On the influence of transition modeling and crossflow effects on open water propeller simulations

Abstract

At model scale propellers, conventional turbulence models assume turbulent regimes all over the blade surface, and consequently do not obtain accurate predictions that can be compared to experimental results. Two aspects could be improved in order to produce a better description of the flow complexity generated in these turbulent rotating systems: the inclusion of transition phenomena assumptions that normally take place in these flows and a particular modeling of those transition mechanisms, such as cross flow, that appear at model scale propellers. In this paper, a new modified γ Reθ correlation-based model for transition prediction, that takes into account crossflow effects is applied to model scale ship propellers for a wide range of advanced ratios, and its results are compared to their corresponding experimental results. The average values of the skin friction coefficients on different parts of the blade and the streamlines distribution are studied and compared between different pro- pellers. The results obtained with these improvements show an agreement of about 1% in terms of efficiency, and below 5% in terms of thrust and torque coefficients when compared to the experimental results at the design point. The dependance of the cross flow mechanism on the Reynolds number is studied by changing the rotating velocity of the different propellers. Results show that the relevance of this mechanism grows when the rotating velocity, the centrifugal forces and Reynolds number increase. Consequently, when the Reynolds numbers grows, the cross flow transition mechanism is stimulated by the action of the centrifugal forces.