Abstract
Dispersed multiphase turbulent flows are present in many industrial and commercial applications like internal combustion engines, turbofans, dispersion of contaminants, steam turbines, etc. Therefore, there is a clear interest in the development of models and numerical tools capable of performing detailed and reliable simulations about these kind of flows. Large Eddy Simulations offer good accuracy and reliable results together with reasonable computational requirements, making it a really interesting method to develop numerical tools for particle-laden turbulent flows. Nonetheless, in multiphase dispersed flows additional difficulties arises in LES, since the effect of the unresolved scales of the continuous phase over the dispersed phase is lost due to the filtering procedure. In order to solve this issue a model able to reconstruct the subgrid velocity seen by the particles is required. In this work a new model for the reconstruction of the subgrid scale effects over the dispersed phase is presented and assessed. This innovative methodology is based in the reconstruction of statistics via Probability Density Functions (PDFs).
Highlights
Multiphase flows of particles and droplets are a kind of flows characterized by the presence of two phases, with one continuous phase and another dispersed phase
The idea is to obtain a function that fits the mean and the standard deviation of the subgrid velocity magnitude (|usgs|) for a certain Stokes number and a filter size. This information is used in Large Eddy Simulations (LES) to reconstruct dynamically a β − pdf representing the statistical information obtained from Direct Numerical Simulations (DNS)
The statistical information for particles with St = 0.5 have been analyzed and fitted in an isotropic turbulence simulation of Reλ = 40. This statistical information has been used as source for the Probability Density Functions (PDFs) employed in the presented model
Summary
Multiphase flows of particles and droplets are a kind of flows characterized by the presence of two (or more) phases, with one continuous phase and another dispersed phase. This flow configuration is present in a large amount of industrial and energy conversion processes like cyclone separators, spray drying, combustion chambers, fluidized beds, etc. Direct Numerical Simulations (DNS) of multiphase turbulent flows with high Reynolds, like the examples presented before, are not feasible nowadays. In Large Eddy Simulations (LES), the large scale structures of the flow are well resolved and only the subgrid scales (sgs) are modeled.
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