Numerical Study of Twist Effect of a Hydrofoil on the Length of Cavity and Lift and Drag Coefficients in Different Reynolds Numbers

Abstract

In this study a cavitating flow around a three dimensional twisted hydrofoil in an incompressible fluid is modeled. The variables in this study are; the twist angle, the angle of attack and the Reynolds number. The twist angle changes from 0.0 to 5.0 degrees with respect to the root, the angles of attack changes from −2 to 12 degrees and all these are computed at two Reynolds numbers of 5.791·107, and 1.99·108. The flow is assumed to be unsteady and isothermal. Coefficients of the drag and lift and also the cavity length are computed numerically. Numerical simulations are carried out and the cavitation number is set at σ = 1.2. The numerical results show that, as the twist angle increases, the cavity length (along the chord) did not change much, but the width of the cavity (along the span) increased very much, and this caused an increase of lift coefficient. However, a twisted hydrofoil has more variation of span-wise lift distribution, which is resulted by the downwash at the center part and an up-wash at the tips of the hydrofoil. Comparing the lift and the drag coefficient results of two twisted and no-twisted hydrofoil, the twisted hydrofoil show some notable increase of lift and a decrease of the drag coefficients. The best results are obtained around 5 degrees of twist angle.