Actuator disk in a two-dimensional non-uniform flow

In this paper a method to calculate the flow field of an infinitely bladed propeller in a non-uniform two-dimensional flow is developed. A computer program has been written, which showed that the mathematical model gives reasonable results and consumes little computing time. With this method it is possible to calculate the effective wake of an open propeller.

The method is confined to lightly loaded and moderately loaded propellers.

It is shown that it is necessary to incorporate the effects of strong vorticity in the onflow into the model.

The main purpose of this work was to examine the effects of various thrust distributions on the actuator disk and the optimum position of two reaction fins.

In a uniform flow there are small differences in efficiency between the various thrust distributions, but in a non-uniform flow they can increase up to 5%. Therefore the advantage of changing the thrust distribution to get higher radial velocities on the reaction fins can be lost by a lower efficiency of the propeller.

If the vorticity in the onflow increases, the radial velocities near the tip of the propeller decrease but at some distance ahead of the propeller they increase. Therefore it can be favourable in certain types of onflow to place the reaction fins ahead of the propeller.

The effects on the radial velocities of moving the maximum of the thrust distribution to the tip are rather local. The radial velocities near the tip increase but become more peaked.

The axial induced velocities on the actuator disk, caused by two reaction fins, strongly depend on their position and the type of onflow. In certain types of non-uniform flow it is completely incorrect to calculate the induced velocities, caused by the reaction fins, with potential theory.