Nonlocality of Mean Scalar Transport in Two-Dimensional Rayleigh-Taylor Instability Using the Macroscopic Forcing Method
arXiv (Cornell University)(2023)
摘要
The importance of nonlocality of mean scalar transport in 2D Rayleigh-Taylor
Instability (RTI) is investigated. The Macroscopic Forcing Method (MFM) is
utilized to measure spatio-temporal moments of the eddy diffusivity kernel
representing passive scalar transport in the ensemble averaged fields.
Presented in this work are several studies assessing the importance of the
higher-order moments of the eddy diffusivity, which contain information about
nonlocality, in models for RTI. First, it is demonstrated through a comparison
of leading-order models that a purely local eddy diffusivity is insufficient in
capturing the mean field evolution of the mass fraction in RTI. Therefore,
higher-order moments of the eddy diffusivity operator are not negligible.
Models are then constructed by utilizing the measured higher-order moments. It
is demonstrated that an explicit operator based on the Kramers-Moyal expansion
of the eddy diffusivity kernel is insufficient. An implicit operator
construction that matches the measured moments is shown to offer improvements
relative to the local model in a converging fashion.
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关键词
mean scalar transport,macroscopic forcing method,instability,two-dimensional,rayleigh-taylor
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