Abstract
Modulation of fluid temperature fluctuations by particles due to thermal interaction in homogeneous isotropic turbulence is studied. For simplicity, only thermal coupling between the fluid and particles is considered, and momentum coupling is neglected. Application of the statistical theory used in cloud turbulence research leads to the prediction that modulation of the intensity of fluid temperature fluctuations by particles is expressed as a function of the Damköhler number, which is defined as the ratio of the turbulence large-eddy turnover time to the fluid thermal relaxation time. Direct numerical simulations are conducted for two-way thermal coupling between the fluid temperature field and point particles in homogeneous isotropic turbulence. The simulation results are shown to agree well with the theoretical predictions.
Highlights
Turbulent flows in a broad range of natural and engineering applications include small particles, such as water droplets in clouds (Chen et al 2018), dust particles in protoplanetary disks (Ishihara et al 2018) and pneumatic transport of solid particles (Ebrahimi & Crapper 2017)
Based on the results of scaling analysis and direct numerical simulations (DNSs), they demonstrated that turbulence modulation by particles can be expressed as a function of the Damköhler number, which is defined as the ratio of the turbulence large-eddy turnover time to the new time scale
In order to further extend the study by Saito et al (2019b), the present study considers the case of thermal coupling, in which particles interact with the fluid temperature field by heat transfer in turbulence
Summary
Turbulent flows in a broad range of natural and engineering applications include small particles, such as water droplets in clouds (Chen et al 2018), dust particles in protoplanetary disks (Ishihara et al 2018) and pneumatic transport of solid particles (Ebrahimi & Crapper 2017). In order to further extend the study by Saito et al (2019b), the present study considers the case of thermal coupling, in which particles interact with the fluid temperature field by heat transfer in turbulence. This case has been investigated through numerous DNS studies, a few of which are described below. The fluid is assumed to be incompressible with a constant mass density Through these simplifications, we can straightforwardly apply the Langevin model to obtain the analytical prediction, which provides a fundamental understanding of the mechanism of the two-way thermal coupling between particles and turbulence.
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