Direct numerical simulation of turbulence and microphysics in the Pi Chamber

MacMillan, Theodore; Shaw, R. Anthony; Cantrell, Will; Richter, David H.

doi:10.1103/physrevfluids.7.020501

Cited by 13 publications

(10 citation statements)

References 41 publications

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“…The same physics of convection and condensation on aerosols applies both to the proposed chamber and the Pi chamber, although they have different injection processes and different temperature differences across the chamber. The experiments and theoretical analyses carried out for the Pi chamber ( [23][24][25][26] and [27]) are consistent with the basic assumptions of the present model. First, there exists a central well-mixed region, where the mean temperature is uniform, with narrow boundary layers at the top and bottom of the chamber.…”

Section: Relation To the Pi Chamber And Scaling Theorysupporting

confidence: 84%

“…Experiments have mainly focussed on reaching a steady state cloud in the chamber in which the rainout of large droplets is balanced by condensational aerosol growth from injected NaCl particles. For a hot surface at 26°C and a cold surface at 7°C, experimental results on the heat transfer, cavity temperatures and the aerosol size distribution have been compared to predictions obtained from numerical turbulence modelling of motions, heat and mass transfer within the cavity ( [24][25][26] and [27]). General theory and associated dimensionless quantities describing the Rayleigh-Bénard convection involved have been discussed by [28] and [29].…”

Section: Introductionmentioning

confidence: 99%

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Washing the air: enhanced condensation of water on aerosols to enable their removal

Clement

2022

Proc. R. Soc. A.

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Previous theory (Clement 1985 Proc. R. Soc. A 398 , 307–339.) is applied to calculate water vapour condensation on aerosol in a chamber with a hot water base, a cooled roof and insulated walls. The fractional aerosol condensation of the water vapour is given by the surface condensation numbers, Cn , at the water surface and the roof. The magnitude of the aerosol condensation rate, M , per unit area of the base is then obtained from theory using heat transfer correlations. The central well-mixed turbulent region in the chamber is generally equilibrated, and maximum and minimum values of M are obtained from the limits of complete vapour condensation, and no condensation, in the boundary layers, respectively. Practically all their difference arises in the cold boundary layer where the supersaturation reaches up to 3 for no condensation. Results for M are obtained for water temperatures of 70 and 80°C and roof temperatures of 5–30°C, and range from 0.1 to 1.0 g m −2 s −1 . Chamber properties are compared to those of the Pi chamber used to investigate cloud condensation. Estimations for aerosol growth in the chamber are made for varying chamber heights and aerosol number concentrations, N . Passage of air through such a chamber could effectively grow aerosols of even the highest N up to an easily removable size range in a matter of seconds, enabling the cleaning of polluted air, including that containing viruses.

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Section: Relation To the Pi Chamber And Scaling Theorysupporting

confidence: 84%

Section: Introductionmentioning

confidence: 99%

Washing the air: enhanced condensation of water on aerosols to enable their removal

Clement

2022

Proc. R. Soc. A.

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“…The Reynolds number is relatively low (1135) but the flow is still turbulent, as the transition Re value for the geometry simulated here (a T-mixer with a square mixing channel cross-section) is about 400 (Telib, Manhart & Iollo 2004). While DNS studies of such interactions have been carried out in related fields that involve interaction of turbulence and particle formation processes such as soot formation (Bisetti et al 2012;Wick et al 2020), aerosol coagulation (Tsagkaridis, Rigopoulos & Papadakis 2022) and cloud microphysics (Grabowski, Thomas & Kumar 2022;Macmillan et al 2022), such a study has not been performed for reaction crystallisation (to the best of the authors' knowledge). Furthermore, while there are common threads between reacting flows with particle formation, reaction crystallisation has some important distinct characteristics.…”

Section: Introductionmentioning

confidence: 96%

“…2020), aerosol coagulation (Tsagkaridis, Rigopoulos & Papadakis 2022) and cloud microphysics (Grabowski, Thomas & Kumar 2022; Macmillan et al. 2022), such a study has not been performed for reaction crystallisation (to the best of the authors’ knowledge). Furthermore, while there are common threads between reacting flows with particle formation, reaction crystallisation has some important distinct characteristics.…”

