Stady state measurement of the velocity around a airfoil were accomblished at different cavitating conditions in the Cavitation Channel of the institute. The cavitation channel is embedded into the large closed-loop test rig of the IHS. The test rig is equipped with two pumps, which can be operated in parallel or serial, depending on the requirements of the experiment. A speed-regulated direct current motor powers the pumps. They convey water to the headwater vessel from where it flows via the cavitation channel into the tailwater vessel. The tailwater vessel is built with an air-subjected dome, in order to vary the pressure level of the test rig. The water flows from the tailwater vessel back to the pumps passing an electromagnetic flow meter (see fig. 1).

The cavitation channel itself consists of a pipe with rectangular cross section. The height is 150 mm and the width is 100 mm. In the centre of the channel an airfoil is mounted. In a further measurement an airfoil with a Göttinger profile (Gö 624) was mounted in the cavitation channel. The chord length of this airfoil is 100 mm, and the width is 50 mm, i.e. half the width of the channel. The angle of incidence is 5°. In this investigation an average flow-velocity of 8 m/s was adjusted.

During the measurement the velocity in horizontal and vertical planes was measured. The time-averaged two-dimensional results of the different measurement planes were assembled afterwards to a three-dimensional velocity vector field. In fig. 3 the velocity-vector-field with the secondary velocity is depicted. This velocity field is derived from the three-dimensional velocity vector field.