in blue and green, have lower wind speeds, there are a few areas, shown in red, where wind speeds are well above the day’s average. This enhancement often occurs in areas where buildings constrict airflow and funnel it together. The buildings create a form of the Venturi effect, where narrowing passages cause local pressure to drop, driving an increase in wind speed. Architects and urban designers are increasingly turning to numerical simulations and CFD to study these effects in urban environments and to search for ways to mitigate problems and keep pedestrians safe. (Image credits: CFD analysis – SimScale; pedestrians – Saltysalt, skolnv)

    (*) This post was sponsored by SimScale, the cloud-based simulation platform. SimScale offers a free Community plan for anyone interested in trying CFD, FEA and thermal simulations in their browser. Sign up for a free account here. 

    For information on FYFD’s sponsored post policy, click here.

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    City Winds Simulated

    Anyone who has spent much time in an urban environment is familiar with the gusty turbulence that can be generated by steady winds interacting with tall buildings. To the atmospheric boundary layer–the first few hundred meters of atmosphere just above the ground–cities, forests, and other terrain changes act like sudden patches of roughness that disturb the flow and generate turbulence. The video above shows a numerical simulation of flow over an urban environment. The incoming flow off the ocean is relatively calm due to the smoothness of the water. But the roughness of an artificial island just off the coast acts like a trip, creating a new and more turbulent boundary layer within the atmospheric boundary layer. It’s this growing internal boundary layer whose turbulence we see visualized in greens and reds. (Video credit: H. Knoop et al.)