Proceedings of the 7 th International Symposium on Cavitation CAV2009 – Paper No. 45 August 17-22, 2009, Ann Arbor, Michigan, USA 1 Cavitating Propeller Flows Predicted by RANS Solver with Structured Grid and Small Reynolds Number Turbulence Model Approach Tuomas Sipilä VTT Technical Research Centre of Finland Espoo, Finland Timo Siikonen Helsinki University of Technology (TKK) Espoo, Finland Ilkka Saisto VTT Technical Research Centre of Finland Espoo, Finland Jussi Martio VTT Technical Research Centre of Finland Espoo, Finland Heru Reksoprodjo Helsinki University of Technology (TKK) Espoo, Finland ABSTRACT Within the EU research project VIRTUE, a propeller is investigated in uniform and non-uniform inflow conditions by means of a RANS equation solver, FINFLO. The analyses are made in wetted and cavitating conditions. The propeller analyzed in this paper is the INSEAN E779A propeller. The paper contains calculations at three different grid resolutions in wetted conditions and at the two finest grid resolutions in cavitating conditions in uniform inflow. The medium-size grid is used for the propeller in non- uniform inflow simulations. The simulations are conducted on a model scale and the results are compared with the measurements and cavitation tests performed by INSEAN. The non-uniform inflow is generated by modeling the geometry of the artificial wake generator used in the cavitation tests in the calculation domain. The experimental results are published in several papers, for example in [1] and [2]. The predicted propeller open water thrust and torque are found to be within 5 % of the measured ones. The pressure peak at the leading edge of a blade is found to be sensitive to the grid resolution. The predicted cavitation behavior of the propeller blades is in reasonable accordance with the cavitation test observations. In uniform inflow the vaporized region is over-predicted. Contrastingly, the vaporized region is under-predicted in the non-uniform inflow calculations. Side entrant jets could be identified in the cavity region in the non- uniform inflow simulations. The predicted vaporized regions in several blade positions together with photographs of the cavitating propeller are shown for comparison. The cavitation behavior trends seemed to be similar in the simulations and observations in non-uniform inflow, except that the roll-up of detached sheet cavitation into a tip vortex could not be captured in the calculations. The total wake is measured between the propeller plane and the wake generator. The predicted wake is found to be too strong, but the width of the wake is relatively close to the measurements. The propeller loading history is shown over one propeller revolution. It shows qualitatively reasonable trends. The loading histories of the wetted and cavitating propeller are almost the same due to the relative small cavitating region in the investigated conditions. The pressure distributions at several blade positions on the suction side of the propeller are shown in wetted and cavitating conditions for comparison. INTRODUCTION Cavitation produces a number of problems in propeller flows. The cavitating tip vortex collapse as well as the fluctuating type of sheet cavitation can cause noise in the interior of the ship and in the environment. The cavitation can also cause erosive behavior on propeller blades and on devices in the slipstream of the propeller, for example on rudders. In practice, a ship’s propeller operates in an inhomogeneous wake field, where the velocity and direction of the flow in relation to the propeller blades vary during the rotation. For practical propeller analysis it is important to model both the cavitation phenomena and the unsteadiness of the inflow. In the mid-1990s VTT Technical Research Centre of Finland started using FINFLO for propeller flow analyses [3]. In the present study FINFLO is used to simulate non- cavitating and cavitating propeller flows. The RANS equation solver – called FINFLO – is developed by Helsinki University of Technology (TKK) [4]. During recent projects, TKK has extended the FINFLO code to the simulation of multi-phase flows. At this stage the Merkle’s mass transfer model for cavitating flows [5] is implemented for the phase transition. The propeller analyzed in this paper is a modified Wageningen type propeller, the INSEAN E779A, which has an extensive experimental database [1], [2]. Because the test results of the propeller are very thoroughly documented, it was