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International Review of Mechanical Engineering (I.RE.M.E), Vol. 2, N. 4 July 2008 Numerical Study of Transonic Flows Using Various Turbulence Models N.Bekka1*, R.Bessaïh2, M. Sellam1 Abstract - In this paper, validation and assessment of various turbulence models are performed in transonic flows, including an algebraic Baldwin Lomax model, Spalart Allmaras one equation, and two equation (k-ε, k-ω and SST k-ω) turbulence models. The NACA 0012 airfoil has been chosen for the turbulence model validation studies. The three test cases selected here included both attached and separated transonic flows. This study shows that the five turbulence models provide satisfactory results for transonic attached flows. However, all models, fail to predict the location of the shock correctly when a strong shock and a shock induced flows separation are present. Compared to other models, it has been shown that the SST k-ω model is the most robust model in the prediction of lift coefficient for all cases. Computed results are performed with the CFD-FASTRAN code by using the fully implicit scheme for time integration, and the upwind Roe flux difference splitting scheme for space discretization augmented by a high order Min-Mod limiter to damp spurious oscillations and to allow for sharp shock resolution. Keywords: Numerical study ,Transonic flows, Turbulence models, Airfoil Nomenclature I. CD drag coefficient CL lift coefficient E total energy k turbulent kinetic energy M∞ Mach number P pressure Pr Prandtl number Prt turbulent Prandtl number q j total heat flux Modern transport and passenger aircraft operate at cruise flight transonic speeds, corresponding to a Mach number interval M∞ =0.75-0.85 and a very high Reynolds numbers. Transonic flow occurs when there is a mixed sub and supersonic local flow in the same flow field [1]-[2]. It is characterized by the development of a closed, wallbounded supersonic flow region at the upper wing surface. Depending on wing curvature and the angle of incidence, the appearance of a closed wall-bounded supersonic flow region at the lower wing surface is also possible. Transonic airfoil flow is to a large degree affected by a strong adverse pressure gradient, shock/boundary-layer interaction, and separation downstream of the shock. These features as well as the compressible properties of the flow pose a special challenge not only for the numerical treatment, but also for turbulence models. The aerodynamics of transonic turbulent flows over airfoils and wings has been studied for decades in experimental and numerical works. A total of 23 sets of numerical results from 15 different author groups are summarized and compared by Holst [3]. These methods vary from momentum integral boundary-layer methods coupled with transonic potential inviscid codes to a full Navier-Stokes methods [4]-[7]. Lai et al. [8] simulated numerically the turbulent transonic flow over the NACA0012 and RAE2822 airfoils with and without shocks, using a pressure-based method, including the Baldwin-Lomax and k-ε models. Four popular Re∞ Reynolds number T temperature t time uj component of the velocity Greek symbols αc corrected angle of attack αg geometric angle of attack γ specific heat ratio ε dissipation rate of the turbulent kinetic energy µ dynamic viscosity µt eddy viscosity density of the fluid τij Reynolds stresses τˆij Introduction total stress tensor 599  1%HNND5%HVVDw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