Blue space evaporation effects in a simplified urban neighbourhood: impact of size and shape under neutral stratification

Petros Ampatzidis, Carlo Cintolesi, Andrea Petronio, Silvana Di Sabatino, Tristan Kershaw

Research output: Contribution to conferencePaper

Abstract

The combined effect of climate change and future urban growth will further increase air temperatures in cities, contributing more to what is known as urban overheating. A growing body of literature recognises the importance of nature-based solutions in providing resilience by mitigating urban heat islands. However, a knowledge gap exists regarding the contribution of blue spaces and how their behaviour varies depending on their geometry. This paper presents the main results of a novel study on the influence of urban blue space size and shape on in-canyon airflow and temperature/vapour distribution, and the associated implications on pollutant removal in a simplified urban neighbourhood. Using a numerical solver that accounts for evaporation effects, we examine the performance of isothermal waterbodies in a neutrally-stratified atmosphere under forced- and mixed-convection regimes and air-water temperature differences indicative of either daytime or night-time conditions. Results for forced convection show minimal impact on the flow structure, whilst temperature/vapour effects are distributed primarily over and around the water surface. Mixed-convection cases show that a cooler waterbody weakens the principal vortex in the open square, whilst temperature/vapour effects reach further upwind and are more widely distributed in the spanwise direction. An adequately sized warmer waterbody disrupts the skimming flow structure, indicating a possible heat and pollutant removal mechanism from around the waterbody and downwind canyons. Inadequately sized warmer waterbodies cannot promote sufficient vertical transport, leading to overturning and increased temperature and humidity levels at pedestrian level, thereby worsening environmental conditions and increasing the risk of heat-related illness and mortality. Hence, larger waterbodies are better suited to nocturnal transport of pollutants and accumulated warm air away from the urban surface, while smaller waterbodies are better suited to providing localised evaporative cooling. Lastly, irregular waterbodies may have a greater cooling effect across a larger area.
Original languageEnglish
Publication statusAcceptance date - 3 Apr 2023
Event11th International Conference on Urban Climate - Sydney, Australia
Duration: 28 Aug 20231 Sept 2023
Conference number: 11th
http://www.icuc11.com

Conference

Conference11th International Conference on Urban Climate
Abbreviated titleICUC11
Country/TerritoryAustralia
CitySydney
Period28/08/231/09/23
Internet address

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