A stochastic model for the simulation of wind turbine blades in static stall

The aim of this work is to improve aeroelastic simulation codes by accounting for the unsteady aerodynamic forces that a blade experiences in static stall. A model based on a spectral representation of the aerodynamic lift force is defined. The drag and pitching moment are derived using a conditional simulation technique for stochastic processes. The input data for the model can be collected either from measurements or from numerical results from a Computational Fluid Dynamics code for airfoil sections at constant angles of attack. An analysis of such data is provided, which helps to determine the characteristics of stall. The model is applied to wind turbine rotor cases, including the stand still condition, and results are compared to experimental data. Copyright © 2009 John Wiley & Sons, Ltd.     

Turbulent diffusion combustion model using chemical equilibrium combined with the eddy dissipation concept for reducing detailed chemical mechanisms: An application of H2‐air turbulent diffusion flame

This research aims at building a turbulent diffusion combustion model based on chemical equilibrium and kinetics for simplifying a complex chemical mechanism. This paper presents the combustion model based on chemical equilibrium combined with an eddy dissipation concept model (CE‐EDC); the model is validated by simulating a H₂‐air turbulent diffusion flame. In the CE‐EDC model, the reaction rate of fuels and intermediate species are estimated by using the equations of the EDC model. Then, the reacted fuels and intermediate species are assumed to be in chemical equilibrium; the amounts of the other species are determined by the Gibbs free energy minimization method by using the amounts of the reacted fuels, intermediate species, and air as reactants. An advantage of the CE‐EDC model is that the amounts of the combustion products can be determined without using detailed chemical mechanisms. Moreover, it can also predict the amounts of the intermediate species. The obtained results are compared with Takagi's experimental data and the data computed by the EDC model, which uses the complex chemical mechanisms. The mole fractions of H₂, O₂, H₂O, temperature, and velocity obtained by using our CE‐EDC model were in good agreement with the reference data without taking into account the chemical reaction rates of the O₂ and H₂O. Furthermore, the mole fractions of OH and H are in good agreement with the results of the EDC model at high temperatures. On the other hand, the chemical equations involving OH and H were used for predicting the mole fractions of OH and H, which were similar to those obtained from the EDC model at low temperatures. Using the present CE‐EDC model, amounts of combustion products can be calculated by using a reduced chemical mechanism and the Gibbs free energy minimization theory. The accuracy of this model is in the same order as that of the EDC model. The CE‐EDC model uses reduced chemical mechanism concerning selected species, while the result of the chemical equilibrium calculation was employed to the other species; further, the accuracy of the CE‐EDC model is the same as that of the EDC model as to major species, T, U, and k. © 2010 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20296