Browsing by Author "Siikonen, Timo, Prof., Aalto University, Department of Applied Mechanics, Finland"

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    Sub-grid Scale Modeling in Large Eddy Simulation with Variable Eddy-Viscosity Coefficient
    (Aalto University, 2015) Taghinia, Javad; Rahman, Mizanur, Dr., Aalto University, Department of Applied Mechanics, Finland; Sovelletun mekaniikan laitos; Department of Applied Mechanics; Fluid Dynamics Group; Insinööritieteiden korkeakoulu; School of Engineering; Siikonen, Timo, Prof., Aalto University, Department of Applied Mechanics, Finland
    Two new sub-grid scale models for large eddy simulation (LES) are presented; namely zero and one-equation SGS models. These models utilize a novel method for calculating Cu in which the model coefficient is determined from the strain-rate and vorticity parameters. Therefore, it responds to both the shear and vorticity dominated flows that are far from equilibrium. The Cu usually ensures realizability of the resolved normal stresses in question. Unlike the dynamic Smagorinsky model (DSM), both models need only a single filter making them more robust for use in the majority of fluid flow problems. In addition, they require no ad-hoc strategies for achieving the numerical stabilization. Finally, one can save some computational effort in the proposed models, since the test-filtering operation on the SGS stress is not required. In other words, the current models can be considered as a good compromise between accuracy and manageability; particularly, as simple as the original Smagorinsky model and as accurate as the DSM. The performance of the new models are demonstrated through the comparison with experimental and DNS data of well-documented flows, consisting of fully developed channel flows, indoor airflow, flow over circular cylinder and jet impingement on a concave surface. The predictions are in good agreement with the available data. The test cases are selected such as to justify the ability of the model to replicate the combined effects of low-Reynolds number (LRN), near-wall turbulence and nonequilibrium. Comparisons also indicate that the present model offers competitiveness with the existing SGS models.