Browsing by Author "Wood, David H."
Now showing 1 - 3 of 3
Results Per Page
Sort Options
- CFD Analysis of NACA4415 Airfoil with ƴ – Re₀ Model considering Natural TransitionIslam, 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.
- Modifications of the k-kL-ω Transition Model based on Pohlhausen and Falkner-Skan ProfilesFuerst, 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].
- Wind Farm Layout Optimization Considering Commercial Turbine Selection and Hub Height VariationAbdulrahman, Mamdouh; Wood, David H. (Virginia Tech, 2015-06)New aspects is added to the wind farm layout optimization problem. A variable hub height non-identical turbines wind farm design is presented. The manufacturers' technical data for 61 commercial horizontal axis wind turbine models is used in order to obtain more realistic results. Three objective functions are considered individually: (1) the total power production, (2) the farm capacity factor, and (3) the capital cost of output power index (based on nominal power and tower height). The results show that the flexibility of using non-identical turbines with different heights in the same wind farm can meet a wide range of preferences. By adapting the objective functions' weighting factors many preferred solutions can be obtained. Summary : The results show that the flexibility of using non-identical turbines with different heights in the same wind farm can meet a wide range of preferences. By adapting the objective functions' weighting factors many preferred solutions can be obtained. The enhancement of such flexible design on both TPP and CCI becomes more significant in limited land (small valued of S) and/or low wind class cases. This makes the presented design suitable for compact designs as well as the relatively low exergy sites.