Identifikace a modelování resuspenze částic v městském prostředí
Loading...
Date
Authors
Linda, Jakub
ORCID
Advisor
Referee
Mark
P
Journal Title
Journal ISSN
Volume Title
Publisher
Vysoké učení technické v Brně. Fakulta strojního inženýrství
Abstract
Resuspenzia častíc (PM) je významným prispievateľom k znečisteniu ovzdušia v mestách, keďže znovu uvoľňuje už usadené častice späť do ovzdušia. Proces vetrom indukovanej resuspenzie sa často opisuje typickým U-tvarovaným vzťahom medzi koncentráciou PM a rýchlosťou vetra, pričom má svoje špecifické charakteristiky. Prahová rýchlosť vetra spôsobujúca resuspenziu (TWSR) a nárast koncentrácie v dôsledku resuspenzie možno identifikovať z rastúcej časti tejto U-krivky – resuspenznej krivky. Táto práca identifikuje TWSR z údajov o kvalite ovzdušia pomocou jedinečnej metodiky, ktorá zohľadňuje environmentálne faktory. Resuspenzia prebieha najmä počas suchých podmienok, keď je relatívna vlhkosť vzduchu nižšia ako 60 %, a prevažne počas dňa. Koncentrácie PM10 spôsobené resuspenziou často presahujú hodnotu 1 g/m, pričom maximá dosahujú až 6 g/m. Zistilo sa, že aj menšie častice môžu podliehať resuspenzii. Intenzita resuspenzie sa líši v závislosti od veľkosti častíc – PM1 sa resuspendujú pri mierne nižšej TWSR než PM10-2.5, no s intenzitou nižšou o 27 %. Napriek podobnostiam vo vlastnostiach resuspenzie medzi frakciami PM je celkový efekt špecifický pre konkrétnu lokalitu, čo je spôsobené rozdielmi v meteorologických a prúdeniových podmienkach a množstve uvoľniteľného prachu (silt loading). Na analýzu mechanizmov resuspenzie bol vyvinutý model výpočtovej dynamiky tekutín (CFD), ktorý zahŕňa model resuspenzie v mikromierke a simuluje prúdenie vzduchu v zjednodušenom 2D ulično-kanónovom profile. Prepojenie medzi oboma modelmi zabezpečujú hodnoty šmykového napätia na stene (šmyková rýchlosť), ktoré vypočítava CFD model a ktoré slúžia ako vstup pre model resuspenzie. Model identifikuje oblasti, kde pravdepodobne dochádza k resuspenzii, a sleduje trajektórie rozptylu častíc. Výsledky ukazujú, že väčšina resuspendovaných častíc ostáva zachytená v ulično-kanónovom priestore a presúva sa z miesta na miesto, čím prispieva k opakovaným epizódam znečistenia. Porovnanie medzi CFD simuláciami a analýzou údajov o kvalite ovzdušia poukazuje na schopnosť modelu predpovedať správanie a charakteristiky resuspenzie, hoci isté nepresnosti pretrvávajú v dôsledku zložitosti reálnych podmienok. Model síce presne zachytáva prahové rýchlosti vetra a všeobecné vzorce resuspenzie, no podhodnocuje jej celkovú intenzitu, čo je spôsobené neistotami v odhade množstva prachu (silt load) a rozdielmi medzi 2D simuláciou a reálnym veľkomestským prostredím. V skutočnosti boli zaznamenané nárasty koncentrácií PM10 až do 6 g/m, zatiaľ čo v modeli len do 3 g/m, čo naznačuje, že resuspenziu v reálnom svete ovplyvňujú ďalšie environmentálne premenné. Tieto zistenia zdôrazňujú potrebu cielenej mitigácie, napríklad optimalizovaného čistenia ulíc, na zníženie resuspenzie PM v mestskom prostredí.
Resuspension of particulate matter (PM) is a significant contributor to urban air pollution, reintroducing deposited particles into the air. Wind-induced resuspension process, often described using typical U-shaped PM concentration vs. wind speed relationship has its own characteristics. Threshold wind speed causing resuspension (TWSR) and concentration increase due to resuspension can be extracted from the increasing part of the U-shaped function, resuspension curve. This thesis identifies TWSR from air quality data using unique methodology accounting for environmental factors. Resuspension occurs predominantly during dry conditions when air humidity is below 60 %, mostly during the day. PM10 concentrations due to resuspension frequently exceed 1 g/m, with peaks reaching 6 g/m. It was found that smaller particles can undergo resuspension too. The intensity of resuspension varies by particle size, with PM1 resuspending at slightly lower TWSR than PM10-2.5, though with 27% lower intensity. Despite similarities in resuspension properties across PM fractions, the overall effect is site-specific due to variations in meteorological and flow factors and silt loading. To analyze resuspension mechanisms, a computational fluid dynamics (CFD) model including micro scale resuspension model was developed, simulating airflow in a simplified 2D street canyon. The connection between the two models was wall shear stress values (friction velocity), calculated by CFD and serving as an input to resuspension model. The model identifies the regions where resuspension is likely to occur and tracks particle dispersion patterns. Results show that most resuspended particles remain trapped in the canyon, moving from one place to another, contributing to repeated pollution events. A comparison between CFD simulations and air quality data analysis highlights the model’s ability to predict resuspension behavior and characteristics, though some discrepancies exist due to the complexity of real-world factors. While the model accurately captures wind speed thresholds and general resuspension patterns, it underestimates the overall magnitude due to uncertainties in silt load estimation and difference between 2D simulation and large-scale real environment. Observed PM10 concentration increases of up to 6 g/m, while in the model only up to 3 g/m, indicating that real-world resuspension is influenced by additional environmental variables. These findings underscore the need for targeted mitigation strategies, such as optimized street cleaning, to reduce PM resuspension in urban areas.
Resuspension of particulate matter (PM) is a significant contributor to urban air pollution, reintroducing deposited particles into the air. Wind-induced resuspension process, often described using typical U-shaped PM concentration vs. wind speed relationship has its own characteristics. Threshold wind speed causing resuspension (TWSR) and concentration increase due to resuspension can be extracted from the increasing part of the U-shaped function, resuspension curve. This thesis identifies TWSR from air quality data using unique methodology accounting for environmental factors. Resuspension occurs predominantly during dry conditions when air humidity is below 60 %, mostly during the day. PM10 concentrations due to resuspension frequently exceed 1 g/m, with peaks reaching 6 g/m. It was found that smaller particles can undergo resuspension too. The intensity of resuspension varies by particle size, with PM1 resuspending at slightly lower TWSR than PM10-2.5, though with 27% lower intensity. Despite similarities in resuspension properties across PM fractions, the overall effect is site-specific due to variations in meteorological and flow factors and silt loading. To analyze resuspension mechanisms, a computational fluid dynamics (CFD) model including micro scale resuspension model was developed, simulating airflow in a simplified 2D street canyon. The connection between the two models was wall shear stress values (friction velocity), calculated by CFD and serving as an input to resuspension model. The model identifies the regions where resuspension is likely to occur and tracks particle dispersion patterns. Results show that most resuspended particles remain trapped in the canyon, moving from one place to another, contributing to repeated pollution events. A comparison between CFD simulations and air quality data analysis highlights the model’s ability to predict resuspension behavior and characteristics, though some discrepancies exist due to the complexity of real-world factors. While the model accurately captures wind speed thresholds and general resuspension patterns, it underestimates the overall magnitude due to uncertainties in silt load estimation and difference between 2D simulation and large-scale real environment. Observed PM10 concentration increases of up to 6 g/m, while in the model only up to 3 g/m, indicating that real-world resuspension is influenced by additional environmental variables. These findings underscore the need for targeted mitigation strategies, such as optimized street cleaning, to reduce PM resuspension in urban areas.
Description
Keywords
Vetrom indukovaná resuspenzia, PM10, numerické modelovanie, CFD simulácia, mestské prostredie, kvalita ovzdušia, atmosférické modelovanie, znečistenie ovzdušia, prúdenie vzduchu v meste, prahová rýchlosť vetra, transport častíc, koncentrácia PM., Wind-induced resuspension, PM10, numerical modelling, CFD simulation, urban environment, air quality, atmospheric modelling, air pollution, urban air flow, threshold wind speed, particle transport, PM concentration.
Citation
LINDA, J. Identifikace a modelování resuspenze částic v městském prostředí [online]. Brno: Vysoké učení technické v Brně. Fakulta strojního inženýrství. 2025.
Document type
Document version
Date of access to the full text
Language of document
cs
Study field
bez specializace
Comittee
doc. Ing. Pavel Rudolf, Ph.D. (předseda)
doc. Ing. Marian Bojko, Ph.D. (člen)
doc. Ing. Lubomír Klimeš, Ph.D. (člen)
prof. Ing. Michal Masaryk, Ph.D. (člen)
doc. Ing. Pavel Charvát, Ph.D. (člen)
doc. Ing. Marek Baláš, Ph.D. (člen)
Date of acceptance
2025-06-23
Defence
Student obhájil zdařile zpracovanou práci. Uspokojivě zdopověděl všechny položené dotazy.
Result of defence
práce byla úspěšně obhájena
Document licence
Standardní licenční smlouva - přístup k plnému textu bez omezení