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Wall-Modeled LES of Turbulent Flow Past Airfoils and Periodic Hills

AMS Seminar Series

Speaker: Ravi Samtaney, The King Abdullah University of Science and Technology (KAUST)

Presentation

Seminar Slide Deck (PDF-20.3MB)

Abstract

We present wall-modeled large-eddy simulation (WMLES) of turbulent flow past airfoils and periodic hills. To avoid the challenging resolution requirements of the near wall region, we develop a virtual wall model in generalized curvilinear coordinates and incorporate the non-equilibrium effects via proper treatment of the momentum equations. By combining the present wall model with the stretched-vortex subgrid-scale model, we apply the WMLES approach to three different airfoil cases, spanning different geometrical parameters, different attack angles and low to high Reynolds number based on chord length (Rec in the range 104 to 2.1 x 106). The numerical results are verified with DNS at low Rec, and validated with experiment data at higher Rec, including typical aerodynamic properties such as pressure coefficient distributions, velocity components, and also more challenging measurements such as skin-friction coefficient and Reynolds stresses. Two techniques to quantify hitherto unexplored physics of flows past airfoils are employed: one is the construction of the anisotropy invariant map, and the second is skin friction portraits with emphasis on flow transition and unsteady separation along the airfoil surface.

The second set of WMLES results pertain to the turbulent flow in a channel constricted by streamwise periodically distributed hill-shaped protrusions of height ‘h’. Three Reynolds number cases, i.e., Reh = 10595, 33000 and 105 are presented. For the first two cases our WMLES results of the pressure and skin friction coefficients on bottom and top walls of the channel, mean velocity profiles and Reynolds stresses are compared with existing experiments in the literature and show good agreement. Additionally, the main large-scale feature of the separation behind the hill, including the bubble size and scaling of the mean velocity profiles are discussed. Furthermore, the instantaneous near-wall flow field is analyzed in terms of skin friction portraits. The anisotropy of the flow is analyzed in terms of the anisotropy invariant map. Furthermore, the instantaneous near-wall flow field is analyzed in terms of skin friction portraits.

Biography

Photo of Ravi Samtaney
Ravi Samtaney is presently a professor in Mechanical Engineering (Physical Science and Engineering Division) with a joint appointment in Applied Mathematics & Computational Science at the King Abdullah University of Science and Technology (KAUST) in the Kingdom of Saudi Arabia. He serves as Chair of the ME Program and Associate Dean of the PSE Division. Prior to KAUST, he was a Research Physicist at the Princeton Plasma Physics Laboratory, Princeton University, a research faculty at the California Institute of Technology, and worked at NASA Ames Research Center. His research is at the intersection of applied mathematics, physics, and engineering, from fundamental processes in fluid mechanics (shocks, turbulence, ablation, ionization, etc.) to numerical methods and large-scale computing (adaptive meshing, scalable solvers, software engineering, etc.). He obtained his Ph.D. from Rutgers University in 1994.