Physical Analysis of the Separated Flow Around an Iced Airfoil Based on ZDES Simulations

Abstract

This paper presents the results of a numerical study of the unsteady flow around a leading-edge iced airfoil. At first, we demonstrate the efficiency of the numerical model used for the unsteady computations, a Zonal Detached Eddy Simulation (ZDES), validated by experimental data. Then, the degradation of the aerodynamic performance due to the ice accretion is better predicted by the ZDES than by steady RANS-SA method. Besides the paper aims at improving the understanding of the unsteady phenomena related to the turbulent separated flows. Nomenclature ZDES : Zonal Detached Eddy Simulation RANS-SA : Reynolds-Averaged Navier-Stokes equations with Spalart-Allmaras turbulent model PIV : Particle Image Velocimetry c = airfoil chord length L y = airfoil span length h = height of the upper ice ridge x = chordwise position along the airfoil from the leading edge y = spanwise position (between -L y and 0) z = normal position from the airfoil chord line α = airfoil angle of attack P i = stagnation pressure in the wind tunnel U 0 = free stream velocity M = Mach number Re = Reynolds number based on chord length dt = time step df = frequency resolution for spectral analyses v x , v y , v z = x-, y-and z-components of the flow velocity C D= drag coefficient C y = force coefficient in the spanwise direction C L = lift coefficient C P = pressure coefficient Q = Q-criterion measuring vorticity in the flow C corrY = coefficient measuring the averaged correlation degree in the spanwise direction

Advanced numerical prediction of iced airfoil aerodynamics

“…Another possibility for the ZDES simulations could be that the spanwise extension of the mesh is too small for the present simulation. However, Duclercq et al did not find any significant effect of spanwise extension from 8.5% chord to 34% chord for this same case [13].…”

“…This particular configuration was also considered by Zhang et al in [14]. It was also used by Duclercq et al [13] to validate their ZDES simulation and the present work is a follow-on of this activity. The roughness shape (right) corresponds to the early stages of ice accretion or it appears during the inter-cycle operation of the ice protection system.…”

“…The grids used for the RANS and URANS simulations are based on a 2D version of a mesh previously used by Duclercq et al [13] to perform a ZDES simulation of the same configuration. This multiblock structured grid was generated with ICEM-CFD Hexa (Figure 2).…”

“…The hybrid methodology also behaved more consistently with grid refinement by comparison to DDES. Duclercq et al [13] applied the Zonal Detached Eddy Simulation method (ZDES) to the computation of the NACA23012 airfoil with a spanwise ridge on both upper and lower surface, showing an improved prediction of the flow separation with respect to RANS. The unsteady nature of the flow with vortex shedding was emphasized.…”

Swept-Wing Ice Accretion Characterization and Aerodynamics

“…This research effort is modeled after a previous successful international collaboration that investigated aerodynamic effects and ice accretion simulation for airfoils and straight wings. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] The overall goal of the previous collaboration was to provide high-fidelity, full-scale, iced-airfoil aerodynamic data and validated subscalemodel simulation methods that produce the essential full-scale aerodynamic characteristics. The research was organized into six phases involving icing wind tunnel and aerodynamic wind tunnel experiments with both subscale and full-scale models using the NACA 23012 airfoil.…”