Section: Introductionmentioning

confidence: 99%

On the interaction of turbulence with nucleation and growth in reaction crystallisation

2022

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The objective of this work is to investigate the interaction of turbulence with the nonlinear processes of particle nucleation and growth that occur in reaction crystallisation, also known as precipitation. A validated methodology for coupling the population balance equation with direct numerical simulation of turbulent flows is employed for simulating an experiment conducted by Schwarzer et al. (Chem. Engng Sci., vol. 61, no. 1, 2006, pp. 167–181), where barium sulphate nanoparticles are formed by mixing and reaction of barium chloride and sulphate acid in a T-mixer, with the spatial resolution resolved down to the Kolmogorov scale. A unity Schmidt number is assumed, since at present it is not possible to resolve the Batchelor scale for realistic Schmidt numbers (order of 1000 or more). The probability density function, filtered averages and spatial distribution of time and length scales are all examined in order to shed light on the interplay of turbulence and precipitation. Separate Damköhler numbers are defined for nucleation and growth and both are found to be close to unity, indicating that the process is neither mixing nor kinetics controlled. The nucleation length scales are also evaluated and compared with the Kolmogorov scale to show the importance of resolving nucleation bursts. In addition, zones of different rate-determining mechanisms are identified. The ultimate aim of precipitation is to obtain control over the product particle size distribution, and the present study elucidates the synergistic or competing roles of mixing, nucleation and growth on the process outcome and discusses the implications for modelling.

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“…In contrast, a convection-cloud chamber is inspired by a turbulent mixed-layer viewpoint, in which microphysical processes exist in a dynamic steady state with aerosols being continuously introduced, and cloud droplets settling to the bottom. The aerosols and cloud particles are exposed to fluctuating velocity, temperature and water vapor fields, resulting in both positive and negative supersaturations, leading to corresponding activation and deactivation of cloud condensation nuclei (MacMillan et al, 2022;Prabhakaran et al, 2020), as well as the growth and evaporation of cloud droplets (Chandrakar et al, 2016) and ice particles (Desai et al, 2019).The Pi Chamber volume is a cylinder with height and radius both equal to 1 m (the name denoting the volume of π m 3 ). The thermodynamic conditions in a convection-cloud chamber, including the supersaturation forcing…”

mentioning

confidence: 99%

Scaling of Turbulence and Microphysics in a Convection–Cloud Chamber of Varying Height

Thomas

Yang

Ovchinnikov

et al. 2023

J Adv Model Earth Syst

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The Pi Chamber is a laboratory convection-cloud chamber in which "fully resolved" by nature aerosol and cloud microphysical processes take place within a turbulent medium (Chang et al., 2016). This is a fundamentally different approach than the traditional expansion cloud chamber, which takes its inspiration from the parcel viewpoint, that is, all particles are exposed to the same environment and have the same lifetime. In contrast, a convection-cloud chamber is inspired by a turbulent mixed-layer viewpoint, in which microphysical processes exist in a dynamic steady state with aerosols being continuously introduced, and cloud droplets settling to the bottom. The aerosols and cloud particles are exposed to fluctuating velocity, temperature and water vapor fields, resulting in both positive and negative supersaturations, leading to corresponding activation and deactivation of cloud condensation nuclei (MacMillan et al., 2022;Prabhakaran et al., 2020), as well as the growth and evaporation of cloud droplets (Chandrakar et al., 2016) and ice particles (Desai et al., 2019).The Pi Chamber volume is a cylinder with height and radius both equal to 1 m (the name denoting the volume of π m 3 ). The thermodynamic conditions in a convection-cloud chamber, including the supersaturation forcing

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Direct numerical simulation of turbulence and microphysics in the Pi Chamber

Cited by 13 publications

References 41 publications

Washing the air: enhanced condensation of water on aerosols to enable their removal

Washing the air: enhanced condensation of water on aerosols to enable their removal

On the interaction of turbulence with nucleation and growth in reaction crystallisation

Scaling of Turbulence and Microphysics in a Convection–Cloud Chamber of Varying Height

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