Investigation of thickness effects on 2D NACA symmetric foils

Abstract

A numerical and experimental study on the hydrodynamic behaviour of 2D NACA (15, 25, 35%) symmetric hydrofoils at high chord (/spl ap/10/sup 6/) Reynolds numbers and high angles of attack is performed. The focus is devoted to the comparison between results particularly for stall conditions corresponding to unsteady separated flow. The effect of thickness on the hydrodynamic coefficients and the topology of the flow are studied and the capacity of commercial code to predict the hydrofoil stall by Reynolds-Averaged Navier Stokes equations is analysed. The hydrodynamic coefficients are measured using a force balance and the flow patterns are investigated using LDV techniques. The cavitating incipient flow has been investigated to determine the minimum pressure coefficient and correlations are proposed to join these results to the thickness effect. All the calculations (steady and unsteady) have been performed using FLUENT/spl reg/ code. The emphasis is on turbulence modelling, grid size and boundary layer conditions on the foil. The computation is validated with very detailed experimental data. A hysteretic behaviour of force coefficient is highlighted and the development of leading edge vortices before and after stall occurrence is characterised.