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oai:recercat.cat:2117/3303462026-03-09T04:20:24Zcom_2072_1033col_2072_452950

Plume or bubble? Mixed-convection flow regimes and city-scale circulations Omidvar, Hamidreza Bou-Zeid, Elie Li, Qi Mellado González, Juan Pedro Klein, Petra Universitat Politècnica de Catalunya. Departament de Física Àrees temàtiques de la UPC::Física::Física de fluids Rayleigh-Bénard convection Boundary layer Heat -- Convection Bénard convection Buoyant boundary layers Atmospheric flows Rayleigh-Bénard, Convecció de Capa límit (Mecànica de fluids) Calor -- Convecció Large-scale circulations around a city are co-modulated by the urban heat islandand by regional wind patterns. Depending on these variables, the circulations fall into different regimes ranging from advection-dominated (plume regime) to convection-driven (bubble regime). Using dimensional analysis and large-eddy simulations, this study investigates how these different circulations scale with urban and rural heat fluxes, as well as up stream wind speed. Two dimensionless parameters are shown to control the dynamics of the flow: (1) the ratio of rural to urban thermal convective velocities that contrasts their respective buoyancy fluxes and (2) the ratio of bulk inflow velocity to the convection velocity in the rural area. Finally, the vertical flow velocities transecting the rural to urban transitions are used to developa criterion for categorizing different large-scale circulations into plume, bubble or transitional regimes. The findings have implications for city ventilation since bubbleregimes are expected to trap pollutants, as well as for scaling analysis in canonical mixed-convection flows. Peer Reviewed Postprint (author's final draft) 2020-08-25 Article Omidvar, H. [et al.]. Plume or bubble? Mixed-convection flow regimes and city-scale circulations. "Journal of fluid mechanics", 25 Agost 2020, vol. 897, p. A5:1-A5:27. 0022-1120 https://hdl.handle.net/2117/330346 10.1017/jfm.2020.360 eng https://www.cambridge.org/core/journals/journal-of-fluid-mechanics/article/plume-or-bubble-mixedconvection-flow-regimes-and-cityscale-circulations/837241B5C692D8751C9D2D2C3D067C32 Open Access application/pdf