Session: 03-09-02 Turbulent Flows (2/3)

Paper Number: 87534

87534 - Vortex Identification in Large Eddy Simulations Under the Lattice Boltzmann Framework With a Smagorinsky Subgrid Model 

The recent emergence of turbulence modeling strategies under the Lattice Boltzmann Method (LBM) framework has opened the door towards highly efficient numerical solutions for the governing fluids equations with potential application to industry. Advantages of the LBM over traditional Navier-Stokes (NS) based methods include its straightforward parallelization and its ability to recover flow dynamics without explicit treatment for pressure. Turbulence models under LBM have already been employed in the literature to study heat transfer in a refrigerated vehicle, decaying isotropic turbulence and square jet flow. Turbulence modeling under LBM has so far been mainly restricted to Large Eddy Simulation (LES), with variation primarily in the choice of model for the subgrid scales. To further evaluate the success of the LES model, it is essential to extract coherent structures in the flow field under the LBM framework. The search for an objective definition for coherent structures has resulted in a variety of vortex identification techniques, including the well-known Delta, Q and Lambda2 criteria. The question of whether such definitions can be used in the identification of coherent structures in turbulent flows has been studied extensively in the literature under the NS framework. A more comprehensive study including the effects of operating under an LBM framework would help reveal potential advantages and limitations of existing vortex identification techniques.

In the present work, Large Eddy Simulation within a Lattice Boltzmann framework is used to study a lid-driven cavity. In particular, a Smagorinsky subgrid scale model is chosen for the unresolved scales within a single-relaxation-time LBM. Simulations are performed in three dimensions at a Reynolds number of 10⁵. One-dimensional energy spectra are computed and the range of energy scales in the numerical solutions are inspected to ensure that turbulence has been captured. Isosurfaces of various vortex identification criteria are examined and compared to the vorticity magnitude and pressure minima. 

Presenting Author: Khodr Jaber University of Toronto