کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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237217 | 465698 | 2012 | 9 صفحه PDF | دانلود رایگان |
![عکس صفحه اول مقاله: A Lagrangian particle random walk model for hybrid RANS/LES turbulent flows A Lagrangian particle random walk model for hybrid RANS/LES turbulent flows](/preview/png/237217.png)
A continuous random walk (CRW) turbulent diffusion model was adapted for Lagrangian particles within gas flowfields simulated by hybrid RANS/LES methodologies. The methodology was designed to model all the particle diffusion in RANS regions and model only the sub-grid diffusion in LES regions. In the RANS approach, the mean flowfield and the turbulent time- and length-scales are obtained with a k–ω (Menter SST) turbulence model. These values are used with a discrete stochastic equation to compute instantaneous gas velocity along an individual particle trajectory. Experimental results for turbulent diffusion of particles in a homogeneous wake flow were first used to calibrate the RANS model. The stochastic diffusion model was then extended to utilize the Nichols–Nelson k–ω hybrid RANS/LES turbulence model in the unsteady three-dimensional wake of a cylinder. In particular, the flow at a Mach number of 0.1 and Reynolds number (ReD) of 800 was computed with a 5th-order upwind-biased scheme. The discrete stochastic equation was used to compute sub-grid fluctuations, which could be added to the resolved velocity field, and specifically took into account combined effects of particle inertia and non-homogeneous turbulence. The combination of resolved diffusion and sub-grid diffusion compared quite reasonably with diffusion based on Direct Numerical Simulation of the Navier–Stokes equations. The results indicate that eddy-crossing effects and inertia-based drift corrections can be critical, even when most of the kinetic energy is captured with the resolved-scales of an LES approach.
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► Stochastic particle diffusion model for RANS/LES approaches is proposed.
► Turbulent kinetic energy data from a hybrid RANS/LES flowfield are utilized.
► Eddy-crossing effects and inertia-based drift corrections are incorporated.
► Model results compare favorably with experimental data and DNS predictions.
► Model transitions seamlessly between RANS and LES regions of the flow.
Journal: Powder Technology - Volume 221, May 2012, Pages 105–113