Aerodynamic Analysis of Low Reynolds Number Flows
Catalano, Pietro (2009) Aerodynamic Analysis of Low Reynolds Number Flows. [Tesi di dottorato] (Inedito)
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An aerodynamic analysis of low-Reynolds number flows is presented. The focus is placed on the laminar separation bubbles, a peculiar phenomenon of these kind of flows. The only simulations techniques feasible to be applied to complex configurations appear to be the methods based on the Reynolds Averaged Navier Stokes equations. A critical point is the turbulence modelling. In fact, the turbulence models are calibrated for flows at high Reynolds number with separation in the turbulent regime. The flow over a flat plate with an imposed pressure gradient, and around the Selig-Donavan 7003 airfoil is considered. Large eddy simulations have also been performed and used as reference for the RANS results. Laminar separation bubbles have been found by the Spalart-Allmaras and the k-w SST turbulence models. The models have been used without prescribing the transition location and assuming low values of the free-stream turbulence. The main results have been achieved for the k-w SST turbulence model. This model is very reliable for transonic flows at high Reynolds number, but has shown limits when applied to low-Reynolds number flows. A modification of the model has been proposed. The modified model, named as k-w SST-LR, has provided a correct simulation of the boundary layer in the tests performed at low and high Reynolds numbers. The laminar separation bubble arising of the SD 7003 airfoil has been well captured. The accuracy of the new model is not reduced in transonic regime.
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