An algebraic hybrid RANS-LES model with application to turbulent heat transfer
Ilyas Yilmaz  1, *@  
1 : Mechanical Eng. Dept., Istanbul Aydin University
* : Corresponding author

An algebraic hybrid RANS-LES model is proposed. The RANS mode employs
a modified mixing-length approach near walls. Instead of using the magnitude
of the resolved strain-rate tensor, the advanced spatial operator used by the WALE
subgrid-scale model is embedded into the formulation due to its better scaling properties
for the turbulent/eddy-viscosity. The LES mode incorporates the well-known
WALE model to resolve flow in the rest of the domain. Similar to the robust, wellcalibrated,
low-cost, algebraic hybrid RANS-LES model (HYB0) which combines
simple mixing length-type RANS near wall with Smagorinsky model away from
wall, the same turbulent length-scale adaptation approach for the RANS-LES interface
is utilized for proper interaction between the modes. In addition to correct
near-wall behaviour, the use of the advanced WALE differential operator should theoretically
ensure smooth transition at the interface, detection of turbulent structures
inside the eddies and better prediction of the log-layer velocity profile. Turbulent
Rayleigh-B´enard problem is studied using both models to examine and compare
their performances without the Boussinesq approximation. It is found that HYB0 is
sligthly dissipative compared to mHYB0. However, HYB0 has interestingly better
near-wall behavior. No interface issues were observed with the usage of the WALE
operator. Further applications are required to characterize the behavior of the both
models.


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