Browsing by Author "Islam, Mazhural"

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    CFD Analysis of NACA4415 Airfoil with ƴ – Re₀ Model considering Natural Transition
    Islam, Mazhural; Langfeldt, Felix; Juretic, Franjo; Guerrero, Joel; Wood, David H. (Virginia Tech, 2015-06)
    Airfoil analysis is essential to wind turbine aerodynamics. In typical operating conditions, airfoils undergo transition from laminar to turbulent flow in the boundary layer in a manner that must be modeled accurately to predict airfoil lift and drag. There are different modes of transition (e.g. natural, by-pass, wake induced, reversed, separated flow) and modeling them is not straight-forward. Over the years, diversified predictions have been developed for the various modes. One of the popular transition models is the local correlation-based ƴ - Re₀ model of Menter et al. (Menter et al., 2004). The model requires data correlations for the transition length and the critical Reynolds numbers.
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    Modifications of the k-kL-ω Transition Model based on Pohlhausen and Falkner-Skan Profiles
    Fuerst, Jiri; Islam, Mazhural; Příhoda, J.; Wood, David H. (Virginia Tech, 2015-06)
    We will present novel modifications of the three-equation k-kL-ω eddy viscosity model proposed by Walters and Cokljat [1] for the adverse pressure gradient flows that occur on wind turbine blades and airfoils. The original model was based on the k-ω framework with an additional transport equation for laminar kinetic energy which allows the prediction of natural or bypass laminar-turbulent transitions. The model uses only local information and is, therefore, easily implemented in modern CFD codes including Fluent and OpenFOAM. The original model shows very good agreement with experimental data for zero pressure gradient flows (see e.g. [1]) but it delays the transition for adverse pressure gradient flows at low free-stream turbulence levels [2]. Both stability analysis and experiments show that the pressure gradient has a big influence on transition [3